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  • CMB statistical isotropy confirmation at all scales using multipole vectors
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-30
    Renan A. Oliveira; Thiago S. Pereira; Miguel Quartin

    We present an efficient numerical code and conduct, for the first time, a null and model-independent CMB test of statistical isotropy using Multipole Vectors (MVs) at all scales. Because MVs are insensitive to the angular power spectrum Cℓ, our results are independent from the assumed cosmological model. We avoid a posteriori choices and use a pre-defined range of scales ℓ∈[2,30], ℓ∈[2,600] and ℓ∈[2

    更新日期:2020-05-30
  • Extended gravitational decoupled solutions in self-interacting Brans–Dicke theory
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-30
    M. Sharif; Amal Majid

    In this paper, we construct anisotropic spherical solutions from known isotropic solutions through extended gravitational decoupling method in the background of self-interacting Brans–Dicke theory. The field equations are decoupled into two sets by applying geometric deformations on radial as well as temporal metric components. The first array corresponds to isotropic fluid while influence of the anisotropic

    更新日期:2020-05-30
  • Interior solutions of compact stars in f(T,T) gravity under Karmarkar condition
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-29
    Rabia Saleem; Faisal Kramat; M. Zubair

    This paper is devoted to develop compact stellar configuration and to evaluate exact interior solutions in the background of f(T,T) gravity, where T be the torsion scalar and T be the trace of energy momentum tensor. We develop a new set up for embedding class I model under well-known Karmarkar condition for LMC X-4 and Vela X-1 compact stars using specific linear function f(T,T)=αT(r)+βT(r)+Φ, where

    更新日期:2020-05-29
  • Neutrino oscillations in dark matter
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-28
    Ki-Young Choi; Eung Jin Chun; Jongkuk Kim

    We study neutrino oscillations in a medium of dark matter which generalizes the standard matter effect. A formula is derived to describe the effect of medium and its mediator to neutrinos. Neutrinos and anti-neutrinos receive opposite contributions from asymmetric distribution of (dark) matter and anti-matter, and thus it could appear in precision measurements of neutrino or anti-neutrino oscillations

    更新日期:2020-05-28
  • Unifying inflation with early and late-time dark energy in F(R) gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-21
    Shin’ichi Nojiri; Sergei D. Odintsov; V.K. Oikonomou

    In this work we shall present models of F(R) gravity which realize in a unified way the inflationary era along with a post-inflationary early dark energy era, with the late-time dark energy era. We shall use two approach methods in order to realize the unified cosmological eras, firstly we specify a Hubble rate which may describe the three distinct acceleration eras, and then by using well known F(R)

    更新日期:2020-05-21
  • Stochastic gravitational wave background from global cosmic strings
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-21
    Chia-Feng Chang; Yanou Cui

    Global cosmic strings are generically predicted in particle physics beyond the Standard Model, e.g., a post-inflationary global U(1) symmetry breaking which may associate with axion-like dark matter. We demonstrate that although subdominant to Goldstone emission, gravitational waves (GWs) radiated from global strings can be observable with current/future GW detectors. The frequency spectrum of such

    更新日期:2020-05-21
  • Dust collapse in 4D Einstein–Gauss–Bonnet gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-20
    Daniele Malafarina; Bobir Toshmatov; Naresh Dadhich

    We consider gravitational collapse in the recently proposed 4D limit of Einstein–Gauss–Bonnet gravity. We show that for collapse of a sphere made of homogeneous dust the process is qualitatively similar to the case of pure Einstein’s gravity. The singularity forms as the endstate of collapse and it is trapped behind the horizon at all times. However, and differently from Einstein’s theory, as a consequence

    更新日期:2020-05-20
  • Effects of electromagnetic field on the structure of massive compact objects
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-20
    M.Z. Bhatti; Z. Tariq

    This paper encompasses a set of stellar equations that administer the formation and evolution of self-gravitating, dissipative spherically symmetric fluid distributions having anisotropic stresses in the presence of electromagnetic field. The Riemann tensor is split orthogonally to procure five scalar functions named as structure scalars which are then utilized in the stellar equations. It is shown

