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  • Compact scalar field solutions in EiBI gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Victor I. Afonso

    We discuss exact scalar field solutions describing gravitating compact objects in the Eddington-inspired Born–Infeld (EiBI) gravity, a member of the class of (metric-affine formulated) Ricci-based gravity (RBG) theories. We include a detailed account of the RBGs/GR correspondence exploited to analytically solve the field equations. The single parameter 𝜖 of the EiBI model defines two branches for

    更新日期:2020-08-05
  • Numerical study of toroidal magnetic field on the self-gravitating protoplanetary disks
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-26
    Hanifeh Ghanbarnejad; Maryam Ghasemnezhad

    In this paper, we study the self-gravitating accretion disks by considering the toroidal component of magnetic field, Bϕ and wind/outflow in the flow and also investigate the effect of two parameters, β0p and 𝒫, corresponding to magnetic field on the latitudinal structure of such accretion disks. The cooling of the disk is parameterized simply as, (du/dt)cool=−u/tcool (where u is the internal energy

    更新日期:2020-08-05
  • Analytical investigation of wave absorption by a rotating black hole analogue
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-08-05
    Leandro A. Oliveira; Carolina L. Benone; Amanda L. Almeida; Luís C. B. Crispino

    Perturbations in a draining vortex can be described analytically in terms of confluent Heun functions. In the context of analogue models of gravity in ideal fluids, we investigate analytically the absorption length of waves in a draining bathtub, a rotating black hole analogue, using confluent Heun functions. We compare our analytical results with the corresponding numerical ones, obtaining excellent

    更新日期:2020-08-04
  • Measure of complexity for dynamical self-gravitating structures
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-09
    Z. Yousaf; M. Z. Bhatti; T. Naseer

    We consider the definition of complexity for dynamical spherically self-gravitating matter distribution in the presence of heat dissipation introduced by Herrera [L. Herrera, A. Di Prisco and J. Ospino, Phys. Rev. D 98 (2018) 104059] and generalize it in f(R,T,RμνTμν) gravity, where R and T are the Ricci scalar and the trace of energy–momentum tensor, respectively. We measure the complexity of structure

    更新日期:2020-08-03
  • First analytical calculation of black hole shadow in McVittie metric
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-09
    Oleg Yu. Tsupko; Gennady S. Bisnovatyi-Kogan

    Cosmic expansion influences the angular size of black hole shadow. The most general way to describe a black hole embedded into an expanding universe is to use the McVittie metric. So far, the exact analytical solution for the shadow size in the McVittie metric, valid for arbitrary law of expansion and arbitrary position of the observer, has not been found. In this paper, we present the first analytical

    更新日期:2020-08-03
  • Is a Bose–Einstein condensate a good candidate for dark matter? A test with galaxy rotation curves
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-13
    Elías Castellanos; Celia Escamilla-Rivera; Jorge Mastache

    We analyze the rotation curves that correspond to a Bose–Einstein Condensate (BEC)-type halo surrounding a Schwarzschild-type black hole to confront predictions of the model upon observations of galaxy rotation curves. We model the halo as a BEC in terms of a massive scalar field that satisfies a Klein–Gordon equation with a self-interaction term. We also assume that the bosonic cloud is not self-gravitating

    更新日期:2020-08-03
  • An effective cosmological constant from an entropic formulation of gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-13
    I. Díaz-Saldaña; J. C. López-Domínguez; M. Sabido

    In this work, we study a Friedmann–Robertson–Walker (FRW) universe derived from a modified entropy–area relationship. By applying the first law of thermodynamics to the so-called apparent horizon and a modified entropy–area relationship, we obtain a modified Friedmann equation. Solving this model for a perfect fluid with vanishing cosmological constant, we find that for early times, the scale factor

    更新日期:2020-08-03
  • Strong gravitational lensing of a 4-dimensional Einstein–Gauss–Bonnet black hole in homogeneous plasma
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-26
    Xing-Hua Jin; Yuan-Xing Gao; Dao-Jun Liu

