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  • A new analytical approximation of luminosity distance by optimal HPM-Padé technique
    Phys. Dark Universe (IF 4.473) Pub Date : 2021-01-14
    Bo Yu; Jian-Chen Zhang; Tong-Jie Zhang; Tingting Zhang

    By the use of homotopy perturbation method-Padé (HPM-Padé) technique, a new analytical approximation of luminosity distance in the flat universe is proposed, which has the advantage of significant improvement for accuracy in approximating luminosity distance over cosmological redshift range within 0≤z≤2.5. Then we confront the analytical expression of luminosity distance that is obtained by our new

    更新日期:2021-01-19
  • New preinflation
    Phys. Dark Universe (IF 4.473) Pub Date : 2021-01-19
    Mauricio Bellini

    I propose a new model of preinflation, where the universe suffers a transition from an initial stable state [such that the universe is initially at the minimum of a ϕ-quartic potential: V(ϕ)∼ϕ4], to an unstable evolving state that drives the initial accelerated expansion. Using Relativistic Quantum Geometry (RQG), I demonstrate that back-reaction produced by the inflaton field fluctuations should be

    更新日期:2021-01-19
  • Wormholes supported by dark energy in f(T) gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2021-01-01
    Kh. Saaidi; S. Tavakoli

    Using the static, spherically symmetry condition for space time, we have obtained several geometries for wormholes which is supported by a general form of dark energy in the f(T) scenario of gravity ( T is the torsion scalar). It has been shown that some obtained geometries can explain the traversable wormhole, but the NEC or WEC are not violated. These solutions are obtained according to some specific

    更新日期:2021-01-12
  • Slow-roll inflation in f(R,T) gravity and a modified Starobinsky-like inflationary model
    Phys. Dark Universe (IF 4.473) Pub Date : 2021-01-04
    Mauricio Gamonal

    In this work, we studied the slow-roll approximation of cosmic inflation within the context of f(R,T) gravity, where R is the scalar curvature, and T is the trace of the energy–momentum tensor. By choosing a minimal coupling between matter and gravity, we obtained the modified slow-roll parameters, the scalar spectral index (ns), the tensor spectral index (nT), and the tensor-to-scalar ratio (r). We

    更新日期:2021-01-10
  • Regularized Lovelock gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2021-01-06
    Alessandro Casalino; Aimeric Colléaux; Massimiliano Rinaldi; Silvia Vicentini

    A four-dimensional regularization of Lovelock–Lanczos gravity up to an arbitrary curvature order is considered. We show that Lovelock–Lanczos terms can provide a non-trivial contribution to the Einstein field equations in four dimensions, for spherically symmetric and Friedmann–Lemaître–Robertson–Walker spacetimes, as well as at first order in perturbation theory around (anti) de Sitter vacua. We will

    更新日期:2021-01-10
  • Perturbations in Regularized Lovelock Gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2021-01-08
    Alessandro Casalino; Lorenzo Sebastiani

    In this paper we study the perturbation theory of the recently proposed Regularized Lovelock Gravity (Glavan and Lin, 2020), on the curved Friedmann–Lemaître–Robertson–Walker (FLRW) space–time. We provide the first order perturbation equations both in the scalar and tensor sector in the presence of an additional minimally coupled scalar field. A general expression for the velocity of gravitational

    更新日期:2021-01-10
  • Hawking–Page phase transitions in four-dimensional Einstein–Gauss–Bonnet gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2021-01-04
    Yuan-Yuan Wang; Bing-Yu Su; Nan Li

    The Hawking–Page (HP) phase transitions of the anti-de Sitter black holes in the extended phase space are studied in a novel four-dimensional Einstein–Gauss–Bonnet (4EGB) gravity, which is proposed by rescaling the Gauss–Bonnet (GB) coupling constant α→α∕(d−4) in d dimensions and redefining the four-dimensional gravity in the limit d→4. The GB term shows nontrivial contributions to both black hole

