Article
Physics, Multidisciplinary
S. K. Tripathy, B. Mishra, Saibal Ray, Rikpratik Sengupta
Summary: Investigations into bouncing models within the framework of extended gravity theory reveal that model behavior is determined by parameters, the minimal matter-geometry coupling parameter in extended gravity can remove singularities, and violation of energy conditions can lead to evolution into phantom phase in some cases.
CHINESE JOURNAL OF PHYSICS
(2021)
Article
Astronomy & Astrophysics
D. Jackson, R. Bufalo
Summary: In this work, the improved Deser-Woodard non-local gravity over five different cosmological models is analyzed, aiming to avoid the initial singular state of the universe. The numerical solution for the non-local distortion function is developed using the reconstruction procedure, providing viable cosmological solutions. The physical aspects and outcomes of the distortion function evolution at the bouncing point for each model are discussed.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Physics, Multidisciplinary
Sanjay Mandal, N. Myrzakulov, P. K. Sahoo, R. Myrzakulov
Summary: Symmetric teleparallel gravity is a theory consistent with the vanishing affine connection and serves as an alternative and simpler geometric formulation of general relativity. Researchers have explored cosmological bouncing scenarios in a flat Friedmann-Limaitre-Robertson-Walker spacetime using two different Lagrangian forms of f(Q). Analysis of energy conditions and stability has been successfully conducted for both models to demonstrate a matter bounce.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Physics, Mathematical
A. Y. Shaikh, Sankarsan Tarai, S. K. Tripathy, B. Mishra
Summary: In this paper, a bouncing cosmological model is presented in the backdrop of an isotropic, homogeneous space-time, in the presence of general relativistic hydrodynamics (GRH) in an extended theory of gravity. The behavior of the model is analyzed by studying the equation of state (EoS) parameter and the energy conditions. The violation of the strong energy condition further supports the behavior of extended gravity. As with traditional bouncing cosmologies, this model also shows instability.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2022)
Article
Astronomy & Astrophysics
Soumya Chakrabarti
Summary: The extended scalar-tensor theory of gravity includes two interacting scalar fields, with scalar profiles as a function of redshift obtained through analysis and model parameter constraints from observational data. The evolution of the Universe, including effective equation of state, matter density contrast, and thermodynamic equilibrium, is studied and compared with the ACDM cosmology model.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
K. Sravan Kumar, Shubham Maheshwari, Anupam Mazumdar, Jun Peng
Summary: The study explores the possibility of realizing a cosmological bouncing solution in a non-local gravity theory in an anisotropic but homogeneous background, showcasing the behavior of anisotropic shear and the matter components required for the bounce. It is found that k-matter exerts anisotropic pressures and the bouncing solution can satisfy positivity of energy density while avoiding ghost/tachyonic modes in the de Sitter phase in non-local gravity.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Kunio Kaneta, Kin-ya Oda, Motohiko Yoshimura
Summary: This paper presents a cosmological analysis of extended Jordan-Brans-Dicke (eJBD) gravity in the Einstein metric frame. It is the first systematic investigation of how to introduce the lagrangian of standard particle physics in the eJBD framework consistently. The study is significant for understanding the time evolution of eJBD gravity and its compatibility with observational and laboratory bounds.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Marcello Miranda, Daniele Vernieri, Salvatore Capozziello, Francisco S. N. Lobo
Summary: This article presents a method to solve the problem of the initial singularity in the Big Bang by using bouncing solutions. By incorporating extended theories of gravity and an order reduction technique, the study aims to find solutions that closely resemble General Relativity.
Article
Physics, Multidisciplinary
A. Y. Shaikh, B. Mishra
Summary: This paper presents a bouncing cosmological model in the extended theory of gravity with the presence of general relativistic hydrodynamics. An additional matter geometry coupling is introduced to describe the relationship between extended gravity and GR, and it is found that the dynamical parameters have a significant impact on the bouncing behavior of the Universe.
