Article
Physics, Nuclear
Sirachak Panpanich, Piyabut Burikham, Supakchai Ponglertsakul, Lunchakorn Tannukij
Summary: Recent low-redshift observations have shown that the current Hubble parameter value is higher than the predicted value based on Planck's observations of the Cosmic Microwave Background radiation and the CDM model. By adding an extra component with negative density to the Friedmann equation, the Hubble tension can be addressed without changing Planck's constraints on matter and dark energy densities. The proposed quintom model, involving two scalar fields, potentially alleviates the Hubble tension while achieving a viable cosmological scenario.
Article
Astronomy & Astrophysics
Hao Wang, Yun-Song Piao
Summary: In studies on pre-recombination early dark energy (EDE), the post-recombination evolution of the universe is often assumed to be Lambda CDM-like, with a dark energy equation of state w = -1. However, in realistic models, w may be evolving. This research explores different models for the evolution of w with respect to redshift z in Axion-like EDE and AdSEDE models. By performing a Monte Carlo Markov chain analysis with recent cosmological data, it is found that the bestfit w(z) is compatible with a constant w(0) = -1, wa = 0 (corresponding to a cosmological constant), and the evolution of w is only marginally favored, having little effect on the bestfit value of H-0.
Article
Astronomy & Astrophysics
Sourav Dutta, Muthusamy Lakshmanan, Subenoy Chakraborty
Summary: In this study, quantum cosmology with quintom dark energy model was investigated through symmetry analysis of the underlying physical system. The study focused on the flat FLRW model and utilized Noether symmetry to obtain an appropriate conserved charge. The Wheeler-DeWitt equation was then constructed on the minisuperspace to obtain solutions using the conserved charge.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Gabriel Gomez
Summary: Scalar fields coupled to dark matter by conformal or disformal transformations give rise to a general class of scalar-tensor theories with rich phenomenology in cosmology. However, the vector case has been barely studied. In this study, we build models based on vector fields coupled to dark matter and derive the interaction term in a covariant form independent of gravity theory, providing insights into general vector-tensor theories. Numerical calculations show that the coupling of vector fields to dark matter significantly affects the cosmological dynamics during different stages of the Universe's evolution.
Article
Astronomy & Astrophysics
Genly Leon, Andronikos Paliathanasis, Emmanuel N. Saridakis, Spyros Basilakos
Summary: This study presents a unified description of the matter and dark energy epochs using a class of scalar-torsion theories. Two specific classes of scalar-field potentials are obtained by applying Noether's theorem and requiring linear-in-momentum conservation laws. The analysis reveals critical points that correspond to different stages in the evolution of the universe, including the dust-matter domination period, the accelerated period, and the de Sitter phase.
Article
Astronomy & Astrophysics
Kishan Sankharva, Shiv Sethi
Summary: In this paper, we consider a nonminimally coupled scalar field as a candidate for cold dark matter and compare it with minimally coupled scalar fields. For the nonminimally coupled field, the energy density behaves as radiation in the early universe and is constrained by a coupling constant. Isocurvature modes are also considered in our analysis.
Article
Astronomy & Astrophysics
Zhiqi Huang
Summary: The study focuses on constructing thawing k-essence models by generating Taylor expansion coefficients of L(0, X) from random matrices and selecting dark energy candidates based on assumptions of negative pressure and non-growth of subhorizon inhomogeneities. The distribution of thawing k-essence dark models in the (w0, wa) space is highly nonuniform, with approximately 90% clustering near a slow-roll line.
Article
Astronomy & Astrophysics
L. Gabriel Gomez, Yeinzon Rodriguez
Summary: In this study, a new class of vector dark energy models is investigated where multi-Proca fields are coupled to cold dark matter by a general function, leading to novel interactions and effects. The coupling function results in a new scaling solution during dark matter dominance and a stable de Sitter-type attractor mimicking dark energy in the late universe evolution. Observational constraints and numerical computations validate the cosmological evolution and features of the system.
