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Characterizations of weakly Riccisymmetric spacetimes and f(ℛ)gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230822
Uday Chand De, Dipankar HazraIn this paper, we characterize weakly Riccisymmetric (shortly, (WRS)4) spacetimes and their solutions in f(ℛ)gravity. It is demonstrated that a (WRS)4 spacetime represents a stiff matter fluid. In addition, we obtain that a conformally flat (WRS)4 spacetime is a space of quasiconstant sectional curvature. Moreover, we establish that a Ricci symmetric (WRS)4 spacetime represents a static spacetime

Universality in binary black hole dynamics: An integrability conjecture Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230821
José Luis Jaramillo, Badri Krishnan, Carlos F. SopuertaThe waveform of a binary black hole coalescence appears to be both simple and universal. In this essay we argue that the dynamics should admit a separation into “fast and slow” degrees of freedom, such that the latter are described by an integrable system of equations, accounting for the simplicity and universality of the waveform. Given that Painlevé transcendents are a smoking gun of integrable structures

In search of the maximum lost momentum Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230821
Carlos O. Lousto, James HealyWe performed a series of 1381 full numerical simulations of high energy collision of two black holes to search for the maximum recoil velocity after their merger. We studied equal mass binaries with opposite spins pointing along the orbital plane to maximize asymmetric gravitational radiation and performed a search of spin orientations in the plane, impact parameters, and initial linear momenta to

Pancakification and negative Hawking temperatures Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230821
Tyler McMakenVacuum models of charged or spinning black holes possess two horizons, the inner of which has the oftoverlooked property that gravitational tidal forces initially spaghettifying a freely falling observer will eventually change signs and flatten the observer like a pancake. Inner horizons also may induce a classical blueshift instability known as mass inflation, and a number of recent studies have

Stability analysis of f(Q) gravity models using dynamical systems Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230821
Pooja Vishwakarma, Parth ShahIn recent years, the modified theory of gravity known as f(Q) gravity has drawn interest as a potential alternative to general relativity. According to this theory, the gravitational force is determined by a function of the socalled “nonmetricity” tensor Q, which expresses how far a particle spacetime is from the metric geometry. In contrast to general relativity, which describes the gravitational

Reconstructing the parameter space of nonanalytical cosmological fixed points Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230821
Santiago GarcíaSerna, J. Bayron OrjuelaQuintana, César A. ValenzuelaToledo, Hernán Ocampo DuránDynamical system theory is a widely used technique in the analysis of cosmological models. Within this framework, the equations describing the dynamics of a model are recast in terms of dimensionless variables, which evolve according to a set of autonomous firstorder differential equations. The fixed points of this autonomous set encode the asymptotic evolution of the model. Usually, these points

Nonlinear sigma models in inflationary cosmology Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230810
Abhishek GoswamiNonlinear Sigma Models in two dimensions (NLSM2) describe the quantumfield theory (QFT) of the Embedding map from a twodimensional surface to a higher dimensional target space. We assume that before the big bang the universe was an abstract space with a twodimensional surface embedded in it. We study QFT of the Embedding map in the universe that is NLSM2. We consider the abstract target space which

Fermion localization mechanisms in f(T,𝒯 )brane Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230809
A. R. P. MoreiraIn this work, we investigate two mechanisms for locating fermions on the brane in a modified teleparallel gravity f(T,𝒯), where T is the torsion scalar and 𝒯 is the trace of the energy–momentum tensor. The first mechanism is a Yukawatype minimal coupling between the fermion and the background scalar field. The second mechanism is a nonminimal coupling between the fermion and the torsion. The geometric

Black hole entropy contributions from Euclidean cores Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230802
Jens BoosThe entropy of a Schwarzschild black hole, as computed via the semiclassical Euclidean path integral in a stationary phase approximation, is determined not by the onshell value of the action (which vanishes), but by the Gibbons–Hawking–York boundary term evaluated on a suitable hypersurface, which can be chosen arbitrarily far away from the horizon. For this reason, the black hole singularity seemingly

