General Relativity and Quantum Cosmology
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Showing new listings for Tuesday, 3 June 2025
- [1] arXiv:2506.00106 [pdf, html, other]
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Title: Notes on a Gaussian-Based Distribution Algebra for the Non-linear Wave Equation of the Shift Vector in Quantum FoamSubjects: General Relativity and Quantum Cosmology (gr-qc)
In these notes, a non-linear distributional algebra is developed, tailored to the geometry of Gaussian Quantum Foam. The construction is based on sequences of smooth Gaussian functions restricted to spacelike hypersurfaces in a sequence of homotopic and globally hyperbolic spacetimes, converging in the sense of distributions to Quantum Foam. A restricted subspace of Schwartz functions is defined, consisting of finite products of scaled Gaussians supported on the hypersurfaces. An associated distribution space is introduced as the space of distributional limits of such sequences. The resulting algebra is closed under addition, multiplication, and arbitrary-order differentiation, with all non-linear operations defined at the level of smooth representatives prior to taking the limit. However, the original algebra is not closed under products involving second-order distributional derivatives-such terms diverge in the limit and must be renormalised. This issue is resolved by extending the algebra through a scaling procedure naturally provided by the Quantum Foam lapse function. The lapse scaling acts as a built-in renormalisation mechanism, ensuring that curvature expressions involving second-order derivatives remain well-defined in the distributional sense. This extended algebra is then applied to the non-linear scalar wave equation governing the shift vector field. A fundamental solution is constructed in the distributional sense, showing that the limiting curvature response of the Quantum Foam dynamics is encoded by a multiple of the second-order distributional derivative. This identifies the second-order distributional derivative as the singular source responsible for initiating the displacement of the vacuum and driving the emergence of classical spacetime.
- [2] arXiv:2506.00108 [pdf, html, other]
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Title: On the analogue of Einstein-Gauss-Bonnet theory in 3+1 dimensionsComments: 5+2 pagesSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
Higher curvature corrections to the Einstein-Hilbert term may play an important role in probing the strong-field regime of gravity. In this letter, we demonstrate that the local effective action reproducing the trace anomaly can resemble the Einstein-Gauss-Bonnet theory in four dimensions on specific backgrounds. The two key observations support this claim: 1) the covariant equation of the trace anomaly coincides with the trace of the metric variation in Einstein-Gauss-Bonnet theory, and 2) on the FRW space-time, the Friedmann-like equations in both frameworks coincide, with this correspondence extending to the quadratic and cubic perturbations. As an intrinsically four-dimensional construct, the trace anomaly effective action emerges as a promising framework for exploring higher curvature corrections to Einstein's General Relativity in a self-consistent manner.
- [3] arXiv:2506.00265 [pdf, html, other]
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Title: The Einstein Equation from an Informational-Geometrical EquivalenceComments: 5 pagesSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)
While any observer perceives its immediate neighborhood as locally flat, the metric field deviates from Minkowski space to relate infinitesimal distances assigned by local observers at distinct spacetime points. In a quantum description, these events should emerge from interactions (and thus correlations) between quantum systems, with one of them acting as a reference frame that defines relational localization. In this context, the metric field connects distances between interactions (events) \textit{from the perspective of} distinct physical local reference frames (LRFs). Building on this idea -- together with the connection between entanglement entropy and area (which, in turn, may be linked to the metric itself), and the fact that the Einstein equation does not require the explicit presence of these material frames -- we propose an \emph{informational-geometrical equivalence} (IGE): for a sufficiently small spacelike region $ B $, let $\rho_B $ and $ \sigma_B$ denote the reduced states of the quantum fields and the LRF within $ B $, respectively. In this picture, the relational content of the entropy of the quantum fields as seen by the LRF -- quantified by the conditional entropy $ \delta_\rho S(\rho_B | \sigma_B) $ -- is encoded in the variation $ \delta_{g,\rho} S(\rho_B) $ induced by a smooth geometric perturbation. When the reference frame has complete information about the infrared sector, this IGE recovers the semiclassical Einstein equation. Furthermore, considering the presence of quantum correlations between the system and the LRF reveals a positive cosmological constant related to the density of quantum correlation within $B$.
- [4] arXiv:2506.00295 [pdf, html, other]
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Title: Extended uncertainty principle inspired black hole in a Gödel UniverseComments: 8 pages. Comments are welcomeSubjects: General Relativity and Quantum Cosmology (gr-qc)
We explore analytically the implications of a curvature-modified extended uncertainty principle (EUP) derived in a rotating Gödel spacetime and apply it to the construction of a semiclassical black hole model. Adapting techniques from corpuscular black hole frameworks, we reinterpret the Gödel-type uncertainty relation as an effective energy bound, leading to a modified lapse function with explicit dependence on the global rotation parameter $a$ and the radial coordinate $ r_0 $. Analytic expressions are derived for key gravitational features, including the event horizon, photon spherehere, shadow radius, and deflection angle, with curvature corrections scaling as $ a^{-2} $ and $ r_0^2 / a^4 $. Series expansion in the limit $ a \to \infty $ shows that global rotation consistently increases all observables relative to the Schwarzschild case. Applying these results to astrophysical data, we use Event Horizon Telescope (EHT) measurements of Sgr A* and M87* to infer lower bounds of $ a/M \sim 10^5 $, while solar system light-bending observations in the parametrized post-Newtonian (PPN) framework yield $ a / M_\odot \sim 5 \times 10^4 $. These large but finite values validate the asymptotic expansion and confirm that Gödel-type rotation remains observationally suppressed, yet theoretically coherent. Our results demonstrate that global rotation, when treated semiclassically via curvature-modified uncertainty, introduces detectable signatures in principle, though well below current observational sensitivity. The framework offers a consistent path toward exploring the quantum-gravitational interplay between global geometry and local black hole structure.
- [5] arXiv:2506.00303 [pdf, html, other]
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Title: Dynamical gravitational Casimir-Polder interactionComments: 13 pages, 1 figures, accepted by Phys. Rev. DSubjects: General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
We explore the time-dependent Casimir-Polder-like quantum gravitational interaction between a nonpointlike object and a gravitational Dirichlet boundary, i.e., the dynamical gravitational Casimir-Polder interaction, based on the theory of linearized quantum gravity. We demonstrate that the dynamical interaction potential is nonzero prior to the radiation, which is generated by the gravitational vacuum-fluctuation-induced mass quadrupole of the object, being reflected by the gravitational boundary and back-reacted to the object (i.e., the mirror image of the object lies outside its causal region). This indicates the nonlocality of the fluctuating gravitational field in vacuum and calls for a reevaluation of the inherent causality within the interaction. Moreover, the dynamical gravitational Casimir-Polder interaction can be either attractive or repulsive depending on the distance of the object with respect to the boundary and the time of interaction. When the interaction time is sufficiently long for the system to approach asymptotic equilibrium, the dynamical gravitational Casimir-Polder interaction potential reduces to the static one, which is time-independent and consistently repulsive in both the near and far regimes.
- [6] arXiv:2506.00367 [pdf, html, other]
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Title: The ringdown of a black hole surrounded by a thin shell of matterComments: 26 pages, 12 figures. Submitted to Physical Review DSubjects: General Relativity and Quantum Cosmology (gr-qc)
Recent studies have shown that far-field perturbations to the curvature potential of a black hole spacetime may destabilize its quasinormal mode (QNM) spectrum while only mildly affecting time-domain ringdown signals. In this work, we study the QNM spectrum and ringdown behavior of a Schwarzchild black hole with a far-field perturbation to its physical environment -- a thin matter shell with finite surface tension. After accounting for the dynamics of the interaction between GWs and the shell, we find that the fundamental mode can migrate perturbatively or be destabilized by the appearance of new modes with no analogue in the vacuum case, much like studies of ``bumps" in the curvature potential. However, unlike these previous works, we find that the coupling between metric perturbations and oscillations of the shell also sources weakly-damped QNMs which are exclusive to the polar sector. We then study whether the analysis tools of least-squares QNM fits and the full and rational ringdown filters can clearly identify the signatures of the shell in representative ringdown waveforms. We conclude that ringdown at sufficiently early times is insensitive to the shell; weakly-damped QNMs (in the polar sector) and echoes, which may enable the analysis methods considered here to infer the presence of a shell, only appear at late times and are generally weak.