    更新日期:2021-01-07
  • Quantifying the S8 tension with the Redshift Space Distortion data set
    Phys. Dark Universe (IF 4.473) Pub Date : 2021-01-01
    David Benisty

    One problem of the ΛCDM model is the tension between the S8 found in Cosmic Microwave Background (CMB) experiments and the smaller one obtained from large-scale observations in the late Universe. The σ8 quantifies the relatively high level of clustering. Likelihood analyses of the Redshift Space Distortion (RSD) selected data set yields: S8=0.700−0.037+0.038. The fit has 3σ tension with the Planck

    更新日期:2021-01-06
  • Emergent Dark Energy, neutrinos and cosmological tensions
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-28
    Weiqiang Yang; Eleonora Di Valentino; Supriya Pan; Olga Mena

    The Phenomenologically Emergent Dark Energy model, a dark energy model with the same number of free parameters as the flat ΛCDM, has been proposed as a working example of a minimal model which can avoid the current cosmological tensions. A straightforward question is whether or not the inclusion of massive neutrinos and extra relativistic species may spoil such an appealing phenomenological alternative

    更新日期:2021-01-04
  • Subhorizon linear Nash–Greene perturbations with constraints on H(z) and the deceleration parameter q(z)
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-17
    Abraão J.S. Capistrano; Paola T.Z. Seidel; Hemerson R. Duarte

    The Hubble parameter H(z), as a function of redshift, is modified by the presence of a new term originated from the extrinsic curvature in a four embedded space–time. Assuming an asymptotic expansion factor a∼0 or, equivalently z→∞, it is obtained a nearly resemblance of the present model (β-model) with the wCDM model with H(z)∼HwCDM(z) at background level. We test the models using a pack of recent

    更新日期:2020-12-31
  • Partition function and coherent states for the quantum multiverse
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-30
    Mir Hameeda; Mario C. Rocca; Aram Bahroz Brzo

    Motivated by a wider acceptance of the quantum cosmology and the idea of multiverse, we follow the second and third quantization formalism for the conceptual comprehension of quantum multiverse. The other motivating feature to pursue the present study is that at the different levels of quantization the equation of quantum state is similar to that of harmonic oscillator, which encourages us to give

    更新日期:2020-12-31
  • Constraining the parameters of modified Chaplygin gas in Brans–Dicke theory
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-24
    Ujjal Debnath

    We have explored the modified Chaplygin gas (MCG) in the background of Brans–Dicke theory in presence of radiation and dark matter. We have assumed that the MCG, radiation and dark matter are conserved separately. To investigate the fitting observational data, we constrain the model using current observations and then compare with ΛCDM model in Einstein’s gravity and in BD theory using the information

    更新日期:2020-12-30
  • Yet another test of Radial Acceleration Relation for galaxy clusters
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-25
    S. Pradyumna; Sajal Gupta; Sowmya Seeram; Shantanu Desai

    We carry out a test of the radial acceleration relation (RAR) for galaxy clusters from two different catalogs compiled in literature, as an independent cross-check of two recent analyses, which reached opposite conclusions. The datasets we considered include a Chandra sample of 12 clusters and the X-COP sample of 12 clusters. For both the samples, we find that the residual scatter is small (0.11-0

    更新日期:2020-12-28
  • On overspinning of black holes in higher dimensions
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-20
    Sanjar Shaymatov; Naresh Dadhich

    It turns out that repulsive effect due to rotation of a rotating black hole dominates over attraction due to mass for large r in dimensions >5. This gives rise to a remarkable result that black hole in these higher dimensions in contrast to lower dimensional ones cannot be overspun even under linear test particle accretion. Further if a black hole in dimension >4 has one of its rotation parameters

    更新日期:2020-12-26
  • Coupled multi-Proca vector dark energy
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-17
    L. Gabriel Gómez; Yeinzon Rodríguez

    We study a new class of vector dark energy models where multi-Proca fields Aμa are coupled to cold dark matter by the term f(X)L̃m where f(X) is a general function of X≡−12AaμAμa and L̃m is the cold dark matter Lagrangian. From here, we derive the general covariant form of the novel interaction term sourcing the field equations. This result is quite general in the sense that encompasses Abelian and

