arXiv subjects

Akira Hasegawa

Publications and source records attributed to Akira Hasegawa.

16 recordsLinked to original sources

arXiv2025

A Case Study on Model Checking and Runtime Verification for Awkernel

In operating system development, concurrency poses significant challenges. It is difficult for humans to manually review concurrent behaviors or to write test cases covering all possible executions, often resulting in critical bugs. Preemption in schedulers serves as a typical example. This paper proposes a development method for concurrent software, such as schedulers. Our method incorporates model checking as an aid for tracing code, simplifying the analysis of concurrent behavior; we refer to this as model checking-assisted code review. While this approach aids in tracing behaviors, the accuracy of the results is limited because of the semantics gap between the modeling language and the programming language. Therefore, we also introduce runtime verification to address this limitation in model checking-assisted code review. We applied our approach to a real-world operating system, Awkernel, as a case study. This new operating system, currently under development for autonomous driving, is designed for preemptive task execution using asynchronous functions in Rust. After implementing our method, we identified several bugs that are difficult to detect through manual reviews or simple tests.

cs.SE↗

arXiv2020

Thermal Conductivity of CaSiO$_3$ Perovskite at Lower Mantle Conditions

Thermal conductivity ($κ$) of mantle minerals is a fundamental property in geodynamic modeling. It controls the style of mantle convection and the time scale of the mantle and core cooling. Cubic CaSiO$_3$ perovskite (CaPv) is the third most abundant mineral in the lower mantle (LM) (7 vol%). However, despite its importance, no theoretical or experimental estimate of CaPv's $κ$ exists. Theoretical investigations of its properties are challenging because of its strong anharmonicity. Experimental measurements at relevant high pressures and temperatures are equally challenging. Here we present $ab$ $initio$ results for CaPv's $κ$ obtained using an established phonon quasiparticle approach that can address its strong anharmonicity. We also offer experimental measurements of $κ$. Predictions and measurements are in good agreement and reveal a surprisingly large $κ$ for cubic CaPv. Despite its relatively low abundance, CaPv's $κ$ might increase the lower mantle $κ$ by approximately 10%, if accounted for. $κ$ of mantle regions enriched in crust material will be more strongly impacted.

cond-mat.mtrl-sci↗

arXiv2004

Electronic Properties of Transuranium Compounds with HoCoGa$_5$-Type Tetragonal Crystal Structure

By using a relativistic linear augmented-plane-wave method with the one-electron potential in the local-density approximation, we investigate energy band structures and the Fermi surfaces of transuranium compounds NpTGa$_5$, PuTGa$_5$, and AmCoGa$_5$ with transition metal atoms T. It is found in common that the energy bands in the vicinity of the Fermi level are mainly due to the large hybridization between $5f$ and Ga $4p$ electrons. For PuTGa$_5$, we observe several cylindrical sheets of Fermi surfaces with large volume for T=Co, Rh, and Ir. The de Haas-van Alphen (dHvA) frequencies are theoretically estimated for PuCoGa$_5$. It is also found that the Fermi surfaces of NpFeGa$_5$, NpCoGa$_5$, and NpNiGa$_5$ are similar to those of UCoGa$_5$, UNiGa$_5$, and PuCoGa$_5$, respectively, except for small details. For AmCoGa$_5$, the Fermi surfaces are found to consist of large cylindrical electron sheets and small closed hole sheets, similar to PuCoGa$_5$. The similarity is basically understood by the change of electron numbers inside the Fermi surfaces on the basis of a rigid-band picture. We discuss our theoretical Fermi surfaces with the dHvA experimental results on NpTGa$_5$.

