Phase Transition in Potts Model with Invisible States

We study phase transition in the ferromagnetic Potts model with invisible states that are added as redundant states by mean-field calculation and Monte Carlo simulation. Invisible states affect the entropy and the free energy, although they do not contribute to the internal energy. The internal energy and the number of degenerated ground states do not change, if invisible states are introduced into the standard Potts model. A second-order phase transition takes place at finite temperature in the standard $q$-state ferromagnetic Potts model on two-dimensional lattice for $q=2,3$, and 4. However, our present model on two-dimensional lattice undergoes a first-order phase transition with spontaneous $q$-fold symmetry breaking ($q=2,3$, and 4) due to entropy effect of invisible states. We believe that our present model is a fundamental model for analysis of a first-order phase transition with spontaneous discrete symmetry breaking.Comment: 8 pages, 4 figure

Successive phase transitions and phase diagrams of the quasi-two-dimensional triangular antiferromagnet Rb4Mn(MoO4)3

Comprehensive experimental studies by magnetic, thermal and neutron measurements have clarified that Rb4Mn(MoO4)3 is a model system of a quasi-2D triangular Heisenberg antiferromagnet with an easy-axis anisotropy, exhibiting successive transitions across an intermediate collinear phase. As a rare case for geometrically frustrated magnetism, quantitative agreement between experiment and theory is found for complete, anisotropic phase diagrams as well as magnetic properties.Comment: 4 pages, 5 figure

Entanglement Spectra of the 2D AKLT Model: VBS/CFT Correspondence

We investigate the entanglement properties of the valence-bond-solid (VBS) state defined on two-dimensional lattices, which is the exact ground state of the Affleck-Kennedy-Lieb-Tasaki model. It is shown that the entanglement entropy obeys an area law and the non-universal prefactor of the leading term is strictly less than $\ln 2$. The analysis of entanglement spectra for various lattices reveals that the reduced density matrix associated with the VBS state is closely related to a thermal density matrix of a {\it holographic} spin chain, whose spectrum is reminiscent of that of the spin-1/2 Heisenberg chain. This correspondence is further supported by comparing the entanglement entropy in the holographic spin chain with conformal field theory predictions.Comment: 10 pages, 9 figures, published versio

The asymptotic behavior of globally smooth solutions of bipolar non-isentropic compressible Euler-Maxwell system for plasma

The bipolar non-isentropic compressible Euler-Maxwell system is investigated in $R^3$ in the present paper, and the $L^q$ time decay rate for the global smooth solution is established. It is shown that the total densities, total temperatures and magnetic field of two carriers converge to the equilibrium states at the same rate $(1+t)^{-3/2+3q/2}$ in $L^q$ norm. But, both the difference of densities and the difference of temperatures of two carriers decay at the rate $(1+t)^{-2-\frac{1}{q}}$, and the velocity and electric field decay at the rate $(1+t)^{-3/2+\frac{1}{2q}}$. This phenomenon on the charge transport shows the essential difference between the non-isentropic unipolar Euler-Maxwell and the bipolar isentropic Euler-Maxwell system.Comment: 27page

Present status of Japanese ethics committees : a survey in Tokushima Prefecture

Clinical research is important to improve medical quality, and ethics review is essential to conduct clinical research. Since the establishment of the first Japanese ethics committee at the University of Tokushima in 1982, Japanese ethics committees have increased. In this study, we surveyed the status of clinical studies and ethics committees in one Japanese region. The survey was conducted in collaboration with the Tokushima Medical Association. A questionnaire was established and mailed to all medical institutions (n=737) registered to the Tokushima Medical Association in 2012. Among 737, 223 (30.3%) questionnaires were returned and 221 were completed and are included in this analysis (respondents). Among respondents, 51 (23.1%) had performed clinical research, and of these, 17 had established ethics committees (though one was omitted from the following analysis due to an unsatisfactory response). Among 16 ethics committees, review of protocol amendments, review of serious adverse events, annual follow-up of approved protocols, and education for committee members were active in 10 (62.5%), 9 (56.3%), 6 (37.5%) and 4 (25.0%), respectively. Research ethics education was active in 4 (25.0%). Based on the results, we attempt to establish an appropriate system for ethical conduct of health-related research in Tokushima Prefecture