- [7] arXiv:2506.00640 [pdf, html, other]
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Title: Qualitative analysis of a quasi-magnetic universeComments: 22 pages and 9 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
We investigate the cosmological dynamics induced by nonlinear electrodynamics (NLED) in a homogeneous and isotropic universe, focusing on the role of primordial electromagnetic fields with random spatial orientations. Building upon a generalization of the Tolman-Ehrenfest averaging procedure, we derive a modified energy-momentum tensor consistent with FLRW symmetry, incorporating the influence of the dual invariant G and its statistical contributions. A specific NLED model with quatratic corrections to Maxwell's Lagrangian is considered, giving rise to what we define as quasi-magnetic universe (qMU), interpolating between purely magnetic and statistically null field configurations. We analyze the resulting cosmological dynamics through qualitative methods. By casting the equations into autonomous dynamical systems, we identify the equilibrium points, determine their stability, and study the behavior of solutions under various spatial curvatures. Our findings reveal the existence of bouncing and cyclic solutions, regions where energy conditions are violated, and scenarios of accelerated expansion. Special attention is given to two limiting cases: the Magnetic Universe (MU) and the Statistical Null Universe (SNU), both of which exhibit qualitatively distinct phase portraits and energy-condition behavior. This work provides a comprehensive framework for understanding the influence of nonlinear electromagnetic fields in the early universe and opens avenues for exploring their observational consequences.
- [8] arXiv:2506.00833 [pdf, html, other]
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Title: Bound on Lyapunov exponent for a charged particle in Kerr-Sen-AdS Black HoleComments: 20 pages, 56 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
We investigate the upper bound of the Lyapunov exponent for a charged particle in the Gibbons--Maeda--Garfinkle--Horowitz--Strominger (GMGHS)--AdS and Kerr--Sen--AdS black hole backgrounds, which originate from the low-energy effective actions of heterotic string theory and gauged supergravity. We analyze the Lyapunov exponent near the unstable orbit to examine possible violations of the bound. Our results indicate that the bound is sensitive to the signs and magnitudes of the charges, the angular momentum of the particle, the black hole spin, and the negative cosmological constant. The violations are pronounced in the extremal or near-extremal regime. Numerical analysis supports the analytical predictions and highlights the interplay between the string-inspired black hole and the charged particle.
- [9] arXiv:2506.00995 [pdf, html, other]
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Title: A simple example of "non-minimal" Pre-Big Bang scenarioComments: 23 pages, 2 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
We give an example of non-minimal pre-big bang scenario able to produce the PTA signal considering a modified evolution of the high-curvature string phase, including the contribution of high-energy string sources. We use a fluid-dinamical model of sources and show that their effective viscosity breaks the $S$-duality symmetry of the tensor-axion perturbation spectra, as in general expected for the non-minimal scenario.
- [10] arXiv:2506.01035 [pdf, html, other]
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Title: Finite Curvature Construction of Regular Black Holes and Quasinormal Mode AnalysisComments: 26 pages, 10 figures, comments are welcome!Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
We develop a class of regular black holes by prescribing finite curvature invariants and reconstructing the corresponding spacetime geometry. Two distinct approaches are employed: one based on the Ricci scalar and the other on the Weyl scalar. In each case, we explore a variety of analytic profiles for the curvature functions, including Gaussian, hyperbolic secant, and rational forms, ensuring regularity, asymptotic flatness, and compatibility with dominant energy conditions. The resulting mass functions yield spacetime geometries free from curvature singularities and exhibit horizons depending on model parameters. To assess the stability of these solutions, we perform a detailed analysis of quasinormal modes (QNMs) under axial gravitational perturbations. We show that the shape of the effective potential, particularly its width and the presence of potential valleys, plays a critical role in determining the QNMs. Models with a large peak-to-valley ratio in the potential barrier exhibit stable, exponentially decaying waveforms, while a small ratio may induce late-time instabilities. Our results highlight the significance of potential design in constructing physically viable and dynamically stable regular black holes, offering potential observational implications in modified gravity and quantum gravity scenarios.
- [11] arXiv:2506.01437 [pdf, html, other]
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Title: Black hole supercollidersComments: 4 pages, 3 figures. Version accepted in Physical Review LettersSubjects: General Relativity and Quantum Cosmology (gr-qc)
We show that collisions between particles free falling from infinity and a disk of material plunging off the retrograde innermost stable circular orbit of a near-extremal Kerr black hole is the unique astronomically natural way in which to create a gravitational particle accelerator with center of mass energies at the $10$'s to $100$'s of teraelectronvolt range, in other words a supercollider.
- [12] arXiv:2506.01693 [pdf, html, other]
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Title: Analytical self-force on scalar particle in eccentric orbits around a Schwarzschild black holeComments: 18 pages, 3 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
In this work, we analytically investigate the effects of scalar self-force exerted by a massless scalar field on a particle in a slightly eccentric orbit around a Schwarzschild black hole. By solving the Klein-Gordon equation in the curved spacetime background, using a combination of post-Newtonian (PN) expansion, and small-eccentricity approximation, we derive explicit expressions for the self-force components at the particle location, as well as for the associated energy and angular momentum fluxes. Our results are valid up to sixth post-Newtonian (6PN) order and fourth order in eccentricity ($e^4$). We compare asymptotic fluxes with those obtained in arXiv:2401.06844 for scalar-tensor (ST) theories. Once that the relation between the two approaches has been established, we found perfect agreement by fixing the asymptotic value of the scalar field in ST theory $\phi_0 = 1$.
- [13] arXiv:2506.01773 [pdf, html, other]
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Title: Spin-induced Scalarized Black Holes in Einstein-Maxwell-scalar ModelsComments: 20 pages, 6 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
We construct spin-induced scalarized black hole solutions in a class of Einstein-Maxwell-scalar models, where a scalar field is non-minimally coupled to the electromagnetic field. Our results show that scalar hair develops only for rapidly rotating black holes, while slowly spinning ones remain well described by the Kerr-Newman (KN) metric. The scalar field contributes only a small fraction of the total mass, indicating suppressed nonlinear effects. This suppression may account for the narrow existence domains of scalarized black holes and the similarities observed in their existence domains across different coupling functions. Moreover, scalarized black holes are found to coexist with linearly stable, entropically favored KN black holes. These results motivate further investigations into the nonlinear dynamics and stability of scalarized black holes in these models.
- [14] arXiv:2506.01889 [pdf, html, other]
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Title: I-Love-Q relations for Neutron Stars with Dark EnergyComments: EPJ AcceptedSubjects: General Relativity and Quantum Cosmology (gr-qc)
We studied the effect of a dark energy fluid in the equation of state of neutron stars. For such models, we performed a detailed analysis, computing the moment of inertia, the quadrupole moment, and the tidal Love number. We then proved that these quantities are linked to each other with the well-known equation of state independent relations, the I-Love-Q relations. This study expands the range of validity of such relations to new models of neutron stars.
- [15] arXiv:2506.01898 [pdf, html, other]
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Title: Multiband parameter estimation with phase coherence and extrinsic marginalization: Extracting more information from low-SNR CBC signals in LISA dataShichao Wu, Alexander H. Nitz, Ian Harry, Stanislav Babak, Michael J. Williams, Collin Capano, Connor WeavingComments: To be submitted to PRX, comments are welcome, code will be public at this https URLSubjects: General Relativity and Quantum Cosmology (gr-qc); Instrumentation and Methods for Astrophysics (astro-ph.IM)
This paper presents a novel coherent multiband analysis framework for characterizing stellar- and intermediate-mass binary black holes using LISA and next-generation ground-based detectors (ET and CE), leveraging the latest developments in the \texttt{PyCBC} pipeline. Given the population parameters inferred from LVK results and LISA's sensitivity limits at high frequencies, most stellar-mass binary black holes would likely have SNRs below 5 in LISA, but the most state-of-the-art multiband parameter estimation methods, such as those using ET and CE posteriors as priors for LISA, typically struggle to analyze sources with a LISA SNR less than 5. We present a novel coherent multiband parameter estimation method that directly calculates a joint likelihood, which is highly efficient; this efficiency is enabled by multiband marginalization of the extrinsic parameter space, implemented using importance sampling, which can work robustly even when the LISA SNR is as low as 3. Having an SNR of $\sim 3$ allows LISA to contribute nearly double the number of multiband sources. Even if LISA only observes for one year, most of the multiband detector-frame chirp mass's 90\% credible interval (less than $10^{-4} \mathrm{M}_\odot$) is still better than that of the most accurately measured events for ET+2CE network in 7.5 years of observation, by at least one order of magnitude. For the first time, we show efficient multiband Bayesian parameter estimation results on the population scale, which paves the way for large-scale astrophysical tests using multibanding.
