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Gravitationally induced matter creation in scalar-tensor [formula omitted] gravity Phys. Dark Universe (IF 5.5) Pub Date : 2024-03-12 Ricardo A.C. Cipriano, Tiberiu Harko, Francisco S.N. Lobo, Miguel A.S. Pinto, João Luís Rosa
In this work, we analyze the possibility of gravitationally induced matter creation in the so-called Energy-Momentum-Squared gravity (EMSG), i.e. gravity, in its dynamically equivalent scalar-tensor representation. Given the explicit nonminimal coupling between matter and geometry in this theory, the energy–momentum tensor is not generally covariantly conserved, which motivates the study of cosmological
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Particle production from non–minimal coupling in a symmetry breaking potential transporting vacuum energy Phys. Dark Universe (IF 5.5) Pub Date : 2024-03-12 Alessio Belfiglio, Youri Carloni, Orlando Luongo
We propose an inflationary scenario where the inflaton field is non-minimally coupled to spacetime curvature and inflation is driven by a vacuum energy symmetry breaking potential without specifying whether the inflaton field is small or large. As we incorporate vacuum energy into our analysis, we further explore the implications of a non-zero potential offset within inflationary dynamics. We propose
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Corrigendum to “Relic abundance of dark matter with coannihilation in non-standard cosmological scenarios” [Physics of the Dark Universe 44 (2024) 101441] Phys. Dark Universe (IF 5.5) Pub Date : 2024-03-07 Fangyu Liu, Hoernisa Iminniyaz
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No Cauchy horizon in a gravitational decoupled Reissner–Nordström spacetime Phys. Dark Universe (IF 5.5) Pub Date : 2024-03-06 Francisco Tello-Ortiz, Muhammad Ali Raza, M. Zubair, Y. Gómez-Leyton
In this article, using gravitational decoupling by means of the extended geometric deformation approach, we obtain a new hairy spherically symmetric and asymptotically flat charged black hole solution starting from the well known Reissner–Nordström manifold. The resulting spacetime, is characterized by a spacelike singularity at , which is protected by an event horizon , where the original Cauchy horizon
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Exploring non-perturbative corrections in thermodynamics of static dirty black holes Phys. Dark Universe (IF 5.5) Pub Date : 2024-03-06 Saheb Soroushfar, Behnam Pourhassan, İzzet Sakallı
This research delves into an extensive exploration of the thermodynamic characteristics exhibited by a contaminated black hole subject to a uniform electric field, within the theoretical framework of the Einstein-Nonlinear Electrodynamics (ENE)-dilaton theory. The investigation encompasses a thorough analysis of diverse thermodynamic facets, encompassing heat capacity, Helmholtz free energy, and internal
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Dynamical system analysis in multiscalar-torsion cosmology Phys. Dark Universe (IF 5.5) Pub Date : 2024-03-05 Genly Leon, Andronikos Paliathanasis, Alfredo D. Millano
We explore the phase-space of a multiscalar-torsion gravitational theory within a cosmological framework characterized by a spatially flat Friedmann–Lemaître–Robertson–Walker model. Our investigation focuses on teleparallelism and involves a gravitational model featuring two scalar fields, where one scalar field is coupled to the torsion scalar. We consider coupling in the two scalar fields’ kinetic
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Thermodynamic topology of 4D Euler–Heisenberg-AdS black hole in different ensembles Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-28 Naba Jyoti Gogoi, Prabwal Phukon
We study the thermodynamic topology of 4D Euler-Heisenberg-AdS (EHAdS) black hole and higher-order QED corrected Euler-Heisenberg-AdS black hole in different ensembles using generalized off-shell free energy. In this approach, black holes are viewed as defects in the thermodynamic space. We work in two ensembles: canonical ensemble in which the charge is kept fixed and grand canonical ensemble in which
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Rotating black holes surrounded by a dark matter halo in the galactic center of M87 and Sgr A∗ Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-28 S.R. Wu, B.Q. Wang, Z.W. Long, Hao Chen
In this paper, we construct the solutions of modified Schwarzschild spacetime with three kinds of dark matter profiles, i.e. the Beta profiles, Moore profiles and Fermionic halos profiles. In order to make the models more realistic, by using the modified Newman–Janis algorithm (MNJA), we extend our solution to obtain three rotating black holes surrounded by dark matter halo and discuss the black hole
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Astrophysical implications of quantum-improved charged black holes: Insights into quantum gravity and black hole phenomena Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-21 Faisal Javed
This study examines the quantum-improved charged black hole and examines the influence of higher-order thermal fluctuations on its corrected energies. The research aims to assess the null geodesics, shadow radius, quasinormal modes, and emission energy of the black hole. Observations are made on the impact of the quantum parameter and charge of the black hole geometry on the Schwarzschild black hole
