On the steady state probability distribution of nonequilibrium stochastic systems

A driven stochastic system in a constant temperature heat bath relaxes into a steady state which is characterized by the steady state probability distribution. We investigate the relationship between the driving force and the steady state probability distribution. We adopt the force decomposition method in which the force is decomposed as the sum of a gradient of a steady state potential and the remaining part. The decomposition method allows one to find a set of force fields each of which is compatible to a given steady state. Such a knowledge provides a useful insight on stochastic systems especially in the nonequilibrium situation. We demonstrate the decomposition method in stochastic systems under overdamped and underdamped dynamics and discuss the connection between them.Comment: 8 page

1-loop Corrections to the \rho Parameter in the Left-Right Twin Higgs Model

We implement a one-loop analysis of the $\rho$ parameter in the Left Right Twin Higgs model, including the logarithmically enhanced contributions from both fermion and scalar loops. Numerical results show that the one-loop contributions are dominant over the tree level corrections in most regions of parameter space. The experimentally allowed values of $\rho$-parameter divide the allowed parameter space into two regions; less than $670 {\rm GeV}$ and larger than $1100 {\rm GeV}$ roughly, for symmetry breaking scale $f$. Our numerical analysis significantly reduces the parameter space which are favorably accessible to the LHC.Comment: Submitted for the SUSY07 proceedings, 4 pages, 3 eps figure

One-loop Radiative Corrections to the ρ\rho Parameter in the Left Right Twin Higgs Model

We implement a one-loop analysis of the $\rho$ parameter in the Left Right Twin Higgs model, including the logarithmically enhanced contributions from both heavy fermion and scalar loops. Numerical analysis indicates that the one-loop corrections are dominant over the tree-level contributions in most regions of parameter space. The experimentally allowed values of the $\rho$-parameter divide the allowed parameter space into two regions; less than $670 {\rm GeV}$ and larger than $1100 {\rm GeV}$ roughly, for the symmetry breaking scale $f$. Therefore our result significantly reduces the parameter space which are favorably accessible to the LHC.Comment: minor revisio

Longitudinal top polarization as a probe of a possible origin of forward-backward asymmetry of the top quark at the Tevatron

If the forward-backward (FB) asymmetry of top quark ($A_{\rm FB}$) observed at the Tevatron deviates from the SM prediction, there must be $P$-violating interactions in $q\bar{q} \rightarrow t\bar{t}$. This new interaction will necessarily affect the top spin polarization. In this letter, we perform a model independent analysis on the longitudinal (anti)top polarization ($P_L$ and $\bar{P}_L$) using an effective lagrangian with dim-6 four-quark operators relevant for $q \bar{q} \rightarrow t \bar{t}$, and show that the $P$-odd observable corresponding to the polarization difference $(P_L - \bar{P}_L)$ gives important informations on the chiral structures of new physics that might be relevant to the $A_{\rm FB}$.Comment: 8 pages, 5 figures, to appear in PL

Complete Condensation in a Zero Range Process on Scale-Free Networks

We study a zero range process on scale-free networks in order to investigate how network structure influences particle dynamics. The zero range process is defined with the particle jumping rate function $p(n)=n^\delta$. We show analytically that a complete condensation occurs when $\delta \leq \delta_c \equiv 1/(\gamma-1)$ where $\gamma$ is the degree distribution exponent of the underlying networks. In the complete condensation, those nodes whose degree is higher than a threshold are occupied by macroscopic numbers of particles, while the other nodes are occupied by negligible numbers of particles. We also show numerically that the relaxation time follows a power-law scaling $\tau \sim L^z$ with the network size $L$ and a dynamic exponent $z$ in the condensed phase.Comment: 4 pages, 2 EPS figures, and 1 table (some revision for relational dynamics parts

Mass and rapidity dependent top quark forward-backward asymmetry in the effective Lagrangian approach

We study the invariant mass and rapidity dependent top quark forward-backward asymmetry from the effective Lagrangian viewpoint. The Wilson coefficients are constrained by the experimental observations and the concrete models that reproduce the low energy effective Lagaragians are considered. Some of them are disfavored and others relatively favored. For each cases, we estimate the appropriacy of the effective Lagrangian approach.Comment: To appear in the proceedings of Top 2012, 5th International Workshop on Top Quark Physics, September 16-21, 2012, Winchester, U.

