arXiv subjects

Toshitaka Tatsumi

Publications and source records attributed to Toshitaka Tatsumi.

At least 73 records · Page 4Linked to original sources

arXiv2008

Multi-antikaonic nuclei in the relativistic mean-field theory

Properties of multi-antikaonic nuclei (MKN), where several numbers of $K^-$ mesons are bound, are studied in the relativistic mean-field model, combined with chiral dynamics for kaonic part of the thermodynamic potential. The density profiles for nucleons and $K^-$ mesons, the single particle energy of the $K^-$ mesons, and binding energy of the MKN are obtained. The effects of the $\bar K-\bar K$ interactions on these quantities are discussed in comparison with other meson ($σ$, $ω$, and $ρ$)-exchange models. It is shown that the $\bar K-\bar K$ interactions originate from two contributions: One is the contact interaction between antikaons inherent in chiral symmetry, and the other is the one generated through coupling between the $K^-$ and meson mean fields. Both effects of the $\bar K-\bar K$ repulsive interactions become large on the ground state properties of the MKN as the number of the embedded $K^-$ mesons increases. A relation between the multi-antikaonic nuclei and kaon condensation in infinite and uniform matter is mentioned.

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arXiv2007

Hyperon-Quark Mixed Phase in Compact Stars

We investigate the properties of the hadron-quark mixed phase in compact stars using a Brueckner-Hartree-Fock framework for hadronic matter and the MIT bag model for quark matter. We find that the equation of state of the mixed phase is similar to that given by the Maxwell construction. The composition of the mixed phase, however, is very different from that of the Maxwell construction; in particular, hyperons are completely suppressed.

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arXiv2007

Hyperon-Quark Mixed Phase in Dense Matter

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arXiv2007

Non-Uniform Structure of Matter and the Equation of State

We investigate the non-uniform structures and the equation of state (EOS) of nuclear matter in the context of the first-order phase transitions (FOPT) such as liquid-gas phase transition, kaon condensation, and hadron-quark phase transition. During FOPT the mixed phases appear, where matter exhibits non-uniform structures called ``Pasta'' structures due to the balance of the Coulomb repulsion and the surface tension between two phases. We treat these effects self-consistently, properly taking into account of the Poisson equation and the Gibbs conditions. Consequently, they make the EOS of the mixed phase closer to that of Maxwell construction due to the Debye screening. This is a general feature of the mixed phase consisting of many species of charged particles.

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arXiv2007

Hadron-quark mixed phase in hyperon stars

We analyze the different possibilities for the hadron-quark phase transition occurring in beta-stable matter including hyperons in neutron stars. We use a Brueckner-Hartree-Fock approach including hyperons for the hadronic equation of state and a generalized MIT bag model for the quark part. We then point out in detail the differences between Maxwell and Gibbs phase transition constructions including the effects of surface tension and electromagnetic screening. We find only a small influence on the maximum neutron star mass, whereas the radius of the star and in particular its internal structure are more affected.

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arXiv2007

Quark deconfinement transition in hyperonic matter

We discuss the properties of the hadron-quark mixed phase in compact stars using a realistic equation of state of hyperonic matter and the MIT bag model. We find that the equation of state of the mixed phase is similar to that given by the Maxwell construction, but that the mixed phase becomes mechanically unstable if the surface tension of the interface between the two pure phases is strong enough. The composition of the mixed phase is very different from that of the Maxwell construction; in particular, hyperons are completely suppressed.

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arXiv2006

Pasta structures in compact stars

We review our recent works about ``pasta'' structures following the first-order phase transition in dense matter, which correspond to the structured mixed phases with geometrical symmetries. Three kinds of phase transitions at different density ranges are examined as the stages of pasta structures: liquid-gas phase transition at subnuclear density, kaon condensation and hadron-quark phase transition at high density. Charge density as well as particle density is non-uniform there. A consistent treatment of the Coulomb potential and the particle densities is presented and a peculiar role of the Coulomb potential is elucidated: the physical picture of the Maxwell construction will be effectively recovered. It largely influences the density regime of pasta structures by the charge screening effect.

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arXiv2006

Microscopic origin of the magnetic field in compact stars

A magnetic aspect of quark matter is studied by the Fermi liquid theory. The magnetic susceptibility is derived with the one-gluon-exchange interaction, and the critical Fermi momentum for spontaneous spin polarization is found to be 1.4fm^{-1}. A scenario about the origin of the magnetic field in compact stars is presented by using this result.

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arXiv2006

Charge screening effect on hadron-quark mixed phase in compact stars

We study the charge screening effect in the hadron-quark mixed phase. By including the charge screening effect, rearrangement of charged particles occurs and some part becomes locally charge-neutral. As a result the equation of state for the mixed phase becomes close to that given by the Maxwell construction, which means that the Maxwell construction would effectively gain the physical meaning again even in the system with two or more chemical potentials. We also discuss the interplay of the surface tension and the Coulomb interaction. Both effects would restrict the region of the mixed phase in the core of hybrid stars.