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Emulating dark energy models with known equation of state via the created cold dark matter scenario Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-20 Víctor H. Cárdenas, Miguel Cruz
In this work we establish only at background dynamics level, the equivalence between the Created Cold Dark Matter (CCDM) model and diverse dark energy (DE) models. We find that for a barotropic or linear equation of state (EoS) for the DE, , and standard matter sector the corresponding CCDM model is described by the same functional structure of the ratio of particle production, . For a different EoS
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Beyond ΛCDM with f(z)CDM: Criticalities and solutions of Padé Cosmography Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-20 A. Turmina Petreca, M. Benetti, S. Capozziello
Recently, cosmography emerged as a valuable tool to effectively describe the vast amount of astrophysical observations without relying on a specific cosmological model. Its model-independent nature ensures a faithful representation of data, free from theoretical biases. Indeed, the commonly assumed fiducial model, the CDM, shows some shortcomings and tensions between data at late and early times that
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Emergence of cosmic space and the maximization of horizon entropy Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-20 P.B. Krishna, Titus K. Mathew
The spatial expansion of the universe can be described as the emergence of space with the progress of cosmic time, through a simple equation, . This law of emergence suggested by Padmanabhan in the context of general relativity for a flat universe has been generalized by Sheykhi to Gauss Bonnet and Lovelock gravity for a universe with any spatial curvature. We investigate whether this generalized holographic
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The excess of diffuse radio emission in galaxy clusters A4038 and A1664 Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-20 Z.Z. Abidin, N. Asmi, M.R. Mat Sabri, M.A. Rohaizi, N. Hashim, U.F.S.U. Ibrahim
In this study, we investigate the potential connection between Dark matter (DM) particles and synchrotron emission in galaxy clusters, with a focus on radio relics. We explore three models beyond the standard model of particle physics and calculate emissions from DM particle candidates, comparing the results to radio observations. Our analysis centres on galaxy clusters A4038 and A1664, considering
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Nonextensive entropies impact onto thermodynamics and phase structure of Kerr–Newman black holes Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-17 S. Ghaffari, G.G. Luciano, A. Sheykhi
Taking the nonextensive Tsallis and Rényi entropies into account, we explore thermodynamic properties and phase transitions of the Kerr–Newman black holes (KNBH) in the microcanonical and canonical ensembles. We also compare our results with those obtained by attributing the Bekenstein–Hawking entropy bound to the mentioned black holes. Our analysis indicates that, similarly to the standard Boltzmann
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Generating exact polytropes in non-conservative unimodular geometries Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-16 Sudan Hansraj, Chevarra Hansraj, Njabulo Mkhize, Abdelghani Errehymy, Christian G. Böhmer
The trace-free Einstein equations contain one equation less than the complete field equations. In a static and spherically symmetric spacetime, the number of field equations is thus reduced to two. The equation of pressure isotropy of general relativity, however, is preserved thus showing that any known perfect fluid spacetime is a suitable candidate for the trace-free scenario. The extra freedom in
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Traversable wormholes with weak gravitational lensing effect in f(R,T) gravity Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-16 Nayan Sarkar, Susmita Sarkar, Abdelmalek Bouzenada, Abhisek Dutta, Moumita Sarkar, Farook Rahaman
In this article, we have introduced completely new asymptotically flat Morris-Thorne traversable wormhole geometries supported by anisotropic matter in the framework of gravity whereas the isotropic matter content does not support the wormhole structure. The reported shape functions are nicely fitted in the construction of wormhole geometries by satisfying all the essential conditions. The wormhole
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Muon g−2, dark matter, and neutrino mass explanations in a modular A4 symmetry Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-15 Parada T.P. Hutauruk, Dong Woo Kang, Jongkuk Kim, Hiroshi Okada
We study a successful model to explain the muon anomalous magnetic moment originating from Yukawa-type interactions in a supersymmetric theory. Thanks to a modular flavor symmetry, any lepton flavor violations that spoil the model are forbidden. We also investigate a predictive radiative seesaw model including a dark matter (DM) candidate. At first, we construct the minimum model to satisfy the neutrino