    更新日期:2020-12-24
  • Constraining alternatives to a cosmological constant: Generalized couplings and scale invariance
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-24
    C.B.D. Fernandes; C.J.A.P. Martins; B.A.R. Rocha

    We present a comparative analysis of observational low-redshift background constraints on three candidate models for explaining the low-redshift acceleration of the universe. The generalized coupling model by Feng and Carloni and the scale invariant model by Maeder (both of which can be interpreted as bimetric theories) are compared to the traditional parametrization of Chevallier, Polarski and Linder

    更新日期:2020-12-24
  • Decoupling gravitational sources in f(R,T) gravity under class I spacetime
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-04
    S.K. Maurya; Francisco Tello-Ortiz; Saibal Ray

    We present a simple and effective new methodology to build up self-gravitating structures driven by an imperfect fluid distributions. This approach is developed within the framework of f(R,T) gravity theory by combining two geometrical schemes, the gravitational decoupling by means of minimal geometric deformation and the embedding technique, specifically the class I grasp. The former, allows to introduce

    更新日期:2020-12-21
  • Cosmic conundra explained by thermal history and primordial black holes
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-11
    Bernard Carr; Sébastien Clesse; Juan García-Bellido; Florian Kühnel

    A universal mechanism may be responsible for several unresolved cosmic conundra. The sudden drop in the pressure of relativistic matter at W±∕Z0 decoupling, the quark–hadron transition and e+e− annihilation enhances the probability of primordial black hole (PBH) formation in the early Universe. Assuming the amplitude of the primordial curvature fluctuations is approximately scale-invariant, this implies

    更新日期:2020-12-15
  • Modelling Casimir wormholes in extended gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-10
    Sunil Kumar Tripathy

    A model of traversable wormhole in an extended gravity theory has been proposed. The Casimir effect and Generalized Uncertainty Principle (GUP) arising out of the concept of minimal length have been considered to obtain the shape function, radial and tangential pressure of the wormhole. The effects of the GUP parameter and the parameter of the extended gravity theory on the wormhole properties have

    更新日期:2020-12-14
  • Black hole solutions in modified gravity induced by quantum metric fluctuations
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-08
    Jin-Zhao Yang; Shahab Shahidi; Tiberiu Harko; Shi-Dong Liang

    The inclusion of the quantum fluctuations of the metric in the geometric action is a promising avenue for the understanding of the quantum properties of gravity. In this approach the metric is decomposed in the sum of a classical and of a fluctuating part, of quantum origin, which can be generally expressed in terms of an arbitrary second order tensor, constructed from the metric, and from the thermodynamic

    更新日期:2020-12-10
  • Nonsingular black holes and nonsingular universes in the regularized Lovelock gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-05
    Changjun Gao; Shuang Yu; Jianhui Qiu

    It is found that, when the coupling constants αp in the theory of regularized Lovelock gravity are properly chosen and the number of Lovelock tensors p→∞, there exist a fairly large number of nonsingular (singularity free) black holes and nonsingular universes. Some nonsingular black holes have numerous horizons and numerous energy levels (a bit like atom) inside the outer event horizon. On the other

    更新日期:2020-12-08
  • Lagrangian formulation for an extended cosmological equation-of-state
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-25
    Grigoris Panotopoulos; Ilídio Lopes; Ángel Rincón

    We show that the extended cosmological equation-of-state developed starting from a Chaplygin equation-of-state, recently applied to stellar modelling, is a viable dark energy model consistent with standard scalar potentials. Moreover we find a Lagrangian formulation based on a canonical scalar field with the appropriate self-interaction potential. Finally, we fit the scalar potential obtained numerically

    更新日期:2020-12-07
  • Structure formation and the matter power-spectrum in the Rh=ct universe
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-12-02
    Manoj K. Yennapureddy; Fulvio Melia

