Location of the Multicritical Point for the Ising Spin Glass on the Triangular and Hexagonal Lattices

A conjecture is given for the exact location of the multicritical point in the phase diagram of the +/- J Ising model on the triangular lattice. The result p_c=0.8358058 agrees well with a recent numerical estimate. From this value, it is possible to derive a comparable conjecture for the exact location of the multicritical point for the hexagonal lattice, p_c=0.9327041, again in excellent agreement with a numerical study. The method is a variant of duality transformation to relate the triangular lattice directly with its dual triangular lattice without recourse to the hexagonal lattice, in conjunction with the replica method.Comment: 9 pages, 1 figure; Minor corrections in notatio

Multicritical Points of Potts Spin Glasses on the Triangular Lattice

We predict the locations of several multicritical points of the Potts spin glass model on the triangular lattice. In particular, continuous multicritical lines, which consist of multicritical points, are obtained for two types of two-state Potts (i.e., Ising) spin glasses with two- and three-body interactions on the triangular lattice. These results provide us with numerous examples to further verify the validity of the conjecture, which has succeeded in deriving highly precise locations of multicritical points for several spin glass models. The technique, called the direct triangular duality, a variant of the ordinary duality transformation, directly relates the triangular lattice with its dual triangular lattice in conjunction with the replica method.Comment: 18 pages, 2, figure

Duality in finite-dimensional spin glasses

We present an analysis leading to a conjecture on the exact location of the multicritical point in the phase diagram of spin glasses in finite dimensions. The conjecture, in satisfactory agreement with a number of numerical results, was previously derived using an ansatz emerging from duality and the replica method. In the present paper we carefully examine the ansatz and reduce it to a hypothesis on analyticity of a function appearing in the duality relation. Thus the problem is now clearer than before from a mathematical point of view: The ansatz, somewhat arbitrarily introduced previously, has now been shown to be closely related to the analyticity of a well-defined function.Comment: 12 pages, 3 figures; A reference added; to appear in J. Stat. Phy

Relation Between Mental Health Status and Psychosocial Stressors Among Pregnant and Puerperium Women in Japan - From the Perspective of Working Status-

Background Mental health problems during pregnancy and postpartum periods are one of the alarming health issues among women in Japan. Many studies have reported that psychosocial risk factors could be correlated with maternal mental health status. Although increased numbers of women who are employed during the pregnancy and postpartum periods have been observed, it is unclear about the link between mental health and psychosocial stressors in terms of working status during pregnancy and postpartum periods. Therefore, this study examined difference in mental health status and the association between mental health and psychosocial stressors by working status amongpregnant and puerperium women, using nationally representative data in Japan. Methods This study analyzed data on the Japanese version of the Kessler 6 (K6), specific psychosocial stressors, and working status of pregnant and puerperium women (n=1126) from respondents in the Comprehensive Survey of Peoples Living Conditions (CSPLC) conducted in 2007 by Ministry of Health, Labour and Welfare in Japan.. The univariate logistic regression analysis and a forward multiple regression analysis were used to examine K6 and related factors including specific psychosocial stressors for working status (employedand unemployed).Results Those who scored five or higher in K6 accounted for 33.2% of 1126 respondents, and mental health had no significant association with working status among pregnant and puerperium women. Multiple logistic analyses showed the significant associations between mental health and psychosocial stressors: family relationship, pregnancy and birth, andincomes/ family budgets/ debts,regardless of employed or unemployed. After stratified by working status, whereas ones job stressor had an association with mental health only for employed females, stressors forones disease/long -term care and housework had associations only for unemployed ones. For employed women, the primary factor for mental health wasfamily relationship stressor. Conclusion Although mental health status measured by K6 was not different between employed or unemployed female population, primary stressors related mental health was revealed to differ with working status. Especially, family relationship stressor was the highest risk factor of mental health in employed women. More importantly, the results provided evidence on the differences in associations between mental health and specific psychosocial stressors by working status. Psychosocial risk assessments and interventions on working status among pregnant and puerperium women should be imperative to pay attention for social politics