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Shadows of R-charged black holes in AdS5 Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-15 Yassine Sekhmani, Dhruba Jyoti Gogoi, M. Koussour, Ratbay Myrzakulov, Javlon Rayimbaev
Motivated by Anti-de Sitter (AdS) black hole solutions of five-dimensional gauged extended supergravities, the shadow behavior of R-charged black holes is examined. This process gets analyzed in terms of four charge configurations, namely, three unequal charges, three equal charges, two equal charges, and one single charge. Results on shadow behavior show the influence of electric charge on the geometry
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Non-perturbative correction on the black hole geometry Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-13 Behnam Pourhassan, Hoda Farahani, Farideh Kazemian, İzzet Sakallı, Sudhaker Upadhyay, Dharm Veer Singh
In this paper, we use the holographic principle to obtain a modified metric of black holes that reproduces the exponentially corrected entropy. The exponential correction of the black hole entropy comes from non-perturbative corrections. It interprets as a quantum effect which affects black hole thermodynamics especially in the infinitesimal scales. Hence, it may affect black hole stability at the
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Relic abundance of dark matter with coannihilation in non-standard cosmological scenarios Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-13 Fangyu Liu, Hoernisa Iminniyaz
We investigate the relic abundance of dark matter from coannihilation in non-standard cosmological scenarios. We explore the effect of coannihilation on the relic density of dark matter and freeze out temperature in quintessence model with kination phase and brane world cosmological scenarios. Since the Hubble expansion rate is enhanced in quintessence and brane world cosmological models, it causes
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The first variation of the matter energy–momentum tensor with respect to the metric, and its implications on modified gravity theories Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-13 Zahra Haghani, Tiberiu Harko, Shahab Shahidi
The first order variation of the matter energy–momentum tensor with respect to the metric tensor plays an important role in modified gravity theories with geometry-matter coupling, and in particular in the modified gravity theory. We obtain the expression of the variation for the baryonic matter described by an equation given in a parametric form, with the basic thermodynamic variables represented
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The effect of quark–antiquark confinement on the deflection angle by the NED black hole Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-13 Erdem Sucu, Ali Övgün
In this study, we explore the influence of quark–antiquark confinement on the deflection angle within the framework of nonlinear electrodynamic (NED) black holes. To achieve this, we establish the appropriate optical spacetime metric and subsequently determine the Gaussian optical curvature. Utilizing the Gauss–Bonnet theorem, we investigate the impact of quark–antiquark confinement on the deflection
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Cosmology of unimodular Born–Infeld-fR gravity Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-13 Salih Kibaroğlu, Sergei D. Odintsov, Tanmoy Paul
We propose a novel modified gravity: unimodular generalization of the Born–Infeld- gravity within the framework of cosmology. After formulating the action corresponding to the generalized Born–Infeld- gravity, we present a reconstruction scheme of this unimodular extension to achieve various cosmological eras of the universe. Interestingly, the unimodular generalization of Born–Infeld- gravity proves
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Topological behavior of 3D regular black hole with zero point length Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-09 M. Umair Shahzad, Aqsa Mehmood, Adnan Malik, Ali Övgün
In this work, we study the thermodynamics and topological classes of regular black holes (RBH) in three dimensions, with charge, zero point length and rotational parameters in canonical, mixed and grand canonical ensembles. We consider the RBH in three dimensions with zero point length as defects with a topological nature within the thermodynamic domain and examine the local and global topology. We
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Static and spherically symmetric wormholes in power-law f(R) gravity model Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-07 Abdelghani Errehymy
By venturing into gravitational frameworks that extend beyond general relativity (GR), it becomes evident that traversable wormholes (WHs) can conceivably be constructed solely through gravitational means. In GR, the intrinsic degrees of freedom are insufficient for assembling these special kinds of objects without incorporating exotic matter forms. Nevertheless, by stretching gravity into altered
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Mapping solutions in nonmetricity gravity: Investigating cosmological dynamics in conformal equivalent theories Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-06 Nikolaos Dimakis, Kevin J. Duffy, Alex Giacomini, Alexander Yu. Kamenshchik, Genly Leon, Andronikos Paliathanasis
