General Relativity and Quantum Cosmology
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Showing new listings for Friday, 19 September 2025
- [1] arXiv:2509.14288 [pdf, other]
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Title: James Burkett Hartle: a Biographical MemoirComments: This memoir is published in the Biographical Memoir Series of the US National Academy of Sciences. 8 pagesSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th); History and Philosophy of Physics (physics.hist-ph)
James Burkett Hartle was a theoretical physicist who made major contributions to our understanding of relativistic stars, black holes, and cosmology. Most of his career, however, was devoted to studying the universe as a quantum system. As a result, he was known as the father of quantum cosmology. He is best known for two seminal papers with Stephen Hawking that introduced two quantum states of fundamental importance: the "Hartle-Hawking vacuum" for matter fields outside a black hole, and the "no-boundary wave function of the universe" for cosmology. Jim (as everyone called him) was a warm and caring person who was genuinely concerned with the success of his students, postdocs, and colleagues. He was generous with his time and helped to foster a culture of a welcoming family among gravitational physicists.
- [2] arXiv:2509.14306 [pdf, other]
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Title: From geometry to cosmology: a pedagogical review of inflation in curvature, torsion, and extended gravity theoriesComments: Review paper published in Eur. Phys. J. C 85, 994 (2025), 119 pages, many tables, figures, a condensed version of the abstract , online version is polished with some referencesJournal-ref: Eur. Phys. J. C (2025) 85:994Subjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th)
We present a simplified review of inflationary cosmology across various modified gravity theories. These include models based on curvature, torsion, and non-metricity. We explore how scalar fields interact with different geometric quantities and how these interactions affect inflationary dynamics. Key cosmological features such as background evolution, reheating, and observable parameters are discussed. We also examine exotic scenarios inspired by string theory, extra dimensions, and non-local models. This work aims to connect theoretical models with observational data and future missions, offering guidance for exploring inflation beyond general relativity.
- [3] arXiv:2509.14309 [pdf, html, other]
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Title: Charting GLOBs in Asymptotically Safe GravityComments: 21 pages + references, 6 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
Computing the gravitational effective action provides a direct route to charting the landscape of admissible black hole spacetimes and their alternatives, which we will collectively call "gravitationally localized objects" (GLOBs). In this work, we provide a proof of principle of this idea within the framework of asymptotically safe gravity. Focusing on the Einstein-Weyl truncation, we identify the unique ultraviolet-complete trajectory emanating from the asymptotically safe fixed point and use it to extract the Wilson coefficient of the Weyl-squared term. This allows us to chart the corresponding GLOBs in a "phase diagram", showing that wormholes dominate a large portion of it, whereas the classical Bachian naked singularities become disfavored. Our results illustrate how quantum gravity can constrain effective field theory and the associated set of allowed spacetimes, yielding a rich landscape of beyond-general-relativity solutions rather than a single alternative to classical black holes.
- [4] arXiv:2509.14440 [pdf, html, other]
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Title: Cosmological dynamical systems of non-minimally coupled fluids and scalar fieldsComments: 31 pages, 6 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)
We study the cosmological dynamics of non-minimally coupled matter models using the Brown's variational approach to relativistic fluids in General Relativity. After decomposing the Ricci scalar into a bulk and a boundary term, we construct new models by coupling the bulk term to the fluid variables and an external scalar field. Using dynamical systems techniques, we study models of this type and find that they can give rise to both early-time inflationary behaviour and late-time accelerated expansion. Moreover, these models also contain very interesting features that are rarely seen in this context. For example, we find dark energy models which exhibit phantom crossing in the recent past. Other possibilities include models that give a viable past evolution but terminate in a matter-dominated universe. The dynamical systems themselves display an array of mathematically interesting phenomena, including spirals, centres, and non-trivial bifurcations depending on the chosen parameter values.
- [5] arXiv:2509.14525 [pdf, html, other]
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Title: Trapped surface formation for the Einstein-Weyl spinor systemComments: 64 pages, 1figureSubjects: General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)
We prove trapped-surface formation for the Einstein-Weyl spinor system (gravity coupled to a massless left-handed two-spinor) without any symmetry assumption. To this end we establish a semi-global solution under double null foliation and show that the focusing of the gravitational waves and the Weyl spinor flux leads to the formation of a trapped surface.
- [6] arXiv:2509.14629 [pdf, html, other]
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Title: Black Hole Quasi-Periodic Oscillations in the Presence of Gauss-Bonnet Trace AnomalyComments: 20 pages, 9 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
We investigate the effects of the Gauss-Bonnet (GB) gravitational trace anomaly on the circular motion of test particles around black holes (BHs) and its implications for quasi-periodic oscillations (QPOs) in various theoretical models. Beginning with the equations of motion, we study the effects on effective potential, angular momentum, specific energy, and the innermost stable circular orbit (ISCO) induced by the anomaly parameter $\alpha$. The fundamental frequencies are calculated. Moreover, we examine several QPO models, including PR, RP, WD, TD, and ER2-ER4, and study the relationship between the upper and lower QPO frequencies as well as the corresponding resonance radii for frequency ratios of 1:1, 3:2, 4:3, and 5:4. Our results show that increasing $\alpha$ leads to deviations from the Schwarzschild case in both upper and lower QPO frequencies correlations and QPO orbital radii, with model-dependent trends. Further, we constrain the BH parameters using the observational data using MCMC analysis. Finally, we calculate the upper and lower QPO frequencies for a few BH candidates on the basis of the RP model using the constrained parameter values and find a good agreement with the observed results.
- [7] arXiv:2509.14663 [pdf, html, other]
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Title: Unified Framework for Geodesic Dynamics with Conservative, Dissipative, and GUP EffectsSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Physics - Theory (hep-th); Mathematical Physics (math-ph); Chaotic Dynamics (nlin.CD)
We derive generalized geodesic equations in curved spacetime that include conservative forces, dissipative effects, and quantum-gravity-motivated minimal-length corrections. Conservative interactions are incorporated through external vector potentials, while dissipative dynamics arise from an exponential rescaling of the particle Lagrangian. Quantum-gravity effects are introduced via Generalized Uncertainty Principle (GUP) deformed Poisson brackets in the Hamiltonian framework. We show that free-particle geodesics remain unaffected at leading order, but external potentials induce velocity-dependent corrections, implying possible violations of the equivalence principle. As an application, we analyze modified trajectories in Friedmann-Lemaitre-Robertson-Walker (FLRW) universes dominated by dust, radiation, stiff matter, and dark energy. Our results establish a unified approach to conservative, dissipative, and GUP-corrected geodesics, providing a framework to probe the interplay between external forces, spacetime curvature, and Planck-scale physics.
