Article
Multidisciplinary Sciences
Charles Schwartz
Summary: Based on the physics theories of Special and General Relativity, this study develops a consistent mathematical description of tachyons using classical and quantum frameworks for particles and fields. The paper discusses the choices made regarding the habits from the study of ordinary particles and presents an alternative set of theories that have severe implications for physical symmetry. Additionally, it summarizes the accomplishments of this work, including the understanding of the gravitational fields created by low energy tachyons and the study of the properties of the cosmic neutrino background. The paper concludes with a discussion of arguments against the existence of tachyons.
Editorial Material
Chemistry, Physical
Faxian Xiu
Summary: Epitaxial topological heterostructures of (Bi,Sb)(2)Te-3/graphene/gallium have been achieved using molecular-beam epitaxy, providing the opportunity to access Majorana zero modes in electrical transport when combined with van der Waals tunnel junctions.
Article
Astronomy & Astrophysics
Henrique Matheus Gauy, Alex E. Bernardini
Summary: The localization of gravity in (5 thorn 1)-dimensional intersecting thick braneworld models is thoroughly investigated. Results show that gravity is localized in the brane, with only zero modes analytically determined for models I to III, and massive modes obtained for models IV and V. The discreteness of the graviton modes prevents gravity from propagating in the codimensions, making the naked singularities at the edges of space harmless. The phenomenological implications of sphere models constructed from models III and IV are also discussed, highlighting the ability of the sphere model assembled from model III to reproduce a consistent Newtonian limit.
Article
Astronomy & Astrophysics
Henrique Matheus Gauy, Alex E. Bernardini
Summary: Two intersecting scalar fields generating extra dimension defects are investigated in the context of two codimensional thick braneworlds. An alternative bulk configuration is examined by constructing a twofold warp factor from two intersecting warp factors. The solvable models obtained from this setup are systematically discussed, including their physical properties and the presence of singularities in the curvature.
Article
Multidisciplinary Sciences
Taishi Chen, Susumu Minami, Akito Sakai, Yangming Wang, Zili Feng, Takuya Nomoto, Motoaki Hirayama, Rieko Ishii, Takashi Koretsune, Ryotaro Arita, Satoru Nakatsuji
Summary: The anomalous Nernst effect (ANE), which converts heat flow into transverse electric voltage, is caused by the Berry phase of the electronic wave function near the Fermi energy EF. Therefore, it can be used as a sensitive probe to detect a topological state with large Berry curvature. In this study, we observe a high ANE exceeding 3 microvolts per kelvin above room temperature in the kagome ferromagnet Fe3Sn with a Curie temperature of 760 kelvin. The large ANE is a result of a nodal plane that produces a flat hexagonal frame with strongly enhanced Berry curvature. Our discovery of the large ANE in Fe3Sn opens up possibilities for exploring the functionality of flat degenerate electronic states and developing flexible film thermopiles and heat current sensors.
Review
Multidisciplinary Sciences
Robert Ehrlich
Summary: This article reviews the searches for empirical evidence of tachyons, superluminal particles with m(2) < 0. It discusses the search for new particles that could be tachyons and presents evidence suggesting neutrinos are tachyonic based on collected data. The second half of the paper focuses on the 3 + 3 neutrino model with a tachyonic mass state, supported by empirical findings from various fields.
Article
Multidisciplinary Sciences
Mengzhu Shi, Fanghang Yu, Ye Yang, Fanbao Meng, Bin Lei, Yang Luo, Zhe Sun, Junfeng He, Rui Wang, Zhicheng Jiang, Zhengtai Liu, Dawei Shen, Tao Wu, Zhenyu Wang, Ziji Xiang, Jianjun Ying, Xianhui Chen
Summary: The authors report a new class of vanadium-based compounds with kagome bilayers that exhibit Dirac nodal lines and superconductivity under pressure. The discovery of these materials provides an opportunity to explore the intertwining between geometry, electronic orders, and band topology.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Multidisciplinary
James Jun He, Yukio Tanaka, Naoto Nagaosa
Summary: Majorana fermions, as charge-neutral quasiparticles, exist on the boundaries of two-dimensional topological superconductors and generate enhanced local optical response. The features of local optical conductivity of chiral Majorana fermions distinguish them from trivial superconductors or insulators, as well as normal fermion edge states in quantum Hall systems. This provides a new applicable method to detect dispersive Majorana fermions and may lead to a novel direction in this research field.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Nuclear
Charles Schwartz
Summary: This study extends the technique used to handle the Group Theoretical issue of spin 1/2 tachyons to tachyons of any spin. By examining the algebraic properties of the generating matrices for spin 5/2, a complete basis for the Cell-Mann matrices that form the Lie algebra for SU(3) is found. An equation similar to the Dirac equation is developed for tachyons of any integer-plus-one-half spin, revealing multiple distinct mass eigenvalues. The primary model roughly mimics the known data on neutrino masses and can be adjusted to precisely fit experimental data.
