Article
Physics, Multidisciplinary
Vinod Kumar Bhardwaj, Priyanka Garg, Anirudh Pradhan, Syamala Krishnannair
Summary: In this study, we investigate the power-law entropy corrected holographic dark energy (PLECHDE) model with Hubble horizon cutoff. Using observational data, we constrain the model and calculate relevant cosmological parameters. The results show that the model is consistent with modern observations and matches well with current datasets.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Physics, Mathematical
Pankaj, Nisha Muttathazhathu Ali, Umesh Kumar Sharma, P. Suresh Kumar, Shikha Srivastava
Summary: In this work, a new Tsallis holographic dark energy model with an apparent horizon as an infrared (IR) cutoff is constructed in a non-flat Friedmann-Lemaitre-Robertson-Walker Universe. The transition of the NTHDE Universe from a decelerating to an accelerating phase is described using the deceleration parameter and equation of state parameter with different values of the NTHDE parameter delta. The behavior of the equation of state parameter and the stability of the model are investigated using Hubble data sets and distance modulus measurements of Type Ia Supernovae.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Astronomy & Astrophysics
Luis M. Sanchez, Hernando Quevedo
Summary: In this study, we investigate the relationship between gravity and thermodynamics in dynamic systems by considering the apparent horizon of the FLRW spacetime as a thermodynamic system. We derive the fundamental equation in the entropy representation and explore the consequences of satisfying classical laws of thermodynamics. Our investigation focuses on FLRW spacetimes with and without a cosmological constant. We find that the interpretation of the apparent horizon as an isolated thermodynamic system is only possible under certain conditions, as the analogy does not hold for all parameter values and the entire evolution of the horizon. However, we demonstrate that the generalized second law of thermodynamics remains valid.
Article
Physics, Particles & Fields
Rownak Kundu, Ujjal Debnath, Anirudh Pradhan
Summary: In this study, we investigated the behavior of non-interacting dark energy and dark matter in a non-flat FRW model. We examined various dark energy models, including Tachyonic Field, Generalized Cosmic Chaplygin Gas, New Variable Modified Chaplygin Gas, Modified Chaplygin-Jacobi Gas, and Modified Chaplygin-Abel Gas. Our analysis focused on the optical depth behavior of these models with different cosmological parameters, and we presented the results graphically. Furthermore, we compared our findings in both flat and non-flat universes with the ACDM model.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Ujjal Debnath
Summary: In this study, the Friedmann-Robertson-Walker (FRW) Universe is considered as a thermodynamic system with the cosmological constant generating thermodynamic pressure. The study focuses on determining the amount of energy crossing the apparent horizon using a unified first law, and the heat flow through the apparent horizon is found to be equal to the amount of energy crossing. The study also derives equations for various thermodynamic quantities and discusses the cooling/heating nature of the FRW Universe, as well as the heat engine phenomena.
Article
Physics, Particles & Fields
Himanshu Chaudhary, Amine Bouali, Niyaz Uddin Molla, Ujjal Debnath, G. Mustafa
Summary: This paper investigates the observational signatures of f(R,G,T) gravity in the FRW universe and proposes a new cosmological model. By using the Markov Chain Monte Carlo technique, the model parameters are constrained, and various diagnostic tests and statistical analyses are conducted to evaluate the model's behavior and consistency with observational data. The findings highlight the potential and validity of the f(R,G,T) framework in understanding the dynamics and evolution of the universe.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Multidisciplinary
Archana Dixit, Vinod Kumar Bhardwaj, Anirudh Pradhan
Summary: This work examines the BHDE model in a non-flat universe, focusing on the equation of state parameter and showing its role in the cosmological evolution. The study suggests that the BHDE model can smoothly transition the expansion phase of the universe and reach the Lambda CDM fixed point in the statefinder trajectory.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Astronomy & Astrophysics
Shin'ichi Nojiri, Sergei D. Odintsov, Tanmoy Paul
Summary: In this study, the Bekenstein-Hawking entropy is modified and a new entropy function is developed to derive the usual FLRW equations for matter fluids with different equation of state parameters. The research finds that by using a general entropy based on the Bekenstein-Hawking entropy, the Friedmann equations of the apparent horizon cosmology can be modified, leading to interesting cosmological consequences.