- [8] arXiv:2509.14667 [pdf, html, other]
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Title: Geodesics and Light Deflection in Schwarzschild-like Spacetime from Cosmology-Inspired Modified GravityComments: 12 pages, 8 figures, comments are welcomeSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
We investigate cosmology-driven modifications to Schwarzschild-like black hole spacetimes and analyze their impact on photon propagation, gravitational lensing, and shadow observation. The gravitational deflection angle is computed using the Rindler-Ishak method, which incorporates finite-distance corrections and provides a consistent framework for non-asym-ptotically flat spacetimes. The effective potential for null geodesics exhibits a single unstable maximum corresponding to the photon sphere, and we study photon orbits classified according to the critical impact parameter into capture, escape, and unstable circular trajectories. Our analysis shows that the deflection angle decreases with increasing model parameter $(\alpha)$, resulting in weaker light bending compared to the Schwarzschild case. In addition, we examine the angular diameter of the black hole shadow as measured by a static observer, highlighting its dependence on the cosmological modification parameters. These results suggest that high-precision astrometric and lensing observations can place meaningful constraints on cosmology-inspired modifications to gravity, thereby linking astrophysical black holes with cosmic expansion and offering a novel probe of gravitational physics in strong-field regimes.
- [9] arXiv:2509.14757 [pdf, html, other]
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Title: Lagrangian Dynamics of Spinning Pole-Dipole-Quadrupole Particles in Metric-Affine GeometriesComments: 6 pages, no figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics - Theory (hep-th)
We construct the Lagrangian formulation of a micro-structured spinning, dilating and shearing (deformable) test body, moving in arbitrary non-Riemannian backgrounds possessing all geometrical entities of curvature, torsion and non-metricity. We start with a Lagrangian of a generic form that depends on the particle's velocity, its material frame and its absolute derivative, and the background geometry consisting of a metric and an independent affine connection. Performing variations of the path and the material frame, we derive the equations of motion for the particle that govern the evolution of its momentum and hypermomentum in this generic background. The reported equations of motion generalize those of a spinning particle (Mathisson \cite{Mathisson:1937zz}, Papapetrou \cite{Papapetrou:1951pa}, Dixon \cite{Dixon:1974xoz}) by the inclusion of the dilation and shear (hadronic) currents of matter. Using the derived equations of motion, a generalized conserved quantity is also found. Further conserved quantities that can be obtained by appropriate supplementary conditions are also discussed.
- [10] arXiv:2509.14849 [pdf, html, other]
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Title: A Comprehensive Framework for F-statistic-based Parameter Estimation of Binary Black Hole SignalsComments: 11 pages, 4 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
We present a comprehensive investigation of the F-statistic method for parameter estimation of gravitational wave (GW) signals from binary black hole mergers. By analytically maximizing the likelihood over the luminosity distance and polarization angle, this approach reduces the dimensionality of the parameter space to enhance computational efficiency. We also introduce a novel formulation for calculating the Bayes factor for the F-statistic, enabling a quantitative assessment of its performance against standard full frequency-domain (FFD) Bayesian inference. Using the benchmark event GW150914, we demonstrate that the F-statistic method is not only approximately $70\%$ faster than FFD but is also statistically stable across different sampler configurations, with a log-Bayes factor between runs smaller than $0.1$. Furthermore, the F-statistic exhibits superior stability against changes in sampler configuration, yielding consistently lower Jensen-Shannon divergence values between analysis runs. While the F-statistic produces slightly broader constraints on some parameters, we argue this represents a more honest uncertainty quantification, particularly in high-dimensional parameter spaces with complex posterior structures. These results highlight the significant advantages of the F-statistic method for GW data analysis, positioning it as a powerful tool for the era of high-rate detections with future observatories.
- [11] arXiv:2509.14924 [pdf, html, other]
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Title: Residual Test for the Third Gravitational-Wave Transient CatalogComments: 13 pages, 5 figures, comments are welcomeSubjects: General Relativity and Quantum Cosmology (gr-qc)
The residual test is commonly used to check the agreement between the gravitational wave signal and the theoretical waveform template. The basic idea of the residual test is to subtract the best-fit waveform from the data and then check whether the remaining data (i.e., the residuals) are consistent with the instrumental noise or not. We apply the Kolmogorov-Smirnov test, the Anderson-Darling test and the chi-squared test as goodness-of-fit test to examine the residuals of events in the third gravitational-wave transient catalog and find no statistically significant deviation from the noise. Although our method is sensitive only to the loud events, it does not rely on the cross-correlation between detectors. A single-detector event suffices for our residual analysis, and the test is simple and computationally inexpensive.
- [12] arXiv:2509.15002 [pdf, html, other]
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Title: Can Hawking effect of multipartite state protect quantum resources in Schwarzschild black hole?Comments: 19 pages, 3 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
Most previous studies on relativistic quantum information have primarily focused on the vacuum state $|0\rangle$ and the first excited state $|1\rangle$ in two-mode entangled systems. In this work, we go beyond these limitations by considering arbitrary $q$-th excited states $|q\rangle$, aiming to investigate their role in preserving quantum resources. We analyze the influence of the Hawking effect on multipartite quantum states in the Schwarzschild spacetime, with particular attention to quantum entanglement and coherence. Our results show that, under the influence of the Hawking effect, increasing the excitation number $q$ leads to a reduction in quantum entanglement and mutual information, while enhancing quantum coherence. This indicates that the Hawking effect on excited multipartite states tends to degrade quantum correlations but simultaneously protects quantum coherence in curved spacetime. Therefore, when implementing quantum information protocols in gravitational settings, reducing the excitation number $q$ is favorable for maintaining entanglement, whereas increasing $q$ may be advantageous for tasks that rely on quantum coherence in relativistic quantum information processing.
- [13] arXiv:2509.15014 [pdf, html, other]
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Title: Importance of Shot Noise in the Search for an Isotropic Stochastic Gravitational-Wave Background with Next Generation DetectorsComments: 20 pages, 16 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc); Cosmology and Nongalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE); Instrumentation and Methods for Astrophysics (astro-ph.IM)
We investigate the impact of shot noise on the stochastic gravitational wave background generated by binary neutron star mergers, and confirm that the overall background can be significantly influenced by relatively few neighboring, loud events. To mitigate the shot noise, we propose a procedure to remove nearby events by notching them out in the time-frequency domain. Additionally, we quantify the cosmic/sample variance of the resulting background after notching, and we study the deviation between the cross-correlation measurement and the theoretical prediction of the background. Taking both effects into account, we find that the resulting sensitivity loss in the search for an isotropic background formed by binary neutron star mergers is minimal, and is limited to $\lesssim 4\%$ below 40 Hz, and to $\lesssim 1\%$ above 40 Hz.
