We study the nature of the finite temperature phase transition for three-flavor QCD. In particular we investigate the location of the critical endpoint along the three flavor symmetric line in the light quark mass region of the Columbia plot. In the
study, the Iwasaki gauge action and the nonperturvatively O($a$) improved Wilson-Clover fermion action are employed. We newly generate data at $N_{rm t}=12$ and set an upper bound of the critical pseudoscalar meson mass in the continuum limit $m_{rm PS,E}lesssim 110$MeV.
We study the two-dimensional complex $phi^{4}$ theory at finite chemical potential using the tensor renormalization group. This model exhibits the Silver Blaze phenomenon in which bulk observables are independent of the chemical potential below the c
ritical point. Since it is expected to be a direct outcome of an imaginary part of the action, an approach free from the sign problem is needed. We study this model systematically changing the chemical potential in order to check the applicability of the tensor renormalization group to the model in which scalar fields are discretized by the Gaussian quadrature. The Silver Blaze phenomenon is successfully confirmed on the extremely large volume $V=1024^2$ and the results are also ensured by another tensor network representation with a character expansion.
We investigate the critical endpoints of the finite temperature phase transition of QCD at zero chemical potential. We employ the renormalization-group improved Iwasaki gauge action and non-perturbatively O(a)-improved Wilson-clover fermion action. T
he critical endpoints are determined by using the intersection point of kurtosis, employing the multi-parameter, multi-ensemble reweighting method. We present results for the critical endline at $N_{rm T}$ = 6 and the continuum extrapolation for the critical endpoint of the SU(3)-flavor symmetric point.
We make a detailed analysis of the spontaneous $Z_{2}$-symmetry breaking in the two dimensional real $phi^{4}$ theory with the tensor renormalization group approach, which allows us to take the thermodynamic limit easily and determine the physical ob
servables without statistical uncertainties. We determine the critical coupling in the continuum limit employing the tensor network formulation for scalar field theories proposed in our previous paper. We obtain $left[ lambda / mu_{mathrm{c}}^{2} right]_{mathrm{cont.}} = 10.913(56)$ with the quartic coupling $lambda$ and the renormalized critical mass $mu_{mathrm{c}}$. The result is compared with previous results obtained by different approaches.
Supersymmetric models with spontaneous supersymmetry breaking suffer from the notorious sign problem in stochastic approaches. By contrast, the tensor network approaches do not have such a problem since they are based on deterministic procedures. In
this work, we present a tensor network formulation of the two-dimensional lattice $mathcal{N}=1$ Wess-Zumino model while showing that numerical results agree with the exact solutions for the free case.
We develop calculational method for fermionic Green functions in the framework of Grassmann higher-order tensor renormalization group. The validity of the method is tested by applying it to three-dimensional free Wilson fermion system. We compare the
numerical results for chiral condensate and two-point correlation functions with the exact ones obtained by analytical methods.
Filtering algorithms for two degenerate quark flavours have advanced to the point that, in 2+1 flavour simulations, the cost of the strange quark is significant compared with the light quarks. This makes efficient filtering algorithms for single flav
our actions highly desirable, in particular when considering 1+1+1 flavour simulations for QED+QCD. Here we discuss methods for filtering the RHMC algorithm that are implemented within BQCD, an open-source Fortran program for Hybrid Monte Carlo simulations.
We present an update of BQCD, our Hybrid Monte Carlo program for simulating lattice QCD. BQCD is one of the main production codes of the QCDSF collaboration and is used by CSSM and in some Japanese finite temperature and finite density projects. Sinc
e the first publication of the code at Lattice 2010 the program has been extended in various ways. New features of the code include: dynamical QED, action modification in order to compute matrix elements by using Feynman-Hellman theory, more trace measurements, a more flexible integration scheme, polynomial filtering, term-splitting for RHMC, and a portable implementation of performance critical parts employing SIMD.
We study the critical point for finite temperature Nf=3 QCD using several temporal lattice sizes up to 10. In the study, the Iwasaki gauge action and non-perturbatively O(a) improved Wilson fermions are employed. We estimate the critical temperature
and the upper bound of the critical pseudo-scalar meson mass.
We study the finite temperature phase structure for three-flavor QCD with a focus on locating the critical point which separates crossover and first order phase transition region in the chiral regime of the Columbia plot. In this study, we employ the
Iwasaki gauge action and the non-perturvatively O($a$) improved Wilson-Clover fermion action. We discuss the finite size scaling analysis including the mixing of magnetization-like and energy-like observables. We carry out the continuum extrapolation of the critical point using newly generated data at $N_{rm t}=8$, $10$ and estimate the upper bound of the critical pseudo-scalar meson mass $m_{rm PS,E} lesssim 170 {rm MeV}$ and the critical temperature $T_{rm E}=134(3){rm MeV}$. Our estimate of the upper bound is derived from the existence of the critical point as an edge of the 1st order phase transition while that of the staggered-type fermions is based on its absence.