New submissions (showing 15 of 15 entries)
- [16] arXiv:2506.00036 (cross-list from hep-lat) [pdf, html, other]
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Title: Unitarity of 4D Lattice Theory of GravityComments: 11 pages, 1 figureSubjects: High Energy Physics - Lattice (hep-lat); General Relativity and Quantum Cosmology (gr-qc)
The unitarity of the 4D lattice theory of gravity in the case of the Minkowski signature is proved. The proof is valid only for lattices that conserve the number of degrees of freedom during time evolution. The Euclidean signature and the Minkowski signature are related by the deformation of the integration contours of dynamic variables in a discrete lattice functional integral. It is important that the result is obtained directly on the lattice. Since the studied lattice theory of gravity in the long-wave limit transforms into the well-known Einstein-Cartan-Palatini theory, the obtained result means that this lattice theory of gravity has the right to be considered as a discrete regularization of the generally accepted continuous physical theory of gravity.
- [17] arXiv:2506.00184 (cross-list from hep-th) [pdf, html, other]
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Title: $\mathrm{SL}(2,\mathbb{R})$ families of Kerr black holesComments: 17 page, 2 figuresSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
The stationary, axisymmetric sector of vacuum general relativity (with zero cosmological constant) enjoys an $\mathrm{SL}(2,\mathbb{R})$ symmetry called the Matzner-Misner group. We study the action of the Matzner-Misner group on the Kerr black hole. We show that the group acts naturally on a three parameter generalization of the usual two parameter Kerr solution. The new parameter represents a large diffeomorphism which gives the spacetime an asymptotic angular velocity. We explain how the $\mathrm{SL}(2,\mathbb{R})$ symmetry organizes the space of three parameter Kerr solutions into the classical analogue of principal series representations. We show that the $\mathrm{SL}(2,\mathbb{R})$ Casimir operator is the Bekenstein-Hawking entropy. The Matzner-Misner group sits inside a much larger Kac-Moody symmetry called the Geroch group. We show that the Kac-Moody level of the Kerr black hole is the Bekenstein-Hawking entropy.
- [18] arXiv:2506.00757 (cross-list from astro-ph.IM) [pdf, html, other]
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Title: RESOLVE: Rare Event Surrogate Likelihood for Gravitational Wave Paleontology Parameter EstimationSubjects: Instrumentation and Methods for Astrophysics (astro-ph.IM); General Relativity and Quantum Cosmology (gr-qc)
The first detection of gravitational waves, recognized by the 2017 Nobel Prize in Physics, has opened up a new research field: gravitational-wave paleontology. When massive stars evolve into black holes and collide, they create gravitational waves that propagate through space and time. These gravitational-waves, now detectable on Earth, act as fossils tracing the histories of the massive stars that created them. Estimating physics parameters of these massive stars from detected gravitational-waves is a parameter estimation task, with the primary difficulty being the extreme rarity of collisions in simulated binary black holes. This rarity forces researchers to choose between prohibitively expensive simulations or accepting substantial statistical variance. In this work, we present RESOLVE, a rare event surrogate model that leverages polynomial chaos expansion (PCE) and Bayesian MCMC to emulate this rare formation efficiency. Our experimental results demonstrate that RESOLVE is the only surrogate model that achieves proper statistical coverage, while effectively learning the underlying distribution of each physics parameter. We construct a likelihood function incorporating both the emulated formation efficiency and LIGO's gravitational wave observations, which we then minimize to produce community-standard credible intervals for each physics parameter. These results enable astronomers to gain deeper insights into how the universe transformed from simple gases into the complex chemical environment that eventually made life possible.
- [19] arXiv:2506.00951 (cross-list from math.NA) [pdf, html, other]
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Title: Physics-Informed Neural Networks for the Relativistic Burgers Equation in the Exterior of a Schwarzschild Black HoleSubjects: Numerical Analysis (math.NA); General Relativity and Quantum Cosmology (gr-qc)
We introduce a Physics-Informed Neural Networks(PINN) to solve a relativistic Burgers equation in the exterior domain of a Schwarzschild black hole. Our main contribution is a PINN architecture that is able to simulate shock wave formations in such curved spacetime, by training a shock-aware network block and introducing a Godunov-inspired residuals in the loss function. We validate our method with numerical experiments with different kinds of initial conditions. We show its ability to reproduce both smooth and discontinuous solutions in the context of general relativity.
- [20] arXiv:2506.01006 (cross-list from hep-th) [pdf, html, other]
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Title: An atom in front of Lorentz violating Kalb-Ramond black hole backgroundComments: 12 pages latex, No FigureSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
We investigate the role of Lorentz violation in the acceleration radiation
produced when an atom falls into a Kalb-Ramond (KR) black hole and observe
that the amplitude and an exponential (Planck-like) factor are both shaped
by the Lorentz-violating parameter, indicating a breach of the equivalence
principle and resembling characteristics observed in bumblebee gravity models.
We further investigate how Lorentz violation and conformal symmetry work
together to determine the thermodynamic behavior of the system and the
implications for the equivalence principle by looking at the transition
probabilities of a two-level atomic detector interacting with the black hole.
These findings provide new information about the interaction of black hole
entropy, symmetry breaking, and possible observational probes of novel physics
beyond general relativity. The horizon brightening acceleration radiation (HBAR) entropy in the KR black hole spacetime is also calculated in detail. Although the corrections are very different from those in bumblebee gravity, our study demonstrates that even though Lorentz-violating events alter the entropy, it nevertheless maintains a structural resemblance to the ordinary Bekenstein-Hawking entropy. - [21] arXiv:2506.01507 (cross-list from astro-ph.HE) [pdf, html, other]
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Title: Interpretation of the binary black hole mass spectrumComments: Contribution to the 2025 Gravitation session of the 59th Rencontres de MoriondSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); General Relativity and Quantum Cosmology (gr-qc)
This is a summary of an invited talk given at the Moriond Gravitation meeting on March 31, 2025. I touch on some of the practical challenges of measuring the mass spectrum of merging binary black holes through their gravitational-wave signatures. I then describe my take on the current state of interpreting the observed binary black hole mass spectrum from the perspective of models for the formation of these sources. I conclude that meaningful progress must rely on the combination of gravitational-wave observations and a broad range of electromagnetic observations of massive stellar binaries at earlier stages of their evolution. This is my very personal and necessarily brief take on the current state of the field and does not aspire to the balance or completeness of a review.
- [22] arXiv:2506.01543 (cross-list from hep-ph) [pdf, html, other]
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Title: Dynamical dark energy in the no-scale Brans-Dicke gravitySubjects: High Energy Physics - Phenomenology (hep-ph); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
We add a new scalar field in the no-scale Brans-Dicke gravity and require it to have a global O(2) symmetry with the original scalar field in the Brans-Dicke gravity. This gives us a new massless scalar field in the Einstein frame due to the SO(2) symmetry. We then explicitly break the O(2) symmetry to a $D_4$ symmetry, and this scalar field gains a periodic potential. This scalar field can serve as the quintessence field to explain dark energy. If we further add the $R^2$ term and the non-minimal coupling to the Higgs field, we can realize inflation and reheating, and this leads to a super-Planckian decay constant of the quintessence potential. The super-Planckian decay constant is consistent with the newly released observational data according to a recent analysis.
- [23] arXiv:2506.01555 (cross-list from hep-th) [pdf, html, other]
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Title: The Exact and Approximate Tales of Boost-Breaking Cosmological CorrelatorsComments: 68 pages, 15 figuresSubjects: High Energy Physics - Theory (hep-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
Cosmological correlators offer a remarkable window into the high-energy physics governing Universe's earliest moments, with the tantalising prospect of discovering new particles. However, extracting new physics from these observables requires both precise theoretical predictions of inflationary theories and accurate, analytical templates suitable for data analysis throughout parameter and kinematic spaces. In this paper, we extend the current analytical results by computing the most general boost-breaking seed correlator mediated by the tree-level exchange of a massive spinning particle. We derive the result using two complementary approaches, bootstrapping from boundary differential equations, and direct spectral integration. Both representations are packaged as a single partially resummed series that converges in all physical kinematics. Computing this correlator marks a milestone for carving out the space of all boost-breaking correlators, and therefore completes the tree-level catalogue. We then introduce a general procedure to obtain accurate approximations for cosmological collider signals based on the saddle-point method. This approach allows for a clear physical intuition of various signals hidden in correlators, as the bulk physics is made manifest through the location of these saddles in the complex time plane, which depend on the external kinematics. Evaluating the time integrals at these saddles yields results given as elementary functions that remain valid beyond soft limits and provide intuitive control over both the signal shape and amplitude. We demonstrate the power of this method in both de Sitter-invariant and boost-breaking scenarios, and uncover novel refined waveform and strength dependence for oscillatory signals from massive fields. We provide a complete cosmological collider shape template capturing all boost-breaking effects for upcoming cosmological surveys.