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2022)
Article
Physics, Multidisciplinary
Zhaoyu Wang, Huading Song, Dong Pan, Zitong Zhang, Wentao Miao, Ruidong Li, Zhan Cao, Gu Zhang, Lei Liu, Lianjun Wen, Ran Zhuo, Dong E. Liu, Ke He, Runan Shang, Jianhua Zhao, Hao Zhang
Summary: This study observed large ZBPs in a thin InAs-Al hybrid nanowire device, with heights close to 2e2/h and remaining stable. By sweeping gate voltages and magnetic field, a phase diagram was mapped out with two plateau regions identified.
PHYSICAL REVIEW LETTERS
(2022)
Article
Physics, Particles & Fields
Giorgio Leone
Summary: This paper extends the analysis of Misaligned Supersymmetry to orientifold vacua. It explores the relationship between the IR properties and UV behavior of closed strings freely propagating between D-branes and O-planes. The results reveal that the sector averaged sums associated to the loop channel control the coupling of closed-string tachyons to D-branes and/or O-planes, while the sector averaged sums associated to tree-level amplitudes encode the presence of tachyons in the physical spectrum.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Physics, Multidisciplinary
Miguel A. J. Herrera, Dario Bercioux
Summary: The authors investigate Dirac states in a lattice with non-symmorphic symmetries, called a herringbone lattice, by using a tight-binding model. They find that non-symmorphic symmetries protect Dirac nodal lines and cones in lattice systems. By breaking the lattice symmetries, the positions of the Dirac cones can be controlled. Additionally, the authors perturb the system by introducing dimerization of the hopping terms, resulting in a flow of Dirac cones describing quasi-hyperbolic curves.
COMMUNICATIONS PHYSICS
(2023)
Article
Multidisciplinary Sciences
Alan Chodos
Summary: In this paper, we introduce a new symmetry called light-cone reflection (LCR) that interchanges timelike and spacelike intervals. We provide a reason for the existence of tachyons based on this symmetry, with a focus on its application to neutrinos. By combining LCR with translations, we find a larger symmetry. We construct an LCR-invariant Lagrangian and discuss its properties. In a simple example, we observe complete symmetry in the spectrum between tachyons and ordinary particles. We also demonstrate the possibility of introducing an additional gauge invariance related to chiral symmetry in this theory.
Article
Nanoscience & Nanotechnology
Shuyu Cheng, Binbin Wang, Igor Lyalin, Nuria Bagues, Alexander J. Bishop, David W. McComb, Roland K. Kawakami
Summary: Magnetic materials with kagome crystal structure have been mainly studied in bulk crystals or polycrystalline films. This study reports the synthesis of high-quality thin films of topological kagome magnet Fe3Sn2 using atomic layer molecular beam epitaxy. The films exhibit highly ordered structure with in-plane magnetic easy axis, and the local magnetic structure reveals micrometer size domains with in-plane orientation. Superlattice structures consisting of Fe3Sn2 and Fe3Sn are also successfully synthesized.
Article
Multidisciplinary Sciences
T. Yokoi, S. Ma, Y. Kasahara, S. Kasahara, T. Shibauchi, N. Kurita, H. Tanaka, J. Nasu, Y. Motome, C. Hickey, S. Trebst, Y. Matsuda
Summary: Recent reports have shown the presence of half-integer thermal quantum Hall conductance in the two-dimensional honeycomb material alpha-RuCl3, even in magnetic fields without out-of-plane components. The measured field-angular variation of the quantized thermal Hall conductance in alpha-RuCl3 has the same sign structure as the topological Chern number of the pure Kitaev spin liquid, indicating that the non-Abelian topological order persists in the presence of non-Kitaev interactions.
Article
Physics, Nuclear
Marlos O. Ribas, Fernando P. Devecchi, Gilberto M. Kremer
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2020)
Article
Multidisciplinary Sciences
Adriano B. Barreto, Gilberto M. Kremer
Article
Physics, Nuclear
Marlos O. Ribas, Fernando P. Devecchi, Gilberto M. Kremer
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2020)
Article
Physics, Multidisciplinary
Gilberto M. Kremer
Summary: A kinetic theory for relativistic gases in the presence of gravitational fields is developed in the second post-Newtonian approximation. By using the Boltzmann equation and equilibrium Maxwell-Juttner distribution function, the components of particle four-flow and energy-momentum tensor are obtained. The Eulerian hydrodynamic equations for mass density, mass-energy density, and momentum density are determined from the Boltzmann equation in the second post-Newtonian approximation.
Article
Physics, Nuclear
Marlos O. Ribas, Fernando P. Devecchi, Gilberto M. Kremer
Summary: This study introduces a model of the early universe involving a scalar field, relativistic fluid, and self-interacting fermionic field. Through classical analysis and quantum equations, it is found that the combination of scalar and fermionic fields can achieve a smooth transition from quantum to classical, with the key being the use of Bohmian mechanics and quantum potential. The influence of the scalar field on the results is also discussed.
