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  • Modeling a 2.5M⊙ compact star with quark matter
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2021-01-11
    J. E. Horvath; P. H. R. S. Moraes

    The detection of an unexpected ∼2.5M⊙ component in the gravitational wave event GW190814 has puzzled the community of high-energy astrophysicists, since in the absence of further information it is not clear whether this is the heaviest “neutron star” ever detected or either the lightest black hole known, of a kind absent in the local neighborhood. We show in this work a few possibilities for a model

    更新日期:2021-01-12
  • Interaction of massless minimally coupled scalar field with spinor field in de Sitter universe
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2021-01-09
    Y. Ahmadi

    The interaction of massless minimally coupled scalar field and spinor field (Ψ+Φm→Ψ+Φm) is investigated and the behavior of interaction and scattering matrix in Minkowski limit is studied. It is seen that the massless minimally coupled scalar field operator, the interaction Lagrangian and the scattering matrix become zero. Also, the incoming and outgoing spinor fields, which in de Sitter spacetime

    更新日期:2021-01-11
  • ΛCDM as a Noether symmetry in cosmology
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-25
    D. Benisty; E. I. Guendelman; E. Nissimov; S. Pacheva

    The standard ΛCDM model of cosmology is formulated as a simple modified gravity coupled to a single scalar field (“darkon”) possessing a nontrivial hidden nonlinear Noether symmetry. The main ingredient in the construction is the use of the formalism of non-Riemannian spacetime volume-elements. The associated Noether conserved current produces stress–energy tensor consisting of two additive parts —

    更新日期:2021-01-08
  • Phase transitions and entropy force of charged de Sitter black holes with cloud of string and quintessence
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-05
    Yubo Ma; Yang Zhang; Ren Zhao; Shuo Cao; Tonghua Liu; Shubiao Geng; Yuting Liu; Yumei Huang

    In this paper, we investigate the combined effects of the cloud of strings and quintessence on the thermodynamics of a Reissner–Nordström–de Sitter black hole. Based on the equivalent thermodynamic quantities considering the correlation between the black hole horizon and the cosmological horizon, we extensively discuss the phase transitions of the spacetime. Our analysis proves that similar to the

    更新日期:2021-01-08
  • Reheating constraints on an inflation model with nonminimal derivative coupling in the light of Planck 2018 data
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-29
    F. S. Mirtalebian; Kourosh Nozari; Tahereh Azizi

    Reheating is a process by which the inflaton’s energy density transfers to conventional matter after cosmic inflation. Currently, there is no cosmic observational evidence to directly detect the reheating era, but it may impose additional constraints on inflationary models. Depending upon the model, e-folding number during reheating Nre and the final reheating temperature Tre, as well as its effective

    更新日期:2020-12-31
  • ‘Mutual complexity’ in hyperscaling violating background
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-29
    N. Ghanbarian; M. Reza Tanhayi

    In this paper, we use complexity equals action proposal and investigate the recently introduced ‘mutual complexity’ [M. Alishahiha, K. Babaei Velni and M. R. Mohammadi Mozaffar, Phys. Rev. D99 (2019) 126016, https://doi.org/10.1103/PhysRevD.99.126016, arXiv:1809.06031 [hep-th]], in the hyperscaling violating backgrounds. For two subregions in order to define holographic complexity, we find the finite

    更新日期:2020-12-31
  • The dark sector cosmology
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-05
    Elcio Abdalla; Alessandro Marins

    The most important problem in fundamental physics is the description of the contents of the Universe. Today, we know that 95% thereof is totally unknown. Two thirds of that amount is the mysterious Dark Energy described in an interesting and important review [E. J. Copeland, M. Sami and S. Tsujikawa, Int. J. Mod. Phys. D 15 (2006) 1753]. We briefly extend here the ideas contained in that review including

    更新日期:2020-12-31
  • Equivalence of nonminimally coupled cosmologies by Noether symmetries
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-17
    Francesco Bajardi; Salvatore Capozziello

    We discuss nonminimally coupled cosmologies involving different geometric invariants. Specifically, actions containing a nonminimally coupled scalar field to gravity described, in turn, by curvature, torsion and Gauss–Bonnet scalars are considered. We show that couplings, potentials and kinetic terms are determined by the existence of Noether symmetries which, moreover, allows to reduce and solve dynamics

    更新日期:2020-12-31
  • Self-gravitating dark matter gets in shape
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-11
    Jenny Wagner