Article
Astronomy & Astrophysics
Ujjal Debnath
Summary: The study investigates the gravitational waves phenomena for various dark energy models, obtaining solutions for energy densities of dark matter and dark energy components and analyzing the wave curves and power spectrums for different candidates of dark energy.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Suresh Chand, Mariana Frank, Poulose Poulose
Summary: In this study, leptogenesis is analyzed in the context of a simple extension of the Standard Model. By introducing two fermions and interacting with three right-handed neutrinos through a charged gauge singlet scalar S, the observed baryon asymmetry of the Universe can be naturally generated.
Article
Astronomy & Astrophysics
Nisha Muttathazhathu Ali, Pankaj, Umesh Kumar Sharma, P. Suresh Kumar, Ambuj Kumar Mishra
Summary: In this study, a new Tsallis holographic dark energy model is constructed in a non-flat universe, considering the effects of different parameter values on the expansion of the universe. By deriving the differential equations for the dark energy density parameter and the equation of state parameter, it is found that there are specific behaviors in both closed and open universes, and the phase transition from deceleration to acceleration can be observed through the evolution of the deceleration parameter. The study shows that the model matches well with Hubble data and exhibits stability.
MODERN PHYSICS LETTERS A
(2022)
Article
Physics, Particles & Fields
Sarfraz Ali, Sabir Iqbal, Khuram Ali Khan, Hamid Reza Moradi
Summary: This study explores the Renyi holographic dark energy model in the theory of Chern-Simons modified gravity, revealing how changes in the equation of state and deceleration parameter can explain the evolution of the universe, with dark energy playing a crucial role in cosmic expansion.
ADVANCES IN HIGH ENERGY PHYSICS
(2021)
Article
Physics, Multidisciplinary
Abdul Jawad, Muhammad Usman
Summary: In this article, we studied the dynamical stability of cosmic models and their cosmographic parameters within the framework of deformed Horava-Liftshiz gravity. We used a dynamical analysis approach to investigate four interaction models with varying vacuum dark energy. Our results showed that, except for one, all critical points in different interaction models were stable and exhibited attractive behavior. Additionally, the cosmographic parameters were consistent with recent cosmic observations and represented the quintessence era under the stability conditions of different cosmic models.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
David Harvey, Nora Elisa Chisari, Andrew Robertson, Ian G. McCarthy
Summary: The study finds that self-interactions of dark matter can leave a long-lasting imprint on galaxy shape correlations, inducing mass-dependent suppression in the intrinsic alignment signal. This suggests that self-interactions can impact structure outside the core of clusters and have a scale-dependent effect on the intrinsic alignment signal.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Song Li, Yun Chen
Summary: In this study, a cosmological model within the framework of the Einstein-Cartan theory is considered. The corresponding relation between the torsion field and holographic dark energy is analyzed, revealing its behavior as quintessence or quintom dark energy. Stability analysis shows that the model is classically stable for c<1. The statefinder parameters also indicate a phase transition from deceleration to acceleration in the universe. The fitting with Type Ia supernovae samples confirms the compatibility of the model with the latest observations.
Article
Astronomy & Astrophysics
K. Fahimi, K. Karami, S. Asadzadeh, K. Rezazadeh
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2018)
Article
Physics, Particles & Fields
S. Rasouli, K. Rezazadeh, A. Abdolmaleki, K. Karami
EUROPEAN PHYSICAL JOURNAL C
(2019)
Article
Astronomy & Astrophysics
Saeid Karimi, Kayoomars Karami
ASTROPHYSICS AND SPACE SCIENCE
(2020)
Article
Astronomy & Astrophysics
Mohammad Sadeghi, Karam Bahari, Kayoomars Karami
Summary: In this paper, kink and sausage oscillations in the presence of longitudinal background flow were studied, with a focus on resonance absorption under magnetic pore conditions. The dispersion relation was determined and solved numerically to find frequencies and damping rates of the slow surface modes. It was shown that resonance absorption in the presence of plasma flow can lead to strong damping for forward waves while reducing the efficiency of damping for backward waves.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Zeinab Teimoori, Kazem Rezazadeh, Kayoomars Karami