    更新日期:2020-05-20
  • Time dependent dark energy and the thermodynamics of many-body systems
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-19
    Behnam Pourhassan; Sudhaker Upadhyay

    In this paper, we study the thermodynamics and statistics of the galaxies clustering affected by the dynamical dark energy. We consider two important dark energy models based on time dependent equation of state to evaluate the gravitational partition function. In the first model, we consider barotropic dark energy with time dependent equation of state. However, in the second model, we consider various

    更新日期:2020-05-19
  • Higher derivative and mimetic models on non flat FLRW space–times
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-16
    Alessandro Casalino; Lorenzo Sebastiani; Luciano Vanzo; Sergio Zerbini

    An effective Lagrangian approach, partly inspired by Quantum Loop Cosmology (QLC), is presented and formulated in a non flat FLRW space–times, making use of modified gravitational models. The models considered are non generic, and their choice is dictated by the necessity to have at least second order differential equations of motion in a non flat FLRW space–time. This is accomplished by a class of

    更新日期:2020-05-16
  • Quasi-normal modes and thermal fluctuations of charged black hole with Weyl corrections
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-15
    M. Sharif; Zunaira Akhtar

    In this paper, we study thermodynamics, quasi-normal modes and thermal fluctuations of a charged black hole with Weyl corrections. We first obtain thermodynamic quantities such as Hawking temperature, entropy, and heat capacity for non-rotating as well as rotating versions of this black hole. We also evaluate temperature through quantum tunneling mechanism which is exactly the same as found through

    更新日期:2020-05-15
  • The static black hole in f(R) gravity with thermal corrections and phase transition
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-12
    M. Rostami; J. Sadeghi; S. Miraboutalebi

    In this paper, we introduce static black hole with accounting of f(R) gravity. First, we study thermal properties and phase transition of corresponding black hole. Also, here we do correction to the entropy and temperature at same time in above mentioned black hole. Second step, we obtain such corrected thermodynamical properties and study the P−V critically and phase transition. We also investigate

    更新日期:2020-05-12
  • Searching for Integrated Sachs–Wolfe Effect from Fermi-LAT diffuse γ-ray map
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-11
    Xiu-Hui Tan; Ji-Ping Dai; Jun-Qing Xia

    In this paper, we estimate the cross-correlation power spectra between the Planck 2018 cosmic microwave background (CMB) temperature anisotropy map and the unresolved γ-ray background (UGRB) from the 9-years Fermi-Large Area Telescope (LAT) data. In this analysis, we use up to nine energy bins over a wide energy range of [0.631, 1000] GeV from the Fermi-LAT UGRB data. Firstly, we find that the Fermi

    更新日期:2020-05-11
  • The measure of complexity in charged celestial bodies in f(R,T,RμνTμν) gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-05-01
    Z. Yousaf; M.Z. Bhatti; T. Naseer; I. Ahmad

    In this paper, we investigate irregularities in a cylindrical self-gravitating system which contains the properties of an imperfect matter and electromagnetic field. For f(R,T,Q) theory, in which R represents the Ricci scalar and T shows the trace of matter stress–energy tensor while Q≡RγδTγδ, the field equations containing electric charge, mass functions and Darmois junction conditions at the hypersurface

    更新日期:2020-05-01
  • Extracting the BAO scale from BOSS DR12 dataset
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-30
    Eugenio Noda; Marco Peloso; Massimo Pietroni

    We present the first application to real data from the BOSS DR12 dataset of the Extractor procedure (Noda et al., 2017, Nishimichi et al., 2018) to determine the acoustic scale imprinted on Baryonic Acoustic Oscillations (BAO). We show that, being largely insensitive to the broadband shape of the Power Spectrum, this procedure requires a lower number of nuisance parameters than those used by the BOSS

