arXiv subjects

Toyoki Matsuyama

Publications and source records attributed to Toyoki Matsuyama.

15 recordsLinked to original sources

arXiv2026

Dynamical Mass Growing of Fermion with Bare Mass in Two Dimensions

We study dynamical mass generation of a fermion with and without a bare mass by coupling with a massive vector field in two-dimensional space-time. To estimate a non-perturbative effect on the fermion mass, we employ the Schwinger-Dyson equations in the lowest-ladder approximation, which are solved by an approximated analytical method and also by a numerical method. We define a purely dynamical mass as a remnant after subtracting the bare mass from a total dynamical mass. We clarify dependence of the purely dynamical mass on the bare mass of the fermion in various region of a coupling constant. Especially we find that the purely dynamical masses growing from the different bare masses coincide with each other at a specific value of the coupling constant where a kind of a duality relation on the bare masses is satisfied.

hep-ph↗

arXiv2020

The Nakano-Nishijima-Gell-Mann Formula From Discrete Galois Fields

The well known Nakano-Nishijima-Gell-Mann (NNG) formula relates certain quantum numbers of elementary particles to their charge number. This equation, which phenomenologically introduces the quantum numbers $I_z$ (isospin), $S$ (strangeness), etc., is constructed using group theory with real numbers $\mathbb{R}$. But, using a discrete Galois field $\mathbb{F}_p$ instead of $\mathbb{R}$ and assuring the fundamental invariance laws such as unitarity, Lorentz invariance, and gauge invariance, we derive the NNG formula deductively from Meson (two quarks) and Baryon (three quarks) representations in a unified way. Moreover, we show that quark confinement ascribes to the inevitable fractionality caused by coprimeness between half-integer (1/2) of isospin and number of composite particles (e.g. three).

hep-ph↗

arXiv2015

Emergence of the Chern structure using Sr$_2$RuO$_4$ nanofilms

We discovered a fractional Chern structure in chiral superconducting Sr$_2$RuO$_4$ nanofilms by employing electric transport. By using Sr$_2$RuO$_4$ single crystals with nanoscale thickness, a fractional Hall conductance was observed without an external magnetic field. The Sr$_2$RuO$_4$ nanofilms enhanced the superconducting transition temperature to about 3 K. We found an anomalous induced voltage with temperature and thickness dependence, and the switching behavior of the induced voltage appeared when we applied a magnetic field. We suggest that there was fractional magnetic-field-induced electric polarization in the interlayer. These anomalous results are related to topological invariance. The fractional axion angle $θ=π/6$ is determined by observing the topological magneto-electric effect in Sr$_2$RuO$_4$ nanofilms.

cond-mat.str-el↗

arXiv2010

Effects of Chern-Simons Corrections on Conserved Quantities of Relativistic Fluid

We consider relativistic fluid flow under Chern-Simons modified Maxwell theory and under Chern-Simons modified gravity theory. We take account of the effects of Chern-Simons corrections on the quantities of fluid flow that are conserved without the Chern-Simons corrections. We find that the conservations of several quantities are generally broken by the Chern-Simons corrections.

gr-qc↗

arXiv2009

Rotating black hole in extended Chern-Simons modified gravity

We investigate a slowly rotating black hole in four-dimensional extended Chern-Simons modified gravity. We obtain an approximate solution that reduces to the Kerr solution when a coupling constant vanishes. The Chern-Simons correction effectively reduces the frame-dragging effect around a black hole in comparison with that of the Kerr solution.

gr-qc↗

arXiv2009

Discovery of parity-violating Majorana fermions in a chiral superconductor Sr2RuO4

We found parity-violating Majorana fermions in a chiral superconductor Sr2RuO4. The current-voltage curves show an anomalous behavior: The induced voltage is an even function of the bias current. The magnetic field dependent results suggest the excitation of the Majorana fermions along the closed chiral edge current of the single domain under bias current. We also discuss the relationship between a change of the chirality and spontaneous magnetization of the single domain Sr2RuO4.

cond-mat.supr-con↗

arXiv2008

Flat rotation curves in Chern-Simons modified gravity

We investigate the spacetime of a slowly rotating black hole in the Chern-Simons modified gravity. The long range feature of frame-dragging effect under the Chern-Simon gravity well explains the flat rotation curves of galaxies which is a central evidence of dark matter. Our solution provides a different scenario of rotating space from Goedel's solution.

gr-qc↗

arXiv2007

Does a black hole rotate in Chern-Simons modified gravity?

