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Hasebe K.,Sendai National College of Technology
International Journal of Modern Physics A | Year: 2016

Noncommutative geometry naturally emerges in low energy physics of Landau models as a consequence of level projection. In this work, we proactively utilize the level projection as an effective tool to generate fuzzy geometry. The level projection is specifically applied to the relativistic Landau models. In the first half of the paper, a detail analysis of the relativistic Landau problems on a sphere is presented, where a concise expression of the Dirac-Landau operator eigenstates is obtained based on algebraic methods. We establish SU(2) "gauge" transformation between the relativistic Landau model and the Pauli-Schrödinger nonrelativistic quantum mechanics. After the SU(2) transformation, the Dirac operator and the angular momentum operators are found to satisfy the SO(3, 1) algebra. In the second half, the fuzzy geometries generated from the relativistic Landau levels are elucidated, where unique properties of the relativistic fuzzy geometries are clarified. We consider mass deformation of the relativistic Landau models and demonstrate its geometrical effects to fuzzy geometry. Super fuzzy geometry is also constructed from a supersymmetric quantum mechanics as the square of the Dirac-Landau operator. Finally, we apply the level projection method to real graphene system to generate valley fuzzy spheres. © 2016 World Scientific Publishing Company. Source

Matsueda H.,Sendai National College of Technology | Ishihara M.,Tohoku University | Hashizume Y.,Tokyo University of Science
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

A tensor-network variational formalism of thermofield dynamics is introduced. The formalism relates the original Hilbert space with its tilde space by a product of two copies of a tensor network. Then, their interface becomes an event horizon, and the logarithm of the tensor rank corresponds to the black hole entropy. Eventually, a multiscale entanglement renormalization ansatz reproduces an anti-de Sitter black hole at finite temperature. Our finding shows rich functionalities of multiscale entanglement renormalization ansatz as efficient graphical representation of AdS/CFT correspondence. © 2013 American Physical Society. Source

Yamanaka K.,Tohoku University | Mori M.,Sendai National College of Technology | Chiba A.,Tohoku University
Materials and Design | Year: 2014

The present study investigated how nitrogen affected the high-temperature deformation and microstructural evolution of biomedical Ni-free Co-Cr-W alloys during hot deformation. Hot compression tests of undoped and N-doped Co-28Cr-9W-1Si-0.05C (mass%) alloys were performed at deformation temperatures ranging from 1323 to 1473K at strain rates of 10-3 to 10s-1. The microstructures, which were subjected to a true strain of 0.92 (60% in compression), were characterized using electron backscatter diffraction (EBSD) analysis and transmission electron microscopy (TEM). Dynamic recrystallization (DRX) was found to occur in both alloys during hot deformation. The grain size (d) decreased considerably with an increase in the Zener-Hollomon (Z) parameter. Although adding nitrogen to the alloys barely affected dynamic-recrystallization-induced grain refinement, it increased the magnitude of the flow stress and delayed static recrystallization during post-deformation cooling. Consequently, the N-doped alloy contained bulk nanostructures whose average grain size was 0.9μm. © 2014 Elsevier Ltd. Source

Matsueda H.,Sendai National College of Technology
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

In quantum spin chains at criticality, two types of scaling for the entanglement entropy exist: one comes from conformal field theory (CFT), and the other is for entanglement support of matrix product state (MPS) approximation. On the other hand, the quantum spin-chain models can be mapped onto two-dimensional (2D) classical ones by the Suzuki-Trotter decomposition. Motivated by the scaling and the mapping, we introduce information entropy for 2D classical spin configurations as well as a spectrum, and examine their basic properties in the Ising and the three-state Potts models on the square lattice. They are defined by the singular values of the reduced density matrix for a Monte Carlo snapshot. We find scaling relations of the entropy compatible with the CFT and the MPS results. Thus, we propose that the entropy is a kind of "holographic" entanglement entropy. At T c, the spin configuration is fractal, and various sizes of ordered clusters coexist. Then, the singular values automatically decompose the original snapshot into a set of images with different length scales, respectively. This is the origin of the scaling. In contrast to the MPS scaling, long-range spin correlation can be described by only few singular values. Furthermore, the spectrum, which is a set of logarithms of the singular values, also seems to be a holographic entanglement spectrum. We find multiple gaps in the spectrum, and in contrast to the topological phases, the low-lying levels below the gap represent spontaneous symmetry breaking. These contrasts are strong evidence of the dual nature of the holography. Based on these observations, we discuss the amount of information contained in one snapshot. © 2012 American Physical Society. Source

Kanamori Y.,Tohoku University | Matsueda H.,Sendai National College of Technology | Ishihara S.,Tohoku University | Ishihara S.,Japan Science and Technology Agency
Physical Review Letters | Year: 2011

A photoinduced spin-state change in the itinerant correlated electron system is studied. A photon introduced in the low-spin band insulator induces a bound state of the high-spin state and a photoexcited hole. This bound state brings a characteristic peak in the pump-probe optical absorption spectra which are completely different from the spectra in thermal-excited states. The present results well explain the recent experiments of the ultrafast optical spectroscopy in perovskite cobaltites. © 2011 American Physical Society. Source

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