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Daisuke Kadoh

Publications and source records attributed to Daisuke Kadoh.

At least 37 records · Page 2Linked to original sources
arXiv2018

Irregular parameter dependence of numerical results in tensor renormalization group analysis

We study the parameter dependence of numerical results obtained by the tensor renormalization group. We often observe an irregular behavior as the parameters are varied with the method, which makes it difficult to perform the numerical derivatives in terms of the parameter. With the use of two-dimensional Ising model we explicitly show that the sharp cutoff used in the truncated singular value decomposition causes this unwanted behavior when the level crossing happens between singular values below and above the truncation order as the parameters are varied. We also test a smooth cutoff, instead of the sharp one, as a truncation scheme and discuss its effects.

hep-lat↗
arXiv2018

Tensor network study of two dimensional lattice $ϕ^{4}$ theory

The tensor renormalization group attracts great attention as a new numerical method that is free of the sign problem. In addition to this striking feature, it also has an attractive aspect as a coarse-graining of space-time; the computational cost scales logarithmically with the space-time volume. This fact allows us to aggressively approach the thermodynamic limit. While taking this advantage, we study the critical coupling of the two dimensional $ϕ^{4}$ theory on large and fine lattices. We present the numerical results along with the extrapolation procedure to the continuum limit and compare them with the previous ones by Monte Carlo simulations.

hep-lat↗
arXiv2018

Tensor network analysis of critical coupling in two dimensional $ϕ^{4}$ theory

We make a detailed analysis of the spontaneous $Z_{2}$-symmetry breaking in the two dimensional real $ϕ^{4}$ theory with the tensor renormalization group approach, which allows us to take the thermodynamic limit easily and determine the physical observables 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 $\left[ λ/ μ_{\mathrm{c}}^{2} \right]_{\mathrm{cont.}} = 10.913(56)$ with the quartic coupling $λ$ and the renormalized critical mass $μ_{\mathrm{c}}$. The result is compared with previous results obtained by different approaches.

hep-lat↗
arXiv2018

Tensor network formulation for two-dimensional lattice $\mathcal{N}=1$ Wess-Zumino model

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.

hep-lat↗
arXiv2018

Direct computational approach to lattice supersymmetric quantum mechanics

We propose a numerical method of estimating various physical quantities in lattice (supersymmetric) quantum mechanics. The method consists only of deterministic processes such as computing a product of transfer matrix, and has no statistical uncertainties. We use the numerical quadrature to define the transfer matrix as a finite dimensional matrix, and find that it effectively works by rescaling variable for sufficiently small lattice spacings. For a lattice supersymmetric quantum mechanics, the correlators can be estimated without statistical errors, and the effective masses coincide with the exact solution within very small errors less than 0.001%. The SUSY Ward identity is also precisely studied in compared with the Monte-Carlo method. Our method is not limited to a lattice SUSY quantum mechanics, but is also applicable to any other lattice models of quantum mechanics.

hep-lat↗
arXiv2018

O(a) Improvement of 2D N=(2,2) Lattice SYM Theory

We perform a tree-level O(a) improvement of two-dimensional N=(2,2) supersymmetric Yang-Mills theory on the lattice, motivated by the fast convergence in numerical simulations. The improvement respects an exact supersymmetry Q which is needed for obtaining the correct continuum limit without a parameter fine tuning. The improved lattice action is given within a milder locality condition in which the interactions are decaying as the exponential of the distance on the lattice. We also prove that the path-integral measure is invariant under the improved Q-transformation.

hep-lat↗
arXiv2017

Application of tensor network method to two dimensional lattice $\mathcal{N}=1$ Wess-Zumino model

We study a tensor network formulation of the two dimensional lattice $\mathcal{N}=1$ Wess-Zumino model with Wilson derivatives for both fermions and bosons. The tensor renormalization group allows us to compute the partition function without the sign problem, and basic ideas to obtain a tensor network for both fermion and scalar boson systems were already given in previous works. In addition to improving the methods, we have constructed a tensor network representation of the model including the Yukawa-type interaction of Majorana fermions and real scalar bosons. We present some numerical results.

hep-lat↗
arXiv2017

Precision test of the gauge/gravity duality in two-dimensional N=(8,8) SYM

The $ε- p$ is calculated from lattice simulations of two dimensional ${\cal N}=(8,8)$ $SU(N)$ SYM to test the gauge gravity duality. We employ the Sugino action with keeping two of sixteen supercharges exactly on the lattice. The thermodynamics of this gauge theory is described by the black 1-branes at low temperature. The internal energy density $ε$ and the pressure $p$ can be analytically estimated in the gravitational theory. The lattice results in $N=12$ show that $ε- p$ of the thermal SYM reproduces the prediction of the gravitational theory for the dimensionless temperature $T_{\rm eff}<0.4$. This clearly indicates that the duality is valid in this system.

hep-lat↗
arXiv2016

Recent progress in lattice supersymmetry: from lattice gauge theory to black holes

Supersymmetry (SUSY) is a fascinating topic in theoretical physics, because of its unique and counterintuitive properties. It is expected to emerge as new physics beyond the standard model, and it is also a building block for supergravity and superstring theory. A number of exact results obtained via SUSY theories provide insights into field theory. However, the dynamics of many SUSY theories are not yet fully understood, and numerical study of SUSY theories through lattice simulations is promising as regards furthering this understanding. In this paper, I overview the current status of lattice SUSY by discussing its development in chronological order, and by reviewing some simple models. In addition, I discuss the numerical verification of gauge/gravity duality, which is one of the recent significant developments in this field.