Punctuated chaos and indeterminism in selfgravitating manybody systems Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230801
Tjarda C. N. Boekholt, Simon F. Portegies Zwart, Douglas C. HeggieDynamical chaos is a fundamental manifestation of gravity in astrophysical, manybody systems. The spectrum of Lyapunov exponents quantifies the associated exponential response to small perturbations. Analytical derivations of these exponents are critical for understanding the stability and predictability of observed systems. This paper presents a new model for chaos in systems with eccentric and crossing

On Chaplygin models in f(G) gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230729
Fidele Twagirayezu, Abraham Ayirwanda, Albert Munyeshyaka, Solange Mukeshimana, Joseph Ntahompagaze, Leon Fidele Ruganzu UwimbabaziThis work treats cosmological perturbation in a mixture of standard matter, Chaplygin gas as well as Gauss–Bonnet fluids using a 1+3 covariant approach in the context of modified f(G) gravity. We define the gradient variables to obtain linear perturbation equations. After scalar and redshift transformations, we consider both an original Chaplygin and generalized Chaplygin gas models under Gauss–Bonnet

BMS symmetry in gravity: Front form versus Instant form Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230728
Sudarshan Ananth, Sucheta MajumdarIn general relativity, the allowed set of diffeomorphisms or gauge transformations at asymptotic infinity forms the BMS group, an infinitedimensional extension of the Poincaré group. We focus on the structure of the BMS group in two distinct forms of Hamiltonian dynamics — the instant and front forms. Both similarities and differences in these two forms are examined while emphasizing the role of noncovariant

The virial theorem for retarded gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230728
Asher YahalomGalaxy Clusters are huge physical systems having a generic size of tens of millions of light years. Thus any modification at the center of the cluster will affect the outskirts only tens of millions of years afterwards. Those retardation considerations seem to be neglected in present day analysis used to estimate the total mass of the galaxy cluster, including those estimates which are based on the

The sound of the event horizon Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230728
R. A. KonoplyaDuring the ringdown phase of a gravitational signal emitted by a black hole, the least damped quasinormal frequency dominates. If modifications to Einstein’s theory induce noticeable deformations of the blackhole geometry only near the event horizon, the fundamental mode remains largely unaffected. However, even a small change near the event horizon can significantly impact the first few overtones

Matter–gravity entanglement entropy and the second law for black holes Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230727
Bernard S. KayHawking showed that a black hole formed by collapse will emit radiation and eventually disappear. We address the challenge to define an objective notion of physical entropy which increases throughout this process in a way consistent with unitarity. We have suggested that (instead of coarsegrained entropy) physical entropy is matter–gravity entanglement entropy and that this may offer an explanation

Dynamic dark energy from the local limit of nonlocal gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230727
Javad Tabatabaei, Abdolali Banihashemi, Shant Baghram, Bahram MashhoonNonlocal gravity (NLG), a classical extension of Einstein’s theory of gravitation, has been studied mainly in linearized form. In particular, nonlinearities have thus far prevented the treatment of cosmological models in NLG. In this essay, we discuss the local limit of NLG and apply this limit to the expanding homogenous and isotropic universe. The theory only allows spatially flat cosmological models;

Buchdahlinspired spacetimes and wormholes: Unearthing Hans Buchdahl’s other “hidden” treasure trove Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230725
Hoang Ky NguyenCirca 1962 Hans A. Buchdahl pioneered a program — and made significant progress — seeking vacuo configurations in pure ℛ2 gravity (H. A. Buchdahl, Nuovo Cimento23 (1962) 141). Unfortunately, he deemed the final step in his calculations impassable and prematurely suspended his pursuit. Since then, his achievements on this front have faded into dormancy. Unbeknownst to Buchdahl himself, the ℛ2 vacua

