Tootfinder

A leading gravitational wave observatory recently detected ripples in spacetime that scientists say came from the collision of a dead, superdense stellar remnant and an unknown object.
LIGO-Virgo-KAGRA detected a unique gravitational wave signal in May 2023, just days after the observatory resumed operations following some upgrades that reduced the amount of noise in the detector.
The signal is dubbed GW230529 for short.
The gravitational wave signal travelled 650 million…

This https://arxiv.org/abs/2402.05049 has been replaced.
link: https://scholar.google.com/scholar?q=a

Symplectic mechanics of relativistic spinning compact bodies II.: Canonical formalism in the Schwarzschild spacetime
This work constitutes the second part of a series of studies that aim to utilise tools from Hamiltonian mechanics to investigate the motion of an extended body in general relativity. The first part of this work [Refs. [1, 2]] constructed a ten-dimensional, covariant Hamiltonian framework encompassing all the linear-in-spin corrections to the geodesic motion in arbitrary spacetime. This framework was proven to be integrable in the Schwarzschild and Kerr spacetimes, specifically. The present work…

This https://arxiv.org/abs/2404.11392 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Quasinormal Modes of Bardeen Black Hole in 5-dimensional Gauss-Bonnet Gravity
This study addressed the scalar field quasinormal ringing behavior of black holes. We investigated scalar field perturbations in Bardeen black hole spacetime in 5-dimensional Einstein-Gauss-Bonnet (EGB) gravity. Using the 3rd-order WKB approximation and the finite-difference method, we computed the frequency of quasinormal modes (QNMs) in the spacetime background. The calculations demonstrated that the real part of the QNMs $ω$ increased, whereas the imaginary part decreased with increase in t…

This https://arxiv.org/abs/2404.03123 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_…

Constraints on the spacetime variation of the fine-structure constant using DESI emission-line galaxies
We present strong constraints on the spacetime variation of the fine-structure constant $α$ using the Dark Energy Spectroscopic Instrument (DESI). In this pilot work, we utilize $\sim110,000$ galaxies with strong and narrow O III $λλ$4959,5007 emission lines to measure the relative variation $Δα/α$ in space and time. The O III doublet is arguably the best choice for this purpose owing to its wide wavelength separation between the two lines and its strong emission in many galaxies. Our gal…

This https://arxiv.org/abs/2012.02266 has been replaced.
link: https://scholar.google.com/scholar?q=a

Four spacetime dimensional simulation of rheological waves in solids and the merits of thermodynamics
The recent results attained from a thermodynamically conceived numerical scheme applied on wave propagation in viscoelastic/rheological solids are generalized here, both in the sense that the scheme is extended to four spacetime dimensions and in the aspect of the virtues of a thermodynamical approach. Regarding the scheme, the arrangement of which quantity is represented where in discretized spacetime, including the question of appropriately realizing the boundary conditions, is nontrivial. In…

This https://arxiv.org/abs/2402.13894 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_mat…

Quantum particle localization observables on Cauchy surfaces of Minkowski spacetime and their causal properties
We introduce and study a general notion of spatial localization on spacelike smooth Cauchy surfaces of quantum systems in Minkowski spacetime. The notion is constructed in terms of a coherent family of normalized POVMs, one for each said Cauchy surface. We prove that a family of POVMs of this type automatically satisfies a causality condition which generalizes Castrigiano's one and implies it when restricting to flat spacelike Cauchy surfaces. As a consequence no conflict with Hegerfeldt's theo…

This https://arxiv.org/abs/2402.09686 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Lorentz violation induces isospectrality breaking in Einstein-Bumblebee gravity theory
In this paper, we investigate the quasinormal modes (QNMs) of a Lorentz-violating spacetime, factoring in a cosmological constant, within the framework of Einstein-Bumblebee gravity. Our findings reveal that the interaction of spacetime with an anisotropic bumblebee field imparts distinct contributions to the axial and polar sectors of the vector perturbations. This subsequently breaks the isospectrality typically observed in vector modes. Numerical evidence strongly indicates isospectral break…

Quadratic Rastall Gravity: from low-mass HESS J1731-347 to high-mass PSR J0952-0607 pulsars
Waleed El Hanafy
https://arxiv.org/abs/2404.04143 https://

Quadratic Rastall Gravity: from low-mass HESS J1731-347 to high-mass PSR J0952-0607 pulsars
Similar to Rastall gravity we introduce matter-geometry nonminimal coupling which is proportional to the gradient of quadratic curvature invariants. Those are mimicking the conformal trace anomaly when backreaction of the quantum fields to a curved spacetime geometry is considered. We consider a static spherically symmetric stellar structure with anisotropic fluid and Krori-Barua metric potentials model to examine the theory. Confronting the model with NICER+XMM-Newton observational constraints…

This https://arxiv.org/abs/2308.15574 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

On the improved dynamics approach in loop quantum black holes
In this paper, we consider the Böhmer-Vandersloot (BV) model of loop quantum black holes obtained from the improved dynamics approach. We adopt the Saini-Singh gauge, in which it was found analytically that the BV spacetime is geodesically complete. We show that black/white hole horizons do not exist in this geodesically complete spacetime. Instead, there exists only an infinite number of transition surfaces, which always separate trapped regions from anti-trapped ones. Comments on the improve…

Fermionic vacuum stresses in models with toroidal compact dimensions
A. A. Saharian, R. M. Avagyan, G. H. Harutyunyan, G. H. Nikoghosyan
https://arxiv.org/abs/2403.04684

Fermionic vacuum stresses in models with toroidal compact dimensions
We investigate vacuum expectation value of the energy-momentum tensor for a massive Dirac field in flat spacetime with a toroidal subspace of a general dimension. Quasiperiodicity conditions with arbitrary phases are imposed on the field operator along compact dimensions. These phases are interpreted in terms of magnetic fluxes enclosed by compact dimensions. The equation of state in the uncompact subspace is of the cosmological constant type. It is shown that, in addition to the diagonal compo…

Exterior stability of Minkowski spacetime with borderline decay
Dawei Shen
https://arxiv.org/abs/2405.00735 https://arxiv.org/pdf/240…

Exterior stability of Minkowski spacetime with borderline decay
In 1993, the global stability of Minkowski spacetime has been proven in the celebrated work of Christodoulou and Klainerman \cite{Ch-Kl}. In 2003, Klainerman and Nicolò \cite{Kl-Ni} revisited Minkowski stability in the exterior of an outgoing null cone. In \cite{Shen23}, the author extended the results of \cite{Ch-Kl} to minimal decay assumptions. In this paper, we prove that the exterior stability of Minkowski holds with decay which is borderline compared to the minimal decay considered in \c…

An axiomatisation of the temporal logic of two dimensional Minkowski spacetime
Robin Hirsch
https://arxiv.org/abs/2405.00618 https://…

An axiomatisation of the temporal logic of two dimensional Minkowski spacetime
We define temporal axioms that are sound and complete for the temporal validities over $(\reals^2, <)$.