PHYSICS OF THE DARK UNIVERSE
(2021)
Article
Astronomy & Astrophysics
Pierre-Henri Chavanis
Summary: This paper constructs cosmological models based on a complex scalar field with a power-law potential. It explores various equation of state scenarios and investigates special cases such as the ACDM model, the Chaplygin gas model, and the Bose-Einstein condensate model. It also presents a two-fluid representation of the Chaplygin gas model.
Article
Astronomy & Astrophysics
Vitor da Fonseca, Tiago Barreiro, Nelson J. Nunes
Summary: In this study, a quintessence model is constructed where the scalar field has a linear dependence on the number of e-folds. The proposed parametrisation conveniently constrains the evolution of the dark energy equation of state and also considers a non-minimal coupling to cold dark matter. Analysis of observational data indicates a non-vanishing coupling with energy transfer from dark energy to dark matter preferred by CMB measurements.
PHYSICS OF THE DARK UNIVERSE
(2022)
Review
Astronomy & Astrophysics
Veronica Motta, Miguel A. Garcia-Aspeitia, Alberto Hernandez-Almada, Juan Magana, Tomas Verdugo
Summary: The article summarizes the characteristics of dark energy models and some commonly used cosmological samples, discusses how to constrain model parameters using observational data, and finally provides an overview of the status of dark energy modeling.
Article
Astronomy & Astrophysics
Jonathan Tot, Balkar Yildirim, Alan Coley, Genly Leon
Summary: We present a comprehensive (compactified) dynamical systems analysis of the Quintom model consisting of an interacting quintessence scalar field and a phantom. By finding a range of parameters Kappa and lambda, we identify expanding Quintom cosmologies that undergo two inflationary periods, unaffected by spatial curvature. We also discuss a class of bouncing cosmologies and examine the linear cosmological perturbations.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Physics, Applied
Alejandro R. Urzua, Hector M. Moya-Cessa
Summary: In this study, we investigate a system of three-coupled quantized fields under the intrinsic decoherence scheme proposed by the Milburn equation. By obtaining the closed analytical form of this equation, we derive an explicit analytical solution for the dynamics of the wavefunction. We demonstrate the decaying behavior in the number of modes for each quantized field under appropriate initial conditions. One of the modes is coherently driven while the others remain in vacuum states. We also discuss the redistribution of excitations.
INTERNATIONAL JOURNAL OF MODERN PHYSICS B
(2023)
Article
Mathematics, Applied
Erik T. K. Mau, Michael Rosenblum, Arkady Pikovsky
Summary: Phase reduction is a general approach for describing coupled oscillatory units by focusing on their phases. This paper presents a general framework for obtaining higher-order coupling terms in terms of the coupling parameter for two-dimensional oscillators with arbitrary coupling terms. The theory is applied to accurately predict Arnold's tongue phenomenon for the van der Pol oscillator using higher-order phase reduction.
Article
Neurosciences
Elisabetta Corti, Joaquin Antonio Cornejo Jimenez, Kham M. Niang, John Robertson, Kirsten E. Moselund, Bernd Gotsmann, Adrian M. Ionescu, Siegfried Karg
Summary: A new in-memory computing platform based on coupled VO2 oscillators fabricated in a crossbar configuration on silicon is proposed in this work. The platform shows promising improvements in area density and oscillation frequency, enabling experiments on 4-coupled oscillators. The concept is tested with a VGG13 architecture on the MNIST dataset, achieving performances of 95% in the recognition task.
FRONTIERS IN NEUROSCIENCE
(2021)
Article
Physics, Particles & Fields
Emmanuel N. Saridakis, Weiqiang Yang, Supriya Pan, Fotios K. Anagnostopoulos, Spyros Basilakos
Summary: Soft cosmology extends the standard cosmology by allowing for different equation-of-state parameters for dark matter and dark energy at different scales. Data analysis suggests that soft cosmology is favored by observational constraints.
