Article
Chemistry, Physical
Luis Perdomo-Hurtado, Nestor Enrique Valadez-Perez, Beatriz Millan-Malo, Ramon Castaneda-Priego
Summary: This work introduces a new parameterization for SAFT-VR coupled with discrete potential theory to represent thermodynamic properties of various fluids. By discretizing Lennard-Jones and Yukawa potentials, vapor-liquid equilibrium properties of molecular and complex liquids are examined. The results are validated through Monte Carlo simulations and theoretical calculations based on the Ornstein-Zernike approximation.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Hertanto Adidharma, Sugata P. Tan
Summary: The new EOS based on the generalized vdW partition function can describe the phase transition of simple fluids in nanopores with uniform size without the need for an auxiliary equation traditionally used for capillary pressure derived from surface tension. Its promising performance calls for further extension to more complex fluids and porous media applications.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Gregory Rassolov, Laura Tociu, Etienne Fodor, Suriyanarayanan Vaikuntanathan
Summary: There is a close relationship between the static structure and dissipation of active systems driven by local non-conservative forces. Liquid-state theories and machine learning tools are used to study this relationship and a neural network is constructed to predict the dissipation rate of the system.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Engineering, Chemical
Wei Xiong, Lie-Hui Zhang, Yu-Long Zhao, Jian-Fa Wu, Jin-Hui Huang, Jian Yao
Summary: The study introduces an improved CPA-vdW model to predict the phase behavior of mixtures, with accurate predictions for different systems, which is helpful for simulating the process of CO2 injection to extract CH4.
CHEMICAL ENGINEERING SCIENCE
(2021)
Article
Astronomy & Astrophysics
Subhra Bhattacharya
Summary: The article discusses the potential impact of thermal fluctuations during the inflationary period on structure formation and reheating dependence, known as warm inflation. It revisits a specific equation of state in the context of warm inflation to investigate whether such matter could serve as a viable candidate for warm inflation.
Article
Astronomy & Astrophysics
Subhra Bhattacharya
Summary: Thermal fluctuations during the inflationary epoch can result in the presence of a thermal component, known as warm inflation. It has been found that matter with specific equation of state can also act as a candidate for warm inflation.
Article
Physics, Multidisciplinary
Chia-Min Lin
Summary: This study examines the homogeneous oscillations of the inflaton field after inflation, specifically focusing on the simplest τ-attractor T-model. The study provides an analytical solution for the average equation of state of the oscillating inflaton field. It also investigates the post-inflationary evolution before inflaton decay, and demonstrates that the duration of oscillating inflation is very limited.
CHINESE JOURNAL OF PHYSICS
(2023)
Article
Astronomy & Astrophysics
A. Rahmansyah, D. Purnamasari, R. Kurniadi, A. Sulaksono
Summary: This study aims to reproduce the relevant equations of the GTOV model using a modified anisotropic energy-momentum tensor, calculate the moment of inertia and tidal deformability of neutron stars, investigate the impact of each free parameter of the GTOV model on neutron star properties, explore the correlations among parameters, and examine the physical ranges of the parameters. The study reveals that the values of GTOV free parameters can be constrained to acceptable ranges, with the θ parameter playing a crucial role in controlling the maximum mass value of neutron stars.
Article
Physics, Fluids & Plasmas
Markus Kulossa, Philipp Marienhagen, Joachim Wagner
Summary: This study provides the second to sixth-order virial coefficients of hard hyperspherocylinders in four dimensions, and compares them with the geometric calculations based on the aspect ratio.
Article
Mathematics, Applied
Jinzhi Huang, Zhongxiao Jia
Summary: This article proposes a method called CPF-JDGSVD to compute a partial generalized singular value decomposition (GSVD) of a large regular matrix pair {A, B}. The method implicitly solves the mathematically equivalent generalized eigenvalue problem, avoiding possible accuracy loss. Experimental results demonstrate the efficiency of the algorithm.
JOURNAL OF SCIENTIFIC COMPUTING
(2023)
Article
Chemistry, Physical
Alexander V. Lazarev, Timur A. Semenov, Elena D. Belega, Vyacheslav M. Gordienko
Summary: A gas dynamic model based on the RedlichKwong equation of state has been developed to describe the supersonic expansion of a real gas flow in a nozzle. The model was tested and verified through calculations and experiments on clustering in Ar and Kr flows, as well as on creating X-ray sources and accelerated electron beams through relativistic laser action on a krypton cluster jet.
