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Tetsuo Hatsuda

Publications and source records attributed to Tetsuo Hatsuda.

At least 73 records · Page 4Linked to original sources
arXiv2017

Dynamical Pattern Selection of Growing Cellular Mosaic in Fish Retina

A Markovian lattice model for photoreceptor cells is introduced to describe the growth of mosaic patterns on fish retina. The radial stripe pattern observed in wild-type zebrafish is shown to be selected naturally during the retina growth, against the geometrically equivalent, circular stripe pattern. The mechanism of such dynamical pattern selection is clarified on the basis of both numerical simulations and theoretical analyses, which find that the successive emergence of local defects plays a critical role in the realization of the wild-type pattern.

q-bio.CB↗
arXiv2017

Mirage in Temporal Correlation functions for Baryon-Baryon Interactions in Lattice QCD

Single state saturation of the temporal correlation function is a key condition to extract physical observables such as energies and matrix elements of hadrons from lattice QCD simulations. A method commonly employed to check the saturation is to seek for a plateau of the observables for large Euclidean time. Identifying the plateau in the cases having nearby states, however, is non-trivial and one may even be misled by a fake plateau. Such a situation takes place typically for the system with two or more baryons. In this study, we demonstrate explicitly the danger from a possible fake plateau in the temporal correlation functions mainly for two baryons ($ΞΞ$ and $NN$), and three and four baryons ($^3{\rm He}$ and $^4{\rm He})$ as well, employing (2+1)-flavor lattice QCD at $m_π=0.51$ GeV on four lattice volumes with $L=$ 2.9, 3.6, 4.3 and 5.8 fm. Caution is given for drawing conclusion on the bound $NN$, $3N$ and $4N$ systems only based on the temporal correlation functions.

hep-lat↗
arXiv2017

Are two nucleons bound in lattice QCD for heavy quark masses? -- Consistency check with Lüscher's finite volume formula --

On the basis of the Lüscher's finite volume formula, a simple test (consistency check or sanity check) is introduced and applied to inspect the recent claims of the existence of the nucleon-nucleon ($NN$) bound state(s) for heavy quark masses in lattice QCD. We show that the consistency between the scattering phase shifts at $k^2 > 0$ and/or $k^2 < 0$ obtained from the lattice data and the behavior of phase shifts from the effective range expansion (ERE) around $k^2=0$ exposes the validity of the original lattice data, otherwise such information is hidden in the energy shift $ΔE$ of the two nucleons on the lattice. We carry out this sanity check for all the lattice results in the literature claiming the existence of the $NN$ bound state(s) for heavy quark masses, and find that (i) some of the $NN$ data show clear inconsistency between the behavior of ERE at $k^2 > 0$ and that at $k^2 < 0$, (ii) some of the $NN$ data exhibit singular behavior of the low energy parameter (such as the divergent effective range) at $k^2<0$, (iii) some of the $NN$ data have the unphysical residue for the bound state pole in S-matrix, and (iv) the rest of the $NN$ data are inconsistent among themselves. Furthermore, we raise a caution of using the ERE in the case of the multiple bound states. Our finding, together with the fake plateau problem previously pointed out by the present authors, brings a serious doubt on the existence of the $NN$ bound states for pion masses heavier than 300 MeV in the previous studies.

hep-lat↗
arXiv2017

Correlations of Energy-Momentum Tensor via Gradient Flow in SU(3) Yang-Mills Theory at Finite Temperature

Euclidean two-point correlators of the energy-momentum tensor (EMT) in SU(3) gauge theory on the lattice are studied on the basis of the Yang-Mills gradient flow. The entropy density and the specific heat obtained from the two-point correlators are shown to be in good agreement with those from the one-point functions of EMT. These results constitute a first step toward the first principle simulations of the transport coefficients with the gradient flow.

hep-lat↗
arXiv2017

$pΞ^- $ Correlation in Relativistic Heavy Ion Collisions with Nucleon-Hyperon Interaction from Lattice QCD

On the basis of the $pΞ^-$ interaction extracted from (2+1)-flavor lattice QCD simulations at the physical point, the momentum correlation of $p$ and $Ξ^-$ produced in relativistic heavy ion collisions is evaluated. $C_{\rm SL}(Q)$ defined by a ratio of the momentum correlations between the systems with different source sizes is shown to be largely enhanced at low momentum due to the strong attraction between $p$ and $Ξ^-$ in the $I=J=0$ channel. Thus, measuring this ratio at RHIC and LHC and its comparison to the theoretical analysis will give a useful constraint on the $pΞ^-$ interaction.

nucl-th↗
arXiv2017

Structure of virtual photon polarization in ultrarelativistic heavy-ion collisions