COMMUNICATIONS IN THEORETICAL PHYSICS
(2021)
Article
Multidisciplinary Sciences
Salih Kibaroglu, Oktay Cebecioglu, Ahmet Saban
Summary: By utilizing the Maxwell symmetry in D space-time dimensions, this paper considers the extension of the general-linear and special-linear algebras. It demonstrates that various Maxwell extensions of ordinary space-time algebras can be obtained through suitable contraction of generalized algebras. These extended Lie algebras may be useful in constructing generalized gravity theories and the objects that interact with them. The gravitational dynamics of these algebras are also explored within the framework of gauge theories of gravity. Additionally, modified gravity models containing the generalized cosmological constant term in four dimensions are presented by adopting the symmetry-breaking mechanism of the Stelle-West model.
Article
Astronomy & Astrophysics
M. Farasat Shamir
Summary: This paper investigates the oscillating universe in f(G, T) gravity through two Gauss-Bonnet cosmological models with logarithmic and linear trace terms, respectively. Bouncing solutions are explored and energy conditions are studied, indicating violations near bouncing points consistent with accelerating universe observations. Hubble and deceleration parameters behavior is examined, predicting initial and future bounces for both models. Analysis also focuses on conservation equation in modified gravity theories, suggesting the possibility of recovering the usual conservation equation of general relativity. Overall, f(G, T) gravity models provide good bouncing solutions in this study.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Paola C. M. Delgado, Ruth Durrer, Nelson Pinto-Neto
Summary: In this paper, the CMB bispectrum for bouncing models motivated by Loop Quantum Cosmology was computed. Despite the decay of the primordial bispectrum above a large pivot scale, it was found that the cumulative signal-to-noise ratio of the bispectrum induced in the CMB from scales t < 30 is larger than 10 in all cases of interest, indicating the potential for detection in the Planck data.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Alexander Ganz, Paul Martens, Shinji Mukohyama, Ryo Namba
Summary: We present an asymmetric bouncing scenario within the VCDM model, a modified gravity theory with two local physical degrees of freedom. This scenario avoids ghost and gradient instability, ad-hoc matching conditions, and anisotropic stress issues. It also successfully reproduces cosmological perturbations compatible with observations. The choice of equation of state and VCDM potential allows for an almost scale-invariant power spectrum, while satisfying the CMB bounds on the tensor-to-scalar ratio results in a blue tensor spectrum.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Seokcheon Lee
Summary: For the varying speed of light (VSL) models to be phenomenologically feasible, at least one dimensionless physical constant must change. Adiabaticity and the dependence of physical constants and quantities on cosmic time are also important. The minimally extended VSL (meVSL) model satisfies these conditions and the redshift-drift formula is the same as the standard model. However, the meVSL cannot be verified experimentally but can be tested using cosmological chronometers (CC).
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Astronomy & Astrophysics
Seokcheon Lee
Summary: The Friedmann-Lemaitre-Robertson-Walker model establishes the correlation between redshifts and distances, incorporating the metric expansion of space. In this model, as the universe expands, the wavelength of photons is stretched, resulting in a cosmological redshift, denoted as z. The relationship between the frequency of light detected by a local observer and that emitted from a distant source is modified in the minimally extended varying speed of light model as 1/(1 + z)(1 - b/4).
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2023)
Article
Physics, Mathematical
Sunil Kumar Tripathy, Subigya Pandey, Alaka Priyadarsini Sendha, Dipanjali Behera
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2020)
Article
Astronomy & Astrophysics
Sunil Kumar Tripathy
Summary: The study proposes a traversable wormhole model in an extended gravity theory, considering the Casimir effect and Generalized Uncertainty Principle. It discusses the effects of GUP and extended gravity theory parameters on wormhole properties, as well as the violation of energy conditions by exotic matter in Casimir wormholes.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
B. Mishra, S. K. Tripathy, Sankarsan Tarai
Summary: In this study, the dynamical aspects of an anisotropic cosmological model in an extended gravity theory are explored, with a focus on a hybrid scale factor and the transition from decelerated to accelerated expansion phases. The parameters of the scale factor are constrained based on cosmic transit behavior and the signature flipping behavior of the deceleration parameter. The model is further analyzed through the evolution of the equation of state parameter and energy conditions, with scalar fields reconstructed using specific techniques. Various diagnostic methods are applied to assess the viability of the constructed model, which exhibits characteristics resembling a cosmological constant for a significant duration of cosmic time without showing signs of slowing down in the near future.