    We investigate the strong gravitational lensing of spherically symmetric black holes in the novel Einstein–Gauss–Bonnet (EGB) gravity surrounded by unmagnetized plasma medium. The deflection angle in the strong deflection limit in EGB spacetime with homogeneous plasma is derived. We find that both the coupling constant α in the novel EGB gravity and the presence of plasma can affect the radius of photon

    更新日期:2020-08-03
  • An interacting holographic dark energy model within an induced gravity brane
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-15
    Moulay-Hicham Belkacemi; Zahra Bouabdallaoui; Mariam Bouhmadi-López; Ahmed Errahmani; Taoufik Ouali

    In this paper, we present a model for the late-time evolution of the universe where a dark energy-dark matter interaction is invoked. Dark energy is modeled through an holographic Ricci dark energy component. The model is embedded within an induced gravity braneworld model. For suitable choices of the interaction coupling, the big rip and little rip induced by the holographic Ricci dark energy, in

    更新日期:2020-08-03
  • Traversable wormholes with exponential shape function in modified gravity and general relativity: A comparative study
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Gauranga C. Samanta; Nisha Godani; Kazuharu Bamba

    We have proposed a novel shape function on which the metric that models traversable wormholes is dependent. Using this shape function, the energy conditions, equation-of-state and anisotropy parameter are analyzed in f(R) gravity, f(R,T) gravity and general relativity. Furthermore, the consequences obtained with respect to these theories are compared. In addition, the existence of wormhole geometries

    更新日期:2020-08-03
  • Kerr-AdS black hole behaviors from dark energy
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-09
    A. Belhaj; A. El Balali; W. El Hadri; M. A. Essebani; M. B. Sedra; A. Segui

    We investigate the critical behaviors of four-dimensional Kerr-AdS black holes from quintessential Dark Energy (DE) contributions. Using a moduli space, coordinated by the DE state parameter ω and the quintessence field intensity α, we deal with three different (ω)-models. By elaborating analytical formulas of relevant thermodynamical quantities denoted by X(ω), we find significant similarities and

    更新日期:2020-08-03
  • Compact objects in general relativity: From Buchdahl stars to quasiblack holes
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-30
    José P. S. Lemos; Oleg B. Zaslavskii

    A Buchdahl star is a highly compact star for which the boundary radius R obeys R=98r+, where r+ is the gravitational radius of the star itself. A quasiblack hole is a maximum compact star, or more generically a maximum compact object, for which the boundary radius R obeys R=r+. Quasiblack holes are objects on the verge of becoming black holes. Continued gravitational collapse ends in black holes and

    更新日期:2020-07-31
  • Non-Abelian firewall
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-30
    Douglas Singleton

    A simple, closed-form solution to the Yang–Mills field equations is presented which has a non-Abelian firewall — a spherical “horizon” where the energy density diverges. By the gravity/gauge duality, this non-Abelian firewall implies the existence of a gravitational firewall. Gravitational firewalls have been proposed as a way of resolving the information loss paradox, but at the cost of violating

    更新日期:2020-07-31
  • α-Attractors and reheating in a nonminimal inflationary model
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-30
    R. Shojaee; K. Nozari; F. Darabi

    We study α-attractor models with both E-model and T-model potential in an extended Nonminimal Derivative (NMD) inflation where a canonical scalar field and its derivatives are nonminimally coupled to gravity. We calculate the evolution of perturbations during this regime. Then by adopting inflation potentials of the model we show that in the large N and small α limit, the value of the scalar spectral

    更新日期:2020-07-31
  • Evolution of cosmological horizons of wormhole cosmology
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-28
    Sung-Won Kim

    Recently, we solved Einstein’s field equations to obtain the exact solution of the cosmological model with the Morris–Thorne-type wormhole. We found the apparent horizons and analyzed their geometric natures, including the causal structures. We also derived the Hawking temperature near the apparent cosmological horizon. In this paper, we investigate the dynamic properties of the apparent horizons under

    更新日期:2020-07-29
  • Explorations of the infinite regions of spacetime
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-25
    Florian Beyer; Jörg Frauendiener; Jörg Hennig

    An important concept in Physics is the notion of an isolated system. It is used in many different areas to describe the properties of a physical system which has been isolated from its environment. The interaction with the “outside” is then usually reduced to a scattering process, in which incoming radiation interacts with the system, which in turn emits outgoing radiation. In Einstein’s theory of

