Article
Astronomy & Astrophysics
Narges Rashidi
Summary: This study examines the primordial perturbations and non-Gaussian features in tachyon inflation with a superpotential, analyzing scalar and tensor perturbations using observational data to explore the model's viability. The research predicts the equilateral non-Gaussianity amplitude and discusses the reheating phase post-inflation. The findings suggest that an observationally viable tachyon model with superpotential may exist within certain parameter ranges.
ASTROPHYSICAL JOURNAL
(2021)
Article
Physics, Multidisciplinary
Amir H. Rezaei, T. Azizi, N. Rashidi
Summary: In this paper, an exponential form of modified gravity is considered. The theory is consistent with local tests and various aspects of the model are investigated, including the static solution, scalar field potential, and stability of critical points. The realization of inflation and its graceful exit in this model are also studied.
Article
Astronomy & Astrophysics
Dmitry Chirkov, Sergey A. Pavluchenko
Summary: The study investigates aspects of dynamical compactification scenario involving stabilization of extra dimensions due to the Gauss-Bonnet term and nonzero spatial curvature. The model proposes a two-stage scenario for the evolution of the Universe, where the space transitions from a totally anisotropic state to one with expanding three-dimensional and contracting D-dimensional isotropic subspaces. Stability of exponential solutions with specific coupling constants is discussed, showing instability in compactification solutions with positively curved extra space, making the two-stage scenario unattainable. Additionally, a new parametrization of the general solution for the model under arbitrary constant curvature of extra dimensions is described, providing an elegant way to describe parameter space existence areas.
MODERN PHYSICS LETTERS A
(2021)
Article
Multidisciplinary Sciences
Sanghati Saha, Ertan Guedekli, Surajit Chattopadhyay
Summary: The study examines the realization of cosmic bounce in two situations with different scale factor selections, one of which is already developed and the other is created by truncating a series expansion. The background fluid in both situations is assumed to be Generalized Chaplygin gas (GCG). The study shows that the GCG energy density decreases during contraction, reaches its lowest point at the bounce, and then increases during expansion. However, the truncation has an impact on the density evolution in the other scale factor scenario.
Article
Physics, Multidisciplinary
A. Singh, A. Beesham, N. K. Tripathi
Summary: This article considers a flat Friedmann-Robertson-Walker (FRW) universe based on the Hubble parameter. The Hubble parameter ansatz leads to de Sitter-like evolution in the early and late times. The phase transitions from an accelerated to decelerated era in the early times and from a decelerated to an accelerated era in the recent past provide a natural way to understand the complete cosmological history of the universe. By exploring inflationary dynamics, cosmological parameters, energy conditions, and the behavior in the w - w' plane, the article identifies regions of thawing and freezing. The statefinder diagnostic indicates that the universe will evolve into a cold dark matter model in the late times. The article also presents the scalar field description corresponding to the considered Hubble parameter ansatz.
CHINESE JOURNAL OF PHYSICS
(2023)
Article
Physics, Multidisciplinary
M. Bilal Amin Sulehri, Abdul Jawad, Shamaila Rani
Summary: The study analyzes the effects of a newly proposed generalized tachyonic teleparallel gravity on cosmological parameters and thermodynamics, deriving three different Hubble parameter models and examining matter and dark energy densities. The research shows that these models are validated in different eras, with the state parameter of the universe exhibiting specific characteristics in certain phases, and the stability of the models being explored. Additionally, the validity of the generalized second law of thermodynamics is confirmed for each case of every model in each era through entropy corrections.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Article
Engineering, Multidisciplinary
Brian Y. Lattimer, Steven Wong, Jonathan Hodges
Summary: This article investigates the parameters and factors affecting the heat transfer from firebrand piles to combustible surfaces, and quantifies the temperature changes of firebrands using a developed two-phase flow analytical model. The results show that the porosity of firebrand piles has a significant impact on heat transfer.
Review
Physics, Multidisciplinary
Theodore Erler
Summary: These notes are derived from review lectures on analytic solutions in open string field theory, which were given at the School for String Field Theory and String Phenomenology at the Harish-Chandra Research Institute in February 2018.