Article
Astronomy & Astrophysics
Shreya Banerjee, Sayantani Bera, David F. Mota
Summary: The Lambda-Cold Dark Matter model is currently the most accurate model for explaining cosmological observations, but there are still issues at galactic scales. Various models of dark matter, such as superfluid dark matter, Bose-Einstein Condensate (BEC) dark matter, and fuzzy dark matter, have been proposed to address these shortcomings. This study investigates these models using the constraint on gravitational wave propagation speed from the detection of the binary neutron star GW170817 by the LIGO-Virgo detector network. The findings suggest that the fuzzy dark matter model is the most feasible scenario to be tested in the near future, especially with detection frequencies < 10-9 Hz.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Theodoros Papanikolaou, Andreas Lymperis, Smaragda Lola, Emmanuel N. Saridakis
Summary: Primordial black holes (PBHs) can be formed through non-canonical inflation, and can provide observational evidence of the early Universe. Constraints on the non-canonical exponents are extracted by requiring significant PBH production. Asteroid-mass PBHs can explain the dark matter, and solar-mass PBHs within the LIGO-VIRGO detection band can be produced. The collapse of enhanced cosmological perturbations that form PBHs can also generate a detectable stochastic gravitational wave (GW) background.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Physics, Multidisciplinary
G. G. L. Nashed, Emmanuel N. Saridakis
Summary: In this study, new classes of anisotropic solutions are extracted within the framework of mimetic gravity. By applying the Tolman-Finch-Skea metric and a specific anisotropy unrelated to it, and smoothly matching the interior solution to the exterior Schwarzschild solution, the authors investigate various properties of these solutions. The results show positive energy density, decreasing pressures towards the center of the star, repulsive anisotropic force, and monotonically increasing equation-of-state parameters. The stability of the solutions is also examined, and it is found that the stars in all cases are stable.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Chemistry, Multidisciplinary
Shreya Banerjee, Sunil K. Gupta, Erode N. Prabhakaran
Summary: The presence of sinusoidal synchronicity between rotational motion along C-alpha-C ' sigma bond and the concomitant pyramidalization of C ' in amides is demonstrated for the first time in solution. It has been found that synchronicity is perturbed when tau-rotation is 'locked' with interactions, resulting in a strain on the amide bond and a decrease in energy barrier for the amide bond cis/trans isomerism by approximately 1.68 kcal/mol.
Article
Astronomy & Astrophysics
Maria Petronikolou, Emmanuel N. Saridakis
Summary: In this study, we investigate scalar-tensor and bi-scalar-tensor modified theories of gravity that can alleviate the H-0 tension. We show that by choosing particular models with specific features, such as a shift-symmetric friction term or phantom behavior of the effective dark-energy equation-of-state parameter, the tension can be alleviated. These theories provide known mechanisms for alleviating the H0 tension.
Article
Astronomy & Astrophysics
Shreya Banerjee, Maria Petronikolou, Emmanuel N. Saridakis
Summary: We investigate the cosmological applications of gravitational scalar-tensor theories and analyze them in the context of the H0 tension. Two specific models are explored, showing negligible effects at high redshifts but an increasing deviation as time passes. At low redshifts, the Hubble parameter takes on higher values in a controlled manner. This behavior is attributed to the phantom nature of the effective dark-energy equation-of-state parameter, providing a possible solution to the H0 tension. Comparison with cosmic chronometer data demonstrates full agreement within 1σ confidence level.
Article
Astronomy & Astrophysics
Petros Asimakis, Spyros Basilakos, Andreas Lymperis, Maria Petronikolou, Emmanuel N. Saridakis
Summary: This study constructs new classes of modified theories that couple the matter sector with the Einstein tensor, specifically considering direct couplings to the energy-momentum tensor and its trace derivatives. The general field equations, without higher-order derivatives, are derived and applied in a cosmological framework, resulting in Friedmann equations with additional terms that give rise to an effective dark energy sector. The study shows successful description of the thermal history of the universe at the background level, with matter and dark energy epochs, and the dark energy equation-of-state parameter can approach -1 as time progresses. Comparison with cosmic chronometer data demonstrates a very good agreement. Detailed investigations of scalar and tensor perturbations validate the predicted behavior of the matter overdensity.
