DR RAVI KANT MISHRA

Scopus Publications

Anisotropic cyclic cosmology in f(T) gravity: A Bianchi type-II framework for periodic big bang big crunch evolution
Rahul Sharma, R.K. Mishra
Physics Letters Section A General Atomic and Solid State Physics, 2026
Nonlinear Perturbation Stability of Cosmological Model in f(R, T) Gravity with Maximum Likelihood Approach
Navya Jain, R.K. Mishra
International Journal of Geometric Methods in Modern Physics, 2026
This study investigates the nonlinear stability of cosmological model within the framework of [Formula: see text] gravity by employing a time-dependent deceleration parameter [Formula: see text], where [Formula: see text] is Hubble parameter and [Formula: see text] is an arbitrary constant. Utilizing nonlinear perturbation analysis, we derive growth rate parameters governing perturbations evolution and investigate their role in determining system’s stability. The study establishes localized stability conditions for varying ranges of model parameters. Additionally, the Maximum Likelihood Estimation (MLE) method is employed to validate theoretical predictions against observational datasets, including the Hubble parameter and Pantheon Type Ia supernova (SNe Ia) data. The best-fit values indicate consistency with empirical observations, reinforcing the model’s viability. This work provides a comprehensive framework for assessing cosmic evolution under nonlinear perturbations in modified gravity theory.
Analytical and numerical investigation of cosmological stability in scalar–tensor gravity
Navya Jain, R. K. Mishra
International Journal of Modern Physics D, 2026
This research explores the stability characteristics of a cosmological model constructed within the framework of scalar–tensor gravity, incorporating both theoretical derivations and numerical simulations. A variable deceleration parameter dependent on time is utilized to obtain explicit expressions for the scale factor, scalar field, pressure and energy density. To examine the physical plausibility of the model, we conduct a linear perturbation study by introducing small deviations in matter and scalar field variables. Through the application of the growth rate parameter approach, the model displays a credible shift from early-time instability to a stable late-time cosmic behavior, aligning with the observed acceleration of the Universe. The analytical outcomes are supported by numerical integration using the fourth-order Runge–Kutta algorithm, which confirms the damping of perturbations over time. Furthermore, the model’s compatibility with current observations is tested using the Maximum Likelihood Estimation technique, employing Hubble parameter datasets and the Pantheon sample of Type Ia supernovae. The close match between theoretical predictions and observational data affirms the robustness of the proposed scenario. Overall, the combined use of analytic modeling, computational methods and statistical comparison indicates that the scalar–tensor theory, when paired with the selected deceleration parameter, offers a reliable and observationally consistent representation of cosmic evolution.
Generalized fractional deceleration as a tool to decode the universe's expansion
R. K. Mishra, Priya Awasthi, Rahul Sharma
Modern Physics Letters A, 2026
In this work, we investigate a cosmological model within the context of [Formula: see text] gravity by considering a bulk viscous fluid as the cosmic source and adopting a Bianchi type [Formula: see text] anisotropic spacetime. To derive an exact solution of the field equations, we assume a specific time-dependent deceleration parameter expressed in terms of the Hubble parameter. This choice facilitates the derivation of analytical expressions for the scale factor and Hubble parameter as functions of cosmic time t and redshift z. Additionally, we conduct a cosmographic analysis by computing higher-order kinematic parameters — jerk, snap, and lerk — which are found to asymptotically approach unity, thereby indicating consistency with the standard [Formula: see text]CDM cosmological model in the late-time limit. To further constrain the model and solve the field equations, we impose a relation between the directional scale factors as [Formula: see text]. This condition plays a crucial role in reducing the complexity of the anisotropic field equations and enables the derivation of exact expressions for key physical quantities. As a result, we obtain the temporal and redshift evolution of the energy density [Formula: see text], effective pressure [Formula: see text], and the equation of state (EoS) parameter w. The dynamical behavior of these quantities suggests a transition from a decelerated to an accelerated phase of cosmic expansion, compatible with current observational evidence.