New submissions (showing 13 of 13 entries)
- [14] arXiv:2509.14312 (cross-list from hep-th) [pdf, html, other]
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Title: Dissipation in Open HolographyComments: 30 pages, 11 FiguresSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
We exploit the holographic realization of a conformal theory coupled to an external bath realized via a double trace deformation and its gravity dual in terms of transparent boundary conditions in order to map out some basic dissipative properties of this simple open holographic system. In particular, we determine the energy transmission coefficient across the boundary, discover a novel duality relating weak and strong coupling to the external bath, and quantify the dissipation in the system by working out the quasi normal modes.
- [15] arXiv:2509.14327 (cross-list from hep-th) [pdf, html, other]
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Title: Towards a holographic description of closed universesComments: 45 pagesSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
We study baby closed universes in AdS, focusing on the Antonini-Sasieta-Swingle (AS$^2$) cosmology, which arises in the gravitational description of partially entangled thermal states (PETS), as well as the classical example of Maldacena-Maoz (MM). We show that the algebraic formulation of AdS/CFT--and in particular the subregion-subalgebra duality--provides a natural framework for describing such universes within the standard AdS/CFT setting, phrased in terms of an operator algebra ${\cal M}$ and a state $\omega$ on that algebra, with no need to introduce observers. The algebra encodes all physical operations in the closed universe, and, in principle, all physical observables are obtainable from the pair $({\cal M},\omega)$. Along the way, we propose a resolution to a puzzle raised by Antonini and Rath (AR) and reinforced by recent arguments of Engelhardt and Gesteau and a no-go theorem of Gesteau: that a semiclassical baby universe in the AS$^2$ cosmology cannot be understood from the boundary in the usual manner. Our analysis motivates an averaged large-$N$ limit as part of the AdS/CFT dictionary and points toward a unified treatment of spacetimes of all asymptotics in terms of operator algebras. Finally, our boundary descriptions of closed universes indicate that for small but finite $G_N$ there should exist a semiclassical description of a macroscopic closed universe, rather than a one-dimensional Hilbert space, and we discuss weaknesses in arguments favoring the latter.
- [16] arXiv:2509.14720 (cross-list from physics.hist-ph) [pdf, html, other]
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Title: Gauge symmetry and the arrow of time: How to count what countsComments: PhD Thesis, University of Groningen. Defended 11 Sept 2025Subjects: History and Philosophy of Physics (physics.hist-ph); General Relativity and Quantum Cosmology (gr-qc)
This thesis addresses two major problems in the philosophy of physics. The first is how to identify the minimal physical content of a theory; that is, what features of a theory are truly needed to make predictions, and what can be removed without changing its empirical consequences. The second is the problem of time's arrow: why time seems to have a direction, even though the fundamental laws of physics treat the past and future symmetrically.
I show that answering the first question leads to insights about the second. In particular, I argue that the overall size of the Universe is not used to make predictions in cosmology, and so should not count as part of the theory's minimal physical content. Describing the Universe without this feature leads to a striking result: the arrow of time becomes a local phenomenon. Observers like us who see a Universe full of matter clumped together to form structures like stars and planets are statistically much more likely to see increasing clumpiness into the future than into the past. This tendency helps explain our experience of time's direction. - [17] arXiv:2509.14763 (cross-list from math.CA) [pdf, html, other]
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Title: Large-order perturbation theory of linear eigenvalue problemsComments: 5 figuresSubjects: Classical Analysis and ODEs (math.CA); General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
We consider a class of linear eigenvalue problems depending on a small parameter epsilon in which the series expansion for the eigenvalue in powers of epsilon is divergent. We develop a new technique to determine the precise nature of this divergence. We illustrate the technique through its application to four examples: the anharmonic oscillator, a simplified model of equitorially-trapped Rossby waves, and two simplified models based on quasinormal modes of Reissner-Normstrom de Sitterblack holes.
- [18] arXiv:2509.15021 (cross-list from hep-th) [pdf, html, other]
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Title: Anisotropic critical points from holographyComments: 61 pages, 10 figuresSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
We present a comprehensive analysis of generic 5-dimensional Einstein-Maxwell-Dilaton-Axion (EMDA) holographic theories with exponential couplings. We find and classify exact, analytic, anisotropic solutions, both zero-temperature vacua and finite-temperature black brane backgrounds, with anisotropy sourced by scalar axions, magnetic fields, and charge densities, that can be interpreted as IR fixed points of renormalisation-group flows from UV-conformal fixed points. The resulting backgrounds feature a hyperscaling violation exponent and up to three independent Lifshitz-like exponents, generated by an equal number of independent coupling constants in the EMDA action. We derive the holographic stress-energy tensor and the corresponding equation of state, and discuss the behavior of the anisotropic speed of sound and butterfly velocity. We show that these theories can be consistently constrained by imposing several natural requirements, including energy conditions, thermodynamic stability, and causality. Additionally, we analyse hard probes in this class of theories, including Brownian motion, momentum broadening and jet quenching, and we demonstrate that a fully analytic treatment is possible, making their dependence on the underlying anisotropy explicit. We highlight the relevance of these models as benchmarks for strongly coupled anisotropic matter in nature, from the quark-gluon plasma created in heavy-ion collisions to dense QCD phases in neutron-star mergers and the cores of compact objects.
- [19] arXiv:2509.15034 (cross-list from hep-th) [pdf, html, other]
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Title: Domain Wall Skyrmions in Holographic Quantum Chromodynamics: Topological Phases and Phase TransitionsComments: 16 pages, 4 figures; Published version; Dedicated Umut Gürsoy, who made valuable contributions to the Holographic QCD and passed away recentlyJournal-ref: Journal of Holography Applications in Physics, 5(3), 12-30 (2025)Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph)
We investigate the domain wall skyrmions phase in the framework of holographic quantum chromodynamics (QCD) using the Sakai-Sugimoto model. Building on previous work regarding chiral soliton lattices (CSLs) in strong magnetic fields, we study the emergence of localized skyrmions a top domain walls formed by CSLs. These skyrmions, realized as undissolved D4-branes embedded in the D8-branes, carry baryon number two and exhibit complex topological and energetic features. We explore the interplay between magnetic field strength, pion mass, and baryon chemical potential in stabilizing these configurations and demonstrate the existence of a mixed CSL-skyrmions phase. Through systematic energy analysis, we establish that the domain wall skyrmions become energetically favorable when $\mu_B |B| \gtrsim \Lambda \cdot m_\pi f_\pi^2$, with the transition occurring around $\mu_B |B| \sim 4.5$ in our holographic framework. Our phase diagram reveals three distinct regions: the CSL phase at low chemical potential and magnetic field, the domain wall skyrmions phase at intermediate scales, and a conjectured skyrmions crystal phase at the highest densities. The instanton density profiles $\text{Tr}(F \wedge F)$ show sharp localization in the domain wall skyrmions phase, contrasting with the smooth, extended distribution characteristic of the pure CSL configuration. These findings provide non-perturbative insights into baryonic matter in the dense QCD and offer a geometrical picture of topological phase transitions via string theory duality, with potential applications to neutron star physics and the broader QCD phase diagram under extreme conditions.
