Article
Physics, Particles & Fields
Matthias Wollensak
Summary: This research is based on the formal solutions of the Weyl-Dirac equation in anisotropic planar Bianchi-type-I background spacetimes with power law scale factors. It introduces suitable equivalence classes and shows how exact solutions for all models of a given class can be generated through a special parameter transformation, as well as approximate solutions that exhibit correct behavior at early and late times. The method is explicitly demonstrated for the case of anisotropic Kasner background with axial symmetry.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Mathematical
Matthias Wollensak
Summary: This paper investigates Dirac's equation in anisotropic Bianchi-type-I background spacetimes with respect to orthonormal frames. It derives an analytical expression of the approximate time evolution operator and generates approximate spinor solutions.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Astronomy & Astrophysics
Ira Wolfson, Azadeh Maleknejad, Tomoaki Murata, Eiichiro Komatsu, Tsutomu Kobayashi
Summary: The study investigates isotropic background solutions of SU(2) gauge fields coupled to an axion field during inflation, showing that these models generally isotropize in Bianchi type-I geometry. By adding axial symmetry to the setup and using a new parametrization, the study revisits numerical analysis showing that reported numerical breakdown in the previous analysis was due to parametrization singularity, demonstrating that the system respects the cosmic no-hair conjecture with anisotropies diluting away within a few e-folds.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Fabrizio Esposito, Sante Carloni, Stefano Vignolo
Summary: By making use of the 1 + 3 covariant formalism, this study explicitly demonstrates the impact of nonmetricity on the dynamics of the Universe. Using the Dynamical System Approach, it analyzes the evolution of Bianchi type-I cosmologies within the framework of f(Q) gravity. The results show that different models of the function f(Q) can manifest isotropic eras of the Universe.
CLASSICAL AND QUANTUM GRAVITY
(2022)
Article
Astronomy & Astrophysics
Andronikos Paliathanasis
Summary: In this paper, we study anisotropic exact solutions in the homogeneous Bianchi I background geometry in a multifield theory. Specifically, we consider the Chiral-Quintom theory and find that Kasner-like and anisotropic exponential solutions exist for specific functional forms of the scalar field potential. Furthermore, Noether symmetry analysis is applied for the classification of the theory according to the admitted symmetries.
Article
Astronomy & Astrophysics
Luis O. Pimentel, Flavio Pineda
Summary: In this study, particle creation by the expansion of the universe was considered using two Bianchi type I anisotropic models for spin 0 and 1/2 particles. The cosmological models with rotational symmetry allowed for exact solutions to the equations of motion. The number density of the created particles was calculated using Bogolubov transformations.
GENERAL RELATIVITY AND GRAVITATION
(2021)
Article
Multidisciplinary Sciences
Ahmed M. Al-Haysah, A. H. Hasmani
Summary: In this paper, the Bianchi type-I string cosmological model is studied by combining Kaluza-Klein (KK) theory and f (R) theory of gravity. Various forms of the function f(R) are assumed to obtain physically significant and viable solutions, and some physical and geometrical properties of the model are discussed.
Article
Physics, Particles & Fields
Damianos Iosifidis, Ioannis Georgios Vogiatzis, Christos G. G. Tsagas
Summary: We investigate the potential effects of spacetime non-metricity in cosmology by replacing torsion with non-metricity in the Einstein-Cartan gravity framework. By considering hyperfluid models and introducing non-vanishing hypermomentum to source spacetime non-metricity, we derive the field equations and conservation laws. Applying our findings to cosmology, we generalize the Friedmann and Raychaudhuri equations in the presence of non-metricity, discovering that non-metricity can mimic unconventional matter with different equation of state and may have played a significant role in the early universe's evolution.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Multidisciplinary
Mrinnoy M. Gohain, Kalyan Bhuyan
Summary: In this study, the consequences of a past geodesically complete emergent Universe scenario in a homogeneous and anisotropic Bianchi type I cosmological model were analyzed. The development of the Universe and its anisotropies were explored by analyzing the cosmological parameters under an emergent scenario in a flat Bianchi type I background. The two-fluid matter composition and the evolution of their energy densities and pressures, as required by an emergent Universe, were also investigated. The study further examined the two-fluid system in the presence of a non-minimal interaction and found that a matter-dominated era of the Universe can be produced only when the interaction coupling matches with the equation of state of the matter component.