INTERNATIONAL JOURNAL OF MODERN PHYSICS A
(2021)
Article
Physics, Particles & Fields
Gilberto M. Kremer
Summary: In this study, Jeans instability is analyzed within the framework of post-Newtonian Boltzmann and Poisson equations. It was found that the necessary mass for an overdensity to initiate gravitational collapse in the post-Newtonian theory is smaller than in the Newtonian theory.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Gilberto M. Kremer
Summary: This study numerically shows Jeans instability in an expanding universe, indicating that the growth of density constrast is slower when considering particle collisions, and oscillations fade away over time for perturbations smaller than the Jeans wavelength.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2022)
Article
Physics, Multidisciplinary
Gilberto M. Kremer
Summary: The post-Newtonian hydrodynamic equations for a non-perfect fluid are derived from a post-Newtonian Boltzmann equation. The energy-momentum tensor components are determined using the relativistic Eckart decomposition for a viscous and heat conducting fluid. The post-Newtonian expression of the relativistic Grad distribution function is obtained. The hydrodynamic equations for mass density, mass-energy density, and momentum density are derived using a post-Newtonian transfer equation and Grad's distribution function. In the non-relativistic limit, the Newtonian hydrodynamic equations are recovered.
Article
Astronomy & Astrophysics
Gilberto Medeiros Kremer
Summary: The post-Newtonian Jeans equation is derived from the post-Newtonian Boltzmann equation in spherical coordinates for stationary self-gravitating systems. It is coupled with the three Poisson equations from the post-Newtonian theory, which are functions of the energy-momentum tensor components determined from the post-Newtonian Maxwell-Juttner distribution function. An application of this equation investigates the influence of a central massive black hole on the velocity dispersion profile of the host galaxy and determines the effects of post-Newtonian corrections.
Article
Physics, Mathematical
Gilberto M. Kremer, Andres Santos
Summary: The paper introduces the development and simplification of granular gas models, proposes a new inelastic rough Maxwell model, and provides exact solutions for the model. The proposed model allows for the evaluation of the dynamic properties of granular gases.
JOURNAL OF STATISTICAL PHYSICS
(2022)
Article
Astronomy & Astrophysics
Gilberto M. M. Kremer
Summary: This work analyzes the influence of post-Newtonian corrections on the equations of stellar structure and calculates the physical quantities for the Sun, white dwarf Sirius B, and neutron stars. The results show that the post-Newtonian corrections can be neglected for the Sun and Sirius B, but become important for stars with strong fields. For the analyzed neutron stars, the post-Newtonian corrections lead to higher central pressure and temperature, and slightly lower central mass density.
RESEARCH IN ASTRONOMY AND ASTROPHYSICS
(2022)
Article
Physics, Multidisciplinary
Gilberto M. M. Kremer
Summary: The influence of reactive cross sections on the reaction rate of a simple chemical reaction A + A -> products, where the products' concentrations are negligible compared to the reagents', is investigated using the Boltzmann equation. This reaction is considered slow, as the time between successive reactions is greater than the time between elastic collisions. The internal degrees of freedom of gas molecules are not considered. Two models for the reactive cross section, the line-of-centers energy model and the modified line-of-centers energy model, are examined. Explicit expressions for the reaction rate as a function of activation energy are provided, demonstrating how the reactant fields of particle number density and temperature evolve with time during the progress of the chemical reaction.
BRAZILIAN JOURNAL OF PHYSICS
(2023)
Article
Physics, Mathematical
Gilberto M. Kremer
Summary: The second post-Newtonian hydrodynamic equations are analyzed using a plane wave solution framework. The coupling of the hydrodynamic equations for mass and momentum density with the Poisson equations for Newtonian and post-Newtonian gravitational potentials is examined. Perturbations of the basic fields and gravitational potentials from a background state using plane wave representations yield a dispersion relation and the emergence of the Jeans instability condition. The study determines the influence of the first and second post-Newtonian approximations on the Jeans mass, showing that the second post-Newtonian approximation requires a smaller mass for an overdensity to initiate gravitational collapse compared to the Newtonian theory.
INTERNATIONAL JOURNAL OF GEOMETRIC METHODS IN MODERN PHYSICS
(2023)
Article
Physics, Multidisciplinary
Gilberto M. Kremer
Summary: The non-equilibrium contributions to the post-Newtonian hydrodynamic equations are determined using a relaxation-time model and the Chapman-Enskog method. The components of the energy-momentum tensor are found from the non-equilibrium and post-Newtonian equilibrium Maxwell-Jüttner distribution functions. The linearized field equations for mass, momentum, and internal energy densities, along with the three Poisson equations of the post-Newtonian approximation, are studied with a plane wave representation of the fields. Constitutive equations for the viscous stress and heat flux vector are obtained, showing that the transport coefficients depend on the Newtonian gravitational potential.
Article
Astronomy & Astrophysics
Gilberto M. Kremer, Leandro C. Mehret
Summary: The study aims to investigate the corrections to the spherical symmetric accretion of an infinity gas cloud into a massive object due to the post-Newtonian approximation. The analysis shows that the correction terms have a more significant impact at lower radial distances, while for alpha(infinity)/c > 10(-2), there is no continuous inflow and outflow velocity at the critical point.