Constraints on the spacetime variation of the fine-structure constant using DESI emission-line galaxies
Linhua Jiang, Zhiwei Pan, Jessica Nicole Aguilar, Steven Ahlen, Robert Blum, David Brooks, Todd Claybaugh, Axel de la Macorra, Arjun Dey, Peter Doel, Kevin Fanning, Simone Ferraro, Jaime E. Forero-Romero, Enrique Gaztanaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Klaus Honscheid, Stephanie Juneau, Martin Landriau, Laurent Le Guillou, Michael Levi, Marc Manera, Ramon Miquel, John M…

Constraints on the spacetime variation of the fine-structure constant using DESI emission-line galaxies
We present strong constraints on the spacetime variation of the fine-structure constant $α$ using the Dark Energy Spectroscopic Instrument (DESI). In this pilot work, we utilize $\sim110,000$ galaxies with strong and narrow O III $λλ$4959,5007 emission lines to measure the relative variation $Δα/α$ in space and time. The O III doublet is arguably the best choice for this purpose owing to its wide wavelength separation between the two lines and its strong emission in many galaxies. Our gal…

Spinoptics in a curved spacetime
Valeri P. Frolov
https://arxiv.org/abs/2405.01777 https://arxiv.org/pdf/2405.01777

Spinoptics in a curved spacetime
In this paper we study propagation of the high frequency electromagnetic waves in a curved spacetime. We discuss a so call spinoptics approach which generalizes a well known geometric optics approximation and allows one to take into account spin-dependent corrections. A new element proposed in this work is the use of effective action which allows one to derive spinoptics equations. This method is simpler and more transparent than the earlier proposed methods. It is explicitly covariant and can …

Global existence and geometry of constant mass aspect function foliation in perturbed Schwarzschild spacetime
Pengyu Le
https://arxiv.org/abs/2404.17137 https://arxiv.org/pdf/2404.17137
arXiv:2404.17137v1 Announce Type: new
Abstract: The constant mass function foliation has been shown useful for studying the null Penrose inequality on a null hypersurface, because of the monotonicity formula of Hawking mass along such a foliation. In this paper, we show the global existence of the constant mass aspect function foliation on a nearly spherically symmetric incoming null hypersurface, emanating from a spacelike surface near the apparent horizon to the past null infinity in a vacuum perturbed Schwarzschild spacetime. Moreover, we study the geometry of the constant mass aspect function foliation, by comparing with the spherically symmetric foliation in the Schwarzschild spacetime. The knowledge about the geometry of the foliation is essential for investigating the perturbation of the constant mass aspect function foliation, which is the core in the application to the null Penrose inequality for a vacuum perturbed Schwarzschild spacetime.

This https://arxiv.org/abs/2307.15140 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_…

Toward General-Relativistic Magnetohydrodynamics Simulations in Stationary Non-Vacuum Spacetimes
Accretion of magnetized gas on compact astrophysical objects such as black holes has been successfully modeled using general relativistic magnetohydrodynamic (GRMHD) simulations. These simulations have largely been performed in the Kerr metric, which describes the spacetime of a vacuum and stationary spinning black hole (BH) in general relativity (GR). The simulations have revealed important clues on the physics of accretion and jets near the BH event horizon, and have been used to interpret re…

Tessellation and interactive visualization of four-dimensional spacetime geometries
Philip Claude Caplan
https://arxiv.org/abs/2403.19036 https://

Tessellation and interactive visualization of four-dimensional spacetime geometries
This paper addresses two problems needed to support four-dimensional ($3d + t$) spacetime numerical simulations. The first contribution is a general algorithm for producing conforming spacetime meshes of moving geometries. Here, the surface points of the geometry are embedded in a four-dimensional space as the geometry moves in time. The geometry is first tessellated at prescribed time steps and then these tessellations are connected in the parameter space of each geometry entity to form tetrah…

On the inefficiency of fermion level-crossing under the parity-violating spin-2 gravitational field
Kohei Kamada, Jun'ya Kume
https://arxiv.org/abs/2404.19726 https://arxiv.org/pdf/2404.19726
arXiv:2404.19726v1 Announce Type: new
Abstract: Gravitational chiral anomaly connects the topological charge of spacetime and the chirality of fermions. It has been known that the chirality is carried by the particles (or the excited states) and also by vacuum. While the gravitational anomaly equation has been applied to cosmology, distinction between these two contributions has been rarely discussed. In the study of gravitational leptogenesis, for example, lepton asymmetry associated with the chiral gravitational waves sourced during inflation is evaluated only by integrating the anomaly equation. How these two contributions are distributed has not been seriously investigated. Meanwhile, a dominance of vacuum contribution is observed in some specific types of Bianchi spacetime with parity-violating gravitational fields, whose application to cosmology is not straightforward. One may wonder whether such a vacuum dominance takes place also in the system with chiral gravitational waves around the flat background, which is more suitable for application to realistic cosmology. In this work, we apply an analogy between U(1) electromagnetism and the weak gravity to the spacetime that resembles the one considered in the gravitational leptogenesis scenario. This approach allows us to obtain intuitive understanding of the fermion chirality generation under the parity-violating spin-2 gravitational field. By assuming the emergence of Landau level-like dispersion relation in our setup, we conjecture that level-crossing does not seem to be efficient while the charge accumulation in the vacuum likely takes place. Phenomenological implication is also discussed in the context of gravitational leptogenesis.

This https://arxiv.org/abs/2305.04862 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hep…

AdS/CFT Correspondence in Hyperbolic Lattices
The celebrated anti-de Sitter/conformal field theory (AdS/CFT) correspondence1-3, also known as the gravity/gauge duality, posits a dual relationship between the quantum gravity in an AdS spacetime and the CFT defined on its lower-dimensional boundary. This correspondence not only offers profound insights into the enigmatic nature of quantum gravity but also shows mighty power in addressing strongly-correlated systems. However, despite its importance in contemporary physics, the AdS/CFT corresp…

This https://arxiv.org/abs/2307.13443 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Decoherence and entropy generation at one loop in the inflationary de Sitter spacetime for Yukawa interaction
The decoherence mechanism is believed to be possibly connected to the quantum to classical transition of the primordial cosmological perturbations in the early universe. In this paper, we extend our previous analysis on decoherence in a fermion and scalar quantum field theory coupled via the Yukawa interaction in the Minkowski spacetime, to the inflationary de Sitter background. We treat the scalar field as the system and the fermions as the environment, and both the fields are taken to be mass…

This https://arxiv.org/abs/2310.18857 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_qu…

Toward Local Madelung Mechanics in Spacetime
It has recently been shown that relativistic quantum theory leads to a local interpretation of quantum mechanics wherein the universal wavefunction in configuration space is entirely replaced with an ensemble of local fluid equations in spacetime. For want of a fully relativistic quantum fluid treatment, we develop a model using the nonrelativistic Madelung equations, and obtain conditions for them to be local in spacetime. Every particle in the Madelung fluid is equally real, and has a definit…

Gravitational field due a moving Schwarzschild object
Ranchhaigiri Brahma, A. K. Sen
https://arxiv.org/abs/2405.01932 https://arxiv.o…

Gravitational field due a moving Schwarzschild object
In this paper we analyze the spacetime geometry due to a Schwarzschild object having accelerated motion. In the beginning we investigated the gravitational field due to a uniformly moving Schwarzschild object and obtained the spacetime line element for such an object. After analyzing the necessary boundary conditions the obtained line element is found to be consistent. Next we extended our work to a uniformly accelerated Schwarzschild object. In that case we obtained the spacetime line element …

Constraints on the spacetime variation of the fine-structure constant using DESI emission-line galaxies
Linhua Jiang, Zhiwei Pan, Jessica Nicole Aguilar, Steven Ahlen, Robert Blum, David Brooks, Todd Claybaugh, Axel de la Macorra, Arjun Dey, Peter Doel, Kevin Fanning, Simone Ferraro, Jaime E. Forero-Romero, Enrique Gaztanaga, Satya Gontcho A Gontcho, Gaston Gutierrez, Klaus Honscheid, Stephanie Juneau, Martin Landriau, Laurent Le Guillou, Michael Levi, Marc Manera, Ramon Miquel, John M…

Constraints on the spacetime variation of the fine-structure constant using DESI emission-line galaxies
We present strong constraints on the spacetime variation of the fine-structure constant $α$ using the Dark Energy Spectroscopic Instrument (DESI). In this pilot work, we utilize $\sim110,000$ galaxies with strong and narrow O III $λλ$4959,5007 emission lines to measure the relative variation $Δα/α$ in space and time. The O III doublet is arguably the best choice for this purpose owing to its wide wavelength separation between the two lines and its strong emission in many galaxies. Our gal…

Q: "What would vacuum decay look like if it occurred far away and spread towards us?"
A: "If a patch of spacetime anywhere in the universe were to change state, the change would radiate from there to the rest of the universe as a sort of “shock front” that propagated at the speed of light. That means we wouldn’t see it coming. We wouldn’t see any effect from it at all, and when it washed over us, we’d simply cease to exist."
God: ARE YOU NOT ENTERTAINED?