Fast radio bursts signal highfrequency gravitational waves Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230725
Ashu Kushwaha, Sunil Malik, S. ShankaranarayananThere is growing evidence for highfrequency gravitational waves (HFGWs) ranging from MHz to GHz. Several HFGW detectors have been operating for over a decade, and two GHz events have been reported recently. However, a confirmed detection might take a decade. This essay argues that unexplained observed astrophysical phenomena, like Fast Radio Bursts (FRBs), might provide indirect evidence for HFGWs

Nomen non est omen: Why it is too soon to identify ultracompact objects as black holes Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230725
Sebastian MurkBlack holes play a pivotal role in the foundations of physics, but there is an alarming discrepancy between what is considered to be a black hole in observational astronomy and theoretical studies. Despite claims to the contrary, we argue that identifying the observed astrophysical black hole candidates as genuine black holes is not justified based on the currently available observational data, and

Stellar equilibrium on a physical vacuum soil Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230722
Julio Arrechea, Carlos BarcelóWe show that the repulsive effects associated to the zeropoint energies of quantum fields are capable of supporting ultracompact stars that overcome the compactness limits present in general relativity for any object in hydrostatic equilibrium. These objects are exact selfconsistent solutions in semiclassical gravity that incorporate the backreaction of the renormalized stressenergy tensor (RSET)

Constraining the bounce realization with holographic background and analytical exploration of the consequences in a modified gravity framework Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230721
Moli Ghosh, Surajit ChattopadhyayThe work reported in this paper explores holographic bounce. In the first phase of the study, we chose a nonsingular bouncing scale factor. Then we reconstructed f(T) gravity and analytically derived constraints on the bouncing parameter σ. These constraints helped us understand the scale factor’s quintessence or phantom behavior. Furthermore, we also explored the statefinder parameters for reconstructed

A new class of generalized Ellis–Bronnikov wormhole in asymptotically safe gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230721
Nisha Godani, Shubham KalaIn this paper, the asymptotically safe gravity has been taken in the gravitational action to derive the wormhole solutions. The paper is aimed at the study of traversable wormhole solutions having repulsive geometry at the throat. The wormhole solutions are produced in two cases: the first case includes the logarithmic form of the shape function while in the second case, the shape function is derived

Cosmological application of the Maxwell gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230721
Salih KibaroğluIn this study, we consider a cosmological model for the Maxwell gravity which is constructed by gauging the semisimple extended Poincaré algebra. Inspired by the Einstein–Yang–Mills theory, we describe the Maxwell gauge field in terms of two additional timedependent scalar fields. Within the context of a homogeneous and isotropic Friedmann–Lemaître–Robertson–Walker universe, we derive the Friedmann

What are neutron stars made of? Gravitational waves may reveal the answer Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230721
Neil Lu, Susan M. Scott, Karl WetteNeutron stars are one of the most mysterious wonders in the universe. Their extreme densities hint at new and exotic physics at work within. Gravitational waves could be the key to unlocking their secrets. In particular, a first detection of gravitational waves from rapidlyspinning, deformed neutron stars could yield new insights into the physics of matter at extreme densities and under strong gravity

Event horizon detection: Zenith view as seen by falling into a Schwarzschild black hole Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230720
Yukiyoshi IidaTo visualize what is seen by an observer in curved spacetime, both general relativistic effects and special relativistic effects need to be considered. In this study, the author analytically proved that the zenith view seen by an observer falling freely into a Schwarzschild black hole (that is, the observer’s view of the point on the opposite side of the black hole) becomes enlarged, “redder,” and

The universality of black hole thermodynamics Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230720
Samir D. Mathur, Madhur MehtaThe thermodynamic properties of black holes — temperature, entropy and radiation rates — are usually associated with the presence of a horizon. We argue that any extremely compact object (ECO) must have the same thermodynamic properties. Quantum fields just outside the surface of an ECO have a large negative Casimir energy similar to the Boulware vacuum of black holes. If the thermal radiation emanating