    更新日期:2020-04-30
  • Latest evidence for a late time vacuum–geodesic CDM interaction
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-30
    Natalie B. Hogg; Marco Bruni; Robert Crittenden; Matteo Martinelli; Simone Peirone

    We perform a reconstruction of the coupling function between vacuum energy and geodesic cold dark matter using the latest observational data. We bin the interaction in seventeen redshift bins but use a correlation prior to prevent rapid, unphysical oscillations in the coupling function. This prior also serves to eliminate any dependence of the reconstruction on the binning method. We use two different

    更新日期:2020-04-30
  • Decoupling gravitational sources by MGD approach in Rastall gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-29
    S.K. Maurya; Francisco Tello-Ortiz

    In the present work, we investigate the possibility of obtaining stellar interiors for static self-gravitating systems describing an anisotropic matter distribution in the framework of Rastall gravity through gravitational decoupling by means of minimal geometric deformation approach. Due to Rastall gravity breaks down the minimal coupling matter principle, we have provided an exhaustive explanation

    更新日期:2020-04-29
  • Compact stars with exotic matter
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-28
    Ksh. Newton Singh; Amna Ali; Farook Rahaman; Salah Nasri

    In this paper we employ Tolman VII solution with exotic matter that may be present in the extremely dense core of compact objects. The Tolman VII solution, an exact analytic solution to the spherically symmetric, static Einstein field equations with a perfect fluid source, has many characteristics that make it interesting for modeling high density stellar astronomical objects. For our purpose we use

    更新日期:2020-04-28
  • Is the cosmological constant of topological origin?
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-25
    M. Le Delliou; J. Lorca Espiro

    The observed value of the cosmological constant poses large theoretical problems. We find that topology of the Universe provides a natural source for it. Restricting dynamically an Einstein–Cartan gravity to General Relativity in our observed Universe allows topological invariants to induce an effective cosmological constant from dynamical quintessence-like topological fields. Its evaluation through

    更新日期:2020-04-25
  • Constraining theories of gravity by fundamental plane of elliptical galaxies
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-25
    Salvatore Capozziello; Vesna Borka Jovanović; Duško Borka; Predrag Jovanović

    We show that fundamental plane of elliptical galaxies can be used to obtain observational constraints on metric theories of gravity. Being it connected to global properties of ellipticals, it can fix parameters of modified gravity. Specifically, we use fundamental plane to constrain modified theories of gravity with Yukawa-like corrections which commonly emerge in the post-Newtonian limit. After giving

    更新日期:2020-04-25
  • On simple analytic models of microlensing amplification statistics
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-24
    Pierre Fleury; Juan García-Bellido

    Gravitational microlensing is a key probe of the nature of dark matter and its distribution on the smallest scales. For many practical purposes, confronting theory to observation requires to model the probability that a light source is highly amplified by many-lens systems. This article reviews four simple analytic models of the amplification probability distribution, based on different approximations:

    更新日期:2020-04-24
  • Weak equivalence principle, swampland and H0 tension with fast single radio bursts FRB 180924 and FRB 190523
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-24
    Deng Wang; Zhaozhou Li; Jiajun Zhang

    Two new fast single radio bursts FRB 180924 and FRB 190523 well localized to massive galaxies have opened a new window to probe and characterize how cosmic baryons are allocated between galaxies, their surroundings and intergalactic medium. We are motivated by testing Einstein’s weak equivalence principle with these two cosmic transients which have accurate redshifts. Using photons with different energies

    更新日期:2020-04-24
  • New definition of complexity factor in f(R,T,RμνTμν) gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-03-24
    Z. Yousaf; M.Z. Bhatti; T. Naseer

    This paper is devoted to present new definition of complexity factor for static cylindrically symmetric matter configurations in f(R,T,RμνTμν) gravity. For this purpose, we have considered irrotational static cylindrical spacetime coupled with a locally anisotropic relativistic fluid. After formulating gravitational field and conservation equations, we have performed orthogonal splitting of the Riemann