This https://arxiv.org/abs/2403.00544 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Carroll swiftons
We construct Carroll-invariant theories with fields propagating outside the Carroll lightcone, i.e., at a speed strictly greater than zero (`Carroll swiftons'). We first consider models in flat Carroll spacetime in general dimensions, where we present scalar and vector Carroll swifton field theories. We then turn to the coupling to gravity and achieve in particular in two dimensions a Carroll invariant scalar swifton by coupling it suitably to Carroll dilaton gravity. Its backreaction on the ge…

Floquet engineered inhomogeneous quantum chaos in critical systems
Bastien Lapierre, Tokiro Numasawa, Titus Neupert, Shinsei Ryu
https://arxiv.org/abs/2405.01642

Floquet engineered inhomogeneous quantum chaos in critical systems
We study universal chaotic dynamics of a large class of periodically driven critical systems described by spatially inhomogeneous conformal field theories. By employing an effective curved spacetime approach, we show that the onset of quantum chaotic correlations, captured by the Lyapunov exponent of out-of-time-order correlators (OTOCs), is set by the Hawking temperature of emergent Floquet horizons. Furthermore, scrambling of quantum information is shown to be strongly inhomogeneous, leading …

Convex surfaces with prescribed induced metrics in anti-de Sitter spacetimes
Qiyu Chen, Jean-Marc Schlenker
https://arxiv.org/abs/2405.01912 https://

Convex surfaces with prescribed induced metrics in anti-de Sitter spacetimes
Let $S$ be a closed surface of genus at least $2$, let $h$ be a smooth metric of curvature $K<-1$ on $S$, and let $h_0$ be a hyperbolic metric on $S$. We show that there exists a unique quasifuchsian AdS spacetime with left metric isotopic to $h_0$, containing a past-convex Cauchy surface with induced metric isotopic to $h$.

This https://arxiv.org/abs/2311.10060 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Unconventional conformal invariance of maximal depth partially massless fields on $dS_{4}$ and its relation to complex partially massless SUSY
Deser and Waldron have shown that maximal depth partially massless theories of higher (integer) spin on four-dimensional de Sitter spacetime ($dS_{4}$) possess infinitesimal symmetries generated by the conformal Killing vectors of $dS_{4}$. However, it was later shown by Barnich, Bekaer, and Grigoriev that these theories are not invariant under the conformal algebra $so(4,2)$. To get some insight into these seemingly contradicting results we write down the full set of infinitesimal transformati…

This https://arxiv.org/abs/2401.16297 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Radial Gravitational Collapse Causes Timelike Incompleteness
We show that a globally hyperbolic spacetime containing a trapped surface and satisfying the strong energy condition and a condition on certain radial tidal forces must be timelike geodesically incomplete. This constitutes a "timelike" version of Penrose's celebrated singularity theorem. Recall that the latter concludes that certain spacetimes are null incomplete, providing the first theoretical evidence that black holes actually exist in our Universe. By concluding timelike instead of null inc…

This https://arxiv.org/abs/2402.18529 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_…

High angular momentum hot differentially rotating equilibrium star evolutions in conformally flat spacetime
The conformal flatness approximation to the Einstein equations has been successfully used in many astrophysical applications such as initial data constructions and dynamical simulations. Although it has been shown that full general relativistic strongly differentially rotating equilibrium models deviate by at most a few percent from their conformally flat counterparts, whether those conformally flat solutions remain stable has not been fully addressed. To further understand the limitations of t…

This https://arxiv.org/abs/2402.18655 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Modular flow in JT gravity and entanglement wedge reconstruction
It has been shown in recent works that JT gravity with matter with two boundaries has a type II$_\infty$ algebra on each side. As the bulk spacetime between the two boundaries fluctuates in quantum nature, we can only define the entanglement wedge for each side in a pure algebraic sense. As we take the semiclassical limit, we will have a fixed long wormhole spacetime for a generic partially entangled thermal state (PETS), which is prepared by inserting heavy operators on the Euclidean path inte…

This https://arxiv.org/abs/2402.19140 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Globally hyperbolic evaporating black hole and the information loss issue
We discuss the information loss issue for completely evaporating black holes in the context of a globally hyperbolic spacetime that maintains unchanged the entire semiclassical picture except for the ``last evaporation breath,'' which pertains to full quantum gravity. Even though observers outside the black hole cannot access information that enters the horizon, there is no actual loss of information since it is carried over from one Cauchy surface to the next (provided the evolution is unitary…

This https://arxiv.org/abs/2403.12899 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Comments Concerning a Hypothetical Mesoscopic Dark Dimension
Motivated by string-theoretic swampland conjectures, the existence of a dark fifth dimension, whose size is roughly 1 -- 10 microns, has been proposed. A great deal of supporting evidence has been presented, and definitive experimental tests are likely to be carried out. The basic idea is that the four-dimensional spacetime that we observe lives on a brane that is localized in the dark dimension. This short note points out that there are two distinct ways to realize such a scenario in string th…

Relativistic time delay analysis of pulsar signals near ultra-compact objects
Viraj Kalsariya, Parth Bambhaniya, Pankaj S. Joshi
https://arxiv.org/abs/2405.01835

Relativistic time delay analysis of pulsar signals near ultra-compact objects
The upcoming discoveries of pulsars orbiting the center of the Milky Way will present unparalleled opportunities to examine the causal structure of the spacetime geometry of Sagittarius A*. In this paper, we investigate the fully relativistic propagation time delay of pulsar signals in the Joshi-Malafarina-Narayan (JMN-1) and Janis-Newman-Winicour (JNW) spacetimes. This delay arises basically from the spacetime curvatures in the vicinity of these ultra-compact objects, induced by the intense gr…

This https://arxiv.org/abs/2209.09997 has been replaced.
link: https://scholar.google.com/scholar?q=a

dS JT Gravity and Double-Scaled SYK
This paper pushes forward a conjecture made in [1] that a high-temperature double-scaled limit of the SYK model ($\mathrm{DSSYK}_{\infty}$) describes a de Sitter-like space. We identify a specific bulk theory which we conjecture to be dual to $\mathrm{DSSYK}_{\infty}$, namely JT gravity with positive cosmological constant (dS-JT). We focus our attention on a specific solution of dS-JT in which spacetime is a particular bounded submanifold of dS$_2$ and the profile of the dilaton coincides with …

Symmetry and pseudosymmetry properties of Vaidya-Bonner-de Sitter spacetime
Absos Ali Shaikh, Shyamal kumar Hui, Mousumi Sarkar, V. Amarendra Babu
https://arxiv.org/abs/2402.10961

Symmetry and pseudosymmetry properties of Vaidya-Bonner-de Sitter spacetime
The primary focus of the current study is to explore the geometrical properties of the Vaidya-Bonner-de Sitter (briefly, VBdS) spacetime, which is a generalization of Vaidya-Bonner spacetime, Vaidya spacetime and Schwarzschild spacetime. In this study we have shown that the VBdS spacetime describes various types of pseudosymmetric structures, including pseudosymmetry due to conformal curvature, conharmonic curvature and other curvatures. Additionally, it is shown that such a spacetime is 2-quas…

This https://arxiv.org/abs/2305.18843 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Bilocal geodesic operators as a tool of investigating the optical properties of spacetimes
In my thesis, I present one particular example of the formalism capable of describing the propagation of a family of light rays in a curved spacetime. It is based on the resolvent operator of the geodesic deviation equation for null geodesics which is known as the bilocal geodesic operator (BGO) formalism. The BGO formalism generalizes the standard treatment of light ray bundles by allowing observations extended in time or performed by a family of neighbouring observers. Furthermore, it provide…

