arXiv subjects

Tetsuo Hatsuda

Publications and source records attributed to Tetsuo Hatsuda.

At least 109 records · Page 6Linked to original sources

arXiv2013

Time-dependent heavy-quark potential at finite temperature from gauge-gravity duality

The potential between a heavy quark and an anti-quark inside the quark-gluon plasma (QGP) is studied on the basis of the gauge/gravity duality. A real-time complex potential V_{Q\bar{Q}}(t,r) is derived from the Wilson loop with the Euclidean five-dimensional anti-de-Sitter black hole metric. To make the analytic continuation from the imaginary time to the real time, specific variational configurations of the string world sheet in the Euclidean metric are introduced. Rapid approach of V_{Q\bar{Q}}(t,r) to its stationary value is found at the time scale t=1/πT independent of the 't Hooft coupling λ. Also, the imaginary part of V_{Q\bar{Q}}(\infty,r) is found to be significant above the length scale r=1.72/πT independent of λ. Implications of these results to the properties of heavy quarkonia in QGP are briefly discussed.

hep-ph↗

arXiv2013

Antiferrosmectic ground state of two-component dipolar Fermi gases -- an analog of meson condensation in nuclear matter

We show that an antiferrosmectic-C phase has lower energy at high densities than the non-magnetized Fermi gas and ferronematic phases in an ultracold gas of fermionic atoms, or molecules, with large magnetic dipole moments. This phase, which is analogous to meson condensation in dense nuclear matter, is a one-dimensional periodic structure in which the fermions localize in layers with their pseudospin direction aligned parallel to the layers, and staggered layer by layer.

cond-mat.quant-gas↗

arXiv2013

Hadron-Quark Crossover and Massive Hybrid Stars

On the basis of the percolation picture from the hadronic phase with hyperons to the quark phase with strangeness, we construct a new equation of state (EOS) with the pressure interpolated as a function of the baryon density. The maximum mass of neutron stars can exceed $2M_{\odot}$ if the following two conditions are satisfied; (i) the crossover from the hadronic matter to the quark matter takes place at around three times the normal nuclear matter density, and (ii) the quark matter is strongly interacting in the crossover region and has stiff equation of state. This is in contrast to the conventional approach assuming the first order phase transition in which the EOS becomes always soft due to the presence of the quark matter at high density. Although the choice of the hadronic EOS does not affect the above conclusion on the maximum mass, the three-body force among nucleons and hyperons plays an essential role for the onset of the hyperon mixing and the cooling of neutron stars.

nucl-th↗

arXiv2012

Construction of energy-independent potentials above inelastic thresholds in quantum field theories

We construct energy independent but non-local potentials above inelastic thresholds, in terms of Nambu-Bethe-Salpeter wave functions defined in quantum field theories such as QCD. As an explicit example, we consider NN --> NN + n pi scattering processes for n=0,1,2,.... We show an existence of energy-independent coupled channel potentials with a non-relativistic approximation, where momenta of all particles are small compared with their own masses. In the case of two-body inelastic scatterings such as Lambda Lambda --> Lambda Lambda, N Xi, Sigma Sigma, on the other hand, we show that energy-independent potentials can be constructed without relying on non-relativistic approximations. We also propose a method to extract these potentials using time-dependence of general correlation functions.

hep-lat↗

arXiv2012

Hadron-Quark Crossover and Massive Hybrid Stars with Strangeness

Using the idea of a smooth crossover from the hadronic matter with hyperons to quark matter with strangeness, we show that the maximum mass of neutron stars with quark matter core can be larger than those without quark matter core. This is in contrast to the conventional softening of equation of state due to exotic components at high density. Essential conditions to reach our conclusion are (i) the crossover takes place at relatively low densities, around 3 times the normal nuclear density, and (ii) the quark matter is strongly interacting in the crossover region. By these, the pressure of the system can be greater than that of purely hadronic matter in the crossover region and leads to the maximum mass greater than 2 solar mass. This conclusion is insensitive to the different choice of the hadronic equation of state with hyperons. Several implications of this result to the nuclear incompressibility, the hyperon mixing, and the neutrino cooling are also remarked.