    In our current best cosmological model, the vast majority of matter in the universe is dark, consisting of yet undetected, nonbaryonic particles that do not interact electro-magnetically. So far, the only significant evidence for dark matter has been found in its gravitational interaction, as observed in galaxy rotation curves or gravitational lensing effects. The inferred dark matter agglomerations

    更新日期:2020-12-31
  • Analytic infinite derivative gravity, R2-like inflation, quantum gravity and CMB
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-22
    Alexey S. Koshelev; K. Sravan Kumar; Alexei A. Starobinsky

    Emergence of R2 inflation, which is the best fit framework for CMB observations till date, comes from the attempts to attack the problem of quantization of gravity which in turn have resulted in the trace anomaly discovery. Further developments in trace anomaly and different frameworks aiming to construct quantum gravity indicate an inevitability of nonlocality in fundamental physics at small time

    更新日期:2020-12-31
  • A possible thermodynamic origin of the spacetime minimum length
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-27
    Ting-Ping Liu; Jin Pu; Yan Han; Qing-Quan Jiang

    In this paper, by applying the generalized uncertainty principle (GUP) at the final stage of black hole evaporation, we have proposed a thermodynamic explanation for the minimal scale of quantum gravity, i.e. it may stem from the basic requirements of the third law of thermodynamics for quantum gravitation system. At the same time, we have interestingly found that the third law of black hole thermodynamics

    更新日期:2020-12-31
  • Quantum weak equivalence principle and the gravitational Casimir effect in superconductors
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-11
    Sebastian Bahamonde; Mir Faizal; James Q. Quach; Richard A. Norte

    We will use Fisher information to properly analyze the quantum weak equivalence principle. We argue that gravitational waves will be partially reflected by superconductors. This will occur as the violation of the weak equivalence principle in Cooper pairs is larger than the surrounding ionic lattice. Such reflections of virtual gravitational waves by superconductors can produce a gravitational Casimir

    更新日期:2020-12-31
  • Resolving Hubble tension with the Milne model
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-17
    Ram Gopal Vishwakarma

    The recent measurements of the Hubble constant based on the standard ΛCDM cosmology reveal an underlying disagreement between the early-Universe estimates and the late-time measurements. Moreover, as these measurements improve, the discrepancy not only persists but becomes even more significant and harder to ignore. The present situation places the standard cosmology in jeopardy and provides a tantalizing

    更新日期:2020-12-31
  • Signatures of minimal length from Casimir–Polder forces with neutrons
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-05
    Fabrizio Pinto

    In this paper, dispersion forces between neutrons are suggested as a probe of the fundamental structure of spacetime. Corrections to standard expressions for the interparticle potentials are obtained through computer algebra system strategies and a novel heuristic argument for comparison with field theory computations. It is confirmed that, to first order in the deformation parameter, the unretarded

    更新日期:2020-12-31
  • Angle deficit and nonlocal gravitoelectromagnetism around a slowly spinning cosmic string
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-28
    Jens Boos

    Cosmic strings, as remnants of the symmetry breaking phase in the Early universe, may be susceptible to nonlocal physics. Here, we show that the presence of a Poincaré-invariant nonlocality—parametrized by a factor exp(−□ℓ2)—regularizes the gravitational field and thereby changes the properties of spacetime: it is now simply connected and the angle deficit around the cosmic string becomes a function

    更新日期:2020-12-31
  • Neutron stars as probes of dark matter
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-07
    M. Ángeles Pérez-García; Joseph Silk

    Neutron Stars (NSs) are compact stellar objects that are stable solutions in General Relativity. Their internal structure is usually described using an equation of state that involves the presence of ordinary matter and its interactions. However there is now a large consensus that an elusive sector of matter in the universe, described as dark matter, remains as yet undiscovered. In such a case, NSs

    更新日期:2020-12-31
  • Quasilocal conservation laws in cosmology: A first look
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-04
    Marius Oltean; Hossein Bazrafshan Moghaddam; Richard J. Epp

    Quasilocal definitions of stress-energy–momentum—that is, in the form of boundary densities (in lieu of local volume densities) — have proven generally very useful in formulating and applying conservation laws in general relativity. In this Essay, we take a basic look into applying these to cosmology, specifically using the Brown–York quasilocal stress-energy–momentum tensor for matter and gravity

    更新日期:2020-12-31
  • Dark matter, dark energy and fundamental acceleration
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-04
    Douglas Edmonds; Djordje Minic; Tatsu Takeuchi