We investigate the impact of conformal transformations on the physical properties of solution trajectories in nonmetricity gravity. Specifically, we explore the phase space and reconstruct the cosmological history of a spatially flat Friedmann–Lemaître–Robertson–Walker universe within scalar-nonmetricity theory in both the Jordan and Einstein frames. A detailed analysis is conducted for three connections
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Tracking Quintessence Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-29 Artur Alho, Claes Uggla, John Wainwright
Tracking quintessence, in a spatially flat and isotropic space–time with a minimally coupled canonical scalar field and an asymptotically inverse power-law potential V(φ)∝φ−p, p>0, as φ→0, is investigated. This is done by introducing a new three-dimensional regular dynamical system, which enables a rigorous explanation of the tracking feature: (1) The dynamical system has a tracker fixed point T with
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Observational constraints on thawing quintessence scalar field model Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-03 Fereshteh Felegary, Kazuharu Bamba
Thawing quintessence scalar field models with the various potential forms to explain the late-time cosmic acceleration are compared to the CDM model in detail by analyzing cosmological parameters with a set of observational data including , BAO, CMB, SNIa, BBN, and at the background and the perturbation levels. At low redshifts for the thawing quintessence scalar field models, the growth rate of the
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Inflation vs. Ekpyrosis — Comparing stability in general non-minimal theory Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-28 Debottam Nandi, Manjeet Kaur
The scalar field is considered to have dominated the early Universe. One subtle yet crucial requirement of this assumption is that the solution must be highly stable, i.e., indifferent to any initial conditions because there are no favored ones. Inflation, which is now the most successful early Universe paradigm, answers most of the early Universe’s problems, including the fact that it is mostly stable
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Direct smooth reconstruction of inflationary models in f(R) gravity Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-28 Gianluca Giacomozzi, Sergio Zerbini
Starting from the parametrization of the spectrum of scalar perturbations generated during inflation in terms of the number of e-folds N and using the approach recently developed by Starobinsky, dubbed “direct smooth reconstruction”, we show that, in the slow-roll approximation, it is possible to reconstruct the inflation potential in the Einstein frame and its corresponding f(R) gravity Lagrangian
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Dark photon Bremsstrahlung and ultra-high-energy cosmic ray Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-29 Predee Tantirangsri, Daris Samart, Chakrit Pongkitivanichkul
A dark photon is a hypothetical particle that is similar to a photon with a small mass and interacts very weakly with ordinary matter through a kinetic mixing with the ordinary photon. In this paper, we propose a new way to probe the existence of dark photons through the Bremsstrahlung effect on ultra-high-energy cosmic rays (UHECRs). Using the standard soft photon calculation, we demonstrate that
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Study of relativistic accretion flow in the f(R) theory of gravity Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-30 Akhil Uniyal, Sayan Chakrabarti, Santabrata Das
We present the properties of relativistic, inviscid, low angular momentum, advective accretion flow in a f(R) gravity theory that satisfactorily mimics the asymptotically flat vacuum solutions of the Einstein’s equations. With this, we solve the governing equations describing the accretion flow and obtain the global transonic accretion solutions in terms of flow energy (E), angular momentum (λ) and
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On dark matter self-interaction via single neutrino exchange potential Phys. Dark Universe (IF 5.5) Pub Date : 2024-02-02 Yue Zhang
Neutrinos – amongst the lightest known particles – can mediate a force driving dark matter self-interaction and the small scale structure of the universe. We explore such a possibility in the simplest neutrino portal dark sector model where neutrino has a Yukawa coupling with a scalar and fermion that are degenerate in mass and together comprise 100% of dark matter in the universe. We derive the non-relativistic
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A new binning method to choose a standard set of Quasars Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-24 M.G. Dainotti, A.Ł. Lenart, M. Ghodsi Yengejeh, S. Chakraborty, N. Fraija, E. Di Valentino, G. Montani
Although the Lambda Cold Dark Matter model is the most accredited cosmological model, information at intermediate redshifts (z) between type Ia Supernovae (z = 2.26) and the Cosmic Microwave Background (z = 1100) is crucial to validate this model further. Here, we present a detailed and reliable methodology for binning the quasars (QSO) data that allows the identification of a golden sample of QSOs