    更新日期:2020-07-26
  • Does gravitational radiation impact the stellar habitable zone?
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-25
    J. A. S. Lima; R. C. Santos; J. V. Cunha; F. E. Silva; C. E. Pellicer

    Substellar objects of ultrashort periods (less than 50 min) orbiting central stars and many ultracompact star binary systems of even smaller periods (less than 10 min) have been optically detected in the last few years. Their gravitational luminosities can be of the same order or even much greater than their electromagnetic counterparts thereby also comprising a special class of targets for the Large

    更新日期:2020-07-26
  • Gravitational fields of the magnetic-type
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-25
    A. Danehkar

    Local conformal symmetry introduces the conformal curvature (Weyl tensor) that gets split into its (gravito-) electric and magnetic (tensor) parts. Newtonian tidal forces are expected from the gravitoelectric field, whereas general-relativistic frame-dragging effects emerge from the gravitomagnetic field. The symmetric, traceless gravitoelectric and gravitomagnetic tensor fields can be visualized by

    更新日期:2020-07-26
  • Perspectives of perihelion precession in torsion modified gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-25
    R. Nitish; Rohit K. Gupta; Supriya Kar

    Killing symmetries are revisited in d=5 bulk geometric torsion (GT) perturbation theory to investigate the perihelion precession. Computation reveals a nonperturbative (NP) modification to the precession known in General Relativity (GR). Remarkably the analysis reassures our proposed holographic correspondence between a perturbative GT in bulk and a boundary GR coupled to B2∧F2. In fact, the topological

    更新日期:2020-07-26
  • Testing the weak cosmic censorship conjecture in torus-like black hole under charged scalar field
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-25
    Wei Hong; Benrong Mu; Jun Tao

    We investigate weak cosmic censorship conjecture in charged torus-like black hole by the complex scalar field scattering. Using the relation between the conserved quantities of a black hole and the scalar field, we can calculate the change of the energy and charge within the infinitesimal time. The change of the enthalpy is connected to the change of energy, then we use those results to test whether

    更新日期:2020-07-26
  • Scalar radiation emitted by a source around a spherically symmetric black hole
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-21
    Rafael P. Bernar

    We analyze the scalar radiation emitted by a source in a circular geodesic orbit around a spherically symmetric black hole. The black hole (BH) spacetime considered is quite general, in the sense that it encompasses the solutions of Schwarzschild and Reissner–Nordström, and also the Bardeen solution of a regular BH. We use the framework of quantum field theory in curved spaces to compute the one-particle

    更新日期:2020-07-24
  • The noise of gravitons
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-21
    Maulik Parikh; Frank Wilczek; George Zahariade

    We show that when the gravitational field is treated quantum-mechanically, it induces fluctuations — noise — in the lengths of the arms of gravitational wave detectors. The characteristics of the noise depend on the quantum state of the gravitational field and can be calculated exactly in several interesting cases. For coherent states, the noise is very small, but it can be greatly enhanced in thermal

    更新日期:2020-07-24
  • Properties of a recent quantum extension of the Kruskal geometry
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-21
    Abhay Ashtekar; Javier Olmedo

    Recently, it was shown that, in an effective description motivated by loop quantum gravity, singularities of the Kruskal spacetime are naturally resolved [A. Ashtekar, J. Olmedo and P. Singh, Phys. Rev. Lett.121 (2018) 241301; A. Ashtekar, J. Olmedo and P. Singh, Phys. Rev. D98 (2018) 126003]. In this paper, we explore a few properties of this quantum corrected effective metric. In particular, we (i)

    更新日期:2020-07-24
  • Hadamard parametrix of the Feynman Green’s function of a five-dimensional charged scalar field
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-13
    Visakan Balakumar; Elizabeth Winstanley

    The Hadamard parametrix is a representation of the short-distance singularity structure of the Feynman Green’s function for a quantum field on a curved spacetime background. Subtracting these divergent terms regularizes the Feynman Green’s function and enables the computation of renormalized expectation values of observables. We study the Hadamard parametrix for a charged, massive, complex scalar field