- [24] arXiv:2506.01679 (cross-list from astro-ph.HE) [pdf, html, other]
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Title: Neutrino pair annihilation driven jets from black-hole torus systemsComments: 24 pages, 14 figures, submitted to PRDSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
We perform axisymmetric general relativistic radiation-viscous hydrodynamics simulations of black hole (BH)-torus systems with full Boltzmann Monte-Carlo neutrino transport to investigate the role of neutrino-antineutrino pair annihilation in launching relativistic outflows. Our models span a wide range of BH spins, torus masses, and viscosity parameters. We find that the pair annihilation leads to the formation of relativistic fireballs in most cases, except for those with low black-hole spin and high viscosity. The isotropic-equivalent energies of these outflows reach $\lesssim 10^{51}\,{\rm erg}$ with durations $\lesssim 0.2\,{\rm s}$. While this is insufficient to explain the brightest short gamma-ray bursts (sGRBs), our results suggest that the pair annihilation may account for some low-luminosity sGRBs and GRB precursors. We also provide updated scaling relations for the pair annihilation energy deposition rate as a function of accretion rate, and discuss the sensitivity of outflow properties to numerical resolution and floor density.
- [25] arXiv:2506.01760 (cross-list from astro-ph.HE) [pdf, html, other]
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Title: First eccentric inspiral-merger-ringdown analysis of neutron star-black hole mergersComments: 13 pages, 4 figures, 1 tableSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
The gravitational wave event GW200105 was the first confident neutron star-black hole (NSBH) merger identified by the LIGO-Virgo-KAGRA collaboration. A recent analysis by Morras et al. with an eccentric precessing waveform model that describes the inspiral phase of the $l=2$ and $m=\{0,\pm 2\}$ modes has identified this event as the first NSBH merger with strong evidence of orbital eccentricity. In this paper we perform the first analysis of this event with an aligned-spin eccentric waveform model that describes the full inspiral, merger, and ringdown, includes subdominant harmonics, and is partially calibrated to numerical relativity simulations. This analysis confirms the results and finds evidence in favor of eccentricity even with a log-uniform prior in eccentricity. We also analyze the NSBH events GW200115 and GW230529, completing the analysis of all NSBHs with IMRPhenomTEHM, and find that these signal are consistent with vanishing eccentricity. Finally, we briefly discuss computational challenges when performing the analysis with time-domain eccentric waveform models.
Cross submissions (showing 10 of 10 entries)
- [26] arXiv:1909.13688 (replaced) [pdf, html, other]
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Title: Bianchi spacetimes as super-curvature modes around isotropic cosmologiesComments: 32 pages and 1 figure. Minor typos correctedJournal-ref: Phys. Rev. D 100, 123534 (2019)Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
A powerful result in theoretical cosmology states that a subset of anisotropic Bianchi models can be seen as the homogeneous limit of (standard) linear cosmological perturbations. Such models are precisely those leading to Friedmann spacetimes in the limit of zero anisotropy. Building on previous works, we give a comprehensive exposition of this result, and perform the detailed identification between anisotropic degrees of freedom and their corresponding scalar, vector, and tensor perturbations of standard perturbation theory. In particular, we find that anisotropic models very close to open (i.e., negatively curved) Friedmann spaces correspond to some type of super-curvature perturbations. As a consequence, provided anisotropy is mild, its effects on all types of cosmological observables can always be computed as simple extensions of the standard techniques used in relativistic perturbation theory around Friedmann models. This fact opens the possibility to consistently constrain, for all cosmological observables, the presence of large scale anisotropies on the top of the stochastic fluctuations.
- [27] arXiv:2106.03914 (replaced) [pdf, html, other]
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Title: Conformalons: a new class of black hole mimickersComments: 21 pages, 4 figures. v2: refereed versionJournal-ref: Eur. Phys. J. C (2025) 85:603Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
In any conformally invariant gravitational theory, the space of exact solutions is greatly enlarged. Therefore, we cannot exclude the Weyl's conformal invariance to be spontaneously broken to spherically symmetric vacuum solutions that exclude the spacetime region inside the black hole's event horizon from our Universe. We baptize these solutions {\it conformalons}. It turns out that for all such spacetimes nothing can reach the Schwarzschild event horizon in a finite amount of proper time for conformally coupled ``massive'' particles, or finite values of the affine parameter for massless particles. Therefore, for such vacuum solutions the surface $r = 2 M$ becomes an asymptotic region of the Universe. As a general feature, all conformalons show a gravitational blueshift instead of a gravitational redshift at the unattainable Schwarzschild event horizon, hence avoiding the Trans-Planckian problem in the Hawking evaporation process. Unexpectedly, the Hawking's temperature of the conformalons turns out to be negative and the thermodynamic interpretation leads us to speculate about a possible maximum energy state of the Hawking radiation. Contrary to the Schwarzschild spacetime, for the conformalons the gravitational collapse consists of matter that falls down forever towards the Schwarzschild horizon without ever reaching it. Hence, the annihilation process between the matter and Hawking's negative energy particles takes place outside the surface at $r = 2 M$. Finally, the information is not lost in the whole process of singularity-free collapse and evaporation.
- [28] arXiv:2401.15451 (replaced) [pdf, html, other]
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Title: Constant-roll inflation and primordial black holes with Barrow holographic dark energySubjects: General Relativity and Quantum Cosmology (gr-qc)
We investigate the constant-roll inflation and the evolution of primordial black holes (PBHs) with Barrow holographic dark energy (BHDE). Using the modified Friedmann equation and the constant-roll condition in BHDE model, we calculate the constant-roll parameters, the scalar spectral index and the tensor-to-scalar ratio for the power-law, periodic, and hilltop potential models. By applying Planck 2018 data, the $r_{0.002}-n_{s}$ plane analysis under $\delta=10^{-4}$ delivers constrained parameter ranges for three inflationary potential models, where the power-law potential imposes $n \leq 1.1$, the periodic potential bounds $f \leq 7$, and the hilltop potential restricts $p \leq 4$. Then, we calculate the primordial curvature perturbation power spectra and PBHs abundance for these models, finding a PBH mass of approximately $10^{-12} M_{\odot}$ and revealing that these models not only generate sufficient PBHs but also contribute one-third of the dark matter content. Subsequently, we analyze the evolution of PBHs and find that when the effective equation of state parameter evolves from $1/3$ to $-1/3$, the accretion mass increases to approximately $10^{2}M_{i}$, while the temperature of the PBHs decreases from $10^{4}K$ to $10^{2}K$, which indicate that PBHs still exist and can be detected today.
- [29] arXiv:2403.16532 (replaced) [pdf, html, other]
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Title: Uncovering faint lensed gravitational-wave signals and reprioritizing their follow-up analysis using galaxy lensing forecasts with detected counterpartsLeo C. Y. Ng, Justin Janquart, Hemantakumar Phurailatpam, Harsh Narola, Jason S. C. Poon, Chris Van Den Broeck, Otto A. HannukselaComments: 16 pages, 29 figures, 3 tablesSubjects: General Relativity and Quantum Cosmology (gr-qc)
Like light, gravitational waves can be gravitationally lensed by massive astrophysical objects. Strong gravitational lensing by galaxies and galaxy clusters is anticipated to become observable in the coming years. This phenomenon will manifest as multiple copies of the original wave, each exhibiting identical frequency evolution but distinct arrival times, amplitudes, and overall phases. Some of these images can be below the detection threshold and require targeted search methods, based on tailor-made template banks. These searches can be made more sensitive by using our knowledge of the typical distribution and morphology of lenses to predict the time delay, magnification, and image-type ordering of the lensed images. Here, we show that when a subset of the galaxy lensed images is super-threshold, they can be used to construct a more constrained prediction of the arrival time of the remaining signals, enhancing our ability to identify lensing candidate signals. Our suggested method effectively reduces the list of triggers requiring follow-up and generally re-ranks the genuine counterpart higher in the lensing candidate list. So, using information provided by the two or three super-threshold images, one can identify additional lensed images, also strengthening the evidence for the lensed signal hypothesis.