    更新日期:2020-04-22
  • The effect of the Generalized Uncertainty Principle on the motion of particles near a black hole horizon
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-20
    Elham Maghsoodi; Marc de Montigny; Won Sang Chung; Hassan Hassanabadi

    We study the behaviour of massive particles under different potentials near a static spherical black hole. Our purposes are to apply the Hamilton–Jacobi method for this study and to investigate the effects of a minimal length on the motion of particles in unstable equilibrium near the black hole horizon by deformation of a canonical position–momentum commutation relation. We also obtain the equation

    更新日期:2020-04-22
  • Duel of cosmological screening lengths
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-22
    Ezgi Canay; Maxim Eingorn

    Two distinct perturbative approaches have been recently formulated within General Relativity, arguing for the screening of gravity in the ΛCDM Universe. In this paper we compare them and show that the offered screening concepts, each characterized by its own interaction range, can peacefully coexist. Accordingly, we advance a united scheme, determining the gravitational potential at all scales, including

    更新日期:2020-04-22
  • Gravastars in f(R,G) gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-21
    M.Z. Bhatti; Z. Yousaf; A. Rehman

    In this paper, we discuss some feasible features of gravastar that was firstly demonstrated by Mazur and Mottola. It is already established that gravastar associates the de-Sitter spacetime in its inner sector with the Schwarzschild geometry at its exterior through the thin shell possessing the ultra-relativistic matter. We have explored the singularity free spherical model with a particular equation

    更新日期:2020-04-21
  • Constraining Bianchi type I universe with type Ia supernova and H(z) data
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-20
    Hassan Amirhashchi; Soroush Amirhashchi

    We use recent 36 observational Hubble data (OHD) in the redshift range 0.07≤z≤2.36, latest “joint light curves” (JLA) sample, comprised of 740 type Ia supernovae (SNIa) in the redshift range 0.01≤z≤1.30, and their joint combination datasets to constrain anisotropic Bianchi type I (BI) dark energy (DE) model. To estimate model parameters, we apply Hamiltonian Monte Carlo technique. We also compute the

    更新日期:2020-04-20
  • f(R) gravity k-Essence late-time phenomenology
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-18
    S.D. Odintsov; V.K. Oikonomou; F.P. Fronimos

    In this work we shall study the late-time behavior of k-Essence f(R) gravity without scalar potential, in the presence of matter and radiation perfect fluids. We quantify the late-time study by using the statefinder function YH(z)=ρDEρm(0), which is a function of the redshift and of the Hubble rate. By appropriately rewriting the Friedmann equation in terms of the redshift and of the function YH(z)

    更新日期:2020-04-18
  • Cosmological consequences of parameterized f(R,∇R) gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-18
    Shamaila Rani; M. Bilal Amin Sulehri; Abdul Jawad

    This paper is based on analysis of cosmological parameters and thermodynamics in a modified theory of gravity whose action contains linear coupling of Ricci scalar R and a second degree term of its covariant derivative. The Friedmann equations obtained in result of considering the spatially flat FRW universe filled with dark energy and pressureless matter, are of fifth-order in the Hubble function

    更新日期:2020-04-18
  • Accelerating universe in hybrid and logarithmic teleparallel gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-15
    Sanjay Mandal; Snehasish Bhattacharjee; S.K.J. Pacif; P.K. Sahoo

    Teleparallel gravity is a modified theory of gravity for which the Ricci scalar R of the underlying geometry in the action is replaced by an arbitrary functional form of torsion scalar T. In doing so, cosmology in f(T) gravity becomes greatly simplified owing to the fact that T contains only the first derivatives of the vierbeins. The article exploits this appealing nature of f(T) gravity and present

    更新日期:2020-04-16
  • Can Gibbons–Hawking radiation and inflation arise due to spacetime quanta?
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-15
    Naouel Boulkaboul