GLANCE -- Gravitational Lensing Authenticator using Non-Modelled Cross-Correlation Exploration of Gravitational Wave Signals
Aniruddha Chakraborty, Suvodip Mukherjee
https://arxiv.org/abs/2403.03982

GLANCE -- Gravitational Lensing Authenticator using Non-Modelled Cross-Correlation Exploration of Gravitational Wave Signals
Gravitational lensing is the effect on a lightlike trajectory by the presence of matter, affecting its trajectory in spacetime. Gravitational lensing of gravitational waves can occur in geometric optics limit (when GW wavelength is much smaller than the Schwarzschild radius of the lens i.e. $λ_{GW} \ll$ R$^{\rm sc}_{\rm lens}$, multiple images with different magnifications are formed) known as strong-lensing or in wave optics limit (when the wavelength of GW is larger than the Schwarzschild ra…

The effective field theory of multi-field inflationary fluctuations
Lucas Pinol
https://arxiv.org/abs/2405.02190 https://arxiv.org/pd…

The effective field theory of multi-field inflationary fluctuations
We build an effective field theory of multi-field inflationary fluctuations based on the adiabatic perturbation and on any number of matter fluctuations in the non-adiabatic sector, without imposing extra symmetries on the latter. Focusing on terms with at most two derivatives in fields' fluctuations, we argue that taking the decoupling limit -- in which gravitational interactions are neglected -- is justified in a quasi de Sitter spacetime with slow-varying Hubble scale. With these working hyp…

Neutrinos as possible probes for quantum gravity
Marco Danilo Claudio Torri, Lino Miramonti
https://arxiv.org/abs/2404.04076 https://…

Neutrinos as possible probes for quantum gravity
In this paper, we aim to explore the interplay between neutrinos and quantum gravity, illustrating some proposals about the use of these particles as probes for the supposed quantized structure of spacetime. The residual signatures of a more fundamental theory of quantum gravity can manifest themselves modifying the free particle dispersion relations and the connected velocity. In neutrino sector these supposed effects can modify the time of flight for astrophysical particles with different ene…

Thermodynamic formulation of vacuum energy density in flat spacetime and potential implications for the cosmological constant
Andr\'e LeClair
https://arxiv.org/abs/2404.02350 …

Thermodynamic formulation of vacuum energy density in flat spacetime and potential implications for the cosmological constant
We propose a thermodynamical definition of the vacuum energy density $ρ_{\rm vac}$, defined as $\langle 0| T_{μν} |0\rangle = - ρ_{\rm vac} \, g_{μν}$, in quantum field theory in flat Minkowski space in $D$ spacetime dimensions, which can be computed in the limit of high temperature, namely in the limit $β= 1/T \to 0$. It takes the form $ρ_{\rm vac} = {\rm const} \cdot m^D$ where $m$ is a fundamental mass scale and ${\rm "const"}$ is a computable constant which can be positive…

This https://arxiv.org/abs/2310.14653 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Black holes in massive Einstein-dilaton gravity
In this paper, we focus on massive Einstein-dilaton gravity including the coupling of dilaton scalar field to massive graviton terms, and then derive static and spherically symmetric solutions of dilatonic black holes in four dimensional spacetime. We find that the dilatonic black hole could possess two horizons (event and cosmological), extreme (Nariai) and naked singularity for the suitably fixed parameters. In addition, we investigate thermodynamic properties of these dilatonic black holes, …

Characterizations of generalized Robertson-Walker spacetimes concerning gradient solitons
Krishnendu De, Mohammad Nazrul Islam Khan, Uday Chand De
https://arxiv.org/abs/2402.15339

Characterizations of generalized Robertson-Walker spacetimes concerning gradient solitons
In this article, we examine gradient type Ricci solitons and $(m,τ)$-quasi Einstein solitons in generalized Robertson-Walker ($GRW$) spacetimes. Besides, we demonstrate that in this scenario the $GRW$ spacetime presents the Robertson-Walker ($RW$) spacetime and the perfect fluid ($PF$) spacetime presents the phantom era. Consequently, we show that if a $GRW$ spacetime permits a gradient $τ$- Einstein solitons, then it also represents a $PF$ spacetime under certain condition.

This https://arxiv.org/abs/2310.05700 has been replaced.
link: https://scholar.google.com/scholar?q=a

Ambient temperature versus ambient acceleration in the circular motion Unruh effect
It is well known that the experience of a linearly accelerated observer with acceleration $a$, interacting with a massless scalar field in its vacuum state in $3+1$ Minkowski spacetime, is identical to that of a static observer interacting with a massless scalar field in a thermal state of temperature $a/2π$ in $3+1$ Minkowski spacetime. We study the robustness of this duality by comparing an observer undergoing circular motion in a thermal bath with an observer that undergoes circular motion …

This https://arxiv.org/abs/2307.16841 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Prospects for Future Experimental Tests of Gravity with Black Hole Imaging: Spherical Symmetry
Astrophysical black holes (BHs) are universally expected to be described by the Kerr metric, a stationary, vacuum solution of general relativity (GR). Indeed, by imaging M87$^\star$ and Sgr A$^\star$ and measuring the size of their shadows, we have substantiated this hypothesis through successful null tests. Here we discuss the potential of upcoming improved imaging observations in constraining deviations of the spacetime geometry from that of a Schwarzschild BH (the nonspinning, vacuum GR solu…

Cutoff Scale of Quadratic Gravity from Quantum Focusing Conjecture
Takamasa Kanai, Kengo Maeda, Toshifumi Noumi, Daisuke Yoshida
https://arxiv.org/abs/2405.01296

Cutoff Scale of Quadratic Gravity from Quantum Focusing Conjecture
We derive the cutoff length scale of the quadratic gravity in $d \geq 5$ dimensional spacetime by demanding that the quantum focusing conjecture for the smeared quantum expansion holds at the classical level. The cutoff scale has different dependence on the spacetime dimension depending on the sign of the coupling constant of the quadratic gravity. We also investigate a concrete example of the 5-dimensional Schwarzschild spacetime and directly confirm that the quantum focusing conjecture holds …

A bonafide model of structure formation from gravitational collapse
Koushiki, Dipanjan Dey, Pankaj S. Joshi
https://arxiv.org/abs/2404.03901 https://

A bonafide model of structure formation from gravitational collapse
This paper explores the cosmological implications of a scalar field with a specific potential, crucial for achieving the final equilibrium state of gravitational collapse. We consider a system with two fluids: minimally coupled matter representing dust-like dark matter and a scalar field acting as dark energy. Our model, akin to the top-hat collapse model, focuses on isolated over-dense regions within a closed FLRW metric, while the background follows a flat FLRW metric. We analyze spacetime co…

High angular momentum hot differentially rotating equilibrium star evolutions in conformally flat spacetime
Patrick Chi-Kit Cheong, Nishad Muhammed, Pavan Chawhan, Matthew D. Duez, Francois Foucart
https://arxiv.org/abs/2402.18529

High angular momentum hot differentially rotating equilibrium star evolutions in conformally flat spacetime
The conformal flatness approximation to the Einstein equations has been successfully used in many astrophysical applications such as initial data constructions and dynamical simulations. Although it has been shown that full general relativistic strongly differentially rotating equilibrium models deviate by at most a few percents from their conformally flat counterparts, whether those solutions share the same dynamical stabilities has not been fully addressed. To further understand the limitatio…

Holographic Carrollian Conformal Scalars
Xavier Bekaert, Andrea Campoleoni, Simon Pekar
https://arxiv.org/abs/2404.02533 https://arxi…