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arXiv2006

Finite-size effects on the hadron-quark mixed phase

We show that the hadron-quark mixed phase is restricted to narrow range of baryon chemical potential by the charge screening effect. Accordingly the mixed phase expected in hadron-quark hybrid stars should be narrow. Although the screening would not have large effect in bulk properties of the star such as mass or radius, it change the internal structure of the star very much, which may be tested by the cooling curve, glitch phenomena or gravitational waves.

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arXiv2005

Charge screening effect in the hadron-quark mixed phase

The Coulomb interaction effect and the surface effect are consistently taken into account in the hadron-quark mixed phase. These two finite-size effects greatly change the properties of the mixed phase and restrict its density region. In particular, the charge screening effect and the rearrangement of the charged particles are elucidated. Keeping the Gibbs conditions throughout the numerical procedure, we show the Maxwell construction effectively regain the physical meaning and the equation of state becomes similar to that given by the Maxwell construction.

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arXiv2005

Finite size effects on kaonic pasta structures

Non-uniform structures of mixed phases at the first-order phase transition to charged kaon condensation are studied using a density functional theory within the relativistic mean field model. Including electric field effects and applying the Gibbs conditions in a proper way, we numerically determine density profiles of nucleons, electrons and condensed kaons. Importance of charge screening effects is elucidated and thereby we show that the Maxwell construction is effectively justified. Surface effect is also studied to figure out its effect on the density profiles.

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arXiv2005

Kaon Condensation and Lambda-Nucleon Loop in the Relativistic Mean-Field Approach

The possibility of kaon condensation in high-density symmetric nuclear matter is investigated including both s- and p-wave kaon-baryon interactions within the relativistic mean-field (RMF) theory. Above a certain density, we have a collective ${\bar K}_s$ state carrying the same quantum numbers as the antikaon. The appearance of the ${\bar K}_s$ state is caused by the time component of the axial-vector interaction between kaons and baryons. It is shown that the system becomes unstable with respect to condensation of $K$-${\bar K}_s$ pairs. We consider how the effective baryon masses affect the kaon self-energy coming from the time component of the axial-vector interaction. Also, the role of the spatial component of the axial-vector interaction on the possible existence of the collective kaonic states is discussed in connection with $Λ$-mixing effects in the ground state of high-density matter. Implications of $K{\bar K}_s$ condensation for high-energy heavy-ion collisions are briefly mentioned.

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arXiv2005

Nuclear pasta structures and the charge screening effect

Non uniform structures of the nucleon matter at subnuclear densities are numerically studied by means of the density functional theory with relativistic mean-fields coupled with the electric field. A particular role of the charge screening effects is demonstrated.

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arXiv2005

Hadron-quark matter phase transition in neutron stars

A structured mixed phase consisting of quark and hadron phases is numerically studied with the Coulomb screening effect and the surface effect. We carefully introduced the Coulomb potential, so that a geometrical structure becomes mechanically unstable when the surface tension is large. Charge densities are largely rearranged by the screening effect, and thereby the equation of state shows the similar behavior to that given by the Maxwell construction. Therefore, although bulk calculations with the Gibbs conditions show that the mixed phase may exist in a wide density region, we can see it is restricted to a narrow density region by the surface effect and the Coulomb screening effect.

hep-ph↗

arXiv2005

Nuclear pasta structures in neutron stars and the charge screening

Non-uniform structures of the nucleon matter are expected at subnuclear densities and above the nuclear density: they are called nuclear pastas and kaon pastas, respectively. We numerically study these phases by means of the density functional theory with relativistic mean-fields and the electric field; the electric field is properly taken into account. Our results demonstrate a particular role of the charge screening effects on these non-uniform structures.

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arXiv2004

Numerical study of the hadron-quark mixed phase

The Coulomb screening effect and the finite-size effect such as surface tension are figured out in the hadron-quark deconfinement phase transition. We study the mixed phase of the quark droplets immersed in hadron matter. We see that the droplet phase is mechanically unstable if the surface tension is strong enough. Once the Coulomb potential is properly taken into account, we could effectively satisfy the condition for charge chemical equilibrium in the Maxwell construction. As a result, we suggest the Maxwell construction revives the physical meaning effectively.

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arXiv2004

Coulomb screening effect on the nuclear-pasta structure

Using the density functional theory (DFT) with the relativistic mean field (RMF) model, we study the non-uniform state of nuclear matter, ``nuclear pasta''. We self-consistently include the Coulomb interaction together with other interactions. It is found that the Coulomb screening effect is significant for each pasta structure but not for the bulk equation of state (EOS) of the nuclear pasta phase.

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