- [30] arXiv:2410.18568 (replaced) [pdf, html, other]
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Title: Late-time dynamics of dark energy EoS in symmetric teleparallel gravityComments: Accepted Manuscript, 19 pages, 9 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
In the symmetric teleparallel gravity framework, we study the cosmic dynamics of the universe with dark energy equation of state (EoS) parameter having non-linear forms. The non-metricity scalar induced by the dark energy EoS parameter evolves with time and, explains the physically reasonable transiting universe evolution in a consistent way. A comparative study has been presented to describe the ability of these models to fit the observational data. By using the Bayesian methods, we constrain the model parameters with the supernovae Ia (SneIa) and expansion rate data. We show that the expansion rate solutions may consistently describe the universe evolution based on cosmological indicators such as the effective EoS parameter, energy density, pressure, current age and the statefinder diagnostic. One may either have the quintom scenario or the future deceleration in these models subjected to the observational constraints.
- [31] arXiv:2410.19968 (replaced) [pdf, html, other]
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Title: Local coordinates and motion of a test particle in the McVittie spacetimeComments: 31 pages, 1 figure and 2 tables (Updated for improvement.)Subjects: General Relativity and Quantum Cosmology (gr-qc)
We consider the orbital motion of a test particle in the gravitational field of a massive body (that might be a black hole) with mass $m$ placed on the expanding cosmological manifold described by the McVittie metric. We introduce the local coordinates attached to the massive body to eliminate nonphysical, coordinates-dependent effects associated with Hubble expansion. The resultant equation of motion of the test particle are analyzed by the method of osculating elements with application of time-averaging technique. We demonstrate that the orbit of the test particle is not subject to the cosmological expansion up to the terms of the second order in the Hubble parameter. However, the cosmological expansion causes the precession of the orbit of the test particle with time and changes the frequency of the mean orbital motion. We show that the direction of motion of the orbital precession depends on the Hubble parameter as well as the deceleration parameter of the universe. We give numeric estimates for the rate of the orbital precession with respect to time due to the cosmological expansion in case of several astrophysical systems.
- [32] arXiv:2412.02144 (replaced) [pdf, html, other]
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Title: The neutrino flavor oscillations in the static and spherically symmetric black-hole-like wormholesSubjects: General Relativity and Quantum Cosmology (gr-qc)
We study the effects of neutrino lensing induced by a Damour-Solodukhin wormhole on the neutrino oscillation. We derive and calculate the flavour transition probabilities in the presence of Damour-Solodukhin factor $\Lambda$ as a shift in the massive source to show that the neutrino flavour oscillation is also sensitive not only to the sign of difference between the squared masses but also to the individual mass of neutrinos in both the two-flavour and the three-flavour cases, which is similar to the results for the black holes in the previous works mentioned here. As a consequence of parameter $\Lambda$ within a region, a series of curves of probability function versus the azimuthal angle $\phi$ with definite masses of neutrino can be plotted and their shapes resemble each other in the case of two-flavoured neutrinos and of three-flavoured ones. In view of the probability functions due to the wormhole, we reveal that the contribution of the factor $\Lambda$ is novel. Based on our analytical and numerical discussions on the probability expressions, the difference of the neutrino flavour oscillation arising from the shift in the wormhole factor $\Lambda$ is detectable. It is crucial that the $\Lambda$ as deviation from the black holes can change the shapes of the curves greatly, in the case of three-flavoured neutrinos in particular. The detailed comparisons can be made among our estimations depicted in the figures for neutrino oscillations and the measurements from the detector, which open a new window for judging whether the remote star as lens is black-hole-like wormhole or just a spherically symmetric black hole and further the wormhole factor $\Lambda$ can be estimated.
- [33] arXiv:2412.12288 (replaced) [pdf, other]
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Title: Mixture equivalence principles and post-quantum theories of gravityComments: 17 pages, 6 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
We examine the mixture equivalence principle (MEP), which states that proper and improper mixed states with the same density matrix are always experimentally indistinguishable, and a weaker version, which states that this is sometimes true in gravity theories. We point out that Moller-Rosenfeld semiclassical gravity violates the weak MEP and that nonlinear extensions of quantum mechanics violate the MEP. We further demonstrate that modifications of the Born rule in quantum theory also typically violate the MEP. We analyse such violations in the context of thermal baths, where proper and improper thermal states induce different physical situations. This has significant implications in the context of black hole physics. We argue that Moller-Rosenfeld semiclassical gravity is not the semiclassical limit of quantum gravity in the context of black hole spacetimes, even in the presence of $N\gg1$ matter fields.
- [34] arXiv:2412.19514 (replaced) [pdf, html, other]
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Title: HBT Interferometry and Quantum Nature of Primordial Gravitational Waves in Hořava-Lifshitz GravityComments: 19 pages, v2: published versionJournal-ref: Phys.Rev.D 111 (2025) 10, 104077Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th); Quantum Physics (quant-ph)
Hořava-Lifshitz gravity (to be precise, its projectable version) is recognized as a renormalizable, unitary, and asymptotically free quantum field theory of gravity. Notably, one of its cosmological predictions is that it can produce scale-invariant primordial density fluctuations and primordial gravitational waves without relying on inflation. In this paper, we investigate the quantum nature of the primordial gravitational waves generated in Hořava-Lifshitz gravity. It has been suggested that, for some inflationary models, the non-classicality of primordial gravitational waves in the squeezed coherent quantum state can be detected using the Hanbury Brown - Twiss (HBT) interferometry. We show that in Hořava-Lifshitz gravity, scale-invariant primordial gravitational waves can be generated during both the radiation-dominated and matter-dominated eras of the Universe. Moreover, the frequency range of their quantum signatures is shown to extend beyond that of inflationary models.
- [35] arXiv:2412.19852 (replaced) [pdf, html, other]
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Title: Parameterized Deceleration in $f(Q,C)$ Gravity: A Logarithmic ApproachComments: 18 pages, 10 figures, 2 tablesJournal-ref: New Astronomy, (2025), 102386Subjects: General Relativity and Quantum Cosmology (gr-qc)
This study explores a distinctive logarithmic parameterization of the deceleration parameter within the $f(Q, C)$ gravity framework, incorporating a nonlinear functional form $f(Q, C) = \gamma_1 Q^n + \gamma_2 C$, where $Q$ and $C$ denote the nonmetricity scalar and boundary term, respectively, and $n \geq 1$. This approach provides a unique perspective on the universe's accelerated expansion without resorting to exotic fields. Using observational data from Hubble measurements (OHD) and the Pantheon+SH0ES Type Ia supernovae dataset, the model parameters were constrained through a $\chi^2$ minimization technique. The analysis reveals a transition from deceleration to acceleration in the expansion history of the universe, with the transition redshifts $z_t \approx 0.98$ (OHD) and $z_t \approx 0.76$ (Pantheon+SH0ES). The model demonstrates consistency with observations, offering insights into the dynamics of dark energy and alternative gravity theories, while effectively modeling cosmic evolution across epochs.
- [36] arXiv:2412.21092 (replaced) [pdf, html, other]
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Title: The (in)stability of quasinormal modes of Boulware-Deser-Wheeler black hole in the hyperboloidal frameworkComments: 29 pages, 14 figures; This revised version includes a new figure, corrected typos, and improved discussions. The manuscript has been accepted for publication as a regular article in SCPMASubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
We study the quasinormal modes of Boulware-Deser-Wheeler black hole in Einstein-Gauss-Bonnet gravity theory within the hyperboloidal framework. The effective potentials for the test Klein-Gordon field and gravitational perturbations of scalar, vector, and tensor types are thoroughly investigated and put into several typical classes. The effective potentials for the gravitational perturbations have more diverse behaviors than those in general relativity, such as double peaks, the existence of the negative region adjacent to or far away from the event horizon, etc. These lead to the existence of unstable modes ($\text{Im} \omega<0$), and the presence of gravitational wave echoes. These rich phenomenons are inherent in Einstein-Gauss-Bonnet theory, rather than artificially introduced by hand. What's more, the (in)stability of quasinormal modes is studied in frequency domain and time domain, respectively. For the frequency-domain, the pseudospectrum is used to account for the instability of the spectrum. For the time-domain, we add a small bump to the effective potential, and find that the new waveform does not differ significantly from the original one, where the comparison is characterized by the so-called mismatch functions. This means that quasinormal modes are stable in time-domain regardless of the shapes of the original effective potentials. In this way, our study reveals the non-equivalence of the stability of quasinormal modes in the frequency-domain and the time-domain. Besides, we also numerically investigate Price's law at both finite distances and infinity with the assistance of the hyperboloidal approach.