    In this study, we provide an alternatively reformulated interpretation of Gibbons–Hawking radiation as well as inflation. By using a spacetime quantization procedure, proposed recently by L.C. Céleri et al., in anti-de Sitter space we show that Gibbons–Hawking radiation is an intrinsic property of the concerned space, that arises due to the existence of a scalar field whose quanta “carry” a length

    更新日期:2020-04-15
  • The double polytrope for anisotropic matter: Newtonian case
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-14
    G. Abellán; E. Fuenmayor; L. Herrera

    A general formalism developed few years ago to model polytropic Newtonian stars with anisotropic pressure is applied to model stars for which, both, radial and tangential pressure satisfy polytropic equations of state. We obtain the corresponding Lane–Emden equation, and integrate it for a wide range of values of the parameters, thereby illustrating the effects of the pressure anisotropy on stellar

    更新日期:2020-04-14
  • Exact solutions of the Wheeler-DeWitt equation with ordering term in a dark energy scenario
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-13
    C.R. Muniz; H.R. Christiansen; M.S. Cunha; H.S. Vieira

    We investigate the quantum evolution of the universe in the presence of two types of dark energies. First, we consider the phantom class (ω<−1) which would be responsible for a super-accelerated cosmic expansion, and then we apply the procedure to an ordinary Λ>0 vacuum (ω=−1). This is done by analytically solving the Wheeler-DeWitt equation with ordering term (WdW) in the cosmology of Friedmann-Robertson-Walker

    更新日期:2020-04-13
  • Dynamical evidence of a dark solitonic core of 109M⊙ in the milky way
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-13
    Ivan De Martino; Tom Broadhurst; S.-H. Henry Tye; Tzihong Chiueh; Hsi-Yu Schive

    A wavelike solution for the non-relativistic universal dark matter (wave-DM) is rapidly gaining interest, following pioneering simulations of cosmic structure as an interference pattern of coherently oscillating bosons. A prominent solitonic standing wave is predicted at the center of every galaxy, representing the ground state solution of the coupled Schrödinger–Poisson equations, and it has been

    更新日期:2020-04-12
  • Gravastars in f(R,T,RμνTμν) gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-03-13
    Z. Yousaf; M.Z. Bhatti; H. Asad

    This work is devoted to study the analytical and regular solutions of a particular self-gravitating object (i.e., gravastar) in a particular theory of gravity. We derive the corresponding field equations in the presence of effective energy momentum tensor associated with the perfect fluid configuration of a spherical system. We then describe the mathematical formulations of the three respective regions

    更新日期:2020-04-12
  • Complexity analysis of cylindrically symmetric self-gravitating dynamical system in f(R,T) theory of gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-03-19
    M. Zubair; Hina Azmat

    In this article, we have studied a cylindrically symmetric self-gravitating dynamical object via complexity factor which is obtained through orthogonal splitting of Reimann tensor in f(R,T) theory of gravity. Our study is based on the definition of complexity for dynamical sources, proposed by Herrera et al. (2019). We actually want to analyze the behavior of complexity factor for cylindrically symmetric

    更新日期:2020-04-12
  • Comprehensive analysis of a non-singular bounce in f(R,T) gravitation
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-03-28
    Snehasish Bhattacharjee; P.K. Sahoo

    The present paper is devoted to the study of bouncing cosmology in f(R,T) modified gravity where we presume f(R,T)=R+2λT, with R the Ricci scalar, T the trace of energy–momentum tensor and λ the model parameter. We present here a novel parametrization of Hubble parameter which is apt in representing a successful bouncing scenario undergoing no singularity. We proceed to present a complete analysis

    更新日期:2020-04-12
  • Super-CMB fluctuations and the Hubble tension
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-02
    Saroj Adhikari; Dragan Huterer

    We study the covariance in the angular power spectrum estimates of CMB fluctuations when the primordial fluctuations are non-Gaussian. The non-Gaussian covariance comes from a nonzero connected four-point correlation function – or the trispectrum in Fourier space – and can be large when long-wavelength (super-CMB) modes are strongly coupled to short-wavelength modes. The effect of such non-Gaussian