    Inflation drives quantum fluctuations beyond the Hubble horizon, freezing them out before the small-scale modes re-enter during the radiation dominated epoch, and subsequently decay, while large-scale modes re-enter later during the matter dominated epoch and grow. This distinction shapes the matter power spectrum and provides observational evidence in support of the standard model. In this paper,

    更新日期:2020-12-05
  • Anisotropic spheres via embedding approach in R+βR2 gravity with matter coupling
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-14
    G. Mustafa; Xia Tie-Cheng; Mushtaq Ahmad; M. Farasat Shamir

    The manifesto of the current article is to investigate the compact anisotropic matter profiles in the context of one of the modified gravitational theories, known as f(R,T) gravity, where R is a Ricci Scalar and T is the trace of the energy–momentum tensor. To achieve the desired goal, we capitalized on the spherical symmetric space–time and utilized the embedding class-1 solution via Karmarkar’s condition

    更新日期:2020-12-01
  • Asymptotically massive-BTZ black holes with nonlinear electrodynamics in massive gravity theory
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-19
    M. Dehghani

    The field equations of Einstein-massive gravity theory has been solved in a three-dimensional spherically symmetric spacetime, and in the presence of three alternative theories of nonlinear electrodynamics, separately. As the result, three novel classes of nonlinearly charged black holes have been obtained in massive gravity theory, which are asymptotically massive-BTZ black holes. The solutions of

    更新日期:2020-11-25
  • Strong deflection gravitational lensing for photon coupled to Weyl tensor in a charged Kiselev black hole
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-21
    G. Abbas; Asif Mahmood; M. Zubair

    Strong deflection gravitational lensing is investigated for photon coupled to Weyl tensor in a charged Kiselev black hole, and its observables have been found. We get the asymptotically flat solutions, for the appropriate range of the equation of state parameter ω̃. Constructing the action corresponding to the electromagnetic field coupled to Weyl tensor, the equation of motion for the photon coupled

    更新日期:2020-11-23
  • Quasinormal modes of the Dirac field in the consistent 4D Einstein–Gauss–Bonnet gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-14
    M.S. Churilova

    Recently a consistent well-defined 4-dimensional Einstein–Gauss–Bonnet theory of gravity was suggested in [K. Aoki, M. Gorji and S. Mukohyama, Phys. Lett. B 810, 135843 (2020)]. While quasinormal modes of bosonic fields for this theory have been recently studied, there is no such study for fermionic fields. Here we calculate quasinormal modes of the Dirac field for spherically symmetric asymptotically

    更新日期:2020-11-21
  • Coronal heating problem solution by means of axion origin photons
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-13
    Vitaliy D. Rusov; Igor V. Sharph; Vladimir P. Smolyar; Maxim V. Eingorn; Margarita E. Beglaryan

    In this paper we advocate for the idea that two seemingly unrelated mysteries with almost 90 year history – the nature of dark matter and the million-degree solar corona – may be but two sides of the same coin – the axions of dark matter born in the core of the Sun and photons of axion origin in the million-degree solar corona, whose modulations are controlled by the anticorrelated modulation of the

    更新日期:2020-11-17
  • Rational orbits around 4D Einstein–Lovelock black holes
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-14
    Hou-Yu Lin; Xue-Mei Deng

    The orbital dynamics in the strong gravitational field might present unique features of quantum gravity and high-dimensional theory. In this paper, a timelike particle’s periodic orbits around the 4-dimensional Einstein–Lovelock (4D−EL) black holes are investigated by employing a classification of the zoom–whirl structure with a rational number q. It is found that these rational (periodic) orbits around

    更新日期:2020-11-17
  • Transitioning universe with hybrid scalar field in Bianchi I space–time
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-10
    Anil Kumar Yadav; A.M. Alshehri; Nafis Ahmad; G.K. Goswami; Mukesh Kumar

    In this paper we investigate a Bianchi type I transitioning Universe in Brans–Dicke theory. To get an explicit solution of the field equations, we assume scalar field as ϕ=ϕ0tαexp(βt)δ with ϕ0, α, β and δ as constants. The values of α and β are obtained by probing the proposed model with recent observational Hubble data (OHD) points. The interacting and non-interacting scenarios between dark matter