- [37] arXiv:2501.05505 (replaced) [pdf, html, other]
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Title: Towards a Non-singular Paradigm of Black Hole PhysicsRaúl Carballo-Rubio, Francesco Di Filippo, Stefano Liberati, Matt Visser, Julio Arrechea, Carlos Barceló, Alfio Bonanno, Johanna Borissova, Valentin Boyanov, Vitor Cardoso, Francesco Del Porro, Astrid Eichhorn, Daniel Jampolski, Prado Martín-Moruno, Jacopo Mazza, Tyler McMaken, Antonio Panassiti, Paolo Pani, Alessia Platania, Luciano Rezzolla, Vania VellucciComments: v2: 39 pages, 3 figures, matches published version; v1: 39 pages, 3 figuresJournal-ref: JCAP 05 (2025) 003Subjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
The study of regular black holes and black hole mimickers as alternatives to standard black holes has recently gained significant attention, driven both by the need to extend general relativity to describe black hole interiors, and by recent advances in observational technologies. Despite considerable progress in this field, significant challenges remain in identifying and characterizing physically well-motivated classes of regular black holes and black hole mimickers. This report provides an overview of these challenges, and outlines some of the promising research directions -- as discussed during a week-long focus programme held at the Institute for Fundamental Physics of the Universe (IFPU) in Trieste from November 11th to 15th, 2024.
- [38] arXiv:2503.07947 (replaced) [pdf, html, other]
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Title: Oscillations of the black hole photon ring as a probe of ultralight dilaton fieldsComments: 19 pages, 6 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Phenomenology (hep-ph)
Advancements of very long baseline interferometry (VLBI) have facilitated unprecedented probing of superradiant phenomena in the vicinities of supermassive black holes (SMBHs), establishing an ideal laboratory to detect ultralight bosons beyond the Standard Model. In this study, we delve into how ultralight dilaton clouds, formed via SMBH superradiance, impact the black hole photon rings. Our focus is on the dilaton-electromagnetic coupling term of the form $f(\phi)F_{\mu\nu}F^{\mu\nu}$. By integrating geometric optics with plasma refractive effects in accretion environments, we demonstrate that the dilaton cloud dynamically alters the plasma frequency. Through systematic ray-tracing simulations covering a range of photon frequencies and dilaton coupling strengths, we reveal a photon ring oscillation that follows the period of that of the dilaton field. As the dilaton mass increases, this oscillation becomes suppressed due to the washout effect of the dilaton-induced correction term over the light path integration. We further evaluated the observability of such dilaton-induced photon ring oscillations with current radio interferometric capabilities. Our estimates indicate that this effect could potentially constrain the dilaton-photon coupling to $g_{\phi\gamma}\lesssim 10^{-11}\text{GeV}^{-1}$ for dilaton masses $\mu \lesssim 10^{-18}\,\mathrm{eV}$.
- [39] arXiv:2503.09918 (replaced) [pdf, html, other]
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Title: Korteweg-de Vries Integrals for Modified Black Hole Potentials: Instabilities and other QuestionsMichele Lenzi (1 and 2), Arnau Montava Agudo (1 and 3), Carlos F. Sopuerta (1 and 2) ((1) ICE-CSIC, (2) IEEC, (3) UIB)Comments: 54 pages, 29 figures (56 files), JCAP style. Revised versionSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th); Exactly Solvable and Integrable Systems (nlin.SI)
Quasi-normal modes (QNMs) and greybody factors are some of the most characteristic features of the dynamics of black holes (BHs) and represent the basis for a number of fundamental physics tests with gravitational wave observations. It is therefore important to understand the properties of these quantities, naturally introduced within BH perturbation theory, in particular the stability properties under modifications of the BH potential. Instabilities in the QNMs have been recently shown to appear in the BH pseudospectrum under certain circumstances. In this work, we give a novel point of view based on the existence of some recently discovered hidden symmetries in BH dynamics and the associated infinite series of conserved quantities, the Korteweg-de Vries (KdV) integrals. We provide different motivations to use the KdV integrals as indicators of some crucial BH spectral properties. In particular, by studying them in different scenarios described by modified BH barriers, we find strong evidence that the KdV conserved quantities represent a useful tool to look for instabilities in the BH spectrum of QNMs and in their greybody factors.
- [40] arXiv:2503.11385 (replaced) [pdf, html, other]
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Title: On the phase transition mechanism of spontaneous scalarizationComments: 13 pages, 11 figures. Results from numerical simulations are included in this versionSubjects: General Relativity and Quantum Cosmology (gr-qc)
In certain modified gravity theories that include additional scalar degrees of freedom, compact objects such as black holes and neutron stars may undergo a process known as spontaneous scalarization, in which the scalar field is suddenly activated beyond a certain critical point. Since its discovery, it has been clear that this effect can be understood in many cases as a continuous phase transition, well described by the phenomenological Landau model. Recently, it has been pointed out that spontaneous scalarization can also manifest as a first-order phase transition. In this paper, we take a closer look at the nature of spontaneous scalarization as a phase transition, analyzing in detail cases where it occurs as either a second- or first-order transition, as well as a more unconventional scenario characterized by a negative scalar susceptibility. Critical exponents are explicitly computed, and implications for dynamical scalarization are discussed. Moreover, the dynamics of a first-order phase transition is probed through fully nonlinear numerical simulations.
- [41] arXiv:2504.06427 (replaced) [pdf, html, other]
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Title: Complex Chern-Simons Theory with $k=8\mathbb{N}$ and An Improved Spinfoam Model with Cosmological ConstantComments: 23+4 pages, 5 figures; v2: typos correctedSubjects: General Relativity and Quantum Cosmology (gr-qc)
This paper presents an improvement to the four-dimensional spinfoam model with cosmological constant ($\Lambda$-SF model) in loop quantum gravity. The original $\Lambda$-SF model, defined via ${\rm SL}(2,\mathbb{C})$ Chern-Simons theory on graph-complement 3-manifolds, produces finite amplitudes and reproduces curved 4-simplex geometries in the semi-classical limit. However, extending the model to general simplicial complexes necessitated ad hoc, non-universal phase factors in face amplitudes, complicating systematic constructions. We resolve this issue by redefining the vertex amplitude using a novel set of phase space coordinates that eliminate the extraneous phase factor, yielding a universally defined face amplitude. Key results include: (1) The vertex amplitude is rigorously shown to be well-defined for Chern-Simons levels $k \in 8\mathbb{N}$, compatible with semi-classical analysis ($k \to \infty$). (2) The symplectic structure of the Chern-Simons phase space is modified to accommodate ${\rm SL}(2,\mathbb{C})$ holonomies, relaxing quantization constraints to $\mathrm{Sp}(2r,\mathbb{Z}/4)$. (3) Edge amplitudes are simplified using constraints aligned with colored tensor models, enabling systematic gluing of 4-simplices into complexes dual to colored graphs. (4) Stationary phase analysis confirms consistency of critical points with prior work, recovering Regge geometries with curvature determined by $\Lambda$. These advancements streamline the spinfoam amplitude definition, facilitating future studies of colored group field theories and continuum limits of quantum gravity. The results establish a robust framework for 4D quantum gravity with non-zero $\Lambda$, free of previous ambiguities in face amplitudes.
- [42] arXiv:2505.05178 (replaced) [pdf, html, other]
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Title: Extended Tsallis-Cirto entropy for black and white holesComments: 7 pages, no figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Other Condensed Matter (cond-mat.other)
In reference [1] we considered the black hole thermodynamics with the non-extensive entropy. This entropy obeys the composition rule which coincides with the composition rule in the non-extensive Tsallis-Cirto $\delta=2$ statistics. Here we extend this approach to the thermodynamics of white holes. The entropy of the white hole is negative as follows from the rate of macroscopic quantum tunneling from black hole to white hole. The white hole entropy is with the minus sign the entropy of the black hole with the same mass, $S_{\rm WH}(M)=-S_{\rm BH}(M)$. This reflects the anti-symmetry with respect to time reversal, at which the shift vector in the Arnowitt-Deser-Misner formalism changes sign. This symmetry allows one to extend the Tsallis-Chirto entropy by adding a minus sign to the Tsallis-Chirto formula applied to white hole. As a result, the composition rule remains the same, with the only difference being that instead of entropy it contains the entropy modulus. The same non-extensive composition rule is obtained for the entropy of the Reissner-Nordström black hole. This entropy is formed by the positive entropy of the outer horizon and the negative entropy of the inner horizon. The model of the black hole formed by "black hole atoms" with Planck-scale mass is also extended to include the negative entropy of white holes.