Article
Chemistry, Multidisciplinary
Mita Dutta, Shreya Banerjee, Mahitosh Mandal, Manish Bhattacharjee
Summary: A self-healable metallohydrogel of Mn(ii) has been successfully prepared using a low molecular weight gelator, Na2HL. It has been characterized by various techniques and encapsulated with drugs IND and GEM. The GEM-loaded metallogel showed enhanced delivery and cytotoxicity against breast cancer cells, while the MOG_IND exhibited improved anti-inflammatory response compared to the drug alone.
Article
Astronomy & Astrophysics
Wompherdeiki Khyllep, Jibitesh Dutta, Emmanuel N. Saridakis, Kuralay Yesmakhanova
Summary: Motivated by the success of f(Q) gravity in fitting observational data, we analyze the behavior of two studied f(Q) models, power-law and exponential, through dynamical system analysis. We find that both models have a matter-dominated saddle point followed by a stable dark-energy-dominated accelerated universe. The models fit observational data well and can be considered as promising alternatives to the ACDM concordance model.
Article
Physics, Particles & Fields
Sebastian Bahamonde, Konstantinos F. Dialektopoulos, Manuel Hohmann, Jackson Levi Said, Christian Pfeifer, Emmanuel N. Saridakis
Summary: This study focuses on the cosmological perturbation theory in f(T) gravity, which is a simple extension of the teleparallel equivalent of general relativity. The authors examine the possibility of a non-flat FLRW background solution and perform perturbations for different spatial geometries. They determine the behavior of the perturbative modes in this non-flat FLRW setting for arbitrary f(T) models and identify propagating modes.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Fotios K. Anagnostopoulos, Viktor Gakis, Emmanuel N. Saridakis, Spyros Basilakos
Summary: The f(Q) theories of modified gravity, based on non-metricity as the fundamental geometric quantity, have shown great effectiveness in describing the late-time Universe. By using Big Bang Nucleosynthesis (BBN) formalism and observations, constraints on various classes of f(Q) models are obtained. The deviations on the freeze-out temperature caused by f(Q) terms are calculated and constraints on the model parameters are imposed by applying the observational bound on |delta Tf/Tf|. It is found that f(Q) gravity can pass the BBN constraints, distinguishing itself from many other gravitational modifications that fail to do so.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Physics, Particles & Fields
Theodoros Papanikolaou, Charalampos Tzerefos, Spyros Basilakos, Emmanuel N. Saridakis
Summary: Research shows that the fluctuations of primordial black holes can be used as a novel tool to test general relativity and constrain possible modified gravity deviations in the framework of f(T) gravity. By investigating three viable mono-parametric models, we find that the deviations from general relativity in terms of the gravitational-wave source and propagation are negligible within the observationally allowed range of f(T) model parameters. Therefore, we conclude that realistic and viable f(T) theories can safely pass the primordial black hole constraints, providing additional support for them.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Yu-Min Hu, Yaqi Zhao, Xin Ren, Bo Wang, Emmanuel N. Saridakis, Yi-Fu Cai
Summary: This study investigates the scalar perturbations and possible strong coupling issues of f(T) gravity using the effective field theory (EFT) approach. The generalized EFT framework of modified teleparallel gravity is revisited and applied to examine both linear and second-order perturbations in f(T) theory. The results suggest that there is no new scalar mode present in f(T) gravity, indicating a strong coupling problem. However, an estimation of the strong coupling scale based on the ratio of cubic to quadratic Lagrangians shows that the strong coupling problem can be avoided for certain modes.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Ali Dehghani, Behnam Pourhassan, Soodeh Zarepour, Emmanuel N. Saridakis
Summary: This study investigates the thermodynamic schemes of charged BTZ-like black holes in arbitrary dimensions. Two possible thermodynamic schemes are identified with different outcomes. In the traditional scheme, the charged black holes violate the reverse isoperimetric inequality and have a fundamental thermodynamic instability. In the second scheme, the black holes are thermodynamically stable and can explain the van der Waals critical phenomenon.
PHYSICS OF THE DARK UNIVERSE
(2023)
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.