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On graviton–photon conversions in magnetic environments Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-18 Jai-chan Hwang, Hyerim Noh
Graviton–photon conversions in a given external electric or magnetic field, known as the Gertsenshtein mechanism, are usually treated using the four-potential for photons. In terms of the electric and magnetic (EM) fields, however, proper identification of the fields in curved spacetime is important. By misidentifying the fields in Minkowski form, as is often practiced in the literature, we show that
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The spooky ghost of vectorization Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-20 Lorenzo Pizzuti, Alexandre M. Pombo
An interesting mechanism for the formation of hairy black holes occurs when a vector field, non-minimally coupled to a source term, grows from a perturbation of the vacuum black hole, aka vectorization. Its study has, however, been lacking, in part due to the constant threat of ghost instabilities that have plagued vector fields. In this work, we show evidence that, in a generic family of extended-vector-tensor
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Cosmological complexity in K-essence Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-15 Ai-chen Li, Xin-Fei Li, Ding-fang Zeng, Lei-Hua Liu
We calculate the cosmological complexity under the framework of scalar curvature perturbations for a K-essence model with constant potential. In particular, the squeezed quantum states are defined by acting a two-mode squeezed operator which is characterized by squeezing parameters rk and ϕk on vacuum state. The evolution of these squeezing parameters are governed by the Schrödinger equation, in which
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Constraints on axion-like particles with the Perseus Galaxy Cluster with MAGIC Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-18 H. Abe, S. Abe, J. Abhir, V.A. Acciari, I. Agudo, T. Aniello, S. Ansoldi, L.A. Antonelli, A. Arbet Engels, C. Arcaro, M. Artero, K. Asano, D. Baack, A. Babić, A. Baquero, U. Barres de Almeida, J.A. Barrio, I. Batković, J. Baxter, J. Becerra González, T. Yamamoto
Axion-like particles (ALPs) are pseudo-Nambu–Goldstone bosons that emerge in various theories beyond the standard model. These particles can interact with high-energy photons in external magnetic fields, influencing the observed gamma-ray spectrum. This study analyzes 41.3 h of observational data from the Perseus Galaxy Cluster collected with the MAGIC telescopes. We focused on the spectra the radio
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Phase-space analysis of the viscous fluid cosmological models in the coincident f(Q) gravity Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-12 Dheeraj Singh Rana, Raja Solanki, P.K. Sahoo
In this article, we consider a newly proposed parameterization of the viscosity coefficient ζ, specifically ζ=ζ̄0ΩmsH, where ζ̄0=ζ0Ωm0s within the coincident f(Q) gravity formalism. We consider a non-linear function f(Q)=−Q+αQn, where α and n are arbitrary model parameters, which is a power-law correction to the STEGR scenario. We find an autonomous system by invoking the dimensionless density parameters
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On the time dependency of a0 Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-13 Antonino Del Popolo, Man Ho Chan
In this paper, we test one of the predictions of the Scale Invariant Vacuum (SIV) theory on MOND. According to that theory, MOND’s acceleration a0 is not a universal quantity but depends on several parameters, including time. To check this prediction, we compare the dependency of a0 from redshift, using the values of a0 obtained in Marra et al. [1] by carrying a Bayesian inference for 153 galaxies
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Singularity free cosmological models in viscous symmetric teleparallel gravity Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-12 Mrinnoy M. Gohain, Kalyan Bhuyan
In this paper, we have investigated the possibility of deriving exact non-singular cosmological solutions in a combined scenario of bulk viscous fluid and symmetric teleparallel gravity (f(Q) gravity). Interestingly, we have found that the general solutions obtained from our models are flexible enough for demonstrating the emergent Universe scenario, inflation and late-time dark-energy-like behaviour
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Testing Weyl geometric gravity with the SPARC galactic rotation curves database Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-12 Maria Crăciun, Tiberiu Harko
We present a detailed investigation of the properties of the galactic rotation curves in the Weyl geometric gravity model, in which the gravitational action is constructed from the square of the Weyl curvature scalar, and of the strength of the Weyl vector. The theory admits a scalar–vector–tensor representation, obtained by introducing an auxiliary scalar field. By assuming that the Weyl vector has
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Thermal properties of Simpson–Visser Minkowski core regular black holes solution in Verlinde’s emergent gravity Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-04 Allah Ditta, Tiecheng Xia, Riasat Ali, Ghulam Mustafa, G. Mustafa, Asif Mahmood