hep-lat↗
arXiv2015

General solution of cyclic Leibniz rule

We study the general solution of the cyclic Leibniz rule (CLR) which was recently proposed as a new approach to the lattice supersymmetry. Introducing some mathematical preliminaries related to the cyclic symmetry, we find the general solution of the 2-body CLR for the naive symmetric difference operator. The main theorems of this paper state that the general solution can be uniquely expressed as (A) a linear combination of the two fundamental solutions with cyclic invariant coefficients, and (B) a linear combination of the minimal solutions with complex coefficients. Moreover, an extension to the general difference operators is also discussed.

hep-lat↗
arXiv2015

Gauge/gravity duality and lattice simulations of one dimensional SYM with sixteen supercharges

We study the gauge/gravity duality for supersymmetric SU(N) Yang-Mills theory in 1+0 dimension with sixteen supercharges using lattice simulations. The conjectured duality states that the gravity side is described by N D0-branes in type IIA superstring at large N, and the thermal gauge theory reproduces the black hole thermodynamics at low temperature. In this paper, we explain the Sugino lattice action used in the simulations in detail, and examine the supersymmetric Ward-Takahashi identity to confirm the restoration of supersymmetry in the continuum limit. We also estimate the internal energy of the black hole from the lattice results for N=14,32, and find that it smoothly approaches the prediction of the gravity side as the temperature decreases.

hep-lat↗
arXiv2015

Restoration of supersymmetry in two-dimensional SYM with sixteen supercharges on the lattice

We perform lattice simulations of two-dimensional supersymmetric Yang-Mills theory with sixteen supercharges with a lattice action which has two exact supercharges (Sugino lattice action). According to the gauge/gravity duality, the theory at finite temperature is expected to be well described by the corresponding black 1-branes, at low temperature in the large N limit. We aim to confirm the duality conjecture by comparing the lattice results with the theoretical predictions obtained in the gravity side. In this article, at the beginning of this study, we examine the supersymmetric Ward-Takahashi identity to test whether the lattice action reproduces the correct continuum theory. Numerical results of the SUSY WTI strongly suggest us that any cut-off effects, which break supersymmetry, disappear in the continuum limit. In addition, we study the issue of degenerate vacua and find that the admissiblilty condition or any other constraints of the link fields which guarantee the unique vacuum are not always needed.

hep-lat↗
arXiv2012

One dimensional supersymmetric Yang-Mills theory with 16 supercharges

We report on numerical simulations of one dimensional maximally supersymmetric SU(N) Yang-Mills theory, by using the lattice action with two exact supercharges. Based on the gauge/gravity duality, the gauge theory corresponds to N D0-branes system in type IIA superstring theory at finite temperature. We aim to verify the gauge/gravity duality numerically by comparing our results of the gauge side with analytic solutions of the gravity side. First of all, by examining the supersymmetric Ward-Takahashi relation, we show that supersymmetry breaking effects from the cut-off vanish in the continuum limit and our lattice theory has the desired continuum limit. Then, we find that, at low temperature, the black hole internal energy obtained from our data is close to the analytic solution of the gravity side. It suggests the validity of the duality.

hep-lat↗
arXiv2010

Supersymmetry restoration in lattice formulations of 2D $\mathcal{N}=(2,2)$ WZ model based on the Nicolai map

For lattice formulations of the two-dimensional $\mathcal{N}=(2,2)$ Wess--Zumino (2D $\mathcal{N}=(2,2)$ WZ) model on the basis of the Nicolai map, we show that supersymmetry (SUSY) and other symmetries are restored in the continuum limit without fine tuning, to all orders in perturbation theory. This provides a theoretical basis for use of these lattice formulations for computation of correlation functions.

hep-lat↗
arXiv2010

Supersymmetric nonperturbative formulation of the WZ model in lower dimensions

A nonperturbative formulation of the Wess-Zumino (WZ) model in two and three dimensions is proposed on the basis of momentum-modes truncation. The formulation manifestly preserves full supersymmetry as well as the translational invariance and all global symmetries, while it is shown to be consistent with the expected locality to all orders of perturbation theory. For the two-dimensional WZ model, a well-defined Nicolai map in the formulation provides an interesting algorithm for Monte Carlo simulations.

hep-th↗
arXiv2009

SUSY WT identity in a lattice formulation of 2D $\mathcal{N}=(2,2)$ SYM

We address some issues relating to a supersymmetric (SUSY) Ward-Takahashi (WT) identity in Sugino's lattice formulation of two-dimensional (2D) $\mathcal{N}=(2,2)$ $SU(k)$ supersymmetric Yang-Mills theory (SYM). A perturbative argument shows that the SUSY WT identity in the continuum theory is reproduced in the continuum limit without any operator renormalization/mixing and tuning of lattice parameters. As application of the lattice SUSY WT identity, we show that a prescription for the hamiltonian density in this lattice formulation, proposed by Kanamori, Sugino and Suzuki, is justified also from a perspective of an operator algebra among correctly-normalized supercurrents. We explicitly confirm the SUSY WT identity in the continuum limit to the first nontrivial order in a semi-perturbative expansion.

hep-lat↗
arXiv2009

Lattice formulation of 2D $\mathcal{N}=(2,2)$ SQCD based on the B model twist

We present a simple lattice formulation of two-dimensional $\mathcal{N}=(2,2)$ $U(k)$ supersymmetric QCD (SQCD) with $N$ matter multiplets in the fundamental representation. The construction uses compact gauge link variables and exactly preserves one linear combination of supercharges on the two-dimensional regular lattice. Artificial saddle points in the weak coupling limit and the species doubling are evaded without imposing the admissibility. A perturbative power-counting argument indicates that the target supersymmetric theory is realized in the continuum limit without any fine tuning.

hep-lat↗