    更新日期:2020-04-12
  • Ghost-free non-local F(R) gravity cosmology
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-06
    Shin’ichi Nojiri; S.D. Odintsov; V.K. Oikonomou

    In this work we shall study ghost-free non-local F(R) gravity models. Firstly we shall demonstrate how the ghost degrees of freedom may occur in the non-local F(R) gravity models, and accordingly we shall modify appropriately the gravitational action of non-local F(R) gravity models in order to eliminate the ghosts. Also we shall investigate how the (anti-)de Sitter and the Minkowski spacetime cosmological

    更新日期:2020-04-12
  • Gravitational decoupling in cosmology
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-09
    Francisco X. Linares Cedeño; Ernesto Contreras

    Whereas the nature of dark components in the Universe remains unknown, alternative models of gravity have been developed to offer a geometric explanation to the origin of such components. In this work we use the Minimal Geometric Deformation approach to study extensions of the theory of General Relativity in a cosmological context. This is possible since such approach allows the decoupling of gravitational

    更新日期:2020-04-12
  • The multi-feature universe: Large parameter space cosmology and the swampland
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-04-10
    Deng Wang

    Under the belief that the universe should be multi-feature and informative, we employ a model-by-model comparison method to explore the possibly largest upper bound on the swampland constant c. Considering the interacting quintessence dark energy as the comparison model, we constrain the large parameter space interacting dark energy model, a 12-parameter extension to the ΛCDM cosmology, in light of

    更新日期:2020-04-12
  • Gravitational waves from binary black holes as probes of the structure formation history
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-01-20
    Tomohiro Nakama

    Gravitational-wave detectors on earth have detected gravitational waves from merging compact objects in the local Universe. In future we will detect gravitational waves from higher-redshift sources, which trace the high-redshift structure formation history. That is, by observing high-redshift gravitational-wave events we will be able to probe structure formation history. This will provide additional

    更新日期:2020-03-26
  • On the absence of a universal surface density, and a maximum Newtonian acceleration in dark matter haloes: Consequences for MOND
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-01-13
    Yong Zhou; A. Del Popolo; Zhe Chang

    We study the dark matter (DM) surface density using the SPARC sample and compare it to Donato et al. (2009) result. By means of MCMC method, we infer the best-fitting parameters for each galaxy. We reobtain the scaling relation between the surface density and luminosity, and several other scaling laws relating the dark matter halo properties to that of the galactic disc properties. We conclude, in

    更新日期:2020-03-26
  • Higgs inflation in complex geometrical scalar-tensor theory of gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-01-24
    José Edgar Madriz Aguilar; J. Zamarripa; M. Montes; C. Romero

    We derive a Higgs inflationary model in the context of a complex geometrical scalar-tensor theory of gravity. In this model the Higgs inflaton scalar field has geometrical origin playing the role of the Weyl scalar field in the original non-riemannian background geometry. The energy scale enough to generate inflation from the Higgs energy scale is achieved due to the compatibility of the theory with

    更新日期:2020-03-26
  • Traversable wormhole solutions in Rastall teleparallel gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-01-10
    Kh. Saaidi; N. Nazavari

    In this manuscript we consider the traversable wormhole solutions in teleparallel gravity formalism with and without Rastall constraint on stress–energy tensor of dark energy. We have studied the isotropic and non-isotropic form of stress–energy tensor of dark energy which the equation of state (EoS) between density and the radial components of pressure is used. This work is done for a diagonal tetrad

    更新日期:2020-03-26
  • Electromagnetic effects on polytropes in f(R) gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-01-27
    M.Z. Bhatti; Z. Tariq

    The center of attention of this article is to examine the dynamics of conformally flat anisotropic spheres in the background of electromagnetic field satisfying the polytropic equations of state. We have resorted to the general framework developed in Herrera and Barreto (2013) that helps to inspect the rudimentary attributes of polytropic spheres in the framework of a particular f(R) gravity. We explored