JOURNAL OF SUPERCRITICAL FLUIDS
(2022)
Article
Mathematics, Applied
Satoru Iwasaki
Summary: This paper tackles the issue of initial state estimation for the heat equation in equilateral metric graphs with cycles. The focus is on determining suitable placements of observation points in order to uniquely determine the initial state from observation data. The paper provides a necessary and sufficient condition for these suitable placements, and verifies their effectiveness through numerical simulations.
Article
Nanoscience & Nanotechnology
Peter Cats, Sander Kuipers, Sacha de Wind, Robin van Damme, Gabriele M. Coli, Marjolein Dijkstra, Rene van Roij
Summary: The density functional theory provides an accurate framework to study thermodynamic and structural properties of interacting many-body systems, but relies on approximate energy functionals in practice. A machine-learning approach was explored to improve the standard mean-field approximation in this study, with a focus on a 3D Lennard-Jones system at a supercritical temperature. The approach showed promise in extracting accurate bulk equations of state but faced challenges in providing reliable direct correlation functions.
Article
Physics, Applied
Ti-Wei Xue, Zeng-Yuan Guo
Summary: In this paper, an ideal dense matter equation of state (EOS) that is symmetric to the ideal gas EOS is proposed. The ideal dense matter EOS makes no assumptions about the structure of matter and is general. By studying specific work and physical constants, it is found that the ideal dense matter EOS has the same theoretical location as the ideal gas EOS.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Chemistry, Physical
Arpit Bansal, Andrew J. Schultz, David A. Kofke
Summary: The method proposed in this paper allows for the computation of osmotic virial coefficients in explicit solvent through simulation in a restricted Gibbs ensemble. It demonstrates greater precision than established techniques and enables accurate computation at smaller system sizes.
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Physics, Multidisciplinary
S. D. Odintsov, V. K. Oikonomou, F. P. Fronimos
Summary: This study explores the combined effects of string and f (R) gravity corrections on canonical scalar field inflation during the inflationary era controlled by a scalar field. By imposing the constraint that the primordial gravitational waves propagate at the speed of light, the dynamics of Einstein-Gauss-Bonnet gravity with alpha R-2 corrections are investigated. The research demonstrates the interconnectedness of Gauss-Bonnet coupling and scalar potential in the model, as well as the feasibility of extracting scalar potential from equations of motion when freely designating Gauss-Bonnet coupling xi(phi).
Article
Astronomy & Astrophysics
V. K. Oikonomou, F. P. Fronimos
Summary: Researchers demonstrate how to modify cosmological theories to produce primordial gravitational waves consistent with the GW170817 event by introducing a kinetic coupling correction in the Einstein-Gauss-Bonnet theory. By studying the conditions on the scalar field dependent coupling function, they prove the viability of this theoretical framework.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Physics, Multidisciplinary
A. Astashenok, S. Capozziello, S. D. Odintsov, V. K. Oikonomou
Summary: Novel implications on neutron stars come from extended gravity. Specifically, new research suggests the possibility of large mass stars in the mass gap region, which may require extensions of General Relativity to successfully describe this phenomenon and speculate on the largest allowed neutron star mass in a quantitative manner.
Article
Physics, Particles & Fields
G. G. L. Nashed, S. D. Odintsov, V. K. Oikonomou
Summary: This paper investigates spherically symmetric spacetime solutions that describe the interior of compact stellar objects within the context of higher-order curvature theory of the f(R) type. By deriving the non-vacuum field equations and solving the system of nonlinear differential equations, the study successfully identifies a specific solution for compact stars. Furthermore, the model is shown to be more stable and different from those in general relativity, with specific implications for the considered compact star Her X-1.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Physics, Mathematical
V. K. Oikonomou, Achilles Gitsis, Maria Mitrou
Summary: This study focuses on the phase space singularities of interactive quintessence model in the presence of matter fluid. The presence of matter fluid affects the dynamical system, making the singularities depend on initial conditions rather than occurring for general initial conditions.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2021)
Biographical-Item
Multidisciplinary Sciences
Sergei D. Odintsov
Review
Multidisciplinary Sciences
Sergei D. Odintsov, Vasilis K. Oikonomou, Ratbay Myrzakulov
Summary: In this work, the authors exhaustively study the effects of modified gravity on the energy spectrum of the primordial gravitational waves background. They provide calculations for various cases of modified gravity, focusing on specific forms of interest. They also present the exact form of a parameter involved in the calculation of the effects of modified gravity on the energy spectrum for the first time.