    更新日期:2020-11-12
  • Hairy black holes by gravitational decoupling
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-11
    J. Ovalle; R. Casadio; E. Contreras; A. Sotomayor

    Black holes with hair represented by generic fields surrounding the central source of the vacuum Schwarzschild metric are examined under the minimal set of requirements consisting of (i) the existence of a well defined event horizon, namely, we require the Killing horizon coincides with the causal horizon and (ii) the strong or dominant energy condition for the hair outside the horizon. We develop

    更新日期:2020-11-12
  • Dirac dark matter in a radiative neutrino model
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-07
    Hiroshi Okada; Yutaro Shoji

    We propose a simple radiative neutrino mass scenario with a Dirac dark matter candidate, which is minimally realized by a Z3 symmetry. We introduce two Dirac neutrinos and two inert doublets. We demonstrate that the model has a large allowed region that satisfies the constraints from neutrino oscillation data, lepton flavor violations, direct/indirect detection of dark matter and dark matter relic

    更新日期:2020-11-12
  • Quasinormal spectra of scale-dependent Schwarzschild–de Sitter black holes
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-07
    Grigoris Panotopoulos; Ángel Rincón

    We compute the quasinormal spectra for scalar, Dirac and electromagnetic perturbations of the Schwarzschild–de Sitter geometry in the framework of scale-dependent gravity, which is one of the current approaches to quantum gravity. Adopting the widely used WKB semi-classical approximation, we investigate the impact on the spectrum of the angular degree, the overtone number as well as the scale-dependent

    更新日期:2020-11-12
  • Generalized gravitational baryogenesis of well-known f(T,TG) and f(T,B) models
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-24
    Nadeem Azhar; Abdul Jawad; Shamaila Rani

    The baryogenesis presents the theoretical mechanism that describes the matter–antimatter asymmetry in the history of early universe. In this work, we investigate the gravitational baryogenesis phenomena in the frameworks of f(T,TG) (where T and TG are the torsion scalar and teleparallel equivalent to the Gauss–Bonnet term respectively) and f(T,B) (where B denotes the boundary term between torsion and

    更新日期:2020-11-09
  • Does emergent scenario in Hořava–Lifshitz gravity demand a ghost field?
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-02
    Akash Bose; Subenoy Chakraborty

    The non-singular model of the Universe i.e. emergent scenario is now very well known in cosmology. In Einstein gravity such type of singularity free solution is possible in the context of non-equilibrium thermodynamical prescription (both in first and 2nd order theory) with particle creation mechanism. Also there are various models of emergent scenario in different gravity theories. The present work

    更新日期:2020-11-09
  • Evolution of matter perturbations and observational constraints on tachyon scalar field model
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-29
    F. Felegary; I.A. Akhlaghi; H. Haghi

    In this paper, the tachyon scalar field model is compared with the ΛCDM standard model using a set of observational data consisting of BBN, H(z), CMB, BAO, SNIa and f(z)σ8. The comparison is carried out at background and perturbation levels. Since the mass of the tachyon scalar field is very small and its effective sound speed is in the order of the speed of light (ceff≈1), the dark energy component

    更新日期:2020-11-06
  • Classical universe arising from quantum cosmology
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-11-02
    S. Jalalzadeh; M. Rashki; S. Abarghouei Nejad

    In this paper, we study the classical limit and unitary evolution of quantum cosmology by applying the Weyl–Wigner–Groenewold–Moyal formalism of deformation quantization to quantum cosmology of a homogeneous and isotropic universe with positive spatial curvature and conformally coupled scalar field. The corresponding quantum cosmology (similar to the Schrödinger interpretation in canonical quantization

    更新日期:2020-11-06
  • Starobinsky inflation in emergent gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-19
    İlim İrfan Çimdiker

    Inflation is the main paradigm for explaining the homogeneity and isotropy of the observed universe. In view of its agreement with the Planck CMB data, we studied in this work Starobinsky inflation in models of induced gravity. Induced gravity theories are attractive because they arise from matter loops and have the potential to qualify as natural.