    We discuss the existence of an acceleration scale in galaxies and galaxy clusters and its relevance for the nature of dark matter. The presence of the same acceleration scale found at very different length scales, and in very different astrophysical objects, strongly supports the existence of a fundamental acceleration scale governing the observed gravitational physics. We comment on the implications

    更新日期:2020-12-31
  • From microscopic black hole entropy toward Hawking radiationc
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-30
    Jun Nian; Leopoldo A. Pando Zayas

    The AdS/CFT correspondence has recently provided a novel approach for counting the microstates of black holes impressively matching the macroscopic Bekenstein–Hawking entropy formula of rotating electrically charged asymptotically AdS black holes in four to seven dimensions. This approach is designed for supersymmetric extremal black holes, but can also be extended to nonsupersymmetric, near-extremal

    更新日期:2020-12-31
  • How close is our ΛCDM physical universe to de Sitter spacetime dS4?
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-11
    Arthur E. Fischer

    We introduce a methodology for quantitatively measuring at all times in its evolution how close our physical spatially flat Λ CDM universe with cosmological constant Λ>0 is to the de Sitter spacetime dS4 with de Sitter radius ℓ=3/Λ. The main idea in this study is to align the respective scale factors aΛCDM(t) and aΛ(t) of these two spacetimes, where de Sitter spacetime is taken with respect to a spatially

    更新日期:2020-12-31
  • Real scalar field solutions of the EKG equations including matter
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-30
    A. Cabo Montes de Oca; D. Suarez Fontanella

    Static (not stationary) solutions of the Einstein–Klein–Gordon (EKG) equations including matter are obtained for real scalar fields. The scalar field interaction with matter is considered. The introduced coupling allows the existence of static solutions in contraposition with the case of the simpler EKG equations for real scalar fields and gravity. Surprisingly, when the considered matter is a photon-like

    更新日期:2020-12-30
  • Threshold of primordial black hole formation in Eddington-inspired-Born–Infeld gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-30
    Che-Yu Chen

    It is believed that primordial black holes (PBHs), if they exist, can serve as a powerful tool to probe the early stage of the cosmic history. Essentially, in the radiation-dominated universe, PBHs could form by the gravitational collapse of overdense primordial perturbations produced during inflation. In this picture, one important ingredient is the threshold of density contrast, which defines the

    更新日期:2020-12-30
  • Gödel and Gödel-type solutions in the Palatini f(R,T) gravity theory
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-23
    J. S. Gonçalves; A. F. Santos

    The Palatini f(R,T) gravity theory is considered. The standard Einstein–Hilbert action is replaced by an arbitrary function of the Ricci scalar R and of the trace T of the energy-momentum tensor. In the Palatini approach, the Ricci scalar is a function of the metric and the connection. These two quantities, metric and connection, are taken as independent variables. Then, it is examined whether Palatini

    更新日期:2020-12-24
  • Modified structure equations and mass–radius relations of white dwarfs arising from the linear generalized uncertainty principle
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-18
    Adrian G. Abac; Jose Perico H. Esguerra; Roland Emerito S. Otadoy

    The generalized uncertainty principle (GUP) is a common feature among several approaches related to quantum gravity. An approach to GUP was recently developed that contains both linear and quadratic terms of momenta, from which an infinitesimal phase space volume was derived up to the linear term of momenta. We studied the effects of this linear GUP approach on the structure equations and mass–radius

    更新日期:2020-12-20
  • Geometric torsion, four-form, Riemann duals and Quintessence
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-18
    R. Nitish; Supriya Kar

    We revisit an emergent gravity scenario in (4+1) dimensions underlying a propagating geometric torsion ℋ3 with a renewed interest. We show that a pair-symmetric 4th-order curvature tensor is sourced by Neveu–Schwarz (NS) two-form in a U(1) gauge theoretic formulation. Interestingly, the new spacetime curvature governs a torsion-free geometry sourced by an NS form and shares the properties of the Riemann

    更新日期:2020-12-20
  • Quantum fluctuations and cosmological particle creation from oscillating massive scalar field in two-mode quantum optical states
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-14
    Meghna Rathore; Renu Dhayal; K. K. Venkataratnam