Article
Astronomy & Astrophysics
Sergei D. Odintsov, Tanmoy Paul
Summary: This work explores the influence of a Type-IV singularity on the dynamics of a bouncing universe in the context of a ghost-free Gauss-Bonnet theory of gravity. It is found that when the singularity has a global effect on spacetime, the scalar power spectrum becomes red-tilted and the tensor-to-scalar ratio is incompatible with observational data. However, if the singularity only locally affects spacetime around the time of occurrence, the observable quantities are compatible with Planck data.
Editorial Material
Multidisciplinary Sciences
Sergei D. D. Odintsov
Editorial Material
Multidisciplinary Sciences
Sergei D. Odintsov
Article
Multidisciplinary Sciences
Artyom V. Astashenok, Sergey D. Odintsov, Vasilis K. Oikonomou
Summary: This study investigates the Chandrasekhar mass limit of white dwarfs in various models of f (R) gravity. Two equations of state for stellar matter are used: the simple relativistic polytropic equation and the realistic Chandrasekhar equation of state. The solution for any model of f (R) = R + beta R-m gravity shows that the stellar mass decreases compared to standard General Relativity. For realistic equations of state, there is a value of the central density for which the mass of a white dwarf peaks. This implies that in modified gravity, there exists a minimum radius for stable white dwarfs, which is greater than in General Relativity. The behavior of the Chandrasekhar mass limit in f (R) gravity is also investigated.
Article
Astronomy & Astrophysics
V. K. Oikonomou
Summary: In this study, we analyze the scenario where the effective gravitational Lagrangian of a minimally coupled scalar field becomes a rescaled Einstein-Hilbert gravity at large curvatures, leading to changes in the inflationary phenomenology and satisfaction of swampland criteria. Two inflation models, fiber inflation and supergravity alpha-attractor models, are discussed to show their viability and satisfaction of swampland criteria. The late-time phenomenology of the fiber inflation potential in the presence of full f(R) gravity is examined, showing the production of a viable dark energy era similar to the Lambda-cold-dark-matter model. The modified gravity model presents a universe described by a rescaled Einstein-Hilbert gravity at early times, with the scalar field mainly controlling dynamics synergistically with f(R) gravity at late times.
Article
Astronomy & Astrophysics
S. D. Odintsov, V. K. Oikonomou, F. P. Fronimos
Summary: This paper investigates the late-time dynamics of scalar coupled f(R, G) gravity through numerical analysis, exploring various models in modified gravity theories. It is found that the contribution of Gauss-Bonnet related terms is minor when f(R) gravity terms are present, with the f(R) sector dominating at late times. The Einstein-Gauss-Bonnet models considered produce a dark energy era free from oscillations, with constraints on scalar coupling functions for compatibility with observational data.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
V. K. Oikonomou
Summary: This article introduces a theoretical model of F(R) gravity that can describe inflation, early and late dark energy eras in the presence of a light axion particle as the dark matter component of the Universe. The model exhibits early and late-time dark energy eras, with an early dark energy era followed by a deceleration era and then a late-time dark energy era. A notable feature is the absence of dark energy oscillations in the dark energy era within the redshift interval z = [0, 10]. The model also shows a sudden jump in the value of the Hubble rate within the redshift interval z ≈ [2, 2.6], increasing and then decreasing until z ≈ 0.
Article
Astronomy & Astrophysics
Artyom Astashenok, Sergei D. Odintsov, V. K. Oikonomou
Summary: By considering the thermal effects induced from Hawking radiation on the apparent horizon of the Universe, various dark energy models were investigated. The study explored the evolution of dark energy density as the Universe expands, leading to different types of singularities, such as sudden future singularities and big rip singularities. The research also looked into the transition between deceleration and acceleration in quintessence dark energy, as well as the potential remedies for crushing-type singularities.
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.