cond-mat.str-el↗

arXiv2004

Effective meson masses, effective meson-nucleon couplings and neutron star radii

Using the generalized mean field theory, we have studied the relation among the effective meson masses, the effective meson-nucleon couplings and the equation of state (EOS) in asymmetric nuclear matter. If the effective omega-meson mass becomes smaller at high density, the EOS becomes stiffer. However, if we require that the omega-meson mean field is proportional to the baryon density, the effective omega-nucleon coupling automatically becomes smaller at the same time as the effective omega-meson mass becomes smaller. Consequently, the EOS becomes softer. A similar relation is found for the effective rho-meson mass and the effective rho-nucleon coupling. We have also studied the relation among the effective meson masses, the effective meson-nucleon couplings and a radius R of a neutron star. The R depends somewhat on the value of the effective omega-meson mass and the effective omega-nucleon coupling.

nucl-th↗

arXiv2002

Electronic Structure and Fermiology of PuCoGa$_5$

By using a relativistic linear augmented-plane-wave method, we clarify energy band structures and Fermi surfaces of recently discovered plutonium-based superconductor PuCoGa$_5$. We find several cylindrical sheets of Fermi surfaces with large volume, very similar to CeMIn$_5$ (M=Ir and Co) isostructural with PuCoGa$_5$, in spite of different $f$-electron numbers between Ce$^{3+}$ and Pu$^{3+}$ ions. The similarity is understood by a concept of electron-hole conversion in a tight binding model constructed based on the $j$-$j$ coupling scheme. Based on the present results, we provide a possible scenario to explain why a transition temperature is so high as 18.5K in PuCoGa$_5$.

cond-mat.str-el↗

arXiv2001

Effective hadron masses and couplings in nuclear matter and incompressibility

The role of effective hadron masses and effective couplings in nuclear matter is studied using a generalized effective Lagrangian for sigma-omega model. A simple relation among the effective masses, the effective couplings and the incompressibility K is derived. Using the relation, it is found that the effective repulsive and the effective attractive forces are almost canceled to each other at the normal density. Inversely, if this cancellation is almost complete, K should be 250-350MeV.

nucl-th↗

arXiv2000

The effective ω-meson mass with a vector field self-interaction

We calculate the effective mass m_ω^* of the ω-meson in nuclear medium by the σ-ωmodel with a vector field self-interaction (VFSI). We found that the direct and the indirect effects of the VFSI almost cancel each other and the result is changed only slightly at the normal density. The VFSI makes m^*_ωsmaller at lower density and makes m_ω^* larger at higher density. However, both effects are not large.

nucl-th↗

arXiv2000

A relation among the effective nucleon mass, the incompressibility and the effective $σ$-meson mass in nuclear matter

A relation among the effective nucleon mass $M^*$, the incompressibility $K$ and the effective $σ$-meson mass $m_{\rm s}^*$ in nuclear matter is studied by using the relativistic nuclear model. We found that there is a strong correlation between $M^*$ and $m_{\rm s}^*$, while there is only a weak correlation between $K$ and $m_{\rm s}^*$. At the normal density, $m_{\rm s}^*$ is smaller than the one at zero density, if $M^*$ is smaller than 0.8 times of the nucleon mass at zero density. It is also found that the off-shell effective mass $μ_{\rm s}^*$ is related directly to $K$ and $M^*$ at the normal density.

nucl-th↗

arXiv2000

Femtosecond soliton amplification in nonlinear dispersive traps and soliton dispersion management

The nonlinear pulse propagation in an optical fibers with varying parameters is investigated. The capture of moving in the frequency domain femtosecond colored soliton by a dispersive trap formed in an amplifying fiber makes it possible to accumulate an additional energy and to reduce significantly the soliton pulse duration. Nonlinear dynamics of the chirped soliton pulses in the dispersion managed systems is also investigated. The methodology developed does provide a systematic way to generate infinite ``ocean'' of the chirped soliton solutions of the nonlinear Schrödinger equation (NSE) with varying coefficients.

physics.optics↗

arXiv1999

Nonlinear effects in Schwinger-Dyson Equation

We study nonlinear effects in the QED ladder Schwinger-Dyson(SD) equation. Without further approximations, we show that all nonlinear effects in the ladder SD equation can be included in the effective couplings and how a linear approximation works well. The analyses is generalized in the case of the improved ladder calculation with the Higashijima-Miransky approximation.