INDIAN JOURNAL OF PHYSICS
(2023)
Article
Astronomy & Astrophysics
C. Beetle, J. S. Engle, M. E. Hogan, P. Mendonca
Summary: This paper explores the embedding of loop quantum cosmology into a homogeneous Bianchi I model, demonstrating the uniqueness and covariance of the embedding under residual diffeomorphisms, as well as the intertwining of operators between the two models. It establishes a precise equivalence between dynamics in the isotropic sector of the Bianchi I model and the quantized isotropic model, beyond just their kinematics.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
Boon Kiat Oh, John A. Peacock, Sadegh Khochfar, Britton D. Smith
Summary: This study compares the standard Lambda cold dark matter cosmology with counterfactual universes through simulations and explores the effects of Lambda and fluctuation amplitude on the evolution of the halo mass function, intergalactic medium, and star formation history. The results show that the peak and decline in star formation rate density are both influenced by the interplay between gravitational attraction and the accelerating effects of Lambda. The cooling of the intergalactic medium is faster in models with larger Lambda and lower sigma(8), resulting in reduced star formation rate density.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
M. Vijaya Santhi, T. Chinnappalanaidu
Summary: This study examines the Tsallis holographic dark energy (THDE) through the analysis of the linearly varying deceleration parameter (LVDP) (q) in the framework of general relativity (GR) and spatially anisotropic Bianchi type (BT) II, VIII and IX Universes. The results show that the deceleration parameter (DP) must flip its signatures at the transition redshift, and the THDE model predicts the expansion of the Universe based on the equation of state parameter (omega(de)) and DP (q). The analysis also confirms the existence of quintessence, phantom dark energy regions, and Lambda cold dark matter (Lambda CDM) limit in the model.
ASTROPHYSICS AND SPACE SCIENCE
(2023)
Article
Physics, Multidisciplinary
E. Gudekli, E. Demir
Summary: This paper discusses the LRS Bianchi type-I universe model in Mimetic Gravity Theory, proposing a potential function to explain the expansion of the universe and discussing the general equation of the state parameter v and its correspondence to fluid components.
CANADIAN JOURNAL OF PHYSICS
(2021)
Article
Astronomy & Astrophysics
Jean -Luc Lehners, Rahim Leung, K. S. Stelle
Summary: String compactifications typically require fluxes for stabilization and moduli control. We find that there exist no-boundary solutions with internal fluxes present from the beginning of the universe. The no-boundary proposal serves as a selection principle, favoring flux values that lead to positive and flat effective potentials for accelerated expansion. Cosmology acts as a filter in a landscape of higher-dimensional solutions, illustrating the importance of understanding the origin of fluxes.
Article
Physics, Nuclear
M. Koussour, S. H. Shekh, M. Bennai
Summary: In this work, we investigated a spatially homogeneous and anisotropic Bianchi type-I space-time with the presence of Barrow holographic dark energy and matter. By considering the deceleration parameter, we studied the physical behavior of important cosmological parameters and constrained the model parameters using Hubble's parameter measurements.
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2022)
Article
Astronomy & Astrophysics
G. Abbas, D. Momeni, M. Aamir Ali, R. Myrzakulov, S. Qaisar
ASTROPHYSICS AND SPACE SCIENCE
(2015)
Article
Astronomy & Astrophysics
R. D. Boko, M. E. Rodrigues, M. J. S. Houndjo, J. B. Chabi Orou, R. Myrzakulov
ASTROPHYSICS AND SPACE SCIENCE
(2015)
Article
Astronomy & Astrophysics
Ertan Gudekli, Nurgissa Myrzakulov, Koblandy Yerzhanov, Ratbay Myrzakulov
ASTROPHYSICS AND SPACE SCIENCE
(2015)
Article
Astronomy & Astrophysics
Ratbay Myrzakulov, Lorenzo Sebastiani
ASTROPHYSICS AND SPACE SCIENCE
(2015)
Article
Physics, Multidisciplinary
M. J. S. Houndjo, D. Momeni, R. Myrzakulov, M. E. Rodrigues
CANADIAN JOURNAL OF PHYSICS
(2015)
Review
Physics, Mathematical
Lorenzo Sebastiani, Ratbay Myrzakulov
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2015)
Article
Physics, Mathematical
Davood Momeni, Muhammad Raza, Ratbay Myrzakulov
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2015)
Article
Physics, Mathematical
Salvatore Capozziello, Mariafelicia De Laurentis, Ratbay Myrzakulov
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2015)
Article
Physics, Mathematical
Salvatore Capozziello, Mariafelicia De Laurentis, Ratbay Myrzakulov
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2015)
Article
Physics, Mathematical
D. Momeni, R. Myrzakulov, L. Sebastiani
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2015)
Article
Astronomy & Astrophysics
R. Myrzakulov, S. D. Odintsov, L. Sebastiani
Article
Astronomy & Astrophysics
Davood Momeni, Hossein Gholizade, Muhammad Raza, Ratbay Myrzakulov
Article
Astronomy & Astrophysics
Ratbay Myrzakulov, Lorenzo Sebastiani
ASTROPHYSICS AND SPACE SCIENCE
(2015)
Article
Astronomy & Astrophysics
Surajit Chattopadhyay, Davood Momeni, Aziza Altaibayeva, Ratbay Myrzakulov
ASTROPHYSICS AND SPACE SCIENCE
(2015)
Article
Astronomy & Astrophysics
M. Khurshudyan, B. Pourhassan, R. Myrzakulov, S. Chattopadhyay
ASTROPHYSICS AND SPACE SCIENCE
(2015)