Brans–Dicke versus f(T) gravity: Comparative insights into modified gravitational theories
Rahul Sharma, R. K. Mishra
Modern Physics Letters A, 2026
This study performs a comparative cosmological analysis of Brans–Dicke theory (BDT) and [Formula: see text] gravity in the anisotropic Bianchi type-I spacetime. By using a hyperbolic sine form of the scale factor, we constrain the free parameters [Formula: see text] and [Formula: see text] against 77 [Formula: see text] data points via [Formula: see text] minimization, obtaining [Formula: see text] and [Formula: see text], with a reduced chi-square [Formula: see text]. The model predicts the present Hubble and deceleration parameters as [Formula: see text] and [Formula: see text], respectively. We derive and examine the dynamical evolution of energy density, pressure, and the equation of state (EoS) parameter. A key outcome is the marked difference in late-time behavior: the [Formula: see text] model exhibits stronger acceleration with an EoS parameter trending toward phantom regimes, whereas the BDT model shows a distinctive late-time re-acceleration phase driven by the scalar field dynamics. These results highlight how geometric and scalar-field modifications of gravity lead to observationally distinguishable cosmic evolution.
Evaluating cosmic expansion f(T) vs f(R,T) gravity theories
Rahul Sharma, R. K. Mishra
Astrophysics and Space Science, 2026
Decoding cosmic acceleration through fðTÞ gravity: A Bianchi type-I perspective
Rahul Sharma, R. K. Mishra
International Journal of Modern Physics A, 2026
This study explores cosmological dynamics in [Formula: see text] gravity within an anisotropic Bianchi type-I space–time using fractional linear varying deceleration parameter (FLVDP), with parameters constrained by 77 observational [Formula: see text] data points via [Formula: see text]-minimization, yielding [Formula: see text] [Formula: see text]km/s/Mpc at [Formula: see text] (13.8[Formula: see text]Gyr). We compare the linear [Formula: see text] model against a power-law form [Formula: see text], deriving analytical expressions for energy density, pressure, and the equation of state (EoS) parameter. Our results show that the power-law model produces a observationally consistent EoS value [Formula: see text], while the linear model exhibits phantom behavior with [Formula: see text]. The FLVDP framework accurately reproduces the deceleration-to-acceleration transition, with the power-law model exhibiting more gradual evolution, indicating torsion-based modifications regulate cosmic dynamics. This work establishes the power-law [Formula: see text] model in anisotropic space–time as a compelling alternative to standard cosmology, aligning better with both theoretical expectations and observational data.
Exploring advanced curvature and linear matter coupling with its impact on the expanding universe
Rahul Sharma, R. K. Mishra
International Journal of Geometric Methods in Modern Physics, 2026
This study extends the scalar curvature term [Formula: see text] within the framework of modified gravity, incorporating both the Ricci scalar [Formula: see text] and the energy–momentum tensor [Formula: see text]. We explore a specific formulation of [Formula: see text] gravity, defined as [Formula: see text], in the context of a spatially homogeneous and anisotropic Bianchi-type-I cosmological model with a perfect fluid. Within this framework, we derive and analyze the modified field equations for both positive and negative values of [Formula: see text]. By utilizing observational datasets, we constrain the model parameters and visualize its cosmological implications. In addition, we examine the validity of the energy conditions (EC) to assess the physical plausibility of the model across cosmic evolution. Our findings show that for [Formula: see text], the model remains stable and aligns with physical expectations. However, for other positive [Formula: see text], anomalous behavior emerges in specific intervals. Furthermore, we validate our model through metric perturbation analysis and cosmological diagnostic tools like [Formula: see text] and [Formula: see text]. The combined analysis of EC and observational diagnostics confirms the physical viability and late-time accelerated expansion behavior of the model within the admissible parameter range.