nucl-th↗

arXiv2012

Phase structure of finite density QCD with a histogram method

We study the phase structure of QCD in the $T-μ$ plane using a histogram method and the reweighting technique by performing phase quenched simulations of two-flavor QCD with RG-improved gauge action and O($a$) improved Wilson quark action. Taking the effects of the complex phase of the quark determinant using the cumulant expansion method, we calculate the probability distribution function of plaquette and phase-quenched determinant as a function of $T$ and $μ$. We discuss the order of the QCD phase transition consulting the shape of the probability distribution function.

hep-lat↗

arXiv2012

Quantum Monte Carlo simulation of three-dimensional Bose-Fermi mixtures

Exploratory simulations of Bose-Fermi mixtures on the three-dimensional optical lattice at finite temperature are performed by adopting the lattice quantum chromodynamics technique. We analyze the bosonic superfluid transition and its dependence on the strength of the boson-fermion coupling. The particle densities and the pair occupancies are also studied to understand the effect of the boson-fermion coupling to the microscopic properties of the system. Effect of the induced fermion-fermion interaction by the boson density fluctuation is clearly seen.

cond-mat.quant-gas↗

arXiv2012

Ferromagnetic neutron stars: axial anomaly, dense neutron matter, and pionic wall

We show that a chiral nonlinear sigma model coupled to degenerate neutrons exhibits a ferromagnetic phase at high density. The magnetization is due to the axial anomaly acting on the parallel layers of neutral pion domain walls spontaneously formed at high density. The emergent magnetic field would reach the QCD scale ~ 10^19 [G], which suggests that the quantum anomaly can be a microscopic origin of the magnetars (highly magnetized neutron stars).

hep-ph↗

arXiv2012

Lattice QCD approach to Nuclear Physics

We review recent progress of the HAL QCD method which was recently proposed to investigate hadron interactions in lattice QCD. The strategy to extract the energy-independent non-local potential in lattice QCD is explained in detail. The method is applied to study nucleon-nucleon, nucleon-hyperon, hyperon-hyperon and meson-baryon interactions. Several extensions of the method are also discussed.

hep-lat↗

arXiv2012

Role of Vector Interaction and Axial Anomaly in the PNJL Modeling of the QCD Phase Diagram

Effects of a flavor singlet vector interaction in the Polyakov - Nambu - Jona-Lasinio (PNJL) model are studied in combination with the axial U(1) breaking Kobayashi - Maskawa - 't Hooft interaction. Using a consistent cutoff scheme we investigate the QCD phase diagram and its dependence on the vector coupling strength $g_v$. We find that the first order chiral phase transition at moderate baryon chemical potentials and its critical point, a generic feature of most NJL-type models without vector coupling, disappear for sufficiently large values of $g_v$ that are consistent with lattice QCD results at imaginary chemical potential. The influence of non-zero $g_v$ on the curvature of the crossover boundary in the $T-μ$ plane close to $μ= 0$ is also examined.

hep-ph↗

arXiv2012

Complex Heavy-Quark Potential at Finite Temperature from Lattice QCD

We calculate for the first time the complex potential between a heavy quark and antiquark at finite temperature across the deconfinement transition in lattice QCD. The real and imaginary part of the potential at each separation distance $r$ is obtained from the spectral function of the thermal Wilson loop. We confirm the existence of an imaginary part above the critical temperature $T_C$, which grows as a function of $r$ and underscores the importance of collisions with the gluonic environment for the melting of heavy quarkonia in the quark-gluon-plasma.

hep-lat↗

arXiv2012

Hadron-Hadron Interactions from Imaginary-time Nambu-Bethe-Salpeter Wave Function on the Lattice

Imaginary-time Nambu-Bethe-Salpeter (NBS) wave function is introduced to extend our previous approach for hadron-hadron interactions on the lattice. Scattering states of hadrons with different energies encoded in the NBS wave-function are utilized to extract non-local hadron-hadron potential. "The ground state saturation", which is commonly used in lattice QCD but is hard to be achieved for multi-baryons, is not required. We demonstrate that the present method works efficiently for the nucleon-nucleon interaction (the potential and the phase shift) in the 1S_0 channel.

hep-lat↗

arXiv2012

Numerical study of QCD phase diagram at high temperature and density by a histogram method

We study the QCD phase structure at high temperature and density adopting a histogram method. Because the quark determinant is complex at finite density, the Monte-Carlo method cannot be applied directly. We use a reweighting method and try to solve the problems which arise in the reweighting method, i.e. the sign problem and the overlap problem. We discuss the chemical potential dependence of the probability distribution function in the heavy quark mass region and examine the applicability of the approach in the light quark region.

