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Search Results: 1 - 10 of 1966 matches for " Shinji Takeda "
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Perturbative analysis of the Neuberger-Dirac operator in the Schr?dinger functional
Shinji Takeda
Physics , 2007, DOI: 10.1016/j.nuclphysb.2007.12.020
Abstract: We investigate the spectrum of the free Neuberger-Dirac operator $\Dov$ on the Schr\"odinger functional (SF). We check that the lowest few eigen-values of the Hermitian operator $\Dov^{\dag}\Dov$ in unit of $L^{-2}$ converge to the continuum limit properly. We also perform a one-loop calculation of the SF coupling, and then check the universality and investigate lattice artifacts of the step scaling function. It turns out that the lattice artifacts for the Neuberger-Dirac operator are comparable in those of the clover action.
Universality check of the overlap fermions in the Schroedinger functional
Shinji Takeda
Physics , 2008,
Abstract: I examine some properties of the overlap operator in the Schroedinger functional formulated by Luescher at perturbative level. By investigating spectra of the free operator and one-loop coefficient of the Schroedinger functional coupling, I confirm the universality at tree and one-loop level. Furthermore, I address cutoff effects of the step scaling function and it turns out that the lattice artifacts for the overlap operator are comparable with those of the clover actions.
Automatic generation of Feynman rules in the Schroedinger functional
Shinji Takeda
Physics , 2008, DOI: 10.1016/j.nuclphysb.2008.11.022
Abstract: We provide an algorithm to generate vertices for the Schr\"odinger functional with an abelian background gauge field. The background field has a non-trivial color structure, therefore we mainly focus on a manipulation of the color matrix part. We propose how to implement the algorithm especially in python code. By using python outputs produced by the code, we also show how to write a numerical expression of vertices in the time-momentum as well as the coordinate space into a Feynman diagram calculation code. As examples of the applications of the algorithm, we provide some one-loop results, ratios of the Lambda parameters between the plaquette gauge action and the improved gauge actions composed from six-link loops (rectangular, chair and parallelogram), the determination of the O(a) boundary counter term to this order, and the perturbative cutoff effects of the step scaling function of the Schroedinger functional coupling constant.
A formulation of domain wall fermions in the Schroedinger functional
Shinji Takeda
Physics , 2009,
Abstract: We present a formulation of domain wall fermions in the Schroedinger functional by following the universality argument given by L\"uscher. To check whether the formulation works, we examine the lowest eigenmode of the free domain wall fermion operator. We confirm that the theory belongs to a correct universality class and that the eigenvector is localized near the boundaries of the fifth dimension. We also investigate the chiral symmetry breaking structure of the four dimentional effective operator. We observe that the bulk chiral symmetry breaking disappears for a large fifth dimensional size, while the breaking originated by the boundary effects persists and exponetially decays away from the time boundaries.
A formulation of domain-wall fermions in the Schr?dinger functional
Shinji Takeda
Physics , 2010, DOI: 10.1103/PhysRevD.87.114506
Abstract: We present a formulation of domain-wall fermions in the Schr\"odinger functional by following a universality argument. To examine the formulation, we numerically investigate the spectrum of the free operator and perform a one-loop analysis to confirm universality and renormalizability. We also study the breaking of the Ginsparg-Wilson relation to understand the structure of chiral symmetry breaking from two sources: The bulk and boundary. Furthermore, we discuss the lattice artifacts of the step scaling function by comparing with other fermion discretizations.
Grassmann tensor renormalization group for one-flavor lattice Gross-Neveu model with finite chemical potential
Shinji Takeda,Yusuke Yoshimura
Physics , 2014, DOI: 10.1093/ptep/ptv022
Abstract: We apply the Grassmann tensor renormalization group (GTRG) to the one-flavor lattice Gross-Neveu model in the presence of chemical potential. We compute the fermion number density and its susceptibility and confirm the validity of GTRG for the finite density system. We introduce a method analogous to the reweighting method for Monte Carlo method and test it for some parameters.
Automatic generation of vertices for the Schroedinger functional
Shinji Takeda,Ulli Wolff
Physics , 2007,
Abstract: We present a multiplication algorithm to recursively construct vertices for the Schroedinger functional in the abelian background field case. The algorithm is suited for automatic perturbative calculations with a variety of actions. As first applications, we derive ratios of the lambda parameters between the lattice scheme (improved gauge actions including six link loops) and the $\bar{\rm MS}$ scheme, and one-loop results for the Schroedinger functional coupling with a lattice $T=L \pm a$, which is motivated by considering staggered fermions.
Tensor renormalization group analysis of ${\rm CP}(N-1)$ model in two dimensions
Hikaru Kawauchi,Shinji Takeda
Physics , 2015,
Abstract: We apply the higher order tensor renormalization group to lattice CP($N-1$) model in two dimensions. A tensor network representation of CP($N-1$) model is derived. We confirm that the numerical results of the CP(1) model without the $\theta$-term using this method are consistent with that of the O(3) model which is analyzed by the same method in the region $\beta \gg 1$ and that obtained by Monte Carlo simulation in a wider range of $\beta$.
A perturbative determination of O(a) boundary improvement coefficients for the Schr?dinger Functional coupling at 1-loop with improved gauge actions
Shinji Takeda,Sinya Aoki,Kiyotomo Ide
Physics , 2003, DOI: 10.1103/PhysRevD.68.014505
Abstract: We determine O($a$) boundary improvement coefficients up to 1-loop level for the Schr\"odinger Functional coupling with improved gauge actions including plaquette and rectangle loops. These coefficients are required to implement 1-loop O($a$) improvement in full QCD simulations for the coupling with the improved gauge actions. To this order, lattice artifacts of step scaling function for each improved gauge action are also investigated. In addition, passing through the SF scheme, we estimate the ratio of $\Lambda$-parameters between the improved gauge actions and the plaquette action more accurately.
On cutoff effects in lattice QCD from short to long distances
Michele Della Morte,Rainer Sommer,Shinji Takeda
Physics , 2008, DOI: 10.1016/j.physletb.2009.01.059
Abstract: We discuss kinematical enhancements of cutoff effects at short and intermediate distances. Starting from a pedagogical example with periodic boundary conditions, we switch to the case of the Schroedinger Functional, where the theoretical analysis is checked by precise numerical data with Nf=2 dynamical O(a)-improved Wilson quarks. Finally we present an improved determination of the renormalization of the axial current in that theory.
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