198 research outputs found
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 -state ferromagnetic Potts model
on two-dimensional lattice for , and 4. However, our present model on
two-dimensional lattice undergoes a first-order phase transition with
spontaneous -fold symmetry breaking (, 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 . 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 in the present paper, and the 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 in norm. But, both the
difference of densities and the difference of temperatures of two carriers
decay at the rate , and the velocity and electric field
decay at the rate . 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
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