Holographic Carrollian Conformal Scalars
We provide holographic realisations in Minkowski spacetime of a free conformal Carrollian scalar field living at null infinity. To this end, we first show that the electric and magnetic limits of a relativistic conformal scalar are equivalent and we study the representation of the Carroll, Poincaré and BMS algebras that is realised on the resulting solution space. We then realise it as a quotient of the solution space of a free massless scalar in Minkowski spacetime with unusual falloff, in fu…

This https://arxiv.org/abs/2403.13058 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Perturbative photon escape cones in the Kerr spacetime
We consider the perturbative, fully explicit, analytical behaviour of photon escape cones in the Kerr spacetime. When one conducts the fully general non-perturbative Kerr analysis, one quickly finds that one must at some point appeal to numerical and/or graphical methods. Herein we find that we are able to say much more if we look at the slow rotation limit (i.e., $a \ll m$). Indeed we give explicit and tractable expressions for the first and second order (in $a$) contributions to both the shap…

This https://arxiv.org/abs/2403.13058 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Perturbative photon escape cones in the Kerr spacetime
We consider the perturbative, fully explicit, analytical behaviour of photon escape cones in the Kerr spacetime. When one conducts the fully general non-perturbative Kerr analysis, one quickly finds that one must at some point appeal to numerical and/or graphical methods. Herein we find that we are able to say much more if we look at the slow rotation limit (i.e., $a \ll m$). Indeed we give explicit and tractable expressions for the first and second order (in $a$) contributions to both the shap…

Relativistic and nonrelativistic Landau levels for the noncommutative quantum Hall effect with anomalous magnetic moment in a conical G\"odel-type spacetime
R. R. S. Oliveira
https://arxiv.org/abs/2402.15720

Relativistic and nonrelativistic Landau levels for the noncommutative quantum Hall effect with anomalous magnetic moment in a conical Gödel-type spacetime
In this paper, we analyze the relativistic and nonrelativistic energy spectra (fermionic Landau levels) for the noncommutative quantum Hall effect with anomalous magnetic moment in the conical Gödel-type spacetime in (2+1)-dimensions, where such spacetime is the combination of the flat Gödel-type spacetime with a cosmic string (conical gravitational topological defect). To analyze these energy spectra, we start from the noncommutative Dirac equation with minimal and nonminimal couplings in po…

Relativistic and nonrelativistic Landau levels for the noncommutative quantum Hall effect with anomalous magnetic moment in a conical G\"odel-type spacetime
R. R. S. Oliveira
https://arxiv.org/abs/2402.15720

Relativistic and nonrelativistic Landau levels for the noncommutative quantum Hall effect with anomalous magnetic moment in a conical Gödel-type spacetime
In this paper, we analyze the relativistic and nonrelativistic energy spectra (fermionic Landau levels) for the noncommutative quantum Hall effect with anomalous magnetic moment in the conical Gödel-type spacetime in (2+1)-dimensions, where such spacetime is the combination of the flat Gödel-type spacetime with a cosmic string (conical gravitational topological defect). To analyze these energy spectra, we start from the noncommutative Dirac equation with minimal and nonminimal couplings in po…

Research on high-frequency quasi-periodic oscillations in generalized black-bounce spacetime
Jianbo Lu, Shining Yang, Yuying Zhang, Liu Yang, Mou Xu
https://arxiv.org/abs/2403.19942

Research on high-frequency quasi-periodic oscillations in generalized black-bounce spacetime
In order to solve problem of spacetime singularity in theoretical physics, researchers proposed the regular black holes (BH). The generalized black-bounce (GBB) spacetime, as a unified treatment of distinct kinds of geometries in the framework of general relativity (e.g. regular BH and wormholes), has been extensively studied. Firstly, we derive to give the explicit forms of Lagrangian for a nonlinear electromagnetic field and potential for a non-canonical phantom field in the action of gravita…

This https://arxiv.org/abs/2305.16570 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Holography and the Page curve of an evaporating black hole
Our goal is to establish a refined version of the Page curve capable of describing an evaporating black hole in an asymptotically flat spacetime. The Page curve traditionally exhibits a singular point, often interpreted as an indication of the Hawking-Page phase transition which occurs for an evaporating black hole in an asymptotically AdS spacetime. Conversely, an evaporating black hole in an asymptotically flat spacetime is not expected to undergo such a transition. Therefore, we require a sm…

This https://arxiv.org/abs/2312.06590 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

A Lensing-Band Approach to Spacetime Constraints
General relativity's prediction that all black holes are described by the Kerr metric, irrespective of their size, can now be empirically tested using electromagnetic observations of supermassive black holes and gravitational waves from mergers of stellar-mass black holes. In this work, we focus on the electromagnetic side of this test and quantify the constraining power of very-long-baseline-interferometry (VLBI) observations of emission generated by hot gas surrounding supermassive black hole…

Photon rings in the metamaterial analog of a gravitomagnetic monopole
A. Parvizi, H. Forghani-Ramandy, E. Rahmani, M. Nouri-Zonoz
https://arxiv.org/abs/2405.01764

Photon rings in the metamaterial analog of a gravitomagnetic monopole
After studying null geodesics in the equatorial plane in NUT spacetime, we show that there are unstable photon rings in this plane. Next we transform the metric of this plane to the isotropic coordinates and introduce its equivalent index of refraction. Using the analog gravity ideas we assign this index of refraction to a metamaterial analog of this plane, and by ray-tracing simulation find its photon rings. Furthermore, we employ wave optics to solve Maxwell's equations numerically for electr…

Circular geodesic orbits in the equatorial plane of a charged rotating disc of dust
David Rumler
https://arxiv.org/abs/2405.01998 https://

Circular geodesic orbits in the equatorial plane of a charged rotating disc of dust
Equatorial circular geodesic orbits of neutral test particles in the exterior spacetime of the charged rotating disc of dust are analyzed in dependence of its specific charge and a relativity parameter. The charged rotating disc of dust is an axisymmetric, stationary solution of the Einstein-Maxwell equations in terms of a post-Newtonian expansion. In particular, photon, marginally bound and marginally stable orbits are discussed. It turns out that general formulae in closed form for angular ve…

Geometrisation of Fermions in Flat Spacetimes
William J. Leigh
https://arxiv.org/abs/2404.03360 https://arxiv.org/pdf/2404.03360

Geometrisation of Fermions in Flat Spacetimes
Requiring physical consistency in a classical flat spacetime geometrisation of fermions is shown to suggest the introduction of torsion. A resulting simple model for that torsion produces a localised quantum-like particle as a solution of a spinor identity that closely resembles the Dirac equation of quantum electrodynamics. All relevant integrals involving solutions of the spinor identity converge and require that the spin, which is no longer intrinsic but arises from circulating currents, be …

This https://arxiv.org/abs/2307.14156 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Spontaneous Deformation of an AdS Spherical Black Hole
In this study, we investigate the real-time dynamics during the spontaneous deformation of an unstable spherical black hole in asymptotically anti-de Sitter (AdS) spacetime. For the initial value, the static solutions with spherical symmetry are obtained numerically, revealing the presence of a spinodal region in the phase diagram. From the linear stability analysis, we find that only the central part of such a thermodynamically unstable spinodal region leads to the emergence of a type of axial…

This https://arxiv.org/abs/2312.17313 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Emerging entanglement on network histories
We show that quantum fields confined to Lorentzian histories of freely falling networks in Minkowski spacetime probe entanglement properties of vacuum fluctuations that extend unrestricted across spacetime regions. Albeit instantaneous field configurations are localized on one-dimensional edges, angular momentum emerges on these network histories and establish the celebrated area scaling of entanglement entropy.