Rotating black hole solutions in the (3+1)-dimensional Chern-Simons modified gravity theory are discussed by taking account of perturbation around the Schwarzschild solution. The zenith-angle dependence of a metric function related to the frame-dragging effect is determined from a constraint equation independently of a choice of the embedding coordinate. We find that at least within the framework of the first-order perturbation method, the black hole cannot rotate for finite black hole mass if the embedding coordinate is taken to be a timelike vector. However, the rotation can be permitted in the limit of $M/r \to 0$ (where $M$ is the black hole mass and $r$ is the radius). For a spacelike vector, the rotation can also be permitted for any value of the black hole mass.

gr-qc↗

arXiv2006

Topologically Linked Crystals

We discovered a new class of topological crystals, namely linked rings of crystals. Two rings of tantalum triselenide (TaSe3) single crystals were linked to each other while crystal growing. The topology of the crystal form is called a "Hopf link", which is the simplest link involving just two component unknots linked together exactly once. The feature of the crystals is not covered by the conventional crystallography.

cond-mat.mtrl-sci↗

arXiv2002

Binding Energy of Scalar Bound State by Topologically Massive Interaction: Fermion and Anti-fermion System with Heavy Mass

A bound state problem in a topologically massive quantum electrodynamics is investigated by using a non-perturbative method. We formulate the Bethe- Salpeter equation for scalar bound states composed of massive fermion and anti-fermion pair under the lowest ladder approximation. In a large mass expansion for the (anti-) fermion, we derive the Schr{ö}dinger equation and solve it by a numerical method. The energy eigenvalues of bound states are evaluated for various values of a topological mass and also a fermion mass. Then we find a novel logarithmic scaling behaviour of the binding energy in varying the topological mass, fermion mass and also a quantum number. There exists a critical value of the topological mass, beyond which the bound states disappear. As the topological mass decreases, the energy eigenvalues of the bound states, which are negative, also decrease with a logarithmic dependence on the topological mass. A Chern-Simons term gives the bound system a repulsive effect.

hep-th↗

arXiv2001

Topological Mass vs. Dynamical Mass: Novelty in (2+1)-dimensional Space-Time

The restriction of space-time dimensions to "2+1" leads us to a novel quantum field theory which has the Chern-Simons term in its action. This term changes the nature of gauge interaction by giving a so-called topological mass to a gauge field without breaking the gauge symmetry. We investigate how a dynamical mass of fermion is affected by the topological mass in the non-perturbative Schwinger-Dyson method.

hep-th↗

arXiv2001

Dynamical Mass and Parity Condensate in Varying Topological Mass

We investigate how a dynamical mass of a fermion is affected by a topological mass of a gauge field in a Maxwell-Chern-Simons $QED_3$ coupled with a two-component fermion. The dynamical mass and also a parity condensate are estimated by using a non-perturbative Schwinger-Dyson method. In particular, we study a limit of vanishing the topological mass in detail and clarify a linking between theories with and without a Chern-Simons term in a non-perturbative level.

hep-th↗

arXiv1999

Dynamical mass generation of a two-component fermion in Maxwell-Chern-Simons QED_3: The lowest ladder approximation

Dynamical mass generation of a two-component fermion in $QED_3$ with a Chern-Simons term is investigated by solving the Schwinger-Dyson equation formulated in the lowest ladder approximation. Dependence of the dynamical fermion mass on a gauge-fixing parameter, a gauge coupling constant, and a topological mass is examined by approximated analytical and also numerical methods. The inclusion of the Chern-Simons term makes impossible to choose a peculiar gauge in which a wave function renormalization is absent. The numerical evaluation shows that the wave function renormalization is fairly close to 1 in the Landau gauge. It means that this gauge is still a specific gauge where the Ward-Takahashi identity is satisfied approximately. We also find that the dynamical mass is almost constant if the topological mass is larger than the coupling constant, while it decreases when the topological mass is comparable to or smaller than the coupling constant and tends to the value in $QED_3$ without the Chern-Simons term.

hep-th↗

arXiv1999

A Mathematical Model with Modified Logistic Approach for Singly-Peaked Population Processes

When a small number of individuals of organism of single species is confined in a closed space with limited amount of indispensable resources, their breading may start initially under suitable conditions, and after peaking, the population should go extinct as the resources are exhausted. Starting with the logistic equation and assuming that the carrying capacity of the environment is a function of the amount of resources, a mathematical model describing such pattern of population change is obtained. An application of this model to typical population records, that of deer herds by Scheffer (1951) and O'Roke and Hamerstrome (1948), yields estimations of the initial amount of indispensable food and its availability or nutritional efficiency which were previously unspecified.

adap-org↗

arXiv1998

Generalized Hamiltonian Formalism of (2+1)-Dimensional Non-Linear $σ$-Model in Polynomial Formulation

We investigate the canonical structure of the (2+1)-dimensional non-linear $σ$ model in a $polynomial$ formulation. A current density defined in the non-linear $σ$ model is a vector field which satisfies a $formal$ flatness (or pure gauge) condition. It is the polynomial formulation in which the vector field is regarded as a dynamical variable on which the flatness condition is imposed as a constraint condition by introducing a Lagrange multiplier field. The model so formulated has gauge symmetry under a transformation of the Lagrange multiplier field. We construct the generalized Hamiltonian formalism of the model explicitly by using the Dirac method for constrained systems. We derive three types of the pre-gauge-fixing Hamiltonian systems: In the first system, the current algebra is realized as the fundamental Dirac Brackets. The second one manifests the similar canonical structure as the Chern-Simons or BF theories. In the last one, there appears an interesting interaction as the dynamical variables are coupled to their conjugate momenta via the covariant derivative.

hep-th↗