In this study, we investigate the thermodynamic characteristics of the Simpson–Visser Minkowski core black hole solution within Verlinde’s emergent gravity framework. Our analysis encompasses the examination of energy emission, Gibbs free energy, and thermal fluctuations. We calculate various quantities such as the Hawking temperature, geometric mass, and heat capacity to assess the local and global
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Corrigendum to “On the time dependency of a0” [Phys. Dark Univ. (2024) DARK 101393] Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-06 Antonino Del Popolo, Man Ho Chan
Abstract not available
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Search for environment-dependent dilatons Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-08 Hauke Fischer, Christian Käding, René I.P. Sedmik, Hartmut Abele, Philippe Brax, Mario Pitschmann
The environment-dependent dilaton field is a well-motivated candidate for dark energy and naturally arises in the strong coupling limit of string theory. In this article, we present the very first experimental constraints on the parameters of this model. For this, we employ data obtained from the qBounce collaboration and the Lunar Laser Ranging (LLR) experiment. Furthermore, we forecast expected constraints
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A mass scale law connecting cosmophysics to microphysics Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-06 Pierre-Henri Chavanis
We introduce different mass scales corresponding to the Universe, fermion stars, mini boson stars, Planck black holes, the electron, the neutrino, and the cosmon. These mass scales are obtained by combining the maximum mass of fermion stars, boson stars and soliton stars set by quantum mechanics and general relativity with the Eddington relation connecting the mass me of the electron to the cosmological
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The Fast and Furious in JWST high-z galaxies Phys. Dark Universe (IF 5.5) Pub Date : 2024-01-02 Maurice H.P.M. van Putten
Recent JWST surveys reveal a striking abundance of massive galaxies at cosmic dawn, earlier than predicted by ΛCDM. The implied speed-up in galaxy formation by gravitational collapse is reminiscent of short-period galaxy dynamics described by the baryonic Tully–Fisher relation. This may originate in weak gravitation tracking the de Sitter scale of acceleration adS=cH, where c is the velocity of light
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Sommerfeld enhancement of right-handed sneutrino dark matter Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-23 A. Elsheshtawy, S. Khalil
The relic abundance of the lightest right-handed sneutrino dark matter in supersymmetric B−L extension of the standard model is revisited. Through the exchange of light B−L Higgs bosons, we investigate the bound state of the attractive Yukawa potential and obtain a large non-perturbative Sommerfeld enhancement effect. We emphasize that with this effect the relic abundance of right-handed sneutrino
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Axially symmetric exponential metric Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-21 S. Habib Mazharimousavi
We present a new family of vacuum axially symmetric static solutions to Einstein’s field equations. This solution is a geometrically modified version of the Yilmaz exponential metric (YEM) which has recently been shown to represent a traversable wormhole. This vacuum solution is a one-parameter static singular solution with its singularity located at r=0. Furthermore, it is shown that both the YEM
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f(T) cosmology in the regime of quasar observations Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-19 Rodrigo Sandoval-Orozco, Celia Escamilla-Rivera, Rebecca Briffa, Jackson Levi Said
The open problems related to cosmological tensions in current times have opened new paths to study new probes to constrain cosmological parameters in standard and extended cosmologies, in particular, to determine at a local level the value of the Hubble constant H0, through independent techniques. However, while standard Cosmological Constant Cold Dark Matter (ΛCDM) model has been well constrained
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Running vacuum in Brans & Dicke theory: A possible cure for the σ8 and H0 tensions Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-20 Javier de Cruz Pérez, Joan Solà Peracaula
Extensions of the gravitational framework of Brans & Dicke (BD) are studied by considering two different scenarios: (i) ‘BD-ΛCDM’, in which a rigid cosmological constant, Λ, is included, thus constituting a BD version of the vanilla concordance ΛCDM model (the current standard model of cosmology with flat three-dimensional geometry), and (ii) ‘BD-RVM’, a generalization of (i) in which the vacuum energy
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Confinement and nonlinear electrodynamics: Asymptotic Schwarzschild charged black hole Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-21 S. Habib Mazharimousavi
