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, Particles & Fields
Christos G. Tsagas
Summary: Large-scale bulk peculiar motions can affect local kinematics, causing the locally measured deceleration parameter to vary due to observers' relative motion. Therefore, information selected from regions inside the transition scale is only applicable locally and cannot be extrapolated to the global universe.
EUROPEAN PHYSICAL JOURNAL C
(2022)
Article
Astronomy & Astrophysics
Kinjalk Lochan
Summary: This paper analyzes the minimally coupled massless scalar field in a Friedmann universe using conformal coordinates, and models the evolution of tensor perturbations. The study finds that the growth of quantum tensor perturbations in the Friedmann universe is limited by causal structure, unlike the scalar perturbations.
GENERAL RELATIVITY AND GRAVITATION
(2022)
Article
Astronomy & Astrophysics
Abhay Ashtekar, Adrian del Rio
Summary: Recent studies have shown that linear quantum fields can be propagated across renormalized observables in Minkowskian quantum field theories. They can also be extended as well-defined distributions even in spacetimes that include the big bang or the big crunch. This generalization has been applied to spatially closed and open FLRW models, demonstrating that the tameness of cosmological singularities is not dependent on spatial flatness.
Article
Astronomy & Astrophysics
Spiros Cotsakis
Summary: By considering the dispersive aspects of standard perfect fluid Friedmann cosmology, we studied the new qualitative behaviors of cosmological solutions that arise as the fluid parameter changes and zero eigenvalues appear in the linear part of the Friedmann equations. We found that the Milne, flat, Einstein-static, and de Sitter solutions cannot properly bifurcate due to their insufficient degeneracy. However, the dispersive versions of Milne and flat universes contained in the versal unfolding of the standard Friedmann equations possess novel long-term properties. We applied these results to the horizon problem and showed that the dispersive Milne and flat solutions completely synchronize in the future, offering a solution to the puzzles of homogeneity, isotropy, and causal connectedness.
GENERAL RELATIVITY AND GRAVITATION
(2023)
Article
Astronomy & Astrophysics
Raphael Bousso, Elizabeth Wildenhain
Summary: In cosmology, spatial curvature has a significant impact on the existence of entanglement islands. Positive curvature guarantees the entire universe to be an island, while subsets of the time-symmetric slice of closed or open universes can also be islands under the condition of negative and sufficiently large cosmological constant.
Article
Astronomy & Astrophysics
Damianos Iosifidis
Summary: Starting from the generalized Raychaudhuri equation with torsion and non-metricity, researchers derived the most general form of acceleration equation in the presence of these effects, discussing how they affect the expansion rate of the Universe.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
Sebastian Cespedes, Senarath P. de Alwis, Francesco Muia, Fernando Quevedo
Summary: This study generalizes quantum tunneling transitions in the WKB approximation and calculates transition rates among different scalar field vacua using a Lorentzian approach. The findings show that there is no obstruction to maintaining the spherically symmetric closed slicing for the new vacuum after a transition, which is the natural Lorentzian realization of the Coleman-De Luccia instanton.
Article
Environmental Sciences
L. Makinistian, L. Zastko, A. Tvarozna, L. E. Dias, I Belyaev
Summary: Research suggests that the static magnetic field generated by the use of earphones can have a wide range of exposure and potential biological effects on the human body. With no scientific consensus on the possible mechanisms of interaction with living tissues, caution in using earphones may be advisable.
ENVIRONMENTAL RESEARCH
(2022)
Article
Physics, Particles & Fields
G. Lambiase, G. G. Luciano, A. Sheykhi
Summary: In this study, a new cosmological scenario is proposed based on Kaniadakis entropy and modified Friedmann equations. The research finds that the Kaniadakis parameter is constrained by observational limits and the correction term has a non-trivial effect on the growth of perturbations in the early stages of the Universe.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Christos G. Tsagas, Miltiadis Kadiltzoglou, Kerkyra Asvesta
Summary: This study examines the implications of large-scale peculiar flows for the interpretation of the deceleration parameter, comparing measurements between Hubble-flow observers and their bulk-flow counterparts. The findings show that Newtonian relative-motion effects generally have little impact on these measurements, but in relativity, the deceleration parameters measured in the two frames differ considerably even at the linear level, potentially leading to a serious misinterpretation of the universe's global kinematic status. The study also discusses the implications and observational viability of the relativistic approach.
ASTROPHYSICS AND SPACE SCIENCE
(2021)
Article
Multidisciplinary Sciences
Krzysztof Urbanowski
Summary: Based on experimental results, the estimated values of the Higgs and top quark masses place the Standard Model in the region of the metastable vacuum. The metastability of the Higgs vacuum leads to the decay of the electroweak vacuum in the early Universe with catastrophic consequences. However, some universes may have survived the decay time and continue to exist due to certain conditions. The quantum theory of unstable states is used to analyze the properties of an ensemble of universes with unstable vacua, and symmetry relations and a relation between the decay rate and the Hubble parameter are found.
Article
Physics, Fluids & Plasmas
Hidetsugu Sakaguchi, Yuta Nakao
Summary: The study on the susceptible-infected-recovered (SIR) model with spatially inhomogeneous infection rate using numerical simulations shows that the total population of infection decays very slowly in some cases, as opposed to the exponential decay of the infected population in the ordinary SIR model. This slow decay suggests that the infection persists locally for a long time, making it difficult for the disease to completely disappear.
Review
Chemistry, Multidisciplinary
Songzhu Luo, Kamal Elouarzaki, Zhichuan J. Xu
Summary: Developing new strategies in magnetoelectrochemistry is crucial to control and understand electrochemical reactions. It combines concepts from multiple disciplines and explores the effects of magnetic fields on fundamental electrochemical principles.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2022)
Article
Physics, Fluids & Plasmas
Kai Xu, Han-Jie Zhu, Guo-Feng Zhang, Wu-Ming Liu
Summary: The research focuses on the charging process of open quantum battery in the weak system-environment coupling regime. It is found that manipulating the spectral density of environment can improve the performance of open quantum battery in a reservoir environment. Furthermore, increasing the coupling strength between nearest-neighbor environments and decreasing the size of the environments can enhance the performance of quantum battery in multiple coupled reservoir environments.