On the inevitable lightness of vacuum Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230720
Laurent Freidel, Jerzy KowalskiGlikman, Robert G. Leigh, Djordje MinicIn this essay, we present a new understanding of the cosmological constant problem, built upon the realization that the vacuum energy density can be expressed in terms of a phase space volume. We introduce a UVIR regularization which implies a relationship between the vacuum energy and entropy. Combining this insight with the holographic bound on entropy then yields a bound on the cosmological constant

Emergence of quantumfield theory in causal diamonds Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230717
Tom BanksThe experimental successes of quantumfield theory do not justify using it to describe even a finite fraction of the entanglement entropy of a causal diamond with its exterior, in the limit of large diamonds. Susskind and Uglum and Jacobson conjectured that this divergent entropy could be thought of as a renormalization of Newton’s constant in the Bekenstein–Hawking formula, if we applied that formula

Born reciprocity and discretized Finsler structure: An approach to quantize GR curvature tensors on threesphere Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230712
Abdel Nasser Tawfik, Tahia F. DabashAt relativistic energies and finite magnetic fields, the noncommutative relation of distance and momentum, the Heisenberg uncertainty principle, the fundamental theory of quantum mechanics, is conjectured to get modifications. Results from various rigorous approaches to quantum gravity, such as string theory, loop quantum gravity and doubly special relativity support the generalization of the noncommutative

Thermal radiation of thin accretion disk around TaubNUT black hole Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230710
Bakhtiyor Narzilloev, Bobomurat AhmedovThe effects of a gravitomagnetic charge on the thermal radiation properties of a thin accretion disk surrounding a nonrotating black hole are studied. The studied system consists of a nonrotating black hole with a nonzero gravitomagnetic charge and a Novikov–Thorne disk that is thin and optically thick. It is found that the gravitomagnetic charge enhances the gravitational field of the central black

Black holes that are too cold to respect cosmic censorship Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230630
Shahar HodIn this essay, it is proved that there are black holes that are dangerously cold. In particular, by analyzing the emission spectra of highly charged black holes we reveal the fact that nearextremal black holes whose Bekenstein–Hawking temperatures lie in the regime TBH≲me6/e3 may turn into horizonless naked singularities, thus violating the cosmic censorship principle, if they emit a photon with the

Quantum black holes as classical space factories Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230630
A. Iorio, L. SmaldoneSpace and matter may both be manifestations of a single fundamental quantum dynamics, as it may become evident during blackhole evaporation. Inspired by the fact that quantum electrodynamics underlies the classical theory of elasticity, that in turn has a natural and wellknown geometric description in terms of curvature and torsion, related to topological defects, here we move some necessary steps

Equivalence principle, deSitter space, and cosmological twistors Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230628
Maciej DunajskiIn this paper, I discuss the impact of the positive cosmological constant on the interplay between the equivalence principle in general relativity, and the rules of quantum mechanics. At the nonrelativistic level, there is an ambiguity in the definition of a phase of a wave function measured by inertial and accelerating observes. This is the cosmological analogue of the Penrose effect, which can also

Energy conditions of traversable wormhole in the deformed f(R) gravitational model Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230628
J. Sadeghi, S. Noori Gashti, M. R. Alipour, M. A. S. AfsharOne of the most important issues in cosmology is the study of a series of hypothetical objects called wormholes. Recently, researchers have studied these hypothetical objects under different conditions. In this paper, we aim to evaluate the traversable wormhole according to a modified f(R) gravitational model, specifically −R2+aR2(1−n), from the perspective of two essential functions in wormhole structure:

Dynamical system approach of interacting dark energy models with minimally coupled scalar field Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230623
Amit Samaddar, S. Surendra Singh, Md Khurshid AlamWe investigated the stability condition of f(Q) gravity theory with interacting and noninteracting models by using dynamical system. We assume the f(Q) function as f(Q)=Q+M22, where M is the free parameter. We evaluated the critical points for this model and examined the stability behavior. We found two stable critical points for interacting model. The phase plots for this system are examined and the