    更新日期:2020-07-24
  • Stationary scalar and vector clouds around Kerr–Newman black holes
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-13
    Nuno M. Santos; Carlos A. R. Herdeiro

    Massive bosons in the vicinity of Kerr–Newman black holes can form pure bound states when their phase angular velocity fulfills the synchronization condition, i.e. at the threshold of superradiance. The presence of these stationary clouds at the linear level is intimately linked to the existence of Kerr black holes with synchronized hair at the nonlinear level. These configurations are very similar

    更新日期:2020-07-24
  • Astrophysical implications of neutron star inspiral and coalescence
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-13
    John L. Friedman; Nikolaos Stergioulas

    The first inspiral of two neutron stars observed in gravitational waves was remarkably close, allowing the kind of simultaneous gravitational wave and electromagnetic observation that had not been expected for several years. Their merger, followed by a gamma-ray burst and a kilonova, was observed across the spectral bands of electromagnetic telescopes. These GW and electromagnetic observations have

    更新日期:2020-07-24
  • Static black holes without spatial isometries: From AdS multipoles to electrovacuum scalarization
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-13
    Carlos Herdeiro; Eugen Radu

    We review recent results on the existence of static black holes (BHs) without spatial isometries in four spacetime dimensions and propose a general framework for their study. These configurations are regular on and outside a horizon of spherical topology. Two different mechanisms allowing for their existence are identified. The first one relies on the presence of a solitonic limit of the BHs; when

    更新日期:2020-07-24
  • Generating solutions of Ricci-based gravity theories from general relativity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Emanuele Orazi

    We generalize the algorithm that establishes the correspondence between metric-affine Eddington-inspired Born-Infeld (EiBI) gravity and General Relativity (GR) to any bosonic matter sector. Along the way, a polished version of the proof of existence of a metric compatible frame associated to any metric-affine Ricci-Based Gravity (RBG) is presented. Particular attention is given to the problem of generating

    更新日期:2020-07-24
  • Tidal forces in the charged Hayward black hole spacetime
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Haroldo C. D. Lima Junior; Luís C. B. Crispino

    Tidal forces produced by black holes are an important result of General Relativity related to the spacetime curvature tensor. Among the astrophysical implications of tidal forces, the tidal disruption events stand out. We analyze the tidal forces in the spacetime of an electrically charged Hayward regular black hole, obtaining the components of the tidal tensor and the geodesic deviation equation.

    更新日期:2020-07-24
  • A proof of the strong cosmic censorship conjecture
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Shahar Hod

    The Penrose strong cosmic censorship conjecture asserts that Cauchy horizons inside dynamically formed black holes are unstable to remnant matter fields that fall into the black holes. The physical importance of this conjecture stems from the fact that it provides a necessary condition for general relativity to be a truly deterministic theory of gravity. Determining the fate of the Penrose conjecture

    更新日期:2020-07-24
  • Cosmological constant in coherent quantum gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Craig Hogan

    It is argued that quantum states of geometry, like those of particles, should be coherent on light cones of any size. An exact classical solution, the gravitational shock wave of a relativistic point particle, is used to estimate gravitational drag from coherent energy flows, and the expected gravitational effect of virtual transverse vacuum energy fluctuations on surfaces of causal diamonds. It is

    更新日期:2020-07-24
  • On deformations of classical mechanics due to plank-scale physics
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Olga I. Chashchina; Abhijit Sen; Zurab K. Silagadze

    Several quantum gravity and string theory thought experiments indicate that the Heisenberg uncertainty relations get modified at the Planck scale so that a minimal length do arises. This modification may imply a modification of the canonical commutation relations and hence quantum mechanics at the Planck scale. The corresponding modification of classical mechanics is usually considered by replacing

    更新日期:2020-07-24
  • Galileon inflation field with three-dark eras of the universe
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    A. I. Keskin

    In this paper, we discuss possible three early eras of the universe in the theoretical context of the Galilean cosmology. The first phase is a slow-roll inflation phase in which the friction term in the equations of motion dominates over the kinetic term. This is the initial vacuum state leading to quasi-de Sitter expansion. The second phase is where the cosmological perturbations are supposed to be