hep-ph↗

arXiv1998

Non-perturbative renormalization group equations and approximate discrete gamma_5-symmetry in quantum hadrodynamics

The quantum hadrodynamics are studied by using non-perturbative renormalization group equations. Approximate discrete gamma_5-symmetry is studied. It is shown that the contributions of one-loop diagrams are important for effective potential. A relation between the local-potential approximation and the usual Hartree approximation is discussed. The local-potential approximation includes contribution of the Fock term to nucleon self-energy, contribution in the usual random phase approximation to meson self-energy and vertex corrections in part as well as the Hartree contribution to the effective potential. Approximate discrete gamma_5-symmetry is studied phenomenologically in the Hartree approximation. This approximate symmetry may exist in nuclear matter.

nucl-th↗

arXiv1997

Meson-nucleon vertex corrections to the vacuum polarization in the cutoff field theory and tensor coupling

At zero-density, meson-nucleon vertex corrections to vacuum polarization are studied in the $σ-ω$ model with the cutoff. It is shown that the properties of the vertex corrections to vacuum polarization are somewhat different from those described by the ordinary renormalization procedures when the cutoff is small (< 5 GeV). The low-energy effective Lagrangian is constructed in the framework of the renormalization group method. The weak tensor and derivative couplings of meson-nucleon interactions may be needed in the low-energy effective theory of mesons and nucleons.

nucl-th↗

arXiv1997

Vacuum Effects and Compressional Properties of Nuclear Matter in Cutoff Field Theory

Including the vacuum effects, the compressional properties of nuclear matter are studied in the cutoff field theory. Under the Hartree approximation, the low-energy effective Lagrangian is derived in the framework of the renormalization group methods. The coefficients are determined in a way where the physical results hardly depend on the value of the cutoff which is conveniently introduced into the theory. It is shown that, to reproduce the empirical data of the nucleus incompressibility, the compressibility of the nuclear matter is favorable to be 250$\sim$350MeV.

nucl-th↗

arXiv1996

Quark condensate in nuclear matter based on Nuclear Schwinger-Dyson formalism

The effects of higher order corrections of ring diagrams for the quark condensate are studied by using the bare vertex Nuclear Schwinger Dyson formalism based on $σ$-$ω$ model. At the high density the quark condensate is reduced by the higher order contribution of ring diagrams more than the mean field theory or the Hartree-Fock .

nucl-th↗

arXiv1995

Nucleon mean free path in nuclear matter based on nuclear Schwinger-Dyson formalism

A mean free path of nucleon moving through nuclear matter with kinetic energy of more than 100MeV is formulated based on the bare vertex nuclear Schwinger-Dyson (BNSD) method in the Walecka model. The self-energy which is derived from the higher order diagrams more than the forth order includes the Feynman part of propagator of energetic nucleon and grows up rapidly as an increase of kinetic energy. To avoid too large growth of these diagrams, meson propagators are modified by introducing some form factors to take account of a internal structure of hadron. It is confirmed that the mean free path calculated by the BNSD method agrees good with experimental data if a reasonable form factor is chosen, i.e., a dipole (quadrupole) type of form factor with a cut-off parameter about 750 MeV $\sim$ 1000 MeV (1200 MeV $\sim$ 1500 MeV).

nucl-th↗

arXiv1995

Bulk properties of nuclear matter in the relativistic Hartree approximation with cut-off regularization

A method of cut-off regularization is proposed to evaluate vacuum corrections in nuclear matter in the framework of the Hartree approximation. Bulk properties of nuclear matter calculated by this method are a good agreement with results analyzed by empirical values. The vacuum effect is quantitatively evaluated through a cut-off parameter and its role for saturation property and compressional properties is clarified.

nucl-th↗