Conformal motions of anisotropic exact Bianchi type II models admitting energy conditions in f(T) gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230621
Sabiha Qazi, Fiaz Hussain, M. Ramzan, Sirajul HaqThe purpose of this paper is to explore the anisotropic exact Bianchi type II solutions in f(T) gravity, where T denotes the torsion scalar. We utilize the solutions to discuss conformal vector fields (CVFs) and energy conditions. In the first slot of this study, we find the CVFs. The CVFs being a generalization of the Killing vector fields (KVFs) are affiliated with the conservation laws of physics

Dark matter in a bimetric universe Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230619
Carlos Maldonado, Fernando MéndezWe study the possibility to describe dark matter in a model of the universe with twoscale factors and a nonstandard Poisson bracket structure characterized by the deformation parameter κ. The dark matter evolution is analyzed in the early stages of the universe, and its relic density is obtained via the FreezeIn and FreezeOut mechanism. We show that by fixing κ and the initial ratio of energy densities

The semiclassical limit of quantum gravity and the problem of time Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230617
R. I. Ayala Oña, M. B. Kalmykov, D. P. Kislyakova, T. P. ShestakovaThe question about the appearance of time in the semiclassical limit of quantum gravity continues to be discussed in the literature. It is believed that a temporal Schrödinger equation for matter fields on the background of a classical gravitational field must be true. To obtain this equation, the Born–Oppenheimer approximation for gravity is used. However, the origin of time in this equation is different

Born reciprocity and relativistic generalized uncertainty principle in Finsler structure: Fundamental tensor in discretized curved spacetime Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230617
Abdel Nasser Tawfik, Tahia F. DabashThe main findings of the generalized uncertainty principle (GUP), the phenomenological approach, for instance, the emergence of a minimal measurable length uncertainty, are obtained in various versions from theories of quantum gravity, such as string theory, loop quantum gravity, doubly special relativity and black hole physics. GUP counts for impacts of relativistic energies and finite gravitational

On de Sitter spacetime and string theory Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230615
Per Berglund, Tristan Hübsch, Djordje MinicWe review various aspects of de Sitter spacetime in string theory: its status as an Effective Field Theory spacetime solution, its relation to the vacuum energy problem in string theory, its (global) holographic definition in terms of two entangled and noncanonical conformal field theories as well as a realization of a realistic de Sitter universe endowed with the observed visible matter and the necessary

On 1 + 3 covariant perturbations of the quasiNewtonian spacetime in modified Gauss–Bonnet gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230615
Albert Munyeshyaka, Joseph Ntahompagaze, Tom Mutabazi, Manasse R. MbonyeThe consideration of a 1+3 covariant approach to cold dark matter universe with no shear cosmological dust model with irrotational flows is developed in the context of f(G) gravity theory in this study. This approach reveals the existence of integrability conditions which do not appear in noncovariant treatments. We constructed the integrability conditions in modified Gauss–Bonnet f(G) gravity basing

On quantum traversability of wormholes Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230615
J. Furtado, C. R. Muniz, M. S. Cunha, J. E. G. SilvaThis paper explores the possibility of scalar quantum particles traversing generalized Ellis–Bronnikov wormholes, taking into account quantum effects like tunneling. We investigate the generalized Ellis–Bronnikov wormhole metric and discover that when the exponent parameter is n=2, there is a single barriershaped effective potential at the throat of the wormhole for any orbital angular momentum value

Dynamical analysis of the Tsallis holographic dark energy models with event horizon as cutoff and interaction with matter Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230612
A. V. Astashenok, A. S. TepliakovThe model of generalized Tsallis holographic dark energy (which is known to be particular representative of Nojiri–Odintsov HDE) with event horizon as cutoff is investigated using methods of dynamical analysis. We take into consideration possible interaction with dark energy and matter in various forms. Critical points are determined. Cosmological evolution of the universe depends from interaction

A MacDowell–Mansouritype formulation for conformally flat Einstein manifolds Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230612
J. E. RosalesQuinteroWe study a pure connection formulation plus algebraic constraints in four spacetime dimensions where the gauge group G⊃SO(1,3). We show that the action has, as particular cases, the MacDowell–Mansouri and the Stelle–West formulations for gravity. Also, under adequate specification of the constraint terms, we obtain a subset of Einstein manifolds that are torsionless conformally flat manifolds.