This https://arxiv.org/abs/2308.10060 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

De Sitter-like configurations with asymptotic quintessence environment
We examine a spherically-symmetric class of spacetimes carrying vacuum energy, while considering the influence of an external dark energy environment represented by a non-dynamical quintessence field. Our investigation focuses on a specific set of solutions affected by this field, leading to distinct kinds of spacetime deformations, resulting in regular, singular, and wormhole solutions. We thoroughly discuss the underlying physics associated with each case and demonstrate that more complex def…

Possible Causes of False General Relativity Violations in Gravitational Wave Observations
Anuradha Gupta, K. G. Arun, Enrico Barausse, Laura Bernard, Emanuele Berti, Sajad A. Bhat, Alessandra Buonanno, Vitor Cardoso, Shun Yin Cheung, Teagan A. Clarke, Sayantani Datta, Arnab Dhani, Jose Mar\'ia Ezquiaga, Ish Gupta, Nir Guttman, Tanja Hinderer, Qian Hu, Justin Janquart, Nathan K. Johnson-McDaniel, Rahul Kashyap, N. V. Krishnendu, Paul D. Lasky, Andrew Lundgren, Elisa Maggio, Parthapr…

Possible Causes of False General Relativity Violations in Gravitational Wave Observations
General relativity (GR) has proven to be a highly successful theory of gravity since its inception. The theory has thrivingly passed numerous experimental tests, predominantly in weak gravity, low relative speeds, and linear regimes, but also in the strong-field and very low-speed regimes with binary pulsars. Observable gravitational waves (GWs) originate from regions of spacetime where gravity is extremely strong, making them a unique tool for testing GR, in previously inaccessible regions of …

This https://arxiv.org/abs/1712.10045 has been replaced.
link: https://scholar.google.com/scholar?q=a

Nonlinear stability of self-gravitating massive fields
We consider the global evolution problem for Einstein's field equations in the near-Minkowski regime and study the long-time dynamics of a massive scalar field evolving under its own gravitational field. We establish the existence of a globally hyperbolic Cauchy development associated with any initial data set that is sufficiently close to a data set in Minkowski spacetime. In addition to applying to massive fields, our theory allows us to cover metrics with slow decay in space. The strategy of…

Anomalous contribution to galactic rotation curves due to stochastic spacetime
Jonathan Oppenheim, Andrea Russo
https://arxiv.org/abs/2402.19459 https://…

Anomalous contribution to galactic rotation curves due to stochastic spacetime
We consider a proposed alternative to quantum gravity, in which the spacetime metric is treated as classical, even while matter fields remain quantum. Consistency of the theory necessarily requires that the metric evolve stochastically. Here, we show that this stochastic behaviour leads to a modification of general relativity at low accelerations. In the low acceleration regime, the variance in the acceleration produced by the gravitational field is high in comparison to that produced by the …

This https://arxiv.org/abs/2312.00363 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_hept…

Searching for discrete series representations at the late-time boundary of de Sitter
The group $SO(d+1,1)$ makes an appearance both as the conformal group of Euclidean space in $d$ dimensions and as the isometry group of de Sitter spacetime in $d+1$ dimensions. While this common feature can be taken as a hint towards holography on de Sitter space, understanding the representation theory has importance for cosmological applications where de Sitter spacetime is relevant. Among the categories of $SO(d+1,1)$ unitary irreducible representations, discrete series is important in physi…

This https://arxiv.org/abs/2307.10290 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Dynamical dark energy from spacetime-symmetry breaking -- late-time behaviour and phantom crossing
We investigate the late-time cosmological dynamics in a simple case of explicit spacetime-symmetry breaking. By expanding in a small symmetry-breaking coefficient we are able to write the Friedmann equations as $Λ$CDM + dynamical dark energy, which we show contains logarithmic dependence of the scale factor. We find that the dark energy equation of state displays divergencies and phantom behaviour for certain values of the symmetry-breaking coefficient, where the NEC is also broken. We discuss…

Massless fermions in black string spacetime
R. Darlla, \"O. Ye\c{s}ilta\c{s}, J. Furtado
https://arxiv.org/abs/2403.17604 https://

Massless fermions in black string spacetime
In this paper we investigate the behaviour of massless fermions in the black string spacetime by computing the eigenvalues and eigenfunctions of the Weyl equations. These solutions allowed us to study the behaviour of such massless fermions in terms of the cosmological constant, the black string's mass and the radial distance of the particle from the black string. The solutions, written in terms of Parabolic Cylinder functions and Laguerre polynomials, were obtained for a particle far from the …

Superrotations at Spacelike Infinity
Adrien Fiorucci, Javier Matulich, Romain Ruzziconi
https://arxiv.org/abs/2404.02197 https://arxi…

Superrotations at Spacelike Infinity
We propose a consistent set of boundary conditions for gravity in asymptotically flat spacetime at spacelike infinity, which yields an enhancement of the Bondi-Metzner-Sachs group with smooth superrotations and new subleading symmetries. These boundary conditions are obtained by allowing fluctuations of the boundary structure which are responsible for divergences in the symplectic form, and a renormalisation procedure is required to obtain finite canonical generators. The latter are then made i…

This https://arxiv.org/abs/2310.08852 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Thin-shell gravastar in a noncommutative BTZ geometry
In this paper, we build a thin-shell gravastar model within a noncommutative BTZ geometry. For this, we consider a noncommutative BTZ metric in the inner region and a geometry associated with a BTZ solution in the outer region, joined by the generalized join technique. After investigating the inner spacetime, surface and outer spacetime, we observe that there is a surface energy density and surface pressure, such as to make gravastar stable. This effect persists even when the cosmological const…

The QCD theta-parameter in canonical quantization
Wen-Yuan Ai, Bjorn Garbrecht, Carlos Tamarit
https://arxiv.org/abs/2403.00747 https://

The QCD theta-parameter in canonical quantization
The role of the QCD theta-parameter is investigated in pure Yang-Mills theory in the spacetime given by the four-dimensional Euclidean torus. While in this setting the introduction of possibly unphysical boundary conditions is avoided, it must be specified how the sum over the topological sectors is to be carried out. To connect with observables in real time, we perceive the partition function as the trace over the canonical density matrix. The system then corresponds to one of a finite tempera…

This https://arxiv.org/abs/2402.11315 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Rigidity aspects of Penrose's singularity theorem
In this paper, we study rigidity aspects of Penrose's singularity theorem. Specifically, we aim to answer the following question: if a spacetime satisfies the hypotheses of Penrose's singularity theorem except with weakly trapped surfaces instead of trapped surfaces, then what can be said about the global spacetime structure if the spacetime is null geodesically complete? In this setting, we show that we obtain a foliation of MOTS which generate totally geodesic null hypersurfaces. Depending on…

Entanglement structures from modified IR geometry
Xin-Xiang Ju, Teng-Zhou Lai, Bo-Hao Liu, Wen-Bin Pan, Ya-Wen Sun
https://arxiv.org/abs/2404.02737 https:/…

Entanglement structures from modified IR geometry
We investigate a new proposal connecting the geometry at various radial scales in asymptotic AdS spacetime with entanglement structure at corresponding real-space length scales of the boundary theory. With this proposal, the bulk IR geometry encodes the long-scale entanglement structure of the dual quantum system. We consider two distinct types of IR geometries, namely the spherical case and the hyperbolic case, which are intimately related to the physics of differential entropy and brane-world…

This https://arxiv.org/abs/2401.01532 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Generating New Spacetimes through Zermelo Navigation
Zermelo navigation is not only a fundamental tool in Finsler geometry but also a fundamental approach to the geometrization of dynamics in physics. In this paper, we consider the Zermelo navigation problem on optical Riemannian space and, via Zermelo/Randers/spacetime triangle, explore the generation of new spacetimes from pre-existing ones. Whether the Randers metric has reversible geodesics corresponds to the presence of time-reversal symmetry in the generated spacetime. In cases where the Ra…

Gravitational Lensing Using Werner's Method in Cartesian-like Coordinates
Zonghai Li
https://arxiv.org/abs/2404.19658 https://arxiv.org/pdf/2404.19658
arXiv:2404.19658v1 Announce Type: new
Abstract: The Gibbons-Werner method for calculating deflection angles using the Gauss-Bonnet theorem and optical/Jacobi metric has become widely popular in recent years. Werner extended this method to stationary spacetimes, where the optical/Jacobi metric takes the form of a Finsler metric of Randers type, by adopting an osculating Riemannian metric. Werner's method is significant as it provides a concise expression for the deflection angle, retains applicability for gravitational lensing in Finsler geometry beyond the Randers type, and has the potential to stimulate widespread application of Finsler geometry across diverse fields. However, because of the cumbersome calculations required in Werner's method using conventional coordinates $(r,\phi)$, it has not been widely adopted. The aim of this paper is to alleviate the computational burden associated with Werner's method. To this end, we introduce Cartesian-like coordinates $(X,Y)$ to construct the osculating Riemannian metric and calculate the deflection angle using the Gauss-Bonnet theorem. We illustrate the current method with examples of the deflection of massive particles in Kerr spacetime, rotating Bardeen (Hayward) regular spacetime, and Teo rotating wormhole spacetime, respectively.