hep-lat↗

arXiv2012

Exploring Three-Nucleon Forces in Lattice QCD

Three-nucleon forces (3NF) are investigated from two-flavor lattice QCD simulations. We utilize the Nambu-Bethe-Salpeter (NBS) wave function to determine two-nucleon forces (2NF) and 3NF in the same framework. As a first exploratory study, we extract 3NF in which three nucleons are aligned linearly with an equal spacing. This is the simplest geometrical configuration which reduces the huge computational cost of calculating the NBS wave function. Quantum numbers of the three-nucleon system are chosen to be (I, J^P)=(1/2,1/2^+) (the triton channel). Lattice QCD simulations are performed using N_f=2 dynamical clover fermion configurations at the lattice spacing of a = 0.156 fm on a 16^3 x 32 lattice with a large quark mass corresponding to m_π= 1.13 GeV. We find repulsive 3NF at short distance in the triton channel. Several sources of systematic errors are also discussed.

hep-lat↗

arXiv2012

Stau-catalyzed d-t Nuclear Fusion

The gravitino of mass 10-100 GeV is a well motivated scenario in supergravity. If the stau is the next lightest supersymmetry particle, its life-time becomes order of $10^{6-8}$ sec. If it is the case the stau makes a big impact on the nuclear fusion, since it is a charged particle. In this paper we perform a detailed calculation of a stau-catalyzed d-t fusion. We find that if certain technical conditions are satisfied, it is not hopeless to use the nuclear fusion as a source of energy.

hep-ph↗

arXiv2012

Two-Baryon Potentials and H-Dibaryon from 3-flavor Lattice QCD Simulations

Baryon-baryon potentials are obtained from 3-flavor QCD simulations with the lattice volume L ~ 4 fm, the lattice spacing a ~ 0.12 fm, and the pseudo-scalar-meson mass M_ps =469 - 1171 MeV. The NN scattering phase shift and the mass of H-dibaryon in the flavor SU(3) limit are extracted from the resultant potentials by solving the Schrodinger equation. The NN phase shift in the SU(3) limit is shown to have qualitatively similar behavior as the experimental data. A bound H-dibaryon in the SU(3) limit is found to exist in the flavor-singlet J^P=0^+ channel with the binding energy of about 26 MeV for the lightest quark mass M_ps = 469 MeV. Effect of flavor SU(3) symmetry breaking on the H-dibaryon is estimated by solving the coupled-channel Schrodinger equation for Lambda Lambda - N Xi - Sigma Sigma with the physical baryon masses and the potential matrix obtained in the SU(3) limit: a resonant H-dibaryon is found between Lambda Lambda and N Xi thresholds in this treatment.

hep-lat↗

arXiv2011

Low-mass dilepton production through transport process in quark-gluon plasma

We attempt to understand the low-mass dielectron enhancement observed by PHENIX Collaboration at Relativistic Heavy Ion Collider (RHIC) by transport peak in the spectral function. On the basis of the second-order formalism of relativistic dissipative hydrodynamics, we parameterize the spectral function in low-frequency and long-wavelength region by two transport coefficients, electric diffusion coefficient $D$ and relaxation time $τ_{\rm J}$, and compared our theoretical dielectron spectra with the experimental data. We study spectrum of dielectrons produced in relativistic heavy ion collisions by using the profile of matter evolution under full (3+1)-dimensional hydrodynamics. We find that the experimental data require the diffusion coefficient to be $D\geq 2/T$, with $T$ being temperature. Our analysis shows that dielectrons emitted through transport process mainly come from high-temperature QGP phase.

nucl-th↗

arXiv2011

Can transport peak explain the low-mass enhancement of dileptons at RHIC?

We propose a novel relation between the low-mass enhancement of dielectrons observed at PHENIX and transport coefficients of QGP such as the charge diffusion constant $D$ and the relaxation time $τ_{\rm J}$. We parameterize the transport peak in the spectral function using the second-order relativistic dissipative hydrodynamics by Israel and Stewart. Combining the spectral function and the full (3+1)-dimensional hydrodynamical evolution with the lattice EoS, theoretical dielectron spectra and the experimental data are compared. Detailed analysis suggests that the low-mass dilepton enhancement originates mainly from the high-temperature QGP phase where there is a large electric charge fluctuation as obtained from lattice QCD simulations.

nucl-th↗