Analysis of isotropic pressure condition in Chameleonic Brans–Dicke gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230606
F. Maqsood, Z. Yousaf, M. Z. Bhatti, Sana RehmanThe prime goal of this paper is to analyze the conditions for the stability of the isotropic pressure condition with hydrostatic equilibrium constraint under the influence of Chameleonic Brans–Dicke gravity. We have formulated various expressions through the field equations, Bianchi identities, mass function, etc., to govern the spherically symmetric dissipative configuration. We have also evaluated

Thermodynamical character and the radiation process of the thin accretion disk of minimum measurable lengthinspired regular black hole Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230605
Himangshu Barman, Homa Shababi, Mohamed Moussa, Anisur RahamanWe investigate the impact of quantum gravity on the thermodynamic characteristics and radiation processes of thin accretion disks surrounding Schwarzschildlike black holes. To incorporate quantum gravity into our study, we apply the framework of generalization of uncertainty, which is equivalent to the renormalization group improved quantum gravity and maintains the limit of asymptotically safe preposition

New limit on magnetic monopole flux from catalysis of proton decay in white dwarfs Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230526
JingJing Liu, DongMei Liu, QiuHe PengWe propose a question that why no late type M and much later type N white dwarfs (WDs) with surface temperatures less than 3000 K have ever been observed? On the basis of proton decay catalyzed by magnetic monopoles(MMs), we have presented four new energysource models associated with MMs to discuss the cooling of WDs by some observations from seven red giant stars with LAMOST. It is found that the

Thinshell wormholes in Ndimensional F (R) gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230526
Griselda FigueroaAguirreIn this work, spherically symmetric thinshell wormholes with a conformally invariant Maxwell field for Ndimensional F(R) gravity and constant scalar curvature R are built. Two cases are considered: wormholes symmetric across the throat and asymmetric ones having different values of the scalar curvature across the throat. Their stability under radial perturbations is analyzed, finding that unstable

Finite temperature considerations in the structure of quadratic GUPmodified white dwarfs Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230525
James David M. Tuñacao, Adrian G. Abac, Roland Emerito S. OtadoyIn quantum gravity phenomenology, the effect of the generalized uncertainty principle (GUP) on white dwarf structure has been given much attention in recent literature. However, these studies assume a zero temperature equation of state (EoS), excluding young white dwarfs whose initial temperatures are substantially high. To that cause, this paper calculates the Chandrasekhar EoS and resulting massradius

Unitary paradox of cosmological perturbations Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230525
Ngo Phuc Duc LocIf we interpret the Bekenstein–Hawking entropy of the Hubble horizon as thermodynamic entropy, then the entanglement entropy of the superhorizon modes of curvature perturbation entangled with the subhorizon modes will exceed the Bekenstein–Hawking bound at some point; we call this the unitary paradox of cosmological perturbations by analogy with black hole. In order to avoid a finetuned problem, the

Quantum origins of scalar gravitational waves: Exploring the conformal factor in scalar–tensor theory of gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230525
Sijo K. JosephDelving into the realm of scalar–tensor theory of gravity, this paper uncovers the intricate details of the conformal factor and its correspondence to quantum mechanical mass fluctuations. Shedding light on the theory’s key findings, we explore the quantum mechanical nature of the wave equation associated with mass fluctuations, predicting the creation of scalar gravitational waves. The association

Thinshell wormhole solution of scalar hairy black hole in Horndeski theory Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230522
N. M. Eman, S. M. Khurshed AlamWe have investigated the linearized stability analysis of thinshell wormhole for scalar hairy black hole solution in Horndeski theory by surgically grafting together two identical copies of this hairy black hole spacetime. The surface stresses at the throat of the wormhole are calculated, and the attractive and repulsive characteristics of this wormhole throat are examined via radial acceleration