    In this paper, by the use of entangled and nonentangled coherent and squeezed state formalism of two-mode nonclassical states, we studied the chaotic inflationary model of a massive scalar field with quadratic potential in the semiclassical gravity, derived from canonical quantum gravity. It was found that the semiclassical quantum gravity leads to the same power-law expansion of the universe as that

    更新日期:2020-12-15
  • Properties of rotating neutron star in density-dependent relativistic mean-field models
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-12
    Rashid Riahi; Seyed Zafarollah Kalantari

    Equilibrium sequences were developed for rotating neutron stars in the relativistic mean-field interaction framework using four density-dependent equations of state (EOSs) for the neutron star matter. These sequences were constructed for the observed rotation frequencies of 25, 317, 346, 716 and 1122Hz. The bounds of sequences, the secular axisymmetric instability, static and Keplerian sequences were

    更新日期:2020-12-14
  • The stability analysis of brane-induced gravity with quintessence field on the brane with a Gaussian potential
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-11
    A. Ravanpak; G. F. Fadakar

    In this paper, we consider a normal branch of the DGP cosmological model with a quintessence scalar field on the brane as the dark energy component. Using the dynamical system approach, we study the stability properties of the model. We find that λ, as one of our new dimensionless variables which is defined in terms of the quintessence potential, has a crucial role in the history of the universe. We

    更新日期:2020-12-13
  • Thermodynamic aspects of entropic cosmology with viscosity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-11
    I. Brevik; A. V. Timoshkin

    We describe the evolution of the early and late universe from thermodynamic considerations, using the generalized nonextensive Tsallis entropy with a variable exponent. A new element in our analysis is the inclusion of a bulk viscosity in the description of the cosmic fluid. Using the generalized Friedmann equation, a description of the early and the late universe is obtained.

    更新日期:2020-12-13
  • Photon spectrum of asymmetric dark stars
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-05
    Andrea Maselli; Chris Kouvaris; Kostas D. Kokkotas

    Asymmetric Dark Stars, i.e. compact objects formed from the collapse of asymmetric dark matter could potentially produce a detectable photon flux if dark matter particles self-interact via dark photons that kinetically mix with ordinary photons. The morphology of the emitted spectrum is significantly different and therefore distinguishable from a typical black-body one. Given the above and the fact

    更新日期:2020-12-05
  • Imprints of the post-recombination dissipation of helical magnetic field on the Cosmic Microwave Background Radiation
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-04
    Sandhya Jagannathan; Ramkishor Sharma; T. R. Seshadri

    Astrophysical magnetic fields decay primarily via two processes, namely ambipolar diffusion and turbulence. Constraints on the strength and the spectral index of nonhelical magnetic fields have been derived earlier in the literature through the effect of the above-mentioned processes on the cosmic microwave background (CMB) radiation. A helical component of the magnetic field is also produced in various

    更新日期:2020-12-04
  • Quantum relativistic cosmology: Dynamical interpretation and tunneling universe
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-12-04
    H. S. Vieira; V. B. Bezerra; C. R. Muniz; M. S. Cunha

    In this work, the wave functions associated to the quantum relativistic universe, which is described by the Wheeler–DeWitt equation, are obtained. Taking into account different kinds of energy density, namely, matter, radiation, vacuum, dark energy and quintessence, we discuss some aspects of the quantum dynamics. In all these cases, the wave functions of the quantum relativistic universe are given

    更新日期:2020-12-04
  • Attractor inflationary solutions in braneworld scenario
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-30
    Saba Qummer; Abdul Jawad; M. Younas

    This paper is devoted to discuss the attractor solutions of inflationary Chaplygin gas models such as generalized Chaplygin gas, modified Chaplygin gas and generalized cosmic Chaplygin gas in the framework of Randall–Sundrum type II braneworld scenario. We investigate the inflationary parameters like scalar spectral index ns, tensor to scalar ratio r, and the running of scalar index dnsdlnκ as a function

    更新日期:2020-12-01
  • On multifluid perturbations in scalar–tensor cosmology
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-30
    Joseph Ntahompagaze; Shambel Sahlu; Amare Abebe; Manasse R. Mbonye

    In this paper, the scalar–tensor theory is applied to the study of perturbations in a multifluid universe, using the 1+3 covariant approach. Both scalar and harmonic decompositions are instituted on the perturbation equations. In particular, as an application, we study perturbations on a background Friedmann-Robertson-Walker (FRW) cosmology consisting of both radiation and dust in the presence of a