- [20] arXiv:2509.15055 (cross-list from hep-th) [pdf, html, other]
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Title: New formalism for perturbations of massive gravity theories around arbitrary background spacetimesComments: 20 pages, 1 figureSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
We develop a new technique for studying the perturbations of dRGT-type massive gravity theories around arbitrary background spacetimes. Built initially from the vielbein formulation of the theory, but switching back to the metric formulation afterwards, our approach bypasses many of the complications that arise in previous metric formulation approaches to linearising massive gravity around generic backgrounds, naturally elucidates the ghost-free structure of the interactions, and readily generalises to higher orders in perturbation theory, as well as to multiple interacting metric tensor fields. To demonstrate the power of our technique, we apply our formalism to a number of commonly occurring example backgrounds - proportional, cosmological, and black hole - recovering and extending many known results from the literature at linear order. Lastly, we provide, for the first time, the cubic order multi-gravity potential around a generic background spacetime.
- [21] arXiv:2509.15125 (cross-list from hep-th) [pdf, html, other]
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Title: Heterotic Warm InflationArjun Berera, Heliudson Bernardo, Suddhasattwa Brahma, Jaime Calderón-Figueroa, Rudnei O. Ramos, Michael W. ToomeyComments: 26 papes, 4 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)
In this paper we propose a two-field model of warm inflation motivated from a heterotic string construction. The model contains an axion and a dilaton-like field. We show that while warm inflation can take place in the axion-field direction, thermal corrections coming from the radiation gauge fields, which couples to both the axion and the dilaton, prevent warm inflation to happen in the dilaton-field direction. We explore the background dynamics for different parameters, and identify a diversity of dynamical behaviors allowed in this model, denoting different regimes of warm inflation.
- [22] arXiv:2509.15146 (cross-list from astro-ph.CO) [pdf, html, other]
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Title: Parameterizing quasi-quintessence and quasi-phantom fields without the nearly flat potential approximationComments: 7 pages, 1 figure, 1 tableSubjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
An alternative dark energy description based on a generalized K-essence scenario is here explored. In particular, we consider a \emph{quasi-quintessence} and/or \emph{quasi-phantom} field, whose pressure does not depend on the kinetic energy, firstly discussed in the context of the cosmological constant problem. In so doing, we fix the background evolution and investigate the main observational signatures of its corresponding fluid-like representation. The corresponding scalar field can be parameterized independently from the potential form and without imposing the condition $\omega \sim -1$ used for quintessence and phantom fields. Additionally, we constrain the model parameters by performing Monte-Carlo Markov chain simulations through the adoption of the Metropolis-Hastings algorithm and perform separated analyses, employing different data catalogs. More precisely, as data sets we employ observational Hubble data, type Ia supernovae and the second data release from the DESI Collaboration, namely DESI DR2. We define a hierarchy among analyses and, precisely, in the first we adopt all three samples, while the second excludes the DESI data points, with the aim of facing its effect on corresponding bounds. Our findings suggest that the \emph{quasi-quintessence} scenario prefers Planck's value of the Hubble constant $H_0$, but suggesting that, when the DESI sample is excluded from our computations, $\omega_0$ enters the phantom regime, although still compatible at $1$-$\sigma$ confidence level with a cosmological constant. Remarkably, these results appear in tension than those found for a standard quintessence, explored within the context of the recent DESI release, likely indicating that the DESI data may furnish inconclusive results depending on the kind of scalar field involved into the computation.
Cross submissions (showing 9 of 9 entries)
- [23] arXiv:1107.2669 (replaced) [pdf, html, other]
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Title: Quantum Noise in Amplifiers and Hawking/Dumb-Hole Radiation as Amplifier NoiseComments: 13 pages, 4 figuresJournal-ref: "Analogue Spacetimes--the first thirty years: Proceedings of the Amazonian workshop II on Analogues" ed: L.C.B. Crispino, V.M.S. Cardoso, S Liberati, E.S. Oliveira, M. Visser LF Editorial, Editora Livraria da Fisica, S\~ao Paulo (2013)Subjects: General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
The quantum noise in a linear amplifier is shown to be thermal noise. The theory of linear amplifiers is applied first to the simplest, single or double oscillator model of an amplifier, and then to linear model of an amplifier with continuous fields and input and outputs. Finally it is shown that the thermal noise emitted by black holes first demonstrated by Hawking, and of dumb holes (sonic and other analogs to black holes), arises from the same analysis as for linear amplifiers. The amplifier noise of black holes acting as amplifiers on the quantum fields living in the spacetime surrounding the black hole is the radiation discovered by Hawking. For any amplifier, that quantum noise is completely characterized by the attributes of the system regarded as a classical amplifier, and arises out of those classical amplification factors and the commutation relations of quantum mechanics.
- [24] arXiv:2311.06416 (replaced) [pdf, html, other]
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Title: TESLA-X: An effective method to search for sub-threshold lensed gravitational waves with a targeted population modelJournal-ref: Mon Not R Astron Soc (2025) 998-1010Subjects: General Relativity and Quantum Cosmology (gr-qc); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Strong gravitational lensing can produce copies of gravitational-wave signals from the same source with the same waveform morphologies but different amplitudes and arrival times. Some of these strongly-lensed gravitational-wave signals can be demagnified and become subthreshold. We present TESLA-X, an enhanced approach to the original GstLAL-based TargetEd Subthreshold Lensing seArch (TESLA) method, for improving the detection efficiency of these potential subthreshold lensed signals. TESLA-X utilizes lensed injections to generate a targeted population model and a targeted template bank. We compare the performance of a full template bank search, TESLA, and TESLA-X methods via a simulation campaign, and demonstrate the performance of TESLA-X in recovering lensed injections, particularly targeting a mock event. Our results show that the TESLA-X method achieves a maximum of $\sim 10\%$ higher search sensitivity compared to the TESLA method within the subthreshold regime, presenting a step towards detecting the first lensed gravitational wave. TESLA-X will be employed for the LIGO-Virgo-KAGRA's collaboration-wide analysis to search for lensing signatures in the fourth observing run.