Carroll swiftons
Florian Ecker, Daniel Grumiller, Marc Henneaux, Patricio Salgado-Rebolledo
https://arxiv.org/abs/2403.00544 https://…

Carroll swiftons
We construct Carroll-invariant theories with fields propagating outside the Carroll lightcone, i.e., at a speed strictly greater than zero (`Carroll swiftons'). We first consider models in flat Carroll spacetime in general dimensions, where we present scalar and vector Carroll swifton field theories. We then turn to the coupling to gravity and achieve in particular in two dimensions a Carroll invariant scalar swifton by coupling it suitably to Carroll dilaton gravity. Its backreaction on the ge…

This https://arxiv.org/abs/2401.15809 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Particle dynamics in spherically symmetric electro-vacuum instantons
In this paper, we study the geodesic motion in spherically symmetric electro-vacuum Euclidean solutions of the Einstein equation. There are two kinds of such solutions: the Euclidean Reissner-Nordström (ERN) metrics, and the Bertotti-Robinson-like (BR) metrics, the latter having constant Kretschmann scalar. First, we derive the motion equations for the ERN spacetime and we generalize the results of Battista-Esposito, showing that all orbits in as ERN spacetime are unbounded if and only if it h…

This https://arxiv.org/abs/2402.19459 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Anomalous contribution to galactic rotation curves due to stochastic spacetime
We consider a proposed alternative to quantum gravity, in which the spacetime metric is treated as classical, even while matter fields remain quantum. Consistency of the theory necessarily requires that the metric evolve stochastically. Here, we show that this stochastic behaviour leads to a modification of general relativity at low accelerations. In the low acceleration regime, the variance in the acceleration produced by the gravitational field is high in comparison to that produced by the Ne…

The Role of Torsion in Trans-Planckian Physics
Elham Arabahmadi, Siamak Akhshabi
https://arxiv.org/abs/2404.03141 https://arxiv.org/p…

The Role of Torsion in Trans-Planckian Physics
The torsion of spacetime, if exists, plays an important role at the very early universe when the spin density of particles was very high. It is generally believed that in extremely high energies of the early universe a new physics called trans-Planckian physics should be considered. Since the initial conditions for inflation are probably a result of this new physics, here we consider spin and torsion as trans- Planckian effects and analyze their influence on the power spectrum of scalar and ten…

This https://arxiv.org/abs/2310.03784 has been replaced.
link: https://scholar.google.com/scholar?q=a

Gapped Phases with Non-Invertible Symmetries: (1+1)d
We propose a general framework to characterize gapped infra-red (IR) phases of theories with non-invertible (or categorical) symmetries. In this paper we focus on (1+1)d gapped phases with fusion category symmetries. The approach that we propose uses the Symmetry Topological Field Theory (SymTFT) as a key input: associated to a field theory in d spacetime dimensions, the SymTFT lives in one dimension higher and admits a gapped boundary, which realizes the categorical symmetries. It also admits …

The Role of Torsion in Trans-Planckian Physics
Elham Arabahmadi, Siamak Akhshabi
https://arxiv.org/abs/2404.03141 https://arxiv.org/p…

The Role of Torsion in Trans-Planckian Physics
The torsion of spacetime, if exists, plays an important role at the very early universe when the spin density of particles was very high. It is generally believed that in extremely high energies of the early universe a new physics called trans-Planckian physics should be considered. Since the initial conditions for inflation are probably a result of this new physics, here we consider spin and torsion as trans- Planckian effects and analyze their influence on the power spectrum of scalar and ten…

This https://arxiv.org/abs/2310.04157 has been replaced.
link: https://scholar.google.com/scholar?q=a

Particle motion in a rotating dust spacetime: the Bonnor solution
We investigate the geometrical properties, spectral classification, geodesics, and causal structure of the Bonnor's spacetime [Journal of Physics A Math. Gen., \textbf{10}, 1673 (1977)], i.e., a stationary axisymmetric solution with a rotating dust as a source. This spacetime has a directional singularity at the origin of the coordinates (related to the diverging vorticity field of the fluid there), which is surrounded by a toroidal region where closed timelike curves (CTCs) are allowed, leadin…

This https://arxiv.org/abs/2402.00081 has been replaced.
link: https://scholar.google.com/scholar?q=a

Comment on "The Tully-Fisher law and dark matter effects derived via modified symmetries" by Arraut Ivan
It has been claimed in I. Arraut, 2023 EPL 144 29003 [arXiv:2311.05652] that General Relativity can generate effects equivalent to dark matter, based on a "new modified symmetry that emerges at galactic scale". We show that (i) the spacetime considered is unphysical, violating energy conditions everywhere; (ii) actually no new symmetry emerges, which results from incorrect definitions of angular momentum, velocity, and arclength in the proposed geometry; (iii) no Tully-Fisher law, or flat rotat…

This https://arxiv.org/abs/2402.00081 has been replaced.
link: https://scholar.google.com/scholar?q=a

Comment on "The Tully-Fisher law and dark matter effects derived via modified symmetries" by Arraut Ivan
It has been claimed in I. Arraut, 2023 EPL 144 29003 [arXiv:2311.05652] that General Relativity can generate effects equivalent to dark matter, based on a "new modified symmetry that emerges at galactic scale". We show that (i) the spacetime considered is unphysical, violating energy conditions everywhere; (ii) actually no new symmetry emerges, which results from incorrect definitions of angular momentum, velocity, and arclength in the proposed geometry; (iii) no Tully-Fisher law, or flat rotat…

This https://arxiv.org/abs/2311.15671 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

The generalized Vaidya spacetime with polytropic equation of state
The process of the gravitational collapse might lead not only to a black hole but also to naked singularity formation. In this paper, we consider the generalized Vaidya spacetime with polytropic and generalized polytropic equations of state. We solve the Einstein and Einstein-Maxwell equations to obtain the explicit form of a mass function. We consider the limiting cases of solutions and find out, that generalized Vaidya spacetime might behave like Vaidya-de Sitter and Bonnor-Vaidya-de sitter s…

Time and frequency transfers in optical spacetime
Adrien Bourgoin (SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\'e, UPMC, Univ. Paris 06, Paris, France), Pierre Teyssandier (SYRTE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universit\'e, UPMC, Univ. Paris 06, Paris, France), Paolo Tortora (Dipartimento di Ingegneria Industriale, Alma Mater Studiorum - Universit\`a di Bologna, Forl\`i, Italy), Marco Zannoni (Dipartimento di …

Time and frequency transfers in optical spacetime
Solving the null geodesic equations for a ray of light is a difficult task even considering a stationary spacetime. The problem becomes even more difficult if the electromagnetic signal propagates through a flowing optical medium. Indeed, because of the interaction between light and matter, the signal does not follow a null geodesic path of the spacetime metric anymore. However, having a clear description of how the time and frequency transfers are affected in this very situation is of a prime …