    更新日期:2020-07-24
  • Gravitational waves in modified Gauss–Bonnet gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Tomohiro Inagaki; Masahiko Taniguchi

    We study the gravitational waves (GWs) in modified Gauss–Bonnet gravity. Applying the metric perturbation around a cosmological background, we obtain explicit expressions for the wave equations. It is shown that the speed of the traceless mode is equal to the speed of light. An additional massive scalar mode appears in the propagation of the GWs. To find phenomena beyond the general relativity, the

    更新日期:2020-07-24
  • Coordinate-time lapse function of FLRW accelerated expanding universe in dRGT massive gravity theory
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-07-07
    Husin Alatas; Ahmad K. Falah; Trio Wibowo; Muhammad A. Qohhar; Bobby E. Gunara

    In this paper, we discuss the behavior of coordinate-time dependent lapse function of FLRW metric of an accelerated expanding universe in the de Rham–Gabadadze–Tolley massive gravity theory. Physically, this function is considered to connect a general observer coordinate-time to the related proper-time and also to another normal observer under specific condition. We find that in the standard dRGT formalism

    更新日期:2020-07-24
  • Quantum superposition of massive bodies
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-26
    Robert M. Wald

    I describe the work done in collaboration with A. Belenchia, F. Giacomini, E. Castro-Ruiz, C. Bruckner and M. Aspelmeyer that analyzes a gedanken experiment involving a massive body that is put into a quantum superposition. Remarkably, even for a nonrelativistic body, both vacuum fluctuations of the gravitational field and the quantization of gravitational radiation are essential in order to avoid

    更新日期:2020-07-24
  • Scalar modes, spontaneous scalarization and circular null-geodesics of black holes in scalar-Gauss–Bonnet gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-26
    Caio F. B. Macedo

    In general relativity, astrophysical black holes (BHs) are simple objects, described by just their mass and spin. These simple solutions are not exclusive to general relativity, as they also appear in theories that allow for an extra scalar degree of freedom. Recently, it was shown that some theories which couple a scalar field with the Gauss–Bonnet invariant can have the same classic black hole solutions

    更新日期:2020-07-24
  • Particle creation by wormholes: A 1 + 1 model
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-26
    Gonzalo Gurrea-Ysasi; Gonzalo J. Olmo

    The propagation of a free massless scalar field in a 1+1-dimensional Minkowski space modeling, a wormhole is considered. The wormhole model consists on two timelike trajectories, which represent the entrance and the exit of the wormhole, connected via some transfer function that specifies how incoming modes that reach the entrance are transferred to the exit. We find that particles and energy fluxes

    更新日期:2020-07-24
  • Principle of equivalence at Planck scales and the zero-point length of spacetime — A synergistic description of quantum matter and geometry —
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-26
    T. Padmanabhan

    At mesoscopic scales close to, but somewhat larger than, Planck length, one could describe quantum spacetime and matter in terms of a quantum-corrected geometry. The key feature of such a description is the introduction of a zero-point length into the spacetime. When we proceed from quantum geometry to quantum matter, the zero-point length will introduce corrections in the propagator of matter field

    更新日期:2020-07-24
  • From fundamental physics to tests with compact objects in metric-affine theories of gravity
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-05-26
    Diego Rubiera-Garcia

    This paper provides a short but comprehensible overview of some relevant aspects of metric-affine theories of gravity in relation to the physics and astrophysics of compact objects. We shall highlight the pertinence of this approach to supersede General Relativity on its strong-field regime, as well as its advantages and some of its difficulties. Moreover, we shall reflect on the present and future

    更新日期:2020-07-24
  • The effect of dark matter on stars at the Galactic center: The paradox of youth problem
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-22
    Ebrahim Hassani; Reza Pazhouhesh; Hossein Ebadi

    Stars that evolve near the Galactic massive black hole show strange behaviors. The spectroscopic features of these stars show that they must be old. But their luminosities are much higher than the amounts that are predicted by the current stellar evolutionary models, which means that they must be active and young stars. In fact, this group of stars shows signatures of old and young stars, simultaneously