    更新日期:2020-03-26
  • A tight correlation between the enclosed gravitational mass and hot gas mass in galaxy clusters at intermediate radii
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-01-28
    Man Ho Chan

    Many studies point out that there exists some tight correlations between dark matter and baryonic matter at different radii in galaxies. However, similar tight correlations can only be found in galaxy clusters for large radii. Here we report extremely tight correlations between the gravitational mass Mgrav and hot gas mass Mgas in galaxy clusters at the hot gas core radius rc and at 2rc (i.e. Mgrav(rc)

    更新日期:2020-03-26
  • On the change of old neutron star masses with galactocentric distance
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-01-30
    Antonino Del Popolo; Maksym Deliyergiyev; Morgan Le Delliou; Laura Tolos; Fiorella Burgio

    We show that the pulsar mass depends on the environment, and that it decreases going towards the centre of the Milky Way. This is due to two combined effects, the capture and accumulation of self-interacting, non-annihilating dark matter by pulsars, and the increase of the dark matter density going towards the galactic centre. We show that mass decrease depends both on the density profile of dark matter

    更新日期:2020-03-26
  • Joint analysis of EDGES 21-cm line observations with standard candles and rulers in ΛCDM and non-adiabatic gCg models
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-04
    C. Pigozzo; S. Carneiro; J.C. Fabris

    A decomposed generalised Chaplygin gas (gCg) with energy flux from dark energy to dark matter, represented by a negative value for the gas parameter α, is shown to alleviate the tension between EDGES data and the cosmological standard model. Using EDGES data and employing a Bayesian statistical analysis, the agreement with the standard model is only marginal. However, if α is negative enough the gCg

    更新日期:2020-03-26
  • Analysis method for detecting topological defect dark matter with a global magnetometer network
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-06
    Hector Masia-Roig; Joseph A. Smiga; Dmitry Budker; Vincent Dumont; Zoran Grujic; Dongok Kim; Derek F. Jackson Kimball; Victor Lebedev; Madeline Monroy; Szymon Pustelny; Theo Scholtes; Perrin C. Segura; Yannis K. Semertzidis; Yun Chang Shin; Jason E. Stalnaker; Ibrahim Sulai; Antoine Weis; Arne Wickenbrock

    The Global Network of Optical Magnetometers for Exotic physics searches (GNOME) is a network of time-synchronized, geographically separated, optically pumped atomic magnetometers that is being used to search for correlated transient signals heralding exotic physics. GNOME is sensitive to exotic couplings of atomic spins to certain classes of dark matter candidates, such as axions. This work presents

    更新日期:2020-03-26
  • A neutron star with a strange quark star-like mass-radius relation
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-07
    A. Savaş Arapoğlu; A. Emrah Yükselci

    We study the structure of spherically symmetric and static objects in the presence of a nonminimally coupled scalar field having a potential of the form V(ϕ)=−μ2ϕ2∕2+λϕ4∕4. We numerically solve equations of the system using two different realistic equations of state for neutron matter and give the mass-radius relations as well as the radial profiles of the scalar field, densities and the mass function

    更新日期:2020-03-26
  • Fuzzy Euclidean wormholes in the inflationary universe
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-05
    Pisin Chen; Daeho Ro; Dong-han Yeom

    In this paper, we investigate complex-valued Euclidean wormholes in the Starobinsky inflation. Due to the properties of the concave inflaton potential, the classicality condition at both ends of the wormhole can be satisfied, as long as the initial condition of the inflaton field is such that it is located sufficiently close to the hilltop. We compare the probabilities of classicalized wormholes with

    更新日期:2020-03-26
  • Dark degeneracy I: Dynamical or interacting dark energy?
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-10
    Rodrigo von Marttens; Lucas Lombriser; Martin Kunz; Valerio Marra; Luciano Casarini; Jailson Alcaniz