- [25] arXiv:2401.14251 (replaced) [pdf, html, other]
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Title: Quasi-local spin-angular momentum and the construction of axial vector fieldsComments: 18 pages, mathed to the published versionJournal-ref: Phys. Rev. D 112, 064044, 2025Subjects: General Relativity and Quantum Cosmology (gr-qc); Mathematical Physics (math-ph); Differential Geometry (math.DG)
A novel procedure is presented which allows the construction of all axial vector fields on Riemannian two-spheres. Using these axial vector fields and the centre-of-mass unit sphere reference systems, a constructive definition of quasi-local spin-angular momentum is introduced. Balance relations are also derived, with respect to arbitrary Lie-propagated unit sphere reference systems, to characterize the angular momentum transports in spacetimes without symmetries.
- [26] arXiv:2412.12901 (replaced) [pdf, html, other]
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Title: Qualitative analysis of viscous cosmologyComments: 26 pages, 14 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
We analyze the effect of higher order viscosity corrections in a spatially homogeneous and isotropic universe. The viscous effects are modeled by introducing a second-order term to the energy density in the equation of state and on the expansion factor. An autonomous dynamical system is then constructed to study the qualitative behavior of the energy density and expansion factor, employing the Raychaudhuri equation and the conservation of energy. We obtain the analytical expressions for the equilibrium points in terms of the model parameters, presenting several phase diagrams. The analysis of these diagrams reveals the presence of bifurcations, which manifest as changes in stability and qualitative behavior. Those changes lead to different configurations for the universe, such as bouncing, rebouncing and cyclic scenarios.
- [27] arXiv:2503.15157 (replaced) [pdf, html, other]
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Title: Covariant effective spacetimes of spherically symmetric electrovacuum with a cosmological constantComments: 17 pages, 1 figureJournal-ref: Phys. Rev. D 112, 064049 (2025)Subjects: General Relativity and Quantum Cosmology (gr-qc)
An algebraic framework was introduced in our previous works to address the covariance issue in spherically symmetric effective quantum gravity. This paper extends the framework to the electrovacuum case with a cosmological constant. After analyzing the notion of covariance in the classical theory, we propose an effective Hamiltonian for the electromagnetic field. The effective Hamiltonian together with the effective Hamiltonian constraint of gravity determines an effective dynamical model of gravity coupled to the electromagnetic field. The resulting model is covariant with respect to both the effective metric and the effective vector potential. By solving the equations of motion derived from the effective Hamiltonian constraint, we obtain several quantum-corrected solutions. Notably, some of these solutions reveal quantum gravity effects manifesting not only in spacetime metrics but also in the electromagnetic field. Finally, the covariance of coupling models with general matter fields is discussed.
- [28] arXiv:2504.20725 (replaced) [pdf, html, other]
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Title: Quasinormal Modes and Shadows of Black Holes in Infinite Derivative Theory of GravityComments: 23 pages, 17 figuresJournal-ref: Eur. Phys. J. C (2025) 85:940Subjects: General Relativity and Quantum Cosmology (gr-qc)
In this work, we study the quasinormal modes (QNMs) and shadow of a Schwarzschild black hole (BH) with higher-order metric corrections, in the framework of the Infinite Derivative theory of Gravity (IDG). We study the effects of corrections to the BH's metric, which arises from the IDG's corrections, on the QNMs and shadow of the BH. We used the 6th-order Padé averaged WKB approximation method to study the QNMs of the BH perturbed by a scalar field. The dependence of the amplitude and damping of QNMs with respect to the free parameters has been analysed. It is found that the BH system becomes unstable for some values of the free parameters. We also studied the time evolution of a scalar field around the BH spacetime. The QNMs have also been calculated from the time profile of the evolution, which show good agreement with the values obtained from the WKB method. The variation of the shadow radius of the BH due to the inclusion of higher-order corrections has been studied. Finally, we constrain the free parameters associated with the correction terms using the data from the Keck and VLTI observation, and we obtain some bounds on the parameters.
- [29] arXiv:2506.09149 (replaced) [pdf, html, other]
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Title: Neutron Star Radial Perturbations for Causal, Viscous, Relativistic FluidsComments: 25 pages, 0 figures. Accepted versionSubjects: General Relativity and Quantum Cosmology (gr-qc)
Which of the multiple models of causal and stable relativistic viscous fluids that have been developed is best suited to describe neutron stars? The modeling of out-of-equilibrium effects in these relativistic, astrophysical objects must be one with care, as simple Newtonian intuition fails to remain causal. Radial stability of neutron stars is one of the primary conditions for the viability of such out-of-equilibrium models. In this paper, we study radial perturbations of neutron stars for the Eckart, the Bemfica-Disconzi-Noronha-Kovtun, and the Müller-Israel-Stewart fluid models of relativistic viscous fluids. We find that for small viscosity, the three models have the same stability properties: they are always stable to bulk and shear viscosity, but they can be unstable to heat conductivity if certain thermodynamic conditions are violated. For the latter case, we derive a necessary criterion for stability to heat conductivity that applies to all three fluids. Moreover, we show that the additional degrees of freedom introduced by the Bemfica-Disconzi-Noronha-Kovtun and the Müller-Israel-Stewart models force the perturbations to evolve on fast timescales. Specifically, the Bemfica-Disconzi-Noronha-Kovtun model has additional oscillatory perturbations that propagate with the speed of second sound, while the Müller-Israel-Stewart model MIS only exhibits decaying behavior on the fast timescale. This work therefore establishes the first formal results and criteria for radial stability of these three out-of-equiblirium fluid models on the non-trivial, relativistic background of neutron stars.
- [30] arXiv:2507.08942 (replaced) [pdf, html, other]
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Title: Electromagnetic Energy Extraction from Kerr Black Holes: Ab-Initio CalculationsComments: v1: 11 pages, 5 figures, 1 table; v2: matches version accepted in ApJLSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE); Plasma Physics (physics.plasm-ph)
The possibility of extracting energy from a rotating black hole via the Blandford-Znajek mechanism represents a cornerstone of relativistic astrophysics. We present general-relativistic collisionless kinetic simulations of Kerr black-hole magnetospheres covering a wide range in the black-hole spin. Considering a classical split-monopole magnetic field, we can reproduce with these ab-initio calculations the force-free electrodynamics of rotating black holes and measure the power of the jet launched as a function of the spin. The Blandford-Znajek luminosity we find is in very good agreement with analytic calculations and compatible with general-relativistic magnetohydrodynamics simulations via a simple rescaling. These results provide strong evidence of the robustness of the Blandford-Znajek mechanism and accurate estimates of the electromagnetic luminosity to be expected in those scenarios involving rotating black holes across the mass scale.