Particle Condensation in Pair Exclusion Process

Condensation is characterized with a single macroscopic condensate whose mass is proportional to a system size $N$. We demonstrate how important particle interactions are in condensation phenomena. We study a modified version of the zero-range process by including a pair exclusion. Each particle is associated with its own partner, and particles of a pair are forbidden to stay at the same site. The pair exclusion is weak in that a particle interacts with only a single one among all others. It turns out that such a weak interaction changes the nature of condensation drastically. There appear a number of mesoscopic condensates: the mass of a condensate scales as $m_{\rm con}\sim N^{1/2}$ and the number of condensates scales as $N_{\rm con} \sim N^{1/2}$ with a logarithmic correction. These results are derived analytically through a mapping to a solvable model under a certain assumption, and confirmed numerically.Comment: 4 pages, 2 figur

Measurement of effective thermal conductivity of LaNi5_5 powder packed bed

Effective thermal conductivity of LaNi$_5$ powder packed bed was analyzed with customized guarded hot-plate (GHP) apparatus. Here, GHP was designed for precise measurement of effective thermal conductivity of metal-hydride powders even with small sample amounts (2.12$\times$10$^4$ mm$^3$). Dimensions of sample container and apparatus were determined through two-dimensional (2-D) steady-state heat conduction analysis. Calibration experiment and uncertainty analysis were conducted to validate the accuracy of the GHP. Based on the measurements of the residual thermal conductivity of the LaNi$_5$ packed bed, effect of particle size on contact factor of LaNi$_5$ packed bed was estimated. By applying the Yagi and Kunii (YK) model to the effective thermal conductivity of LaNi$_5$ packed bed, effect of contact factor and gas thermal conductivity on characteristic length of gas film were newly analyzed. Factors of YK model were modified in present work and validated through comparison with experimental data from previous literature.Comment: 8 figure

Epidemic Threshold of Susceptible-Infected-Susceptible Model on Complex Networks

We demonstrate that the susceptible-infected-susceptible (SIS) model on complex networks can have an inactive Griffiths phase characterized by a slow relaxation dynamics. It contrasts with the mean field theoretical prediction that the SIS model on complex networks is active at any nonzero infection rate. The dynamic fluctuation of infected nodes, ignored in the mean field approach, is responsible for the inactive phase. It is proposed that the question whether the epidemic threshold of the SIS model on complex networks is zero or not can be resolved by the percolation threshold in a model where nodes are occupied in the degree-descending order. Our arguments are supported by the numerical studies on scale-free network models.Comment: 5 pages, 4 figure

Percolation transitions with nonlocal constraint

We investigate percolation transitions in a nonlocal network model numerically. In this model, each node has an exclusive partner and a link is forbidden between two nodes whose $r$-neighbors share any exclusive pair. The $r$-neighbor of a node $x$ is defined as a set of at most $N^r$ neighbors of $x$, where $N$ is the total number of nodes. The parameter $r$ controls the strength of a nonlocal effect. The system is found to undergo a percolation transition belonging to the mean field universality class for $r< 1/2$. On the other hand, for $r>1/2$, the system undergoes a peculiar phase transition from a non-percolating phase to a quasi-critical phase where the largest cluster size $G$ scales as $G \sim N^{\alpha}$ with $\alpha = 0.74 (1)$. In the marginal case with $r=1/2$, the model displays a percolation transition that does not belong to the mean field universality class.Comment: 4 pages, 5 figure