- [43] arXiv:2505.13298 (replaced) [pdf, html, other]
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Title: Polarization modes of gravitational waves in general symmetric teleparallel gravityComments: 24 pages, 2 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
In this paper, we investigate the polarization modes of gravitational waves within the most general symmetric teleparallel gravity theory that allows for second-order field equations We consider both scenarios where test particles either carry or do not carry a hypermomentum charge. Our findings reveal the existence of tensor, vector, and scalar modes of gravitational waves. Firstly, the theory supports the + and $\times$ tensor modes propagating at the speed of light. Secondly, in the case where particles do not carry hypermomentum, vector modes propagating at the speed of light exist only within a very specific parameter space. However, when particles do carry hypermomentum, there are two shear modes that propagate at the speed of light, while the vector-$x$ and vector-$y$ modes emerge only under very specific conditions. Thirdly, in the presence of hypermomentum, there is always a longitudinal mode propagating at the speed of light. The universal existence of the shear modes and the longitudinal mode in the presence of hypermomentum is a key feature of symmetric teleparallel gravity, distinguishing it from the Riemannian framework through gravitational wave polarization detection. We also analyze the polarization modes in two widely studied special theories: $f(Q)$ theory and quadratic non-metricity theory. Our study reveals that, within the $f(Q)$ gravity framework, it is crucial to assume that matter fields are independent of the connection, as any dependence would lead to unphysical results.
- [44] arXiv:2206.00780 (replaced) [pdf, other]
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Title: The BRST Double Complex for the Coupling of Gravity to Gauge TheoriesComments: 26 pages, article; minor revisions and added material; version to appear in Advances in Theoretical and Mathematical PhysicsSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)
We consider (effective) Quantum General Relativity coupled to the Standard Model (QGR-SM) and clarify whether graviton-ghosts couple to matter particles. To this end, we examine the corresponding BRST and anti-BRST symmetries, which are generated by infinitesimal diffeomorphisms and infinitesimal gauge transformations. In particular, we study their properties and relations: We find that all differentials mutually anticommute, which implies that they form a double complex. In particular, we introduce the total BRST differential as the sum of the diffeomorphism and gauge BRST differentials and similarly the total anti-BRST differential as the sum of the respective anti-BRST differentials. Furthermore, we identify the functionals in particle fields that are (co)cycles up to total derivatives with respect to the diffeomorphism differentials as scalar tensor densities of weight one: This implies that graviton-ghosts decouple from matter particles if and only if the Yang--Mills gauge fixing Lagrange density has said tensor density weight. Moreover, we discuss the relevant gauge fixing fermions: Starting from the de Donder and Lorenz gauge fixing conditions, we introduce a total gauge fixing fermion that generates the complete gauge fixing and ghost Lagrange density of QGR-SM. Finally, we show that the BRST cocomplexes are isomorphic to their corresponding anti-BRST complexes via ghost conjugation. Notably, this relates the BRST cohomologies to their respective anti-BRST homologies.
- [45] arXiv:2305.08943 (replaced) [pdf, html, other]
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Title: Cosmology of Single Species Hidden Dark MatterComments: Match the published version in JCAPSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph)
Cosmology and astrophysics provide various ways to study the properties of dark matter even if they have negligible non-gravitational interactions with the Standard Model particles and remain hidden. We study a type of hidden dark matter model in which the dark matter is completely decoupled from the Standard Model sector except gravitationally, and consists of a single species with conserved comoving particle number and conserved comoving entropy. This category of hidden dark matter includes models that act as warm dark matter but is more general. In particular, in addition to having an independent temperature from the Standard Model sector, it includes cases in which dark matter is in its own kinetic equilibrium or is free-streaming, obeys fermionic or bosonic statistics, and processes a chemical potential that controls the particle occupation number. While the usual parameterization using the free-streaming scale or the particle mass no longer applies, we show that all cases can be well approximated by a set of functions parameterized by only one parameter as long as the chemical potential is nonpositive: the characteristic scale factor at the time of the relativistic-to-nonrelativistic transition. We study the constraints from Big Bang Nucleosynthesis, the cosmic microwave background, the Lyman-$\alpha$ forest, and the smallest halo mass. We show that the most significant phenomenological impact is the suppression of the small-scale matter power spectrum -- a typical feature when the dark matter has a velocity dispersion or pressure at early times. So far, the Lyman-$\alpha$ forest and the small dark matter halo population provide the strongest constraints, limiting the transition redshift to be larger than $\sim6.2\times10^7$.
- [46] arXiv:2403.06006 (replaced) [pdf, html, other]
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Title: Real-time observables in de Sitter thermodynamicsComments: 32 pages (+ appendices), 8 figures. Typos corrected; references added; discussions in section 4.2 and appendix C revisedSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)
We study real-time finite-temperature correlators for free scalars of any mass in a $dS_{d+1}$ static patch in any dimension. We show that whenever the inverse temperature is a rational multiple of the inverse de Sitter temperature, certain Matsubara poles of the symmetric Wightman function disappear. At the de Sitter temperature, we explicitly show how the Lorentzian thermal correlators can all be obtained by analytic continuations from the round $S^{d+1}$. We establish the precise relation between the Harish-Chandra character for $SO(1,d+1)$ and the integrated spectral function, providing a novel dynamical perspective on the former and enabling generalizations. Furthermore, we study scalars with exceptional non-positive masses. We provide a physical picture for the distinctive structures of their characters. For the massless case, we perform a consistent static patch quantization, and find the unique $S^{d+1}$ correlator that analytically continues to the correlators in the quantum theory.
- [47] arXiv:2408.08740 (replaced) [pdf, html, other]
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Title: Anisotropic universe with anisotropic dark energyComments: 14 pages, 6 figures, 3 tables. Version accepted in PRDJournal-ref: Physical Review D, 111, 083508 (2025)Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
We investigate the anisotropic parameterization of the dark energy equation of state within the framework of an axisymmetric (planar) Bianchi-I universe. Using the latest Pantheon+ Type Ia Supernova dataset, augmented by SH0ES Cepheid distance calibrators, we constrain both the equation of state for anisotropic dark energy and other standard cosmological parameters. Additionally, we examine the presence of an underlying anisotropic axis. Our analysis yields a mean anisotropic dark energy equation of state of $\bar{w} = -0.86^{+0.15}_{-0.11}$ and a difference in the equation of states in and perpendicular to the plane of the axisymmetric Bianchi-I spacetime of $\delta_w = -0.129^{+0.090}_{-0.064}$. We also identify an axis of anisotropy at approximately $(272^{\circ}, 21^{\circ})$ in galactic coordinates. Through a comparative study of different cosmological models, we find that the data favor a Bianchi-I universe with anisotropic dark energy, where the equation of state deviates from ``-1'' along the axis of anisotropy (the $w_b$CDM model), over both other anisotropic models considered and the standard flat $\Lambda$CDM or $w$CDM models.
- [48] arXiv:2410.02270 (replaced) [pdf, html, other]
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Title: Beyond the ensemble paradigm in low dimensional quantum gravity: Schwarzian density, quantum chaos and wormhole contributionsComments: 9 pages, 2 figures. Matches version to be published in Physical Review DSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph); Chaotic Dynamics (nlin.CD)
Based on periodic orbit theory we address the individual-system versus ensemble interpretation of quantum gravity from a quantum chaos perspective. To this end we show that the spectrum of geodesic motion on high-dimensional hyperbolic manifolds, described by the Selberg trace formula, displays a Schwarzian ($\sinh 2\pi\sqrt{E}$) mean level density. Due to its chaotic classical limit, this quantum system also shows all universal signatures of quantum chaos. These two properties imply a possible duality to Jackiw-Teitelboim-type quantum gravity at the level of a single system instead of an ensemble of systems like matrix theories and SYK models. Beyond the universal regime we show how the full wormhole geometry on the gravity side emerges from the discreteness of the set of periodic orbits. Thereby, we take initial steps towards a duality between gravitational and mesoscopic chaotic quantum systems through the topological, respectively, periodic orbit expansions of their correlators.
- [49] arXiv:2411.13637 (replaced) [pdf, html, other]
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Title: Do Observations Prefer Thawing Quintessence?Comments: Accepted for publication in PRD. 12 pages, 8 figures. v2,v3,v4 replacements feature minor revisionsSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Theory (hep-th)
In light of recent observations by the Dark Energy Spectroscopic Instrument (DESI), we study evidence for thawing quintessence over a cosmological constant as dark energy, with emphasis on the effect of the choice of priors. Working with a parametrization for the equation of state parameter motivated by the theory, we analyse the DESI BAO data jointly with Planck 2018 and Pantheon+ or Dark Energy Survey supernovae data, and find a preference for thawing quintessence compared to a bare cosmological constant only if we use priors which are heavily informed by the data itself. If we extend the priors to physically better motivated ranges, the evidence for thawing quintessence disappears.