    更新日期:2020-12-01
  • Circular motion and the innermost stable circular orbit for spinning particles around a charged Hayward black hole background
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-30
    Eduard Larrañaga

    The circular orbits of a spinning test particle moving around a charged Hayward black hole is investigated by using the Mathisson–Papapetrou–Dixon equations together with the Tulczyjew spin-supplementary condition. By writing the equations of motion, the effective potential for the description of the test particle is obtained to study the properties of the Innermost Stable Circular Orbit (ISCO). The

    更新日期:2020-12-01
  • Quantum magnetic collapse of a partially bosonized npe-gas: Implications for astrophysical jets
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-30
    R. González Felipe; A. Pérez Martínez; H. Pérez Rojas; G. Quintero Angulo

    We study the quantum magnetic collapse of a partially bosonized npe-gas and obtain that this type of collapse might be one of the mechanisms behind matter expulsion out of compact objects. We check also that this gas might form a stable stream of matter whose collimation is due to its strong self-generated magnetic field. Possible astrophysical applications of these results, in particular related to

    更新日期:2020-12-01
  • Surface tension: Accelerated expansion, coincidence problem & Hubble tension
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-27
    C. Ortiz

    In this paper, we give a physical explanation to the accelerated expansion of the universe, alleviating the tension between the discrepancy of Hubble constant measurements. By the EulerCauchy stress principle, we identify a controversy on the lack of consideration of the surface forces contemplated in the study of the expansion of the universe. We distinguish a new general relativistic effect that

    更新日期:2020-11-27
  • Nonsingular solution with anisotropic fluid in mini bang cosmology
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-27
    Saibal Ray; Anil Kumar Yadav; F. Rahaman; U. Debnath

    In this work, we study cosmological evolution in the mini creation event with anisotropic fluid under the Bianchi-I spacetime. After providing the basic mathematical formalism of the model, we find out the exact solutions in its particular form to the field equations. In order to get physical validity, we have presented elaborate discussions on the graphical results, especially nonsingular behaviour

    更新日期:2020-11-27
  • Prospects for testing the inverse-square law and gravitomagnetism using quantum interference
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-27
    Fayçal Hammad; Alexandre Landry; Kaleb Mathieu

    We examine a simple tabletop experimental setup for probing the inverse-square law of gravity and detecting eventual deviations therefrom. The nature of the setup allows indeed to effectively reach for shorter distances compared to what is allowed by other methods. Furthermore, we show that the same setup could also in principle be used to probe the interaction between gravitomagnetism and the intrinsic

    更新日期:2020-11-27
  • Tunneling under the influence of quantum gravity in black rings
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-25
    Riasat Ali; Kazuharu Bamba; Muhammad Asgher; Syed Asif Ali Shah

    We explore the Lagrangian equation in the background of generalized uncertainty principle. The tunneling radiation through the black ring horizon is observed. We investigated the tunneling radiation through the Hamilton–Jacobi method for solutions of Einstein–Maxwell-dilation gravity theory. The radiation of black ring without back reaction and self-interaction of particles are studied. Furthermore

    更新日期:2020-11-25
  • Black hole entropy from soft hair
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-02
    Malcolm J. Perry

    We start by looking at why we believe that black holes have entropy. According to Boltzmann, the entropy is a measure of the number of microstates of a system. We suggest here that the entropy arises from a holographic conformal field theory on the black hole horizon. Finally, we discuss some of the implications for the information paradox.

    更新日期:2020-11-03
  • Axial gravitational waves in Bianchi I universe
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-11-02
    Sarbari Guha; Sucheta Datta

    In this paper, we have studied the propagation of axial gravitational waves in Bianchi I universe using the Regge–Wheeler gauge. In this gauge, there are only two nonzero components of hμν in the case of axial waves: h0(t,r) and h1(t,r). The field equations in absence of matter have been derived both for the unperturbed as well as axially perturbed metric. These field equations are solved simultaneously

    更新日期:2020-11-03
  • Building models of inflation in no-scale supergravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-22
    John Ellis; Marcos A. G. García; Natsumi Nagata; Dimitri V. Nanopoulos; Keith A. Olive; Sarunas Verner

    After reviewing the motivations for cosmological inflation formulated in the formalism of supersymmetry, we argue that the appropriate framework is that of no-scale supergravity. We then show how to construct within this framework inflationary models whose predictions for the tilt in the spectrum of scalar perturbations, ns, and the ratio, r, of tensor and scalar perturbations coincide with those of