- [31] arXiv:2509.00469 (replaced) [pdf, html, other]
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Title: Probing Formation Channels of Extreme Mass-Ratio InspiralsComments: 39 pages, 32 figures, 2 tables, submitted to PRDSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
The population study of stellar-mass black hole (sBH) binaries with ground-based gravitational wave detection has achieved tremendous success in recent years. Future observation of extreme mass-ratio inspirals will similarly require proper population analysis that identify the formation channels, measuring the branch ratio(s) and characterizing major properties within each major channel. In this work, we propose that the measurement of eccentricity, inclination, and component mass provides critical information to distinguish different formation channels and probe detailed formation mechanisms. Focusing on the dry and wet extreme mass-ratio inspirals, we establish the theoretical expectation of these observables in each formation channel. We also discuss how their distributions can be used to probe lifetime and turbulence level of active galactic nuclei disks, accretion patterns of supermassive black holes and population properties of sBHs within nuclear star clusters.
- [32] arXiv:2509.08690 (replaced) [pdf, html, other]
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Title: An Einstein ring fingerprint around SMBHs illuminated by BLR spectral linesComments: 6 pages, 4 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
The continuum emission from the hot and ionized inner regions of a supermassive black hole (SMBH) accretion disk that is strongly lensed by the light-ring (i.e., the unstable photon orbit), is always superimposed on that of the locally emitting plasma near the innermost stable circular orbit (ISCO), masking strong-gravity effects and making their study difficult. A cleaner image of the light-ring against a non-luminous background, not affected by the emission and all the dynamical effects taking place near the ISCO, would thus be preferable. A more distant SMBH illumination source that could accommodate this can be provided by the unique spectral lines emitted by the cooler parts of the accretion disk, the so-called Broad Line Region (BLR). Spectral line emission from the transitional region between the inner disk and the outer BLR may be ideal for obtaining a cleaner image of the light-ring, and better suited for strong gravity tests. A crucial first order effect of a BLR spectral line illumination of the SMBHs in galactic centers, and a possible smoking gun signal of strong SMBH lensing, will be an Einstein ring, whose presence could be evident even in unresolved sources where only the total line profile can be acquired. In resolved sources, the combination of information from the image and the spectrum can even facilitate the measurement of the mass of the SMBH.
- [33] arXiv:2509.08728 (replaced) [pdf, html, other]
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Title: SMBH shadows: gravity fingerprints revealed by spectral line background radiationComments: 23 pages, 22 figuresSubjects: General Relativity and Quantum Cosmology (gr-qc)
SMBHs at the centers of galaxies, illuminated by their accretion disks, can reveal valuable information on BH spacetimes via their shadows, which can be used for strong-gravity tests. However, the continuum emission from their highly turbulent hot plasma is expected to be strongly time-varying and with very inhomogeneous brightness. This can mask important SMBH-related effects, like the appearance of the light-ring, rendering them ineffective as probes of strong gravitational lensing physics. Besides being an inhomogeneous and strongly time-varying ''illuminator'', the hot plasma emission extends all the way to the ISCO. This then leads to the superposition of the strongly-lensed radiation from the area of the light-ring to the continuum emission from the ISCO, effectively making gravitational lensing physics hard to separate from accretion disk Astrophysics. These problems could be overcome if one utilizes the spectral line radiation field emanating from the cooler parts of the extended accretion disk, the so-called BLR, and especially its expected neutral phase, as a more distant, but still adequately strong SMBH illuminator, typically found at $r\sim (10^2-10^4)\, R_s$. This kind of illumination can provide a cleaner image of the light-ring region, and thus allow more information on the spacetime geometry around the SMBH to be obtained. Here, we examine some of the benefits of such an illumination in discerning strong-gravity physics near SMBHs and their observability. We expand on the fact that such emission can provide a smoking gun signal of lensing, in the form of an Einstein ring. To first order, the imaging of the Einstein ring and its spectroscopic signature can facilitate the measurement of the SMBH mass, while the second order effects associated with the light-ring can constrain the SMBH spin, and even identify deviations from the Kerr spacetime.
- [34] arXiv:2509.10395 (replaced) [pdf, html, other]
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Title: Ten years of gravitational-wave astronomyComments: Invited contribution to an upcoming special edition of the Portuguese Physical Society's "Gazeta de Física" dedicated to gravitational waves. v2: Fixed a typoSubjects: General Relativity and Quantum Cosmology (gr-qc); High Energy Astrophysical Phenomena (astro-ph.HE)
Ten years ago humankind achieved the first direct observation of gravitational waves. I give some personal recollections of that first detection. I also present an incomplete summary of what we have learned since then, and some speculations on what we may learn in the future.
- [35] arXiv:2509.13321 (replaced) [pdf, html, other]
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Title: Towards detecting the temporal fluctuations from gravitational waves in asynchronous gaugesComments: 52 pages, 5 figures, minor changes, corrected typosSubjects: General Relativity and Quantum Cosmology (gr-qc)
The experimental possibility of detecting gravitational waves via their induced time perturbations is explored here, expanding from previous work. The oscillations of the time-time component in the metric are made explicit when working in asynchronous gauges: the desynchronization between a perturbed clock and a reference unperturbed clock constitutes the corresponding observable core target of a detector. To this end we explore the experimental techniques currently available for a preliminary assessment towards a feasibility study. We survey the state of the art in the fields of high precision timing and information preservation, necessary for achieving geodesic non-locality. A synthesis for a feasible prototype detector with the desired characteristics is presented. The optimum point between existing technologies is found around the 1 Hz frequency band, opening the window for the observation of classes of speculated sources of gravitational radiation such as intermediate mass black hole binaries.
- [36] arXiv:2412.06884 (replaced) [pdf, other]
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Title: Counting microstates of out-of-equilibrium black hole fluctuationsComments: 49 pages, 12 figures, 2 appendices. v2: minor changes. v3: minor changesSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
We construct and count the microstates of out-of-equilibrium eternal AdS black holes in which a shell carrying an order one fraction of the black hole mass is emitted from the past horizon and re-absorbed at the future horizon. Our microstates have semiclassical interpretations in terms of matter propagating behind the horizon. We show that they span a Hilbert space with a dimension equal to the exponential of the horizon area of the intermediate black hole. This is consistent with the idea that, in a non-equilibrium setting, entropy is the logarithm of the number of microscopic configurations consistent with the dynamical macroscopic state. In our case, therefore, the entropy should measure the number of microstates consistent with a large and atypical macroscopic black hole fluctuation due to which part of the early time state becomes fully known to an external observer.