PHYSICS REPORTS-REVIEW SECTION OF PHYSICS LETTERS
(2022)
Article
Astronomy & Astrophysics
Elham Nouri, Hossein Motavalli, Amin Rezaei Akbarieh
Summary: This paper presents a generalized tachyonic dark energy scenario in a homogeneous and isotropic FLRW flat universe, where a noncanonical scalar field is nonminimally coupled to gravity. The tachyon field accelerates the evolution of the universe in the early times and plays a key role in dark energy in the late times. The study shows a cosmological degeneracy in the model, indicating the potential of the generalized tachyon field as a dark energy candidate.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Astronomy & Astrophysics
Hossein Motavalli, Elham Nouri
Summary: This paper studies a cosmological model governed by a generalized scalar field nonminimally coupled to scalar torsion in the framework of teleparallel gravity. By applying the Noether symmetry approach, the explicit forms of the coupling function and the scalar field potential in the Friedmann-Lemaitre-Robertson-Walker (FLRW) flat spacetime are explored. The existence of such symmetry simplifies the equations of motion and provides an exponential form cosmological solution for both the scale factor and scalar field. It is shown that the tachyon field behaves as the origin of inflation and contributes significantly to the accelerating expansion of the universe in the early times. In the late times, the gravitational sources consist of a pressureless matter field together with the tachyon field, which plays the essential role of dark energy and is the origin of deceleration-acceleration phase transition. The paper also discusses the cosmological degeneracy of the model, indicating that different coupling parameters and tachyonic potentials can contribute to the same cosmological behaviors.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Mechanics
H. K. Moffatt
Summary: This paper provides an informal introduction to topics in fluid dynamics with a topological character, covering flows with boundary singularities, Lagrangian chaos, magnetohydrodynamic analogies, magnetic relaxation, and more. The conclusion poses several open questions regarding these topics.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mathematics, Applied
Muhammad Qasim, Arbaz Jehan Khan, Samirah Alsulami, Shoaib Assar
Summary: In this paper, we investigate the characteristics of separated objects, T0, T1, Pre-T2, and various types of Hausdorff objects in the category of interval spaces and interval-preserving mappings. We also examine their relationships with each other. Additionally, we study the properties of closedness and D-connectedness in interval spaces and introduce the notion of zero-dimensionality in this category, demonstrating its connection to D-connectedness.
Article
Physics, Multidisciplinary
Andrey A. Grib, Yuri V. Pavlov
Summary: This paper summarizes the analysis of the dynamics of radial movement in different reference frames used in cosmology. The use of different frames leads to differences in inertial forces, resulting in different observable effects. One important effect is the appearance of acceleration proportional to distance in the system, analogous to the action of the cosmological constant.
EUROPEAN PHYSICAL JOURNAL PLUS
(2021)
Review
Chemistry, Multidisciplinary
Kyuichi Yasui
Summary: This article reviews the theoretical studies on bulk nanobubbles (UFBs) and discusses their stability, generation, and interaction with solid surfaces. The dynamic equilibrium model is found to be a promising model for UFB stability, and the formation of UFBs is attributed to the production of OH radicals during hydrodynamic or acoustic cavitation. The presence of UFBs accelerates the rupture of liquid film and reduces surface tension. Additionally, the interaction between UFBs and solid surfaces is explored.
Article
Astronomy & Astrophysics
Chanyong Park
Summary: We investigate the time evolution of entanglement entropy in expanding universes with different matters. Using a braneworld model in an asymptotic AdS space with a uniform p-brane gas, we describe expanding universes holographically. The entanglement entropy of expanding universes increases according to the volume law in the early time and the area law in the late time. We also study the time-dependent quantum entanglement across the cosmological horizon.