    更新日期:2020-10-29
  • Perfect fluid filled universe in odd dimensional pure Lovelock gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-13
    Sudan Hansraj; Nomfundo Gabuza

    It is well known that d=2N+1 dimensional pure Lovelock metrics do not describe bounded distributions neither do they admit nontrivial vacuum solutions. On this basis it has been variously claimed that matter fields should be nondynamical. However, from earlier work it has long been demonstrated fairly generally that 2N+1 pure Lovelock solutions are not kinematic. In this work we find perfect fluid

    更新日期:2020-10-29
  • Anisotropic compact stellar objects in modified Gauss–Bonnet gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-22
    M. Sharif; Amna Ramzan

    This paper is devoted to studying anisotropic compact stellar structures by adopting embedding class-1 technique in the background of modified Gauss–Bonnet gravity. The unknown constants are evaluated by the matching of interior spacetime with the Schwarzschild exterior geometry corresponding to f(G)=χGn model, where χ and n are positive constants. The observed masses of compact star candidates (SAX

    更新日期:2020-10-29
  • Computing the luminosity distance via optimal homotopy perturbation method
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-14
    Bo Yu; Zi-Hua Wang; De-Zi Liu; Tong-Jie Zhang

    We propose a new algorithm for computing the luminosity distance in the flat universe with a cosmological constant based on Shchigolev’s homotopy perturbation method, where the optimization idea is applied to prevent the arbitrariness of initial value choice in Shchigolev’s homotopy. Compared with the some existing numerical methods, the result of numerical simulation shows that our algorithm is a

    更新日期:2020-10-15
  • The expansion of the universe in binary star systems
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-05
    Kazuhiro Agatsuma

    Can all binary star systems merge in infinite time by emitting gravitational waves? The answer is no. The orbital radius shrinks from the gravitational wave emission; simultaneously, the universe is expanding if the Hubble–Lemaître law is universal on all distance scales. Inside the gravitational bound state, the cosmic expansion becomes visible near the critical radius given by the equilibrium between

    更新日期:2020-10-13
  • Clouds of strings in 4D Einstein–Gauss–Bonnet black holes
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-05
    Dharm Veer Singh; Sushant G. Ghosh; Sunil D. Maharaj

    Recently there has been significant interest in regularizing, a D→4 limit, of EGB gravity, and the resulting regularized 4D EGB gravities have nontrivial gravitational dynamics — namely the 4D EGB gravity. We present an exact charged black hole solution to the 4D EGB gravity surrounded by clouds of string (CS) and also analyse their thermodynamic properties. Owing to the corrected black hole due to

    更新日期:2020-10-11
  • H0 ex machina: Vacuum metamorphosis and beyond H0
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-08
    Eleonora Di Valentino; Eric V. Linder; Alessandro Melchiorri

    We do not solve tensions with concordance cosmology; we do obtain H0≈74km/s/Mpc from CMB+BAO+SN data in our model, but that is not the point. Discrepancies in Hubble constant values obtained by various astrophysical probes should not be viewed in isolation. While one can resolve at least some of the differences through either an early time transition or late time transition in the expansion rate, these

    更新日期:2020-10-11
  • A Kaluza–Klein inspired Brans–Dicke gravity with dark matter and dark energy model
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-05
    Chakrit Pongkitivanichkul; Daris Samart; Nakorn Thongyoi; Nutthaphat Lunrasri

    We propose the Kaluza–Klein inspired Brans–Dicke gravity model containing possible existence of dark matter and dark energy. The massive scalar field coupled with gravity in 5 dimensional space–time can be reduced to 4 dimensional gravity along with the dilaton ϕ, gauge fields Aμ, and the tower of scalar fields ηn. Two additional gauge fields are introduced to form “Cosmic Triad” vector field scenario

    更新日期:2020-10-08
  • On cosmic acceleration in four-dimensional Einstein–Gauss–Bonnet gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-30
    H. Mohseni Sadjadi