- [50] arXiv:2412.13800 (replaced) [pdf, html, other]
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Title: $e^+ e^- \to μ^+ μ^-$ in the Asymptotically Safe Standard ModelComments: 17 pages, 8 figuresJournal-ref: Phys.Rev.D 111 (2025) 10, 106005Subjects: High Energy Physics - Phenomenology (hep-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
We study the electron-positron to muon--anti-muon cross-section in the asymptotically safe Standard Model. In particular, we include the graviton contributions to the scattering amplitude, which is computed from momentum-dependent timelike one-particle-irreducible correlation functions. Specifically, we employ reconstruction techniques for the graviton spectral functions. We find that the full asymptotically safe quantum cross section decreases in the ultraviolet with the centre-of-mass energy, and is compatible with unitarity bounds. Importantly, our findings provide non-trivial evidence for the unitarity of the asymptotically safe Standard Model.
- [51] arXiv:2501.03294 (replaced) [pdf, html, other]
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Title: Are Hilbert Spaces Unphysical? Hardly, My Dear!Comments: Title changed; revised and enlarged; published in Found of Phys (view only at this https URL). Previous version (v2) rejected by Quantum Stud.: Math. Found. by unethical device of having it reviewed by the same person responsible for the acceptance of the criticized paper. Managing editor Eliahu Cohen turned a blind eye to obvious conflict of interest. Rebuttal of arXiv:2308.06669v3Journal-ref: Found. Phys. 55, 46 (2025)Subjects: Quantum Physics (quant-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
It is widely accepted that the states of any quantum system are vectors in a Hilbert space. Not everyone agrees, however. The recent paper ``The unphysicality of Hilbert spaces'' by Carcassi, Calderón and Aidala is a thoughtful dissection of the mathematical structure of quantum mechanics that seeks to pinpoint supposedly unsurmountable difficulties inherent in postulating that the physical states are elements of a Hilbert space. Its pivotal charge against Hilbert spaces is that by a change of variables, which is a change-of-basis unitary transformation, one ``can map states with finite expectation values to those with infinite ones''. In the present work it is shown that this statement is incorrect and the source of the error is spotted. In consequence, the purported example of a time evolution that makes ``the expectation value oscillate from finite to infinite in finite time" is also faulty, and the assertion that Hilbert spaces ``turn a potential infinity into an actual infinity'' is unsubstantiated. Two other objections to Hilbert spaces on physical grounds, both technically correct, are the isomorphism of separable Hilbert spaces and the unavoidable existence of infinite-expectation-value states. The former turns out to be quite irrrelevant but the latter remains an issue without a fully satisfactory solution, although the evidence so far is that it is physically innocuous. All in all, while the authors' thesis that Hilbert spaces must be given up deserves some attention, it is a long way from being persuasive as it is founded chiefly on a misconception and, subsidiarily, on immaterial or flimsy arguments.
- [52] arXiv:2501.12905 (replaced) [pdf, html, other]
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Title: The impact of hyperons on neutron star mergers: gravitational waves, mass ejection and black hole formationHristijan Kochankovski, Georgios Lioutas, Sebastian Blacker, Andreas Bauswein, Angels Ramos, Laura TolosComments: 31 pages, 28 figures, accepted for publication in PRDSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
We study the influence of hyperons in binary neutron star (NS) mergers considering a total of 14 temperature dependent equations of state (EoSs) models which include hyperonic degrees of freedom and partly delta resonances. Thermally produced hyperons induce a higher heat capacity and a lower thermal index, i.e. a reduced thermal pressure for a given amount of thermal energy, compared to purely nucleonic models. We run a large set of relativistic hydrodynamics simulations of NS mergers to explore the impact on observables of these events. In symmetric binaries, we describe a characteristic increase of the dominant postmerger gravitational-wave (GW) frequency by a few per cent, which is specifically linked to the occurrence of hyperons and can thus be potentially used as a discriminator between purely nucleonic and hyperonic systems. We corroborate that this effect occurs similarly for asymmetric binaries and becomes more prominent with increasing total binary mass. Hyperonic models tend to stick out in relations between the dominant postmerger GW frequency and the tidal deformability of massive stars providing a signature to identify the presence of hyperons. Distinct secondary postmerger GW spectral features are differently affected by the presence of hyperons, in the sense that one feature exhibits a characteristic frequency shift due to the specific thermal properties of hyperonic EoSs while the other does not. The dynamical mass ejection of mergers is tentatively enhanced for hyperonic models in comparison to nucleonic EoSs which yield roughly the same stellar properties of cold NSs. This may serve useful to identify exotic degrees of freedom in these systems by kilonova observations. Also, for hyperonic EoSs the threshold mass for prompt black hole formation is reduced by about 0.05 $M_{\odot}$ in comparison to nucleonic systems with the same stellar parameters of cold NSs.
- [53] arXiv:2503.14370 (replaced) [pdf, html, other]
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Title: Quantum thermal machines in BTZ black hole spacetimeComments: 9 pages, 5 figuresJournal-ref: Phys. Rev. D 111, 105030 (2025)Subjects: Quantum Physics (quant-ph); Statistical Mechanics (cond-mat.stat-mech); General Relativity and Quantum Cosmology (gr-qc)
We investigate an Otto thermodynamic cycle with a qubit Unruh-DeWitt detector as the working medium, coupled to a massless, conformally coupled scalar quantum field in the Hartle-Hawking vacuum in a (2+1)-dimensional BTZ black hole spacetime. We employ the thermal properties of the field to model heat and cold reservoirs between which the thermal machine operates. Treating the detector as an open quantum system, we employ a master equation to study its finite-time dynamics during each cycle stroke. We evaluate the output performance of the Otto heat engine and refrigerator by computing, respectively, the total work output and the cooling power for each of the Neumann, transparent, and Dirichlet boundary condition cases satisfied by the field at spatial infinity. Furthermore, we evaluate the optimal performance of the thermal machine by analyzing its efficiency at maximum power output and ecological impact. Our study presents a general framework for understanding the finite-time operation of relativistic quantum thermal machines, focusing on their energy optimization.
- [54] arXiv:2505.00761 (replaced) [pdf, html, other]
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Title: What is a photon in de Sitter spacetime?Comments: 45+16 pages. Added references and fixed typos in v2Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
The states of a single photon in four-dimensional de Sitter (dS) spacetime form a Unitary Irreducible Representation (UIR) of SO(1,4), which we call the photon UIR. While in flat spacetime photons are intimately tied to gauge symmetry, we demonstrate that in de Sitter, photon states emerge generically in any quantum field theory, even without an underlying U(1) gauge field. We derive a Källén-Lehmann representation for antisymmetric tensor two-point functions and show that numerous composite operators constructed from massive free fields can create states in the photon UIR. Remarkably, we find that some of these operators exhibit two-point functions with slower late-time and large-distance decay than the electromagnetic field strength itself, challenging the conventional notion that photons dominate the infrared regime. Using our spectral representation, we establish non-perturbative bounds on the late-time behavior of electric and magnetic fields in de Sitter, with potential implications for primordial magnetogenesis. Through one-loop calculations, we demonstrate that both the creation of photon states and the enhanced late-time large-distance behavior persist in weakly interacting theories.
- [55] arXiv:2505.16026 (replaced) [pdf, html, other]
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Title: Edge modes of tetrad gravity: Unlike diffeomorphisms, all shifts are integrableComments: 10 pages + 14 appendix. V2: Important clarifications regarding existence of L[phi] and embedding into eBF phase spaceSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
We present an improved notion of internal tetrad shifts in 4 dimensions which is always integrable in the presence of corners. This allows us to study the fully extended corner symmetry algebra of gauge charges, which is a deformation of $ISO(1,3)^S$ involving spacetime curvature. We argue this implies corner noncommutativity of the spin connection $\omega$. The latter in particular hints that an extended BF theory might be a better way understand the dynamics of tetrad gravity. This result presents us with an integrable, complete set of edge modes for gravity in 4D, with potential ramifications for asymptotic symmetries and quantisation.
- [56] arXiv:2505.23664 (replaced) [pdf, html, other]
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Title: Measurements $\mathit{with}$ probabilities in the final state proposalComments: Minor editsSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
Bousso and Stanford (BS) argued that the black hole final state proposal leads to acausal effects and ill-defined probabilities for the AMPS experiment. We identify a loophole in their analysis using insights from entanglement wedge reconstruction and replica wormholes. We trace the cause of the BS problems to the misidentification of the physical interior where the second AMPS measurement happens from among the multiple interiors introduced by the first measurement.