- [37] arXiv:2412.09461 (replaced) [pdf, html, other]
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Title: Constraints on Pre-Big-Bang Cosmology from Advanced LIGO and Advanced Virgo's First Three Observing RunsComments: 8 pages, 3 figures, CTP accepted;Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum Cosmology (gr-qc)
We search for the stochastic gravitational-wave background (SGWB) predicted by pre-big-bang (PBB) cosmology using data from the first three observing runs of Advanced LIGO and Advanced Virgo. PBB cosmology proposes an alternative to cosmic inflation where the Universe evolves from a weak-coupling, low-curvature state to the hot Big Bang through a high-curvature bounce phase, predicting a distinctive SGWB spectrum. We perform a Bayesian analysis of the cross-correlation data to constrain the model parameters characterizing the PBB spectrum. We find no evidence for a PBB-induced SGWB, with a Bayes factor of $0.03$ between the PBB and noise-only model, strongly favoring the noise-only hypothesis. Our analysis establishes a lower bound $\beta \gtrsim -0.19$ at $95\%$ confidence level, which is compatible with the theoretical requirement $\beta \geq 0$ for a smooth bounce transition. While we do not detect a signal, our constraints remain consistent with the basic theoretical framework of PBB cosmology, demonstrating the potential of gravitational-wave observations to test early Universe theories.
- [38] arXiv:2503.19744 (replaced) [pdf, html, other]
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Title: Dip and non-linearity in the curvature perturbation from inflation with a transient non-slow-roll stageComments: 35 pages, 15 figuresJournal-ref: JCAP09(2025)046Subjects: 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)
We consider models of inflation that contain a transient non-slow-roll stage and investigate the conditions under which a dip appears in the power spectrum of the curvature perturbation. Using the $\delta N$ formalism, we derive a general relation between the comoving curvature perturbation ${\cal{R}}$ and the scalar field perturbation $\delta\varphi$ and its velocity perturbation $\delta\pi$. Compared with the result obtained in linear perturbation theory, it turns out that properly taking account of the $\delta\pi$ contribution is essential to reproduce the dip in the power spectrum. Namely, the curvature perturbation is proportional to a specific linear combination of $\delta\varphi$ and $\delta\pi$ at the linear order. We also investigate the non-linearity at the dip scale and find that models with a bump or an upward step exhibit much larger non-linearity than ultra-slow-roll and Starobinsky's linear potential models. Finally, we demonstrate the importance of non-linearity by computing the probability density functions (PDFs) for the above-mentioned models and show that highly asymmetric PDFs are realised for models with a bump or a step.
- [39] arXiv:2503.20399 (replaced) [pdf, html, other]
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Title: Energy transport in holographic non-conformal interfacesComments: 24 pages, 3 figures; v2: published versionJournal-ref: JHEP 09 (2025) 143Subjects: High Energy Physics - Theory (hep-th); Strongly Correlated Electrons (cond-mat.str-el); General Relativity and Quantum Cosmology (gr-qc)
We study energy transport in a system of two dimensional conformal field theories exchanging energy across a non-conformal interface involving a localised scalar operator, using holographic duality. By imposing the sourceless boundary condition, or equivalently, enforcing energy conservation at the interface, we show that the sum of the transmission and reflection coefficients is equal to one. Unlike conformal interfaces, we find that both the energy transmission and reflection coefficients are generally complex and frequency dependent. When the interface brane connects two distinct AdS$_2$ geometries, the transmission coefficient approaches the value expected for a conformal interface in the UV regime at high frequencies and in the IR regime at low frequencies. In the intermediate frequency range, the transmission coefficient may exhibit oscillatory behavior. Moreover, we present a nontrivial example of a fully transmissive interface, which exhibits similarities to a topological interface.
- [40] arXiv:2504.02897 (replaced) [pdf, html, other]
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Title: On the Derivation of the Cosmological Gurzadyan's TheoremSubjects: Classical Physics (physics.class-ph); General Relativity and Quantum Cosmology (gr-qc)
In cosmology, the Gurzadyan's theorem identifies the most general force law consistent with the finding of Newton's first shell theorem -- that a spherical symmetric mass exerts the same gravitational force as a point mass at its center. This theorem has found important applications in cosmological modeling, particularly in the context of MoND (Modified Newtonian Dynamics), which has recently gained renewed attention as a potential alternative to dark matter. The derivation by Gurzadyan is written in an extremely concise and dense style, making it difficult to follow. Recent proofs of the theorem based on power-series methods offer valuable perspectives, though they differ from the original derivation, which is based on perturbation analysis. Our note aims to clarify the underlying logic in a pedagogical way -- accessible to advanced high school or undergraduate students -- while preserving conceptual clarity and mathematical elegance of his insight.
- [41] arXiv:2506.03601 (replaced) [pdf, html, other]
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Title: Essential Renormalization Group Equation for Gravity coupled to a Scalar fieldComments: 32pages, Version published in Phys.Rev.DSubjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc)
We study the essential renormalization group equation, in which inessential couplings are removed via field redefinitions, for Einstein gravity coupled to a massive scalar field in the presence of a cosmological constant. Our results indicate that perturbatively nonrenormalizable terms can be eliminated due to the cosmological term, in contrast to the case of perturbation around flat spacetime. We find a nontrivial fixed point for the Newton coupling and the cosmological term.
- [42] arXiv:2506.17105 (replaced) [pdf, html, other]
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Title: GW200208_222617 as an eccentric black-hole binary merger: properties and astrophysical implicationsIsobel Romero-Shaw, Jakob Stegmann, Hiromichi Tagawa, Davide Gerosa, Johan Samsing, Nihar Gupte, Stephen R. GreenComments: 13 pages, 3 figures. Accepted for publication in PRDSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); Astrophysics of Galaxies (astro-ph.GA); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
Detecting orbital eccentricity in a stellar-mass black-hole merger would point to a non-isolated formation channel. Eccentric binaries can form in dense stellar environments such as globular clusters or active galactic nuclei, or from triple stellar systems in the Galactic field. However, confidently measuring eccentricity is challenging -- short signals from high-mass eccentric mergers can mimic spin-induced precession, making the two effects hard to disentangle. This degeneracy weakens considerably for longer-duration signals. Here, GW200208_222617 provides a rare opportunity. Originating from a relatively low-mass binary with source-frame chirp mass $\sim20$ M$_\odot$, its gravitational-wave signal spanned $\sim14$ orbital cycles in band, with no indication of data quality issues. Previous analyses for quasi-circular binaries found no evidence for spin precession, and multiple subsequent studies found the data to favour an eccentric merger despite notable technical differences. All in all, we believe GW200208_222617 is the black-hole merger event from GWTC-3 with the least ambiguous detection of eccentricity. We present a critical discussion of properties and astrophysical interpretation of GW200208_222617 as an eccentric black-hole merger using models of field triples, globular clusters, and active galactic nuclei. We find that if GW200208_222617 was indeed eccentric, its origin is consistent with a field triple or globular cluster. Formation in the inner regions of an active galactic nucleus is disfavoured. The outer regions of such a disk remain a viable origin for GW200208_222617; we demonstrate how future detections of eccentric mergers formed in such environments could be powerful tools for constraining the disk geometry.
