Toru T. Takahashi

Chaotic behavior in classical Yang-Mills dynamics

Institut fu¨r Theoretische Physik, Universita¨t Regensburg, D-93040 Regensburg, Germany(Dated: August 9, 2010)Understanding the underlying mechanisms causing rapid thermalization deduced for high-energyheavy ion collissons is still a challenge. To estimate the thermalization time, entropy growth forclassical Yang-Mills theories is studied, based on the determination of Lyapunov exponents. Distinctregimes for short, medium and long sampling times are characterized by different properties of theirspectrum of Lyapunov exponents. Clarifying the existence of these regimes and their implications forgauge-field dynamics is one of the results of this contribution. As a phenomenological application weconclude that for pure gauge theories with random initial conditions thermalization occures withinfew fm/c, an estimate which can be reduced by the inclusion of fermions, specific initial conditionsetc.I. INTRODUCTION

Detailed analysis of the tetraquark potential and flip-flop in SU(3) lattice QCD

We perform the detailed study of the tetraquark (4Q) potential V{sub 4Q} for various QQ-QQ systems in SU(3) lattice QCD with {beta}=6.0 and 16{sup 3}x32 at the quenched level. For about 200 different patterns of 4Q systems, V{sub 4Q} is extracted from the 4Q Wilson loop in 300 gauge configurations, with the smearing method to enhance the ground-state component. We calculate V{sub 4Q} for planar, twisted, asymmetric, and large-size 4Q configurations, respectively. Here, the calculation for large-size 4Q configurations is done by identifying 16{sup 2}x32 as the spatial size and 16 as the temporal one, and the long-distance confinement force is particularly analyzed in terms of the flux-tube picture. When QQ and QQ are well separated, V{sub 4Q} is found to be expressed as the sum of the one-gluon-exchange Coulomb term and multi-Y-type linear term based on the flux-tube picture. When the nearest quark and antiquark pair is spatially close, the system is described as a two-meson state. We observe a flux-tube recombination called a flip-flop between the connected 4Q state and the two-meson state around the level-crossing point. This leads to infrared screening of the long-range color forces between (anti)quarks belonging to different mesons, and results in the absencemorexa0» of the color van der Waals force between two mesons.«xa0less

Vector and axial-vector couplings of D and D⁎ mesons in 2+1 flavor lattice QCD

Abstract Using the axial-vector coupling and the electromagnetic form factors of the D and D⁎ mesons in 2 + 1 flavor lattice QCD, we compute the D⁎Dπ, DDρ and D ⁎ D ⁎ ρ coupling constants, which play an important role in describing the charm hadron interactions in terms of meson-exchange models. We also extract the charge radii of D and D⁎ mesons and determine the contributions of the light and charm quarks separately.

Search for the possible S = +1 pentaquark states in quenched lattice QCD

We study spin (1/2) hadronic states in quenched lattice QCD to search for a possible S=+1 pentaquark resonance. Simulations are carried out on 8{sup 3}x24, 10{sup 3}x24, 12{sup 3}x24, and 16{sup 3}x24 lattices at {beta}=5.7 at the quenched level with the standard plaquette gauge action and the Wilson quark action. We adopt a Dirichlet boundary condition in the time direction for the quark to circumvent the possible contaminations due to the (anti)periodic boundary condition for the quark field, which are peculiar to the pentaquark. By diagonalizing the 2x2 correlation matrices constructed from two independent operators with the quantum numbers (I,J)=(0,(1/2)), we successfully obtain the energies of the lowest state and the 2nd-lowest state in this channel. The analysis of the volume dependence of the energies and spectral weight factors indicates that a resonance state is likely to exist slightly above the nucleon-Kaon (NK) threshold in (I,J{sup P})=(0,(1/2){sup -}) channel.

Look inside charmed-strange baryons from lattice QCD

The electromagnetic form factors of the spin-3/2 Ω baryons, namely Ω, Ωc*, Ωcc* and Ωccc, are calculated in full QCD on 323×64 PACS-CS lattices with a pion mass of 156(9)xa0MeV. The electric charge radii and magnetic moments from the E0 and M1 multipole form factors are extracted. Results for the electric quadrupole form factors, E2, are also given. Quark sector contributions are computed individually for each observable and then combined to obtain the baryon properties. We find that the charm quark contributions are systematically smaller than the strange-quark contributions in the case of the charge radii and magnetic moments. E2 moments of the Ωcc* and Ωccc provide a statistically significant data to conclude that their electric charge distributions are deformed to an oblate shape. Properties of the spin-1/2 Ωc and Ωcc baryons are also computed and a thorough comparison is given. This complete study gives valuable hints about the heavy-quark dynamics in charmed hadrons.

Electromagnetic structure of charmed baryons in lattice QCD

A bstractAs a continuation of our recent work on the electromagnetic properties of the doubly charmed Ξcc baryon, we compute the charge radii and the magnetic moments of the singly charmed Σc, Ωc and the doubly charmed Ωcc baryons in 2+1 flavor Lattice QCD. In general, the charmed baryons are found to be compact as compared to the proton. The charm quark acts to decrease the size of the baryons to smaller values. We discuss the mechanism behind the dependence of the charge radii on the light valence- and sea-quark masses. The magnetic moments are found to be almost stable with respect to changing quark mass. We investigate the individual quark sector contributions to the charge radii and the magnetic moments. The magnetic moments of the singly charmed baryons are found to be dominantly determined by the light quark and the role of the charm quark is significantly enhanced for the doubly charmed baryons.

Electromagnetic properties of doubly charmed baryons in Lattice QCD

Abstract We compute the electromagnetic properties of Ξ c c baryons in ( 2 + 1 )-flavor Lattice QCD. By measuring the electric charge and magnetic form factors of Ξ c c baryons, we extract the magnetic moments, charge and magnetic radii as well as the Ξ c c Ξ c c ρ coupling constant, which provide important information to understand the size, shape and couplings of the doubly charmed baryons. We find that the two heavy charm quarks drive the charge radii and the magnetic moment of Ξ c c to smaller values as compared to those of, e.g., the proton.

Axial charges of octet baryons in two-flavor lattice QCD

Abstract We evaluate the strangeness-conserving NN , ΣΣ , ΞΞ , ΛΣ and the strangeness-changing ΛN , ΣN , ΛΞ , ΣΞ axial charges in lattice QCD with two flavors of dynamical quarks and extend our previous work on pseudoscalar-meson–octet-baryon coupling constants so as to include πΞΞ , KΛΞ and KΣΞ coupling constants. We find that the axial charges have rather weak quark mass dependence and the breaking in SU ( 3 ) -flavor symmetry is small at each quark-mass point we consider.

Axial charges of N(1535) and N(1650) in lattice QCD with two flavors of dynamical quarks

We show the first lattice QCD results on the axial charge

Meson-Meson and Meson-Baryon Interactions in Lattice QCD

{g}_{A}^{{N}^{*}{N}^{*}}