Anisotropy in heavy-ion collisions leads to polarization of both direct and virtual photons, the latter detected via internal conversion to dileptons pairs. Thus measurement of photon polarization probes the anisotropy at all stages of collisions. In order to characterize the polarization of virtual photons, we derive here the general structure of the photon polarization operator, rho^(mu nu), in an anisotropic medium, in terms of the four spectral functions, two transverse and one longitudinal, as usual, plus a new spectral function that reflects anisotropy in asymmetric collisions; and derive the local production rate of dilepton pairs in terms of these four functions.

hep-ph↗
arXiv2017

Lambda-Nucleon and Sigma-Nucleon interactions from lattice QCD with physical masses

We present our recent study on baryon-baryon ($BB$) interactions from lattice QCD with almost physical quark masses corresponding to $(m_π,m_K)\approx(146,525)$ MeV and large volume $(La)^4=(96a)^4\approx$ (8.1 fm)$^4$. In order to perform a comprehensive study of $BB$ interactions based on lattice QCD calculation with almost physical masses and to make better use of such large scale computer resources, a large number of $BB$ interactions from $NN$ to $ΞΞ$ are calculated simultaneously. In this report, we focus on the strangeness $S=-1$ channels of the hyperon interactions by means of HAL QCD method. The coupled-channel HAL QCD method is briefly outlined. The snapshots of central and tensor potentials in $^1S_0$ and $^3S_1-^3D_1$ channels are presented for $ΛN$, $ΣN$ (both the isospin $I=1/2, 3/2$) and their coupled-channel systems.

hep-lat↗
arXiv2017

Baryon interactions from lattice QCD with physical masses -- Overview and $S = 0, -4$ sectors --

Nuclear forces and hyperon forces are studied by lattice QCD. Simulations are performed with (almost) physical quark masses, $m_π\simeq 146$ MeV and $m_K \simeq 525$ MeV, where $N_f=2+1$ nonperturbatively ${\cal O}(a)$-improved Wilson quark action with stout smearing and Iwasaki gauge action are employed on the lattice of $(96a)^4 \simeq (8.1\mbox{fm})^4$ with $a^{-1} \simeq 2.3$ GeV. In this report, we give the overview of the theoretical framework and present the numerical results for two-nucleon forces ($S=0$) and two-$Ξ$ forces ($S=-4$). Central forces are studied in $^1S_0$ channel, and central and tensor forces are obtained in $^3S_1$-$^3D_1$ coupled channel analysis.

hep-lat↗
arXiv2017

Baryon interactions from lattice QCD with physical masses -- $S=-2$ sector --

The strangeness $S=-2$ baryon-baryon interaction is investigated directly from the fundamental theory of the strong interaction, QCD. The HAL QCD method enables us to extract baryon interactions from the Nambu-Bethe-Salpeter wave functions without using any experimental information. We present our latest result on the $S = -2$ baryon interactions and discuss the H-dibaryon state using potentials which are calculated by using the (almost) physical point gauge configurations with large lattice volume of$(8.1{\rm{fm}})^4$ generated on the K-computer.

hep-lat↗
arXiv2017

Virtual photon polarization in ultrarelativistic heavy-ion collisions

The polarization of direct photons produced in an ultrarelativistic heavy-ion collision reflects the momentum anisotropy of the quark-gluon plasma created in the collision. This paper presents a general framework, based on the photon spectral functions in the plasma, for analyzing the angular distribution and thus the polarization of dileptons in terms of the plasma momentum anisotropies. The rates of dilepton production depend, in general, on four independent spectral functions, corresponding to two transverse polarizations, one longitudinal polarization, and -- in plasmas in which the momentum anisotropy is not invariant under parity in the local rest frame of the matter -- a new spectral function, $ρ_n$, related to the anisotropy direction in the collision. The momentum anisotropy appears in the difference of the two transverse spectral functions, as well as in $ρ_n$. As an illustration, we delineate the spectral functions for dilepton pairs produced in the lowest order Drell-Yan process of quark-antiquark annihilation to a virtual photon.

nucl-th↗
arXiv2017

Equation of State for SU(3) Gauge Theory via the Energy-Momentum Tensor under Gradient Flow

The energy density and the pressure of SU(3) gauge theory at finite temperature are studied by direct lattice measurements of the renormalized energy-momentum tensor obtained by the gradient flow. Numerical analyses are carried out with $β=6.287$--$7.500$ corresponding to the lattice spacing $a= 0.013$--$0.061\,\mathrm{fm}$. The spatial (temporal) sizes are chosen to be $N_s= 64$, $96$, $128$ ($N_τ=12$, $16$, $20$, $22$, $24$) with the aspect ratio, $5.33 \le N_s/N_τ \le 8$. Double extrapolation, $a\rightarrow 0$ (the continuum limit) followed by $t\rightarrow 0$ (the zero flow-time limit), is taken using the numerical data. Above the critical temperature, the thermodynamic quantities are obtained with a few percent precision including statistical and systematic errors. The results are in good agreement with previous high-precision data obtained by using the integral method.