A comparative analysis in f (R, T) and Brans-Dicke theories with novel deceleration parameter
Navya Jain, R. K. Mishra
Modern Physics Letters A, 2025
This study conducts a comprehensive comparative analysis of two influential cosmological theories, namely Brans–Dicke and [Formula: see text] theory of gravity, within the context of a new form of the deceleration parameter, i.e. Fractional Quadratic Deceleration Parameter. This investigation explores the unique features and intrinsic beauty of each theory, highlighting the adaptability of Brans–Dicke with its scalar field and the importance of [Formula: see text] through its modified geometric interactions. The new form of the deceleration parameter i.e. [Formula: see text] serves as a catalyst for redefining our understanding of cosmic dynamics. Precautions have been taken to ensure the robustness of the comparison, including the consideration of model dependence, numerical stability, and sensitivity analysis.
Decoding the universe: A comparative study of cosmographic parameters within f(R,T) gravity
R. K. Mishra, Rahul Sharma
Modern Physics Letters A, 2025
This study explores the interplay between cosmic acceleration and deceleration within the framework of [Formula: see text] gravity, employing distinct deceleration parameter models. We derive solutions to the Einstein field equations and analyze the evolution of key cosmological parameters concerning cosmic time. The implications of [Formula: see text] gravity on cosmic expansion are examined through both analytical and graphical approaches. Notably, the violation of the strong energy condition (SEC) in all models indicates the necessity of dark energy or modified gravity to explain the universe’s accelerated expansion. Additionally, we present a comparative analysis of Model-I, Model-II, and the [Formula: see text]CDM model, highlighting their distinct evolutionary behaviors. A tabulated summary of all cosmographic parameters provides a comprehensive overview, facilitating direct comparisons with the standard [Formula: see text]CDM model.
Numerical and statistical insights into f(R,T) cosmology: GRP, RK4, and MLE approaches
Navya Jain, R. K. Mishra
Astrophysics and Space Science, 2025
Beyond four dimensions: An extended study of f (R, T) theory with multidimensional metric
R. K. Mishra, Navya Jain
International Journal of Geometric Methods in Modern Physics, 2025
EXPLORING f(T) GRAVITY DYNAMICS & COSMOLOGICAL PARAMETERS
, MISHRA R.K, SHARMA RAHUL, and
Romanian Journal of Physics, 2025
Investigating Accelerating Universe in f(T) Gravity
Rahul Sharma, R. K. Mishra
Springer Proceedings in Materials, 2025
Investigating a New Form of Deceleration Parameter with FLRW Metric
Navya Jain, R. K. Mishra
Springer Proceedings in Materials, 2025
Comparative study of linear & non-linear f(T) gravity models in Bianchi type-III space-time
R. K. Mishra, Rahul Sharma
Astrophysics and Space Science, 2025
Exploring the Bianchi-IX universe within Brans-Dicke theory and a deceleration parameter
R. K. Mishra, Rahul Sharma
Modern Physics Letters A, 2024
Beyond general relativity: comparative analysis between BDT and f(R, T) with NLDP
R. K. Mishra, Rahul Sharma
European Physical Journal Plus, 2024
Cosmic acceleration & deceleration with f (R, T) gravity
R. K. Mishra, Rahul Sharma
Modern Physics Letters A, 2024
Dynamics of the universe with variable parameters that govern the gravitational interactions
R. K. Mishra, Navya Jain
General Relativity and Gravitation, 2024
Cosmic Dynamics Beyond Einstein Theory: Mathematical Analysis with f(R, T) Gravity
R. K. Mishra, Navya Jain
International Journal of Theoretical Physics, 2024
STABILITY ANALYSIS IN COSMOLOGICAL MODELS USING PERTURBATIVE METHODS IN f(R, T) THEORY