    We study the possibility that in the model introduced in Glavan and Lin (2020), the Gauss–Bonnet term alone gives rise to the cosmic acceleration and super-acceleration in four-dimensional FLRW space–time at the late time. We also discuss transitions from deceleration to acceleration and acceleration to super-acceleration. We show that the Gauss–Bonnet invariant can drive the acceleration in the low

    更新日期:2020-10-05
  • A new coupled three-form dark energy model and implications for the H0 tension
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-10-01
    Yan-Hong Yao; Xin-He Meng

    We propose a new coupled three-form dark energy model to relieve the Hubble tension in this paper. Firstly, by performing a dynamical analysis with the coupled three-form dark energy model, we obtain four fixed points, including a saddle point representing a radiation dominated Universe, a saddle point representing a matter dominated Universe, and two attractors representing two saturated de Sitter

    更新日期:2020-10-05
  • Scale-dependent slowly rotating black holes with flat horizon structure
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-21
    Ángel Rincón; Grigoris Panotopoulos

    We study slowly rotating four-dimensional black holes with flat horizon structure in scale-dependent gravity. First, we obtain the solution, and then we study thermodynamic properties as well as the invariants of the theory. The impact of the scale-dependent parameter is investigated in detail. We find that the scale-dependent solution exhibit a new singularity not present in the classical solution

    更新日期:2020-09-30
  • Deep+ wide lensing surveys can measure the dark matter halos of dwarf galaxies
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-29
    Alexie Leauthaud; Sukhdeep Singh; Yifei Luo; Felipe Ardila; Johnny P. Greco; Peter Capak; Jenny E. Greene; Lucio Mayer

    The advent of new deep+ wide photometric lensing surveys will open up the possibility of direct measurements of the dark matter halos of dwarf galaxies. The HSC wide survey will be the first with the statistical capability of measuring the lensing signal with high signal-to-noise at log(M∗)∼8. At this same mass scale, The Rubin Observatory LSST will have the most overall constraining power with a predicted

    更新日期:2020-09-30
  • Probing phenomenological emergent dark energy model in a Bianchi type-I spacetime with the recent observational data
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-16
    Shivani Sharma

    In this work, we investigate the recently introduced phenomenological emergent dark energy (PEDE) model and the anisotropic extension of PEDE (APEDE) via Bianchi type-I spacetime metric with the latest observational data involving both low and high redshift datasets as, Hubble, Cosmic Microwave Background (CMB), Baryon Acoustic Oscillations (BAO) and Pantheon. We perform Bayesian inference analysis

    更新日期:2020-09-29
  • Unified dark fluid and cosmic transit models in Brans–Dicke theory
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-24
    Sunil K. Tripathy; Sasmita Kumari Pradhan; Zashmir Naik; Dipanjali Behera; B. Mishra

    Some dark energy cosmological models are constructed in the framework of a generalised Brans–Dicke theory which contains a self interacting potential and a dynamical coupling parameter. The models are constructed in the background of an anisotropic metric. The dark sector of the universe is considered through a unified linear equation of state. The parameters of the unified dark fluid have been constrained

    更新日期:2020-09-29
  • Repulsive regions in Lemaître–Tolman–Bondi gravitational collapse
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-21
    Roberto Giambò; Orlando Luongo; Hernando Quevedo

    We show that in the inhomogeneous Lemaître–Tolman–Bondi space–time there are specific regions in which repulsive gravity exists. To find these regions, we use an invariant definition of repulsive gravity based upon the behavior of the curvature eigenvalues. In addition, we analyze the effects of repulsive gravity on the dynamics of the gravitational collapse. In particular, we investigate the collapse

    更新日期:2020-09-26
  • Effects of dark matter in red giants
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-24
    Sunny Clea; Arun Kenath; C. Sivaram; S.B. Gudennavar

    Dark matter (DM) which constitutes five-sixths of all matter is hypothesized to be a weakly interacting non-baryonic particle, created in the early stages of cosmic evolution. It can affect various cosmic structures in the Universe via gravitational interactions. The effect of DM in main sequence stars and stellar remnants like neutron stars and white dwarfs has already been studied. Red giant phase