    更新日期:2020-10-30
  • Mass-spin relation of black holes obtained by twin high-frequency quasi-periodic oscillations
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-22
    Ivan Zhivkov Stefanov

    The paper studies the uniqueness and the monotonicity of the mass-spin relation of black holes (BHs) the X-ray power density spectra of which contain twin high-frequency quasi-periodic oscillations in 3:2 ratio. Some of the results are valid for a relatively large class of models — the geodesic models, which attribute the observed pair of HF QPOs to the frequencies of epicyclic motion of inhomogeneities

    更新日期:2020-10-30
  • Deformed phase-space in supersymmetric Kantowski–Sachs model
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-22
    A. Crespo-Hernández; E. A. Mena-Barboza

    We study some consequences of a wave packet resulting as a solution in a class of Supersymmetric Wheeler–DeWitt equation in Kantowski–Sachs minisuperspace. As a result of our analysis, we show that the Supersymmetric noncommutative proposal can modify significantly the universe evolution. The volume expansion, the shear and the characteristic volume are calculated explicit.

    更新日期:2020-10-30
  • Beyond Einstein’s General Relativity: Hybrid metric-Palatini gravity and curvature-matter couplings
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-09-09
    Tiberiu Harko; Francisco S. N. Lobo

    Einstein’s General Relativity (GR) is possibly one of the greatest intellectual achievements ever conceived by the human mind. In fact, over the last century, GR has proven to be an extremely successful theory, with a well established experimental footing, at least for weak gravitational fields. Its predictions range from the existence of black holes and gravitational radiation (now confirmed) to the

    更新日期:2020-10-30
  • Update constraints on neutrino mass and mass hierarchy in light of dark energy models
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-09-07
    Zhenjie Liu; Haitao Miao

    Combining cosmic microwave (CMB) background data from Planck satellite data, Baryon Acoustic Oscillations (BAO) measurements and Type Ia supernovae (SNe Ia) data, we obtain the bounds on total neutrino masses Mν with the approximation of degenerate neutrino masses and for three dark energy models: the cosmological constant (ΛCDM) model, a phenomenological emergent dark energy (PEDE) model and a model-independent

    更新日期:2020-10-30
  • Thermodynamical correspondence of f(R) gravity in the Jordan and Einstein frames
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-09-03
    G. G. L. Nashed; W. El Hanafy; S. D. Odintsov; V. K. Oikonomou

    We study the thermodynamical aspects of f(R) gravity in the Jordan and the Einstein frame, and we investigate the corresponding equivalence of the thermodynamical quantities in the two frames. We examine static spherically symmetric black hole solutions with constant Ricci scalar curvature R, and as we demonstrate, the thermodynamical quantities in the two frames are equivalent. However, for the case

    更新日期:2020-10-30
  • Magnetized cosmological model with variable deceleration parameter
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-09-09
    Sankarsan Tarai; Fakhereh Md. Esmaeili; B. Mishra; S. K. Tripathy

    In this paper, we have derived the field equations in an extended theory of gravity in an anisotropic spacetime background and in the presence of magnetic field. The physical and geometrical parameters of the models are determined with respect to the Hubble parameter using some algebraic approaches. A time varying scale factor has been introduced to analyze the behavior of the model. From some diagnostic

    更新日期:2020-10-30
  • De Sitter scalar–spinor interaction in Minkowski limit
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-09-09
    Y. Ahmadi

    The scalar–spinor interaction Lagrangian is presented by the Yukawa potential. In dS ambient space formalism, the interaction Lagrangian of scalar–spinor fields was obtained from a new transformation which is very similar to the gauge theory. The interaction of massless minimally coupled (mmc) scalar and spinor fields was investigated. The Minkowski limit of the mmc scalar field and massive spinor

    更新日期:2020-10-30
  • The cosmological constant of emergent spacetime in the Newtonian approximation
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-09-03
    J. C. Castro-Palacio; P. Fernández de Córdoba; J. M. Isidro

    We present a simple quantum-mechanical estimate of the cosmological constant of a Newtonian Universe. We first mimic the dynamics of a Newtonian spacetime by means of a nonrelativistic quantum mechanics for the matter contents of the Universe (baryonic and dark) within a fixed (i.e. nondynamical) Euclidean spacetime. Then we identify an operator that plays, on the matter states, a role analogous to

    更新日期:2020-10-30
  • Spinor field solutions in F(B2) modified Weyl gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-09-03
    Vladimir Dzhunushaliev; Vladimir Folomeev