, R.K. MISHRA, NAVYA JAIN, and
Romanian Journal of Physics, 2024
FRACTIONAL QUADRATIC DECELERATION PARAMETER (FQDP): OBSERVATIONAL AND THEORETICAL PERSPECTIVES
R. K. MISHRA, , NAVYA JAIN, and
Romanian Journal of Physics, 2024
Investigation on behavior of deceleration parameter with LRS Bianchi type-I cosmological models
R. K. Mishra, Heena Dua
Indian Journal of Physics, 2023
Cosmological model in f(R, T) theory with time-varying FLVDP
Rahul Sharma, Avtar Chand, R K Mishra
Journal of Physics Conference Series, 2023
Cosmological models with variable parameters
Navya Jain, Heena Dua, R K Mishra
Journal of Physics Conference Series, 2023
Dynamics of Bianchi type-I universe in Brans-Dicke gravity
Heena Dua, R. K. Mishra
Aip Conference Proceedings, 2021
Bianchi type-I cosmological model in Sáez-Ballester theory with variable deceleration parameter
R. K. Mishra, Heena Dua
Astrophysics and Space Science, 2021
Evolution of FLRW universe in Brans-Dicke gravity theory
R. K. Mishra, Heena Dua
Astrophysics and Space Science, 2021
Phase transition of cosmological model with statistical techniques
R. K. Mishra, Heena Dua
Astrophysics and Space Science, 2020
Cosmological models in Sáez-Ballester theory with bilinear varying deceleration parameter
R. K. Mishra, Avtar Chand
Astrophysics and Space Science, 2020
Bulk viscous string cosmological models in Saez-Ballester theory of gravity
R. K. Mishra, Heena Dua
Astrophysics and Space Science, 2019
Bianchi-III cosmological model with BVDP in modified f(R, T) theory
R. K. Mishra, Heena Dua, Avtar Chand
Astrophysics and Space Science, 2018
A comparative study of cosmological models in alternative theory of gravity with LVDP & BVDP
R. K. Mishra, Avtar Chand
Astrophysics and Space Science, 2017
Cosmological models in alternative theory of gravity with bilinear deceleration parameter
R. K. Mishra, Avtar Chand
Astrophysics and Space Science, 2016
Dark Energy Models in f(R, T) Theory with Variable Deceleration Parameter
R. K. Mishra, Avtar Chand, Anirudh Pradhan
International Journal of Theoretical Physics, 2016
FRW cosmological models in Brans-Dicke theory of gravity with variable q and dynamical Λ-term
Avtar Chand, R. K. Mishra, Anirudh Pradhan
Astrophysics and Space Science, 2016
Phase transition in cosmology with magnetic field
Avtar Chand, R. K. Mishra
Aip Conference Proceedings, 2015
A new class of accelerating cosmological models with variable G & ∧ in sáez and ballester theory of gravitation
Romanian Journal of Physics, 2014
Bianchi type-I transit cosmological models with time dependent gravitational and cosmological constants
A Pradhan, A K Pandey, R K Mishra
Indian Journal of Physics, 2014
Anisotropic BIANCHI-I cosmological model in string cosmology with variable deceleration parameter
Romanian Journal of Physics, 2013
Anisotropic Viscous Fluid Cosmological Models from Deceleration to Acceleration in String Cosmology
R. K. Mishra, Anirudh Pradhan, Chanchal Chawla
International Journal of Theoretical Physics, 2013
Bianchi type-I viscous fluid cosmological models with variable deceleration parameter
Romanian Reports of Physics, 2013
Design of a optimal wave reflector to protect the beaches: (A mathematical modelling approach)
Global Journal of Pure and Applied Mathematics, 2012
String cosmological models from early deceleration to current acceleration phase with varying G and Λ
Chanchal Chawla, R. K. Mishra, Anirudh Pradhan
European Physical Journal Plus, 2012
Variable cosmology with "Big-rip"
R.K. Mishra, A. Singh
Eas Publications Series, 2009
Cosmological models with variable cosmological constant and gravitational constant
Indian Journal of Pure and Applied Mathematics, 2000

DR RAVI KANT MISHRA

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Scopus Publications