    更新日期:2020-09-26
  • f(R) gravity phase space in the presence of thermal effects
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-25
    V.K. Oikonomou; F.P. Fronimos; N.Th. Chatzarakis

    In this paper, we shall consider f(R) gravity and its cosmological implications, when an extra matter term generated by thermal effects is added by hand in the Lagrangian. We formulate the equations of motion of the theory as a dynamical system, that can be treated as an autonomous one only for specific solutions for the Hubble rate, which are of cosmological interest. Particularly, we focus our analysis

    更新日期:2020-09-25
  • Phase transition and thermal fluctuations of quintessential Kerr–Newman–AdS black hole
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-23
    M. Sharif; Qanitah Ama-Tul-Mughani

    This paper is devoted to analyzing the critical phenomenon and phase transition of quintessential Kerr–Newman-anti-de Sitter black hole in the framework of Maxwell equal-area law. For this purpose, we first derive thermodynamic quantities such as Hawking temperature, entropy and angular momentum in the context of extended phase space. These quantities satisfy Smarr–Gibbs–Dehum relation in the presence

    更新日期:2020-09-24
  • Growth of matter density perturbations in 4D Einstein–Gauss–Bonnet gravity
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-18
    Zahra Haghani

    Recently, a novel Einstein–Gauss–Bonnet gravity in four dimensions has been introduced (Glavan and Lin, 2020). We will investigate cosmological consequences of this model in details. We will consider linear matter density perturbations and also estimate relevant modified gravity parameters. Specially we will concentrate on the growth rate of non-relativistic matter perturbations on top of FRW geometry

    更新日期:2020-09-21
  • GW170817-compatible constant-roll Einstein–Gauss–Bonnet inflation and non-Gaussianities
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-15
    S.D. Odintsov, V.K. Oikonomou, F.P. Fronimos, S.A. Venikoudis

    In this paper we investigate the inflationary phenomenology of an Einstein–Gauss–Bonnet theory compatible with the GW170817 event, by imposing the constant-roll evolution on the scalar field. We develop the constant-roll GW170817-compatible Einstein–Gauss–Bonnet formalism, and we calculate the slow-roll indices and the observational indices of inflation, for several models of interest. As we demonstrate

    更新日期:2020-09-15
  • Einstein–Maxwell-scalar black holes with massive and self-interacting scalar hair
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-09-05
    Pedro G.S. Fernandes

    Recently, spontaneous scalarization of charged black holes has attracted a great deal of attention and motivated several studies of Einstein–Maxwell-scalar models. These studies have, however, only considered a massless and non-self-interacting scalar field. In this work a more realistic treatment of the problem is considered by studying the effects of scalar field mass and self-interacting terms on

    更新日期:2020-09-05
  • Dynamics of magnetized particles around 4-D Einstein Gauss–Bonnet black hole
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-08-29
    Ahmadjon Abdujabbarov, Javlon Rayimbaev, Bobur Turimov, Farruh Atamurotov

    In this paper, we have investigated the dynamics of magnetized particles around 4-D Einstein Gauss–Bonnet black hole immersed in an external asymptotically uniform magnetic field. We have shown that the magnetic interaction parameter responsible for circular orbits decreases for negative values of the Gauss–Bonnet parameter α and the range where magnetized particle’s stable circular orbits are allowed

    更新日期:2020-08-29
  • Dynamics of particles around the time conformal quantum corrected Schwarzschild black hole
    Phys. Dark Universe (IF 4.473) Pub Date : 2020-08-26
    Amir Sultan Khan, Farhad Ali

    In this paper, we explore the dynamics of neutral and charged particles in presence/absence of magnetic field around the quantum corrected-Schwarzschild black hole as well as the time conformal quantum corrected-Schwarzschild black hole. We investigate the conditions under which the particles move towards or away from the vicinity of black hole when they collide with other particles. We study the effective

    更新日期:2020-08-26
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