While most nonlinear electrodynamics (NED) models tend to Maxwell’s linear theory in the weak field regime, very recently a model of NED has been proposed in the context of heavy quark–antiquark confinement that gives the same limit in the strong field regime. This form of correction to Maxwell’s linear theory is shown to be applicable in such a confined system. In this model, the radial electric field
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Minisuperspace description of f(Q)-cosmology Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-21 A. Paliathanasis, N. Dimakis, T. Christodoulakis
We investigate the existence of minisuperspace description for the homogeneous cosmological field equations within the framework of symmetric teleparallel f(Q)-gravity. We consider the background space to be described by the isotropic Friedmann–Lemaître–Robertson–Walker geometry, the anisotropic Kantowski-Sachs and the anisotropic Bianchi III geometries. Across all these models, we establish that the
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New gravastar model in generalised cylindrically symmetric space–time and prediction of mass limit Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-21 Debadri Bhattacharjee, Pradip Kumar Chattopadhyay, Bikash Chandra Paul
We present a class of new Gravastar solutions following the works of Mazur and Mottola for a Gravitational Bose–Einstein Condensate (GBEC) star in generalised cylindrically symmetric space–time. A stable gravastar consists of 3 distinct regions, namely: (i) an interior de-Sitter space (p=−ρ), which exerts an outwards repulsive force at all points on the thin shell, (ii) an intermediate thin shell with
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Aschenbach effect and circular orbits in static and spherically symmetric black hole backgrounds Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-20 Shao-Wen Wei, Yu-Xiao Liu
The Aschenbach effect, the increasing behavior of the angular velocity of a timelike circular orbit with its radius coordinate, is found to extensively exist in rapidly spinning black holes to a zero-angular-momentum observer. It also has potential observation in the high-frequency quasi-periodic oscillations of X-ray flux. However, observing such effect remains to be a challenge in static and spherically
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Non-minimal unimodular inflation Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-23 Manda Malekpour, Kourosh Nozari, Fateme Rajabi, Narges Rashidi
We study an extension of the unimodular cosmological inflation in the context of the non-minimal coupling of a generic scalar field with gravitational sector. We consider the non-minimal coupling of the scalar field and gravity as the only source of energy–momentum tensor in this setup. Without introducing new particles other than those already existing in electroweak theory, the generic scalar field’s
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Cosmic evolution in f(Q,T) gravity: Exploring a higher-order time-dependent function of deceleration parameter with observational constraints Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-23 Madhur Khurana, Himanshu Chaudhary, Saadia Mumtaz, S.K.J. Pacif, G. Mustafa
In this research paper, we explore a well-motivated parametrization of the time-dependent deceleration parameter, characterized by a cubic form in cosmic time t, in the context of late-time cosmic acceleration. The whole analysis of our work is within the framework of f(Q,T) gravity theory, where we consider the background metric as the homogeneous and isotropic one represented by the Friedmann–Le
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Revisiting f(R,T) cosmologies Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-15 Ana Paula Jeakel, Jonas Pinheiro da Silva, Hermano Velten
We review the status of f(R,T) cosmological models, where T is the trace of the energy momentum tensor Tμν. We start focusing on the modified Friedmann equations for the minimally coupled gravitational Lagrangian of the type f(R,T)=R+αeβT+γnTn. We show that in such a minimally coupled case there exists a useful constraining relation between the effective fractionary total matter density with an arbitrary
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Cosmological models in f(T,T) gravity and the dynamical system analysis Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-15 L.K. Duchaniya, Santosh V. Lohakare, B. Mishra
The study addresses matter-coupled modified gravity, particularly f(T,T) gravity, unveiling distinct formalism. The research further discusses stability analysis, and the dynamical system approach, exploring the dynamics of critical points to understand these models’ viability better. The dynamical system analysis of the cosmological models in f(T,T) gravity, where T and T respectively represent the
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Testing of κ(R,T)-gravity through gravastar configurations Phys. Dark Universe (IF 5.5) Pub Date : 2023-12-16 G.R.P. Teruel, Ksh. Newton Singh, Tanmoy Chowdhury, Farook Rahaman, Monimala Mondal
In this article, we are reporting for the first time the existence of gravastar configurations in the framework of κ(R,T)-gravity, which can be treated as an alternative to a black hole (Mazur and Mottola). This strengthens how much this new gravity theory may be physically demanding to the gravity community in the near future. We first develop the gravastar field equations for a generic κ(R,T) functional