This https://arxiv.org/abs/2401.09170 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Splitting the spacetime: A systematic analysis of foliation dependence in cosmic averaging
It is a fundamental unsolved question in general relativity how to unambiguously characterize the effective collective dynamics of an ensemble of fluid elements sourcing the local geometry, in the absence of exact symmetries. In a cosmological context this is sometimes referred to as the averaging problem. At the heart of this problem in relativity is the non-uniqueness of the choice of foliation within which the statistical properties of the local spacetime are quantified, which can lead to am…

Conservative wormholes in generalized $\kappa(\mathcal{R},\mathcal{T})$-function
Ksh. Newton Singh, G. R. P. Teruel, S. K. Maurya, Tanmoy Chowdhury, Farook Rahaman
https://arxiv.org/abs/2403.19733

Conservative wormholes in generalized $κ(\mathcal{R},\mathcal{T})$-function
We present an exhaustive study of wormhole configurations in $κ(\mathcal{R},\mathcal{T})$ gravity with linear and non-linear functions. The model assumed Morrison-Thorne spacetime where the redshift and shape functions linked with the matter contain and geometry of the spacetime through non-covariant conservation equation of the stress-energy tensor. The first solution was explored assuming a constant redshift function that leads to a wormhole (WH) which is asymptotically non-flat. The remaini…

This https://arxiv.org/abs/2309.04962 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Scalar fields around a loop quantum gravity black hole in de Sitter spacetime: Quasinormal modes, late-time tails and strong cosmic censorship
Loop quantum gravity, as one branch of quantum gravity, holds the potential to explore the fundamental nature of black holes. Recently, according to the quantum Oppenheimer-Snyder model in loop quantum cosmology, a novel loop quantum corrected black hole in de Sitter spacetime has been discovered. Here, we first investigate the corresponding quasinormal modes and late-time behavior of massless neutral scalar field perturbations based on such a quantum-modified black hole in de Sitter spacetime.…

This https://arxiv.org/abs/2310.06490 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Kerr black hole shadows from the axion-photon coupling
We have investigated the motion for photons in the Kerr black hole spacetime under the axion-photon coupling. The birefringence phenomena arising from the axion-photon coupling can be negligible in the weak coupling approximation because the leading-order contributions to the equations of motion come from the square term of the coupling parameter. We find that the coupling parameter makes the size of shadows slightly increase for arbitrary spin parameter. For the rapid rotating black hole case …

This https://arxiv.org/abs/2310.06490 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Kerr black hole shadows from the axion-photon coupling
We have investigated the motion for photons in the Kerr black hole spacetime under the axion-photon coupling. The birefringence phenomena arising from the axion-photon coupling can be negligible in the weak coupling approximation because the leading-order contributions to the equations of motion come from the square term of the coupling parameter. We find that the coupling parameter makes the size of shadows slightly increase for arbitrary spin parameter. For the rapid rotating black hole case …

This https://arxiv.org/abs/2404.15792 has been replaced.
link: https://scholar.google.com/scholar?q=a

Orbits around a black bounce spacetime
In this work, the trajectories of particles around a black bounce spacetime are considered, with the Simpson-Visser model serving as an example. Trajectories for massless and massive particles are obtained through the study of null and time-like geodesics. As the Simpson-Visser solution is derived via the Einstein equations for a source involving nonlinear electrodynamics and a scalar field, photon trajectories are investigated by considering an effective metric in which photons follow null geo…

Quantum Gravity: are we there yet?
Shahn Majid
https://arxiv.org/abs/2402.18536 https://arxiv.org/pdf/2402.18536

Quantum Gravity: are we there yet?
The turn of the millennium was a time of optimism about an approach to noncommutative geometry inspired by rich mathematical objects called `quantum groups' and its applications to quantum spacetime. This would model quantum gravity effects as noncommutativity of spacetime coordinates and was arguably going to solve quantum gravity itself. It took a further 20 years from that point to develop a particularly suitable formalism of `quantum Riemannian geometry', but this was largely done and has b…

Quantum Gravity: are we there yet?
Shahn Majid
https://arxiv.org/abs/2402.18536 https://arxiv.org/pdf/2402.18536

Quantum Gravity: are we there yet?
The turn of the millennium was a time of optimism about an approach to noncommutative geometry inspired by rich mathematical objects called `quantum groups' and its applications to quantum spacetime. This would model quantum gravity effects as noncommutativity of spacetime coordinates and was arguably going to solve quantum gravity itself. It took a further 20 years from that point to develop a particularly suitable formalism of `quantum Riemannian geometry', but this was largely done and has b…

This https://arxiv.org/abs/2312.07486 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Dark energy from topology change induced by microscopic Gauss-Bonnet wormholes
It is known that the appearance of microscopic objects with distinct topologies and different Euler characteristics, such as instatons and wormholes, at the spacetime-foam level in Euclidean quantum gravity approaches, leads to spacetime topology changes. Such changes, in principle, may affect the field equations that arise through the semiclassical variation procedure of gravitational actions. Although in the case of Einstein-Hilbert action the presence of microscopic wormholes does not lead t…

Viable Wormhole Solutions in Modified Gauss-Bonnet Gravity
M. Zeeshan Gul, M. Sharif
https://arxiv.org/abs/2403.00035 https://arxiv.o…

Viable Wormhole Solutions in Modified Gauss-Bonnet Gravity
In this paper, we use the embedding class-I technique to examine the effect of charge on traversable wormhole geometry in the context of $f(\mathcal{G})$ theory, where $\mathcal{G}$ is the Gauss-Bonnet term. For this purpose, we consider static spherical spacetime with anisotropic matter configuration to investigate the wormhole geometry. The Karmarkar condition is used to develop a shape function for the static wormhole structure. Using this developed shape function, we construct a wormhole ge…

This https://arxiv.org/abs/2402.15156 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Spacetime singularities and caustic of outgoing null hypersurfaces
In this paper, we investigate the caustic point developed by outgoing null hypersurfaces and the behavior of null curves. We analyze three cases: Future, past, and zero caustic point terminology for outgoing null hypersurfaces in the marginally bound Lemaitre-Tolman-Bondi (LTB) metric for homogenous and inhomogeneous cases defined in the present work. We show the criteria to form local and globally visible singularity in terms of the tangent on the apparent horizon curve.

This https://arxiv.org/abs/2302.01338 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

General perturbations in D+1 standard and brane cosmology revisited
In the present work, we generalize the theory of perturbations in a D + 1 dimensional space-time with cosmological constant, studying scalar, vector and tensor perturbations, as well as its structure in Newtonian and Synchronous gauge. We also show the theory of perturbations in the context of brane cosmology, where branes are embedded in a set of D-spatial dimensions, a temporal dimension, and an additional spatial dimension. In both, standard and brane cosmology an unperturbed spacetime is pr…

This https://arxiv.org/abs/2302.01338 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

General perturbations in D+1 standard and brane cosmology revisited
In the present work, we generalize the theory of perturbations in a D + 1 dimensional space-time with cosmological constant, studying scalar, vector and tensor perturbations, as well as its structure in Newtonian and Synchronous gauge. We also show the theory of perturbations in the context of brane cosmology, where branes are embedded in a set of D-spatial dimensions, a temporal dimension, and an additional spatial dimension. In both, standard and brane cosmology an unperturbed spacetime is pr…

This https://arxiv.org/abs/2307.13374 has been replaced.
initial toot: https://mastoxiv.page/@arXiv_grqc_…

Classical radiation fields for scalar, electromagnetic, and gravitational waves with spacetime-symmetry breaking
An effective field theory framework is used to investigate some Lorentz-violating effects on the generation of electromagnetic and gravitational waves, complementing previous work on propagation. Specifically we find solutions to a modified, anisotropic wave equation, sourced by charge or fluid matter. We derive the radiation fields for scalars, classical electromagnetic radiation, and partial results for gravitational radiation. For gravitational waves, the results show longitudinal and breath…