hep-lat↗
arXiv2017

Baryon interactions from lattice QCD with physical masses ---S=-3 sector: XiSigma and XiLambda-XiSigma---

We present lattice QCD results of baryon-baryon potentials in S=-3 sector, i.e., ΞΣ(I=3/2) potentials and ΞΛ-ΞΣcoupled channel potentials (I=1/2) by using the 2+1 flavor gauge configurations with almost the physical quark masses generated on 96^4 lattice with 1/a \simeq 2.3 GeV and L = 96a \simeq 8.1 fm where m_pi \simeq 146 MeV and m_K \simeq 525 MeV. These potentials are obtained based on the time-dependent HAL QCD method with a non-relativistic approximation. Qualitative behaviors of the results are found to be consistent with those in the flavor SU(3) limit.

hep-lat↗
arXiv2016

Fate of the Tetraquark Candidate Zc(3900) from Lattice QCD

The possible exotic meson $Z_{c}(3900)$, found in $e^+ e^-$ reactions, is studied by the method of coupled-channel scattering in lattice QCD. The interaction among $πJ/ψ$, $ρη_{c}$ and $\bar{D}D^{*}$ channels is derived from (2+1)-flavor QCD simulations at $m_π=410$-$700$ MeV. The interaction is dominated by the off-diagonal $πJ/ψ$-$\bar{D}D^{*}$ and $ρη_{c}$-$\bar{D}D^{*}$ couplings, which indicates that the $Z_{c}(3900)$ is not a usual resonance but a threshold cusp. Semi-phenomenological analyses with the coupled-channel interaction are presented to confirm this conclusion.

hep-lat↗
arXiv2016

Probing Multi-Strange Dibaryon with Proton-Omega Correlation in High-energy Heavy Ion Collisions

Two-particle intensity correlation between the proton ($p$) and the Omega-baryon ($Ω$) in high-energy heavy ion collisions is studied to unravel the possible spin-2 $pΩ$ dibaryon recently suggested by lattice QCD simulations. The ratio of correlation functions between small and large collision systems, $C_{\rm SL}(Q)$, is proposed to be a new measure to extract the strong $pΩ$ interaction without much contamination from the Coulomb attraction. Relevance of this quantity to the experimental observables in heavy-ion collisions is also discussed.

hep-ph↗
arXiv2016

Multi-Regulator Functional Renormalization Group for Many-Fermion Systems

We propose a method of multi-regulator functional renormalization group (MR-FRG) which is a novel formulation of functional renormalization group with multiple infrared regulators. It is applied to a two-component fermionic system with an attractive contact interaction to study crossover phenomena between the Bardeen-Cooper-Schrieffer (BCS) phase and the Bose-Einstein condensation (BEC) phase. To control both the fermionic one-particle excitations and the bosonic collective excitations,IR regulators are introduced, one for the fermionic two-point function and another for the four-fermion vertex. It is shown that the Nozières-Schmitt-Rink (NSR) theory, which is successful to capture qualitative features of the BCS-BEC crossover, can be derived from MR-FRG. Some aspects of MR-FRG to go beyond the NSR theory are also discussed.

cond-mat.quant-gas↗
arXiv2016

Towards Lattice QCD Baryon Forces at the Physical Point: First Results

Lattice QCD calculations of baryon forces are performed for the first time with (almost) physical quark masses. $N_f = 2+1$ dynamical clover fermion gauge configurations are generated at the lattice spacing of $a \simeq 0.085$ fm on a $(96 a)^4 \simeq (8.2 {\rm fm})^4$ lattice with quark masses corresponding to $(m_π, m_K) \simeq (146, 525)$ MeV. Baryon forces are calculated using the time-dependent HAL QCD method. In this report, we study $ΞΞ$ and $NN$ systems both in $^1S_0$ and $^3S_1$-$^3D_1$ channels, and the results for the central and tensor forces as well as phase shifts in the $ΞΞ$ $(^1S_0)$ channel are presented.

hep-lat↗
arXiv2016

A Fast Algorithm for Lattice Hyperonic Potentials

We describe an efficient algorithm to compute a large number of baryon-baryon interactions from $NN$ to $ΞΞ$ by means of HAL QCD method, which lays the groundwork for the nearly physical point lattice QCD calculation with volume $(96a)^4\approx$($8.2$fm)$^4$. Preliminary results of $ΛN$ potential calculated with quark masses corresponding to ($m_π$,$m_{K}$)$\approx$(146,525)MeV are presented.

hep-lat↗