    We consider modified Weyl gravity where a Dirac spinor field is nonminimally coupled to gravity. It is assumed that such modified gravity is some approximation for the description of quantum gravitational effects related to the gravitating spinor field. It is shown that such a theory contains solutions for a class of metrics which are conformally equivalent to the Hopf metric on the Hopf fibration

    更新日期:2020-10-30
  • Erratum: Dispersion of gravitational waves in cold spherical interstellar medium
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-09-19
    Dániel Barta; Mátyás Vasúth

    The study published in IJMPD27(4):1850040, 2018 provided a numerical result for the frequency-shift of GWs due to dispersion in interstellar medium. In order to adjust the metric functions of the originally improperly matched ‘background’ spacetime in Sec. 2.1, the authors have adopted Darmois–Israel junction conditions. In Sec. 4.1 the code used in the original paper erroneously computed the magnitude

    更新日期:2020-10-30
  • Dark energy and neutrino mass from a transient vacuum particle pair model
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-27
    Allan Rosencwaig

    We propose that the transient vacuum fluctuations of quantum fields can be represented by transient vacuum quanta where both the lifetime and spatial extent are given by the Heisenberg Uncertainty Principle, HUP. Accordingly, a quantum field fluctuation at any spatial site results in the creation of a transient HUP-limited vacuum pair, corresponding to the particle and the antiparticle associated with

    更新日期:2020-10-27
  • A pure connection formulation with real fields for gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-27
    J. E. Rosales-Quintero

    We study an SO(1,3) pure connection formulation in four dimensions for real-valued fields, inspired by the Capovilla, Dell and Jacobson complex self-dual approach. By considering the CMPR BF action, also, taking into account a more general class of the Cartan–Killing form for the Lie algebra 𝔰𝔬(1,3) and by refining the structure of the Lagrange multipliers, we integrate out the metric variables in

    更新日期:2020-10-27
  • On extended thermodynamics: From classical to the relativistic regime
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-22
    J. Felix Salazar; Thomas Zannias

    The recent monumental detection of gravitational waves by LIGO, the subsequent detection by the LIGO/VIRGO observatories of a binary neutron star merger seen in the gravitational wave signal GW170817, the first photo of the event horizon of the supermassive black hole at the center of Andromeda galaxy released by the EHT telescope and the ongoing experiments on Relativistic Heavy Ion Collisions at

    更新日期:2020-10-22
  • Three-dimensional slowly rotating black hole in Einstein-power-Maxwell theory
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-19
    M. B. Tataryn; M. M. Stetsko

    A three-dimensional slowly rotating black hole solution in the presence of negative cosmological constant in the Einstein-power-Maxwell theory is studied. It is shown that in the small rotation limit, the electric field, diagonal metric function and thermodynamic properties are the same as for static case, whereas the small rotation gives in addition a nondiagonal metric function and magnetic field

    更新日期:2020-10-21
  • Effective anisotropic stresses of the relic gravitons
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-19
    Massimo Giovannini

    The effective anisotropic stresses induced by the scalar modes of the geometry depend on the coordinate system so that the comparison of the competing results is ultimately determined by the evolution of the pivotal variables in each particular gauge. After arguing that the only reasonable physical coordinate systems for this problem are the ones where the gauge freedom is completely fixed (like the

    更新日期:2020-10-21
  • Nonsingular black holes from charged dust collapse: A concrete mechanism to evade interior singularities in general relativity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-19
    Rodrigo Maier

    In this paper, we examine the gravitational collapse of a nonrelativistic charged perfect fluid interacting with a dark energy component. Given a simple factor for the energy transfer, we obtain a nonsingular interior solution which naturally matches the Reissner–Nordström–de Sitter exterior geometry. We also show that the interacting parameter is proportional to the overall charge of the final black

    更新日期:2020-10-19
  • Role of collisional matter in the framework of extended teleparallel theory
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-10-19
    Muhammad Zeeshan; M. Zubair; Rabia Saleem

    The purpose of this work is to examine the cosmic evolution in the presence of collisional matter (CM) with and without radiations in a modified Teleparallel theory involving a generic function f(T,B) which depends on the scalar torsion T and the boundary term associated to the divergence of torsion 2∇μTμ=B. We select seven novel f(T,B) models including power law, logarithmic models and exponential

    更新日期:2020-10-19
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