Summary: This study investigates the formation of primordial black holes (PBHs) as a possible candidate for dark matter, utilizing a gravitationally enhanced friction mechanism. By considering a nonminimal derivative coupling between the scalar field and gravity, three parameter sets were identified that resulted in ultra slow-roll inflation, leading to the formation of PBHs. The model also predicts the presence of secondary gravitational waves (GWs) at frequencies within the sensitivity region of certain GW detectors, allowing for observational compatibility assessment.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Mohammad Sadeghi, Karam Bahari, Kayoomars Karami
Summary: Observations indicate the existence of twisted magnetic flux tubes and plasma flow in the solar atmosphere. The goal of this study is to determine the damping rate of sausage modes in the presence of magnetic twist and plasma flow. By numerically solving the dispersion relation for sausage modes in a non-uniform layer with magnetic pores under the condition of slow continuity, we find that the effect of twisted magnetic field on resonance absorption is greater for low speed plasma flow than for high speed.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
S. Amiri, K. Karami, Z. Ebrahimi
Summary: This paper evaluates the effects of inclination and asymmetry of solar coronal loops on kink magnetohydrodynamic oscillations. It is found that the frequencies and damping rates of the oscillations are smaller in inclined and asymmetric loops compared to uninclined loops. The ratios of mode frequency to damping rate remain unchanged approximately regardless of inclination or asymmetry, and these ratios can reliably infer the physical parameters of coronal loops and medium.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Physics, Multidisciplinary
K. Rezazadeh, S. Asadzadeh, K. Fahimi, K. Karami, A. Mehrabi
Article
Astronomy & Astrophysics
Zanyar Ebrahimi, Roberto Soler, Kayoomars Karami
ASTROPHYSICAL JOURNAL
(2020)
Article
Astronomy & Astrophysics
Mohammad Sadeghi, Kayoomars Karami
ASTROPHYSICAL JOURNAL
(2019)
Article
Astronomy & Astrophysics
Zeinab Teimoori, Kayoomars Karami
ASTROPHYSICAL JOURNAL
(2018)
Article
Astronomy & Astrophysics
Roonak Amani, Kazem Rezazadeh, Asrin Abdolmaleki, Kayoomars Karami
ASTROPHYSICAL JOURNAL
(2018)
Article
Astronomy & Astrophysics
Zanyar Ebrahimi, Kayoomars Karami, Roberto Soler
ASTROPHYSICAL JOURNAL
(2017)
Article
Astronomy & Astrophysics
K. Rezazadeh, K. Karami, S. Hashemi
Article
Astronomy & Astrophysics
Kazem Rezazadeh, Asrin Abdolmaleki, Kayoomars Karami
ASTROPHYSICAL JOURNAL
(2017)
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Octavio C. Junqueira
Summary: This study investigates the influence of rotation on the transition temperature of strongly interacting matter produced in non-central heavy ion collisions. By using a holographic description of an AdS black hole, the authors extend the analysis to the more realistic case where the matter spreads over a region around the rotational axis. The results show the coexistence of confined and deconfined phases and are consistent with the concept of local temperature in rotating frames developed by Tolman and Ehrenfest.
Article
Astronomy & Astrophysics
Bing Sun, Jiachen An, Zhoujian Cao
Summary: This paper investigates the effect of gravitational constant variation on the propagation of gravitational waves. By employing two analytical methods, the study finds that variations in the gravitational constant result in amplitude and phase corrections for gravitational waves, and the time variation of the gravitational constant can be constrained through the propagation of gravitational waves.
Article
Astronomy & Astrophysics
Abdellah Touati, Zaim Slimane
Summary: This letter presents the first study of Hawking radiation as a tunneling process within the framework of non-commutative gauge theory of gravity. The non-commutative Schwarzschild black hole is reconstructed using the Seiberg-Witten map and the star product. The emission spectrum of outgoing massless particles is computed using the quantum tunneling mechanism. The results reveal pure thermal radiation in the low-frequency scenario, but a deviation from pure thermal radiation in the high-frequency scenario due to energy conservation. It is also found that noncommutativity enhances the correlations between successively emitted particles.
Article
Astronomy & Astrophysics
Shahar Hod
Summary: The travel times of light signals between two antipodal points on a compact star's surface are calculated for two different trajectories. It is shown that, for highly dense stars, the longer trajectory along the surface may have a shorter travel time as measured by asymptotic observers. A critical value of the dimensionless density-area parameter is determined for constant density stars to distinguish cases where crossing through the star's center or following a semi-circular trajectory on the surface has a shorter travel time as measured by asymptotic observers.