JOURNAL OF ASTROPHYSICS AND ASTRONOMY
(2021)
Article
Physics, Multidisciplinary
Pratik P. Ray, Sankarsan Tarai, B. Mishra, S. K. Tripathy
Summary: In this paper, we explore the big rip and pseudo rip cosmological models in an extended theory of gravity. Both models violate strong energy conditions to facilitate late-time cosmic acceleration. The choice of coupling parameter significantly impacts the evolution of the universe.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2021)
Article
Astronomy & Astrophysics
A. S. Agrawal, Laxmipriya Pati, S. K. Tripathy, B. Mishra
Summary: This paper investigates the role of f(Q, T) gravity in obtaining viable cosmological models, considering two different scenarios mimicking non-singular matter bounces. The analysis shows that the strong energy condition and null energy condition are violated in this theory. The models are validated through cosmographic tests and stability analysis.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
S. A. Narawade, Laxmipriya Pati, B. Mishra, S. K. Tripathy
Summary: Two accelerating cosmological models based on symmetric teleparallel f(Q) gravity are introduced, with Q representing non-metricity. These models are constructed with different functional forms of f(Q) and a dynamically changing deceleration parameter. The dark energy in f(Q) gravity exhibits a dynamical equation of state parameter and crosses the phantom divide line.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Astronomy & Astrophysics
Laxmipriya Pati, S. A. Kadam, S. K. Tripathy, B. Mishra
Summary: This paper investigates rip cosmological models in an extended symmetric teleparallel gravity theory, including Little Rip, Big Rip, and Pseudo Rip. Energy conditions and cosmographic parameters are derived and analyzed for all these models to provide a detailed understanding.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Astronomy & Astrophysics
S. A. Kadam, B. Mishra, S. K. Tripathy
Summary: In this paper, we explored the field equations of f(T,B) gravity and determined the dynamical parameters using the hyperbolic function of Hubble parameter. The results showed the existence of accelerating behavior in the model, and the behavior of equation of state parameter indicated the presence of the Lambda CDM model at late time. The importance of model parameters in assessing the accelerating behavior was emphasized, and the stability of the model was verified through the presentation of scalar perturbation.
MODERN PHYSICS LETTERS A
(2022)
Article
Astronomy & Astrophysics
Santosh V. Lohakare, Francisco Tello-Ortiz, S. K. Tripathy, B. Mishra
Summary: In this paper, the bouncing behavior of cosmological models in the background of the Hubble function in the F(R,G) theory of gravity was studied. It was found that both models satisfy the bouncing cosmological properties and exhibit accelerating behavior at the late evolution time. The results of this study are of great significance for understanding cosmic evolution and solving cosmological problems.
Article
Physics, Particles & Fields
Laxmipriya Pati, S. A. Narawade, S. K. Tripathy, B. Mishra
Summary: We investigated the accelerating behavior of the Universe in f(Q,T) gravity in isotropic and homogeneous space-time. We derived the dynamical parameters in the general form of f(Q,T) and split it into two cases. We constructed models using an assumed hyperbolic scale factor and studied their evolutionary behaviors, obtaining the geometric parameters and equation of state parameter within the preferred range of cosmological observations. The violation of strong energy conditions was shown in both cases.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
L. K. Duchaniya, Santosh Lohakare, B. Mishra, S. K. Tripathy
Summary: In this paper, the stability analysis of accelerating cosmological models obtained in f(T) gravity theory is emphasized. The phantom-like behavior of the models at the present epoch is observed based on the evolution of the equation of state parameter. Perturbation technique and dynamical system analysis are used to demonstrate the stability and critical points of the models. In each of the two specific f(T) gravity models, at least one stable critical point is observed.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Physics, Multidisciplinary
Dipanjali Behera, S. K. Tripathy, T. R. Routray, B. Behera
Summary: In this study, neutron skin thickness and electric dipole polarizability in heavy nuclei were calculated using finite range effective interactions within the droplet model framework. Experimental data on these quantities were used to deduce information on the density slope parameter of nuclear symmetry energy at saturation and subsaturation densities, leading to constraints on the parameter values.
Article
Physics, Multidisciplinary
Sunil K. Tripathy, Sasmita Kumari Pradhan, Priyabrata Parida, Dipanjali Behera, Rakesh K. Khuntia, B. Mishra
Article
Physics, Multidisciplinary
D. Behera, S. K. Tripathy, T. R. Routray, B. Behera