- [43] arXiv:2507.10657 (replaced) [pdf, html, other]
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Title: A Black Hole Airy TailComments: 6 pages, 4 figures; v4: Added discussion of physical meaning of semi-quenched entropies and positivity of quenched entropies. See comment section of v3 for relation to Ref. [4]Subjects: High Energy Physics - Theory (hep-th); General Relativity and Quantum Cosmology (gr-qc); Quantum Physics (quant-ph)
In Jackiw-Teitelboim (JT) gravity, which is dual to a random matrix ensemble, the annealed entropy differs from the quenched entropy at low temperatures and goes negative. However, computing the quenched entropy in JT gravity requires a replica limit that is poorly understood. To circumvent this, we define an intermediate quantity called the semi-quenched entropy, which has the positivity properties of the quenched entropy, while requiring a much simpler replica trick. We compute this in JT gravity in different regimes using i) a bulk calculation involving wormholes corresponding to the Airy limit of the dual matrix integral and ii) a boundary calculation involving one-eigenvalue instanton saddles proposed by Hernández-Cuenca, demonstrating consistency between these two calculations in their common regime of validity. We also clarify why similar one-eigenvalue instanton saddles cannot be used to compute the quenched entropy due to a breakdown of the saddle-point approximation for the one-eigenvalue instanton in the replica limit. Our results show how to use the gravitational path integral to prove that black holes in JT gravity have isolated ground states and to study their properties.
- [44] arXiv:2508.15441 (replaced) [pdf, other]
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Title: Lorentzian Cheeger-Gromov convergence and temporal functionsComments: Sharpening of Theorem 1.1 and new discussion in Remark 5.22. Minor modifications including corrections in the statement of Prop. 3.13 and Remark 4.6. Two new references. 57 pages, 5 figuresSubjects: Differential Geometry (math.DG); General Relativity and Quantum Cosmology (gr-qc)
Uniqueness (up to isometries) and existence of limits are analyzed in the context of Cheeger-Gromov convergence of spacetimes. To face the non-compactness of the vector isometry group in the semi-Riemanian setting, standard \em{pointed} convergence is strenghtened to \em{anchored} convergence (which requires the convergence of a timelike direction in the Lorenzian case). Then, a local isometry between the neighborhoods of the basepoints is found, and extended globally under geodesic completeness and simple connectedness. In spacetimes, by using Cauchy temporal functions as both strengthenings of the anchor and tools to ``Wick rotate'' metrics, a new notion of convergence for globally hyperbolic spacetimes (including the case of timelike boundaries) is introduced. The machinery of Riemannian Cheeger-Gromov theory becomes applicable after revisiting the tools related to time functions and studying their connections with Sormani-Vega null distance. In particular, several results with interest on its own right are obtained such as: time functions are locally Lipschitz up to rescaling, global and local characterizations of $h$-steep functions, independence of steepness and $h$-steepness for temporal functions, compatibility of both conditions for Cauchy temporal functions, and the stability of the latter.
- [45] arXiv:2508.18083 (replaced) [pdf, html, other]
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Title: GWTC-4.0: Population Properties of Merging Compact BinariesThe LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration: A. G. Abac, I. Abouelfettouh, F. Acernese, K. Ackley, C. Adamcewicz, S. Adhicary, D. Adhikari, N. Adhikari, R. X. Adhikari, V. K. Adkins, S. Afroz, D. Agarwal, M. Agathos, M. Aghaei Abchouyeh, O. D. Aguiar, S. Ahmadzadeh, L. Aiello, A. Ain, P. Ajith, T. Akutsu, S. Albanesi, R. A. Alfaidi, A. Al-Jodah, C. Alléné, A. Allocca, S. Al-Shammari, P. A. Altin, S. Alvarez-Lopez, O. Amarasinghe, A. Amato, C. Amra, A. Ananyeva, S. B. Anderson, W. G. Anderson, M. Andia, M. Ando, T. Andrade, M. Andrés-Carcasona, T. Andrić, J. Anglin, S. Ansoldi, J. M. Antelis, S. Antier, M. Aoumi, E. Z. Appavuravther, S. Appert, S. K. Apple, K. Arai, A. Araya, M. C. Araya, M. Arca Sedda, J. S. Areeda, L. Argianas, N. Aritomi, F. Armato, S. Armstrong, N. Arnaud, M. Arogeti, S. M. Aronson, K. G. Arun, G. Ashton, Y. Aso, M. Assiduo, S. Assis de Souza Melo, S. M. Aston, P. Astone, F. Attadio, F. Aubin, K. AultONeal, G. Avallone, S. Babak, F. Badaracco, C. Badger, S. Bae, S. Bagnasco, E. Bagui, L. Baiotti, R. Bajpai, T. Baka, T. Baker, M. Ball, G. Ballardin, S. W. Ballmer, S. Banagiri, B. Banerjee, D. Bankar, T. M. Baptiste, P. Baral, J. C. Barayoga, B. C. Barish, D. Barker, N. Barman, P. Barneo, F. Barone, B. Barr, L. Barsotti, M. BarsugliaComments: As part of the Astrophysical Journal Letters Focus Issue on the Gravitational Wave Transient CatalogSubjects: High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc)
We detail the population properties of merging compact objects using 158 mergers from the cumulative Gravitational-Wave Transient Catalog 4.0, which includes three types of binary mergers: binary neutron star, neutron star--black hole binary, and binary black hole mergers. We resolve multiple over- and under-densities in the black hole mass distribution: features persist at primary masses of $10\,M_\odot$ and $35\,M_\odot$ with a possible third feature at $\sim 20\,M_\odot$. These are departures from an otherwise power-law-like continuum that steepens above $35\,M_\odot$. Binary black holes with primary masses near $10\,M_\odot$ are more likely to have less massive secondaries, with a mass ratio distribution peaking at $q = 0.74^{+0.13}_{-0.13}$, potentially a signature of stable mass transfer during binary evolution. Black hole spins are inferred to be non-extremal, with 90\% of black holes having $\chi < 0.57$, and preferentially aligned with binary orbits, implying many merging binaries form in isolation. However, we find a significant fraction, 0.24--0.42, of binaries have negative effective inspiral spins, suggesting many could be formed dynamically in gas-free environments. We find evidence for correlation between effective inspiral spin and mass ratio, though it is unclear if this is driven by variation in the mode of the distribution or the width. (Abridged)