Article
Physics, Multidisciplinary
Mohsen Khodadi, Kourosh Nozari, Anha Bhat, Sina Mohsenian
PROGRESS OF THEORETICAL AND EXPERIMENTAL PHYSICS
(2019)
Article
Physics, Multidisciplinary
Mohsen Khodadi, Kourosh Nozari
COMMUNICATIONS IN THEORETICAL PHYSICS
(2019)
Article
Physics, Particles & Fields
Kourosh Nozari, M. Hajebrahimi, M. Khodadi, A. Etemadi
EUROPEAN PHYSICAL JOURNAL C
(2019)
Article
Astronomy & Astrophysics
R. Shojaee, K. Nozari, F. Darabi
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2020)
Article
Physics, Particles & Fields
M. Roushan, K. Nozari
EUROPEAN PHYSICAL JOURNAL C
(2020)
Article
Astronomy & Astrophysics
R. Shojaee, K. Nozari, F. Darabi
Summary: In this study, we investigated cosmological inflation in a Galileon inflationary model with the E-model potential to identify possible alpha-attractors. By analyzing the evolution of perturbations and considering the reheating phase post-inflation, we found universal values for the scalar spectral index and tensor-to-scalar ratio. Comparing our results with Planck data, we discovered constraints on the model's parameter space, including the potential for a longer reheating phase and observational viable values of ns associated with a larger temperature range.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2021)
Article
Astronomy & Astrophysics
Narges Rashidi
Summary: This study examines the primordial perturbations and non-Gaussian features in tachyon inflation with a superpotential, analyzing scalar and tensor perturbations using observational data to explore the model's viability. The research predicts the equilateral non-Gaussianity amplitude and discusses the reheating phase post-inflation. The findings suggest that an observationally viable tachyon model with superpotential may exist within certain parameter ranges.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
Narges Rashidi
Summary: In this paper, the effects of the tachyon field on a black hole are studied. It is shown that the time evolution of the black hole mass depends on the potential of this field, unlike the ordinary canonical scalar field. By considering different types of potential, the behavior of the black hole mass and its time evolution are examined, revealing some interesting results. The presence of the tachyon field is found to cause mass accretion into the black hole. It is also demonstrated that, in certain parameter ranges, the mass of the black hole can decrease without any Hawking radiation.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Physics, Multidisciplinary
Maryam Roushan, Narges Rashidi, Kourosh Nozari
Summary: Quantum gravitational effects are not only important on small scales but also significant on cosmological scales. The existence of a minimal measurable momentum plays a crucial role in the accelerating expansion of the universe.
CHINESE JOURNAL OF PHYSICS
(2022)
Article
Physics, Multidisciplinary
Narges Rashidi, Mohaddeseh Heidarzadeh, Kourosh Nozari
Summary: In this study, we investigate the cosmological dynamics of constant-roll inflation with a hilltop potential. By analyzing the model parameters and comparing the results with observational data, we find constraints on the deviation parameter. We also show that reheating can be completed with few e-folds in the constant-roll inflation with hilltop potential.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Physics, Multidisciplinary
Marzie Faraji, Narges Rashidi, Kourosh Nozari
Summary: This study investigates the cosmological dynamics of energy-momentum squared gravity and reveals that the introduction of the zeta T-2 term breaks the conservation of the energy-momentum tensor of matter fields. However, an effective energy-momentum tensor in this model is conserved over time. The findings suggest that the zeta T-2 gravity is an observationally viable model of inflation for certain parameter ranges.
EUROPEAN PHYSICAL JOURNAL PLUS
(2022)
Article
Astronomy & Astrophysics
Narges Rashid
Summary: In this study, we investigate tachyon inflation with constant sound speed using intermediate and power-law scale factors and compare the results with observational data. We find the observationally viable ranges of the model's parameters and analyze the non-Gaussian features in different configurations.
ASTROPHYSICAL JOURNAL
(2022)
Article
Astronomy & Astrophysics
Narges Rashidi, Kourosh Nozari
Article
Astronomy & Astrophysics
Narges Rashidi, Kourosh Nozari
ASTROPHYSICAL JOURNAL
(2020)
Article
Astronomy & Astrophysics
Kourosh Nozari, Narges Rashidi
ASTROPHYSICAL JOURNAL
(2019)