Horizon scale tests of quantum gravity using the event horizon telescope observations Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230520
Stuart MarongweIn this paper, we test the fundamental physics of the Nexus Paradigm of quantum gravity using horizon scale images and shadows of the supermassive black holes (SMBHs) Sagittarius (Sgr)A* and M87* as imaged by the Event Horizon Telescope (EHT). We consider the angular diameter of the emission ring peak as predicted by the Nexus Paradigm including the size of the central dark depression and the base

Chameleonic dark matter and reheating constraints in a logarithmic f(R) gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230517
Arief Hermanto, Yusmantoro, Romy H. S. BudhiWe investigated the viability of a logarithmic f(R) gravity in calculating the reheating temperature and describing dark matter. We discovered that the logarithmic model possessed a chameleon problem, and we addressed this by modifying the model to incorporate the R2 term from the Starobinsky model. We examined the viability of the corrected model and revealed that it provided the same reheating temperature

Reheating constraints in modified natural inflation with the decaying inflaton Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230516
Yusmantoro, Arifin Achmad, Rian JuliantoThis research investigates the reheating constraints in two modified natural inflation models. The models are Special Generalized Natural Inflation (SNI) model and the Natural Inflation Inspired (NII) model. In this paper, we consider the decaying inflaton into radiation, which leads to an timedependent effective EquationofState (EoS) parameter. We assume that the decay rate of inflaton takes the

Electromagnetic vacuum stresses and energy fluxes induced by a cosmic string in de Sitter spacetime Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230512
A. A. Saharian, V. F. Manukyan, V. Kh. Kotanjyan, A. A. GrigoryanFor the electromagnetic field in (D+1)dimensional locally de Sitter (dS) spacetime, we analyze the effects of a generalized cosmic string type defect on the vacuum expectation value of the energymomentum tensor. For the Bunch–Davies vacuum state, the topological contributions are explicitly extracted in both the diagonal and offdiagonal components. The latter describes the presence of radially directed

Internal heating mechanisms in neutron stars Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230512
F. Köpp, J. E. Horvath, D. Hadjimichef, C. A. Z. Vasconcellos, P. O. HessThe cooling mechanisms of a neutron star (hereafter referred to as NS) have the potential to reveal important features of superdense matter. The values of the surface temperatures are known for a good sample of NSs aged ≤106 years and, with some exceptions, can be explained through standard cooling mechanisms (neutrinos and photons emissions without internal heating), as confirmed in our study. However

The constrained cosmological model in Lyra geometry Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230510
J. K. Singh, Shaily, Shri Ram, Joao R. L. Santos, Jéferson A. S. FortunatoIn this paper, we study a flat homogeneous FLRW model in Lyra geometry which is described by a timedependent displacement vector. We consider an appropriate parametrization of the energy density of scalar field ρϕ in terms of the cosmic scale factor. The result shows two transitions from deceleration to acceleration. Furthermore, we constrain the model parameter α and the displacement field vector

New regular 2+1 black hole solutions in bilocal gravity Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230510
H. R. Christiansen, Milko Estrada, M. S. Cunha, J. Furtado, C. R. MunizWe obtain new regular black hole solutions for an action in 2+1 dimensions with a bilocal Ricci scalar and a negative cosmological constant. Besides their connection to the cosmological constant, these solutions depend on a fundamental length due to their nonlocal nature. The effective profile densities that result from the nonlocal geometries have quasilocalized mass/energy since they are finite

Toy models of compact anisotropic stars and their Love numbers Int. J. Mod. Phys. D (IF 2.2) Pub Date : 20230504
Bikram Keshari Parida, Shyam Das, Megandhren GovenderIn this paper, we investigate the influence of tidal Love numbers on the equationofstate (EoS) governing the interior matter distribution of a compact star within the framework of classical general relativity. By invoking a linear EoS for a spherically symmetric anisotropic matter configuration, we solve the Einstein field equations for an arbitrary EoS parameter. We subject our model to rigorous