    We revisit the dark degeneracy that arises from the Einstein equations relating geometry to the total cosmic substratum but not resolving its individual components separately. We establish the explicit conditions for the dark degeneracy in the fluid description of the dark sector. At the background level, this degeneracy can be formally understood in terms of a unified dark sector Equation of State

    更新日期:2020-03-26
  • Stability of self-gravitating anisotropic fluids in f(R,T) gravity
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-14
    M.Z. Bhatti; Z. Yousaf; M. Yousaf

    This manuscript aims to discuss the factors holding in/stability of axially symmetric compact system with anisotropic environment in the background of f(R,T) gravity, where R is invariant Ricci curvature and T stands for trace of energy–momentum tensor. We constituted field and conservation equations in the background of f(R,T) gravity. To establish the collapse equation, we make use of perturbation

    更新日期:2020-03-26
  • Galaxy cluster hydrostatic masses using Tolman–Oppenheimer–Volkoff equation
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-13
    Sajal Gupta; Shantanu Desai

    Motivated by previous studies in literature about the potential importance of relativistic corrections to galaxy cluster hydrostatic masses, we calculate the masses of 12 relaxed clusters (with Chandra X-ray data) using the Tolman–Oppenheimer–Volkov (TOV) equation of hydrostatic equilibrium and the ideal gas equation of state. Analytical formulae for gas density and temperature profiles for these clusters

    更新日期:2020-03-26
  • Stratospheric temperature anomalies as imprints from the dark Universe
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-14
    K. Zioutas; A. Argiriou; H. Fischer; S. Hofmann; M. Maroudas; A. Pappa; Y.K. Semertzidis

    The manifestation of the dark Universe begun with unexpected large-scale astronomical observations. Here we are investigating the possible origin of small-scale anomalies, like that of the annually observed temperature anomalies in the stratosphere (38.5 – 47.5 km). Unexpectedly within known physics, we observe a planetary relationship of the daily stratospheric temperature distribution. Interestingly

    更新日期:2020-03-26
  • Beta-function formalism for k-essence constant-roll inflation
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-24
    Abolhassan Mohammadi; Tayeb Golanbari; Khaled Saaidi

    The beta-function formalism is being used to study the constant-roll inflation in k-essence models. Assuming the second slow-roll parameter as a constant leads to a first-order differential equation for β-function which much easier to solve and find a solution than the second (non-linear) order equation that we have in the corresponding standard constant-roll inflation. Many cosmological models are

    更新日期:2020-03-26
  • Effects of dark matter on the upper bound mass of neutron stars
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-24
    Sandeep S. Kumar; Arun Kenath; C. Sivaram

    Observations have indicated that we do not see neutron stars (NS) of mass near the theoretical upper limit as predicted. Here we invoke the role of dark matter (DM) particles in star formation, and their role in lowering the mass of remnants eventually formed from these stars. Massive stars can capture DM particles more effectively than the lower mass stars, thus further softening the equation of state

    更新日期:2020-03-26
  • Construction of charged cylindrical gravastar-like structures
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-27
    Z. Yousaf

    In this work, we extend the work of gravastars to analyze the role of electromagnetic field in f(R,T) gravity. We consider the irrotational cylindrically symmetric geometry and established the f(R,T) field equations and conservation laws. After considering charged exterior geometry, the mathematical quantities for evaluating Israel junction conditions are being calculated. The mass of the gravastar-like

    更新日期:2020-03-26
  • Black holes and naked singularities from Anton–Schmidt’s fluids
    Phys. Dark Universe (IF 5.66) Pub Date : 2020-02-26
    Salvatore Capozziello; Rocco D’Agostino; Daniele Gregoris

    Adopting the Tolman–Oppenheimer–Volkoff formalism, we propose a new analytical solution for a static and spherically symmetric black hole where the cosmological constant is generalized to a non-isotropic Anton–Schmidt fluid acting as a unified dark energy–dark matter source. Our novel result can describe a black hole in energetic equilibrium with the surrounding universe. We thus investigate the interplay

    更新日期:2020-03-26
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