    更新日期:2020-07-24
  • Geometrothermodynamics of black hole binary systems
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-05-20
    Hernando Quevedo; María N. Quevedo; Alberto Sánchez

    We study a stationary and axisymmetric binary system composed of two identical Kerr black holes, whose physical parameters satisfy the Smarr thermodynamic formula. Then, we use the formalism of geometrothermodynamics to show that the spatial distance between the black holes must be considered as a thermodynamic variable. We investigate the main thermodynamic properties of the system by using the contact

    更新日期:2020-07-24
  • Bianchi type I cosmological model with perfect fluid and string in f(T) theory of gravitation
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-03
    V. R. Chirde; S. P. Hatkar; S. D. Katore

    We have studied LRS Bianchi type I cosmological models with barotropic perfect fluid and cosmic string in the framework of f(T) theory of gravitation. We have assumed that expansion of the model is proportional to the shear scalar. Hybrid law of expansion is also used to solve the field equations. Three different functional forms of the function f(T) such as f(T)=η(−T)m+c,f(T)=emT and f(T)=γT+ηTm are

    更新日期:2020-07-24
  • Study of warm inflationary models and their parameter estimation from CMB
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-16
    Richa Arya; Raghavan Rangarajan

    Warm inflation is a natural and well-motivated description of cosmic inflation which accounts for the inflaton dissipation and radiation production during the inflationary phase, neglected in the standard cold description. It results in crucial differences in the imprints on the Cosmic Microwave Background (CMB) radiation from the standard cold description. In this study, we consider warm inflation

    更新日期:2020-07-24
  • Impact of orbital orientations and radii on TianQin constellation stability
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-07
    Zhuangbin Tan; Bobing Ye; Xuefeng Zhang

    TianQin is a proposed space-based gravitational-wave observatory mission to be deployed in high circular Earth orbits. The equilateral-triangle constellation, with a nearly fixed orientation, can be distorted primarily under the lunisolar perturbations. To accommodate science payload requirements, one must optimize the orbits to stabilize the configuration in terms of arm-length, relative velocity

    更新日期:2020-07-24
  • Quintessence and tachyon dark energy in interaction with dark matter: Observational constraints and model selection
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-22
    Sandro M. R. Micheletti

    We derive two field theory models of interacting dark energy, one in which dark energy is associated with the quintessence and another in which it is associated with the tachyon. In both, instead of choosing arbitrarily the potential of scalar fields, these are specified implicitly by imposing that the dark energy fields must behave as the new agegraphic dark energy. The resulting models are compared

    更新日期:2020-07-24
  • Constraints on light dark matter particles using white dwarf stars
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-03
    Grigoris Panotopoulos; Ilídio Lopes

    We report constraints on the nucleon-dark matter particle cross-section using the internal luminosity of observed white dwarf stars in the globular cluster Messier 4. Our results cover the parameter space corresponding to relatively light dark matter particles, in the sub GeV range, which is known to be very difficult to be probed by direct dark matter searches. The additional luminosity coming from

    更新日期:2020-07-24
  • Quantum fluctuations and the Casimir effect
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-07
    Daniel Chemisana; Jaume Giné; Jaime Madrid

    The most important observable consequence of the vacuum fluctuations is the Casimir effect. Its classical manifestation is a force between two uncharged conductive plates placed a few nanometers apart. In this work, we improve the deduction of the Casimir effect from the uncertainty principle by using an effective radius for the quantum fluctuations. Moreover, the existence of this effective distance

    更新日期:2020-07-24
  • Solar system tests of a new class of f(z) theory
    Int. J. Mod. Phys. D (IF 2.154) Pub Date : 2020-06-22
    Ji-Yao Wang; Chao-Jun Feng; Xiang-Hua Zhai; Xin-Zhou Li

    Recently, a new kind of f(z) theory is proposed to provide a different perspective for the development of reliable alternative models of gravity in which the f(R) Lagrangian terms are reformulated as polynomial parametrizations f(z). In the previous study, the parameters in the f(z) models have been constrained by using cosmological data. In this paper, these models will be tested by the observations

    更新日期:2020-07-24
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