Vortices in U(1) Noncommutative Gauge Fields

Charged vortex solutions for noncommutative Maxwell-Higgs model in 3+1 dimensions are found. We show that the stability of these vortex solutions is spoiled out for some, large enough, noncommutativity parameter. A non topological charge, however, is induced by noncommutative effects.Comment: references added, slight modifications in the introduction and conclusions. To be published in PR

Photospheric Abundances of Volatile and Refractory Elements in Planet-Harboring Stars

By using the high-dispersion spectra of 14 bright planet-harboring stars (along with 4 reference stars) observed with the new coude echelle spectrograph at Okayama Astrophysical Observatory, we investigated the abundances of volatile elements (C, N, O, S, Zn; low condensation temperature Tc) in order to examine whether these show any significant difference compared to the abundances of other refractory elements (Si, Ti, V, Fe, Co, Ni; high Tc) which are known to be generally overabundant in those stars with planets, since a Tc-dependence is expected if the cause of such a metal-richness is due to the accretion of solid planetesimals onto the host star. We found, however, that all elements we studied behave themselves quite similarly to Fe (i.e., [X/Fe]~0) even for the case of volatile elements, which may suggest that the enhanced metallicity in those planet-bearing stars is not so much an acquired character (by accretion of rocky material) as rather primordial.Comment: 22 pages, 8 figures, to appear in PAS

Theory for Magnetic Anisotropy of Field-Induced Insulator-to-Metal Transition in Cubic Kondo Insulator YbB_{12}

Magnetization and energy gap of Kondo insulator YbB_{12} are calculated theoretically based on the previously proposed tight-binding model composed of Yb 5d$\epsilon$ and 4f $\Gamma_8$ orbitals. It is found that magnetization curves are almost isotropic, naturally expected from the cubic symmetry, but that the gap-closing field has an anisotropy: the gap closes faster for the field in (100) direction than in (110) and (111) directions, in accord with the experiments. This is qualitatively understood by considering the maximal eigenvalues of the total angular momentum operators projected on each direction of the magnetic field. But the numerical calculation based on the band model yields better agreement with the experiment.Comment: 4 pages, 4 figures, to appear in J. Phys. Soc. Jp

Pressure-induced unconventional superconductivity in the heavy-fermion antiferromagnet CeIn3: An 115In-NQR study under pressure

We report on the pressure-induced unconventional superconductivity in the heavy-fermion antiferromagnet CeIn3 by means of nuclear-quadrupole-resonance (NQR) studies conducted under a high pressure. The temperature and pressure dependences of the NQR spectra have revealed a first-order quantum-phase transition (QPT) from an AFM to PM at a critical pressure Pc=2.46 GPa. Despite the lack of an AFM quantum critical point in the P-T phase diagram, we highlight the fact that the unconventional SC occurs in both phases of the AFM and PM. The nuclear spin-lattice relaxation rate 1/T1 in the AFM phase have provided evidence for the uniformly coexisting AFM+SC phase. In the HF-PM phase where AFM fluctuations are not developed, 1/T1 decreases without the coherence peak just below Tc, followed by a power-law like T dependence that indicates an unconventional SC with a line-node gap. Remarkably, Tc has a peak around Pc in the HF-PM phase as well as in the AFM phase. In other words, an SC dome exists with a maximum value of Tc = 230 mK around Pc, indicating that the origin of the pressure-induced HF SC in CeIn3 is not relevant to AFM spin fluctuations but to the emergence of the first-order QPT in CeIn3. When the AFM critical temperature is suppressed at the termination point of the first-order QPT, Pc = 2.46 GPa, the diverging AFM spin-density fluctuations emerge at the critical point from the AFM to PM. The results with CeIn3 leading to a new type of quantum criticality deserve further theoretical investigations