Quantum corrections to the spin-independent cross section of the inert doublet dark matter

The inert Higgs doublet model contains a stable neutral boson as a candidate of dark matter. We calculate cross section for spin-independent scattering of the dark matter on nucleon. We take into account electroweak and scalar quartic interactions, and evaluate effects of scattering with quarks at one-loop level and with gluon at two-loop level. These contributions give an important effect for the dark matter mass to be around m_h/2, because a coupling with the standard model Higgs boson which gives the leading order contribution should be suppressed to reproduce the correct amount of the thermal relic abundance in this mass region. In particular, we show that the dark matter self coupling changes the value of the spin-independent cross section significantly.Comment: 38 pages, 18 figure

Muon specific two-Higgs-doublet model

We investigate a new type of a two-Higgs-doublet model as a solution of the muon $g-2$ anomaly. We impose a softly-broken $Z_4$ symmetry to forbid tree level flavor changing neutral currents in a natural way. This $Z_4$ symmetry restricts the structure of Yukawa couplings. As a result, extra Higgs boson couplings to muons are enhanced by a factor of $\tan\beta$, while their couplings to all the other standard model fermions are suppressed by $\cot\beta$. Thanks to this coupling property, we can avoid the constraint from leptonic $\tau$ decays in contrast to the lepton specific two-Higgs-doublet model, which can explain the muon $g-2$ within the 2$\sigma$ level but cannot within the $1\sigma$ level due to this constraint. We find that the model can explain the muon $g-2$ within the 1$\sigma$ level satisfying constraints from perturbative unitarity, vacuum stability, electroweak precision measurements, and current LHC data.Comment: 24 pages, 3 figure

Theory of spin accumulation and spin transfer torque in a magnetic domain wall

We study spin accumulation and spin transfer torque in a domain wall by solving the Boltzmann equation with a diffusion approximation. We obtained the analytical expressions of spin accumulation and spin transfer torque. Both the adiabatic and the non-adiabatic components of the spin transfer torque oscillate with the thickness of the domain wall. We show that the oscillation plays a dominant role in the non-adiabatic torque when the domain wall thickness is less than the spin-flip length, which is defined by the product of the Fermi velocity and the spin-flip scattering time

Effects of Dispersed Sulfides in Bronze During Sintering

Bronze material sintered as sliding bearing is used. In particular, lead bronze is often used because lead acting as a solid lubricant has excellent friction characteristics. However, lead was replaced by another material according to environmental regulations. One candidate for a lead-free material is a sulfide that is well known as a solid lubricant. In this chapter we describe sintering properties and their mechanical properties. First, we investigate chemical components of copper sulfide system and realize stable phase in bronze matrix. After that, we consider the sintering condition of bronze with sulfide dispersed. The sulfides in the bronze may be subject to chemical reduction during sintering, especially when this is carried out under a reducing atmosphere containing hydrogen gas. The effect of the sulfides on the bronze, with a focus on the hardness of the bronze matrix and the reaction between sulfides and hydrogen gas, was investigated. Not only sinterability but also mechanical properties as hardness are discussed

Temporary jobs and globalization

Deregulation of the use of temporary workers in 2004 (the Worker Dispatching Act of 2004) has been regarded as an important reason for the recent rise of temporary workers in Japan. However, the shift from permanent to temporary workers began long before. This paper empirically explores links between the shift from permanent to temporary workers in the Japanese manufacturing sector and economic globalization, using industry-level data. We find that outsourcing is positively correlated with the replacement of permanent workers with temporary workers in domestic production. In addition, we find that industries losing world share of value added tend to decrease the employment of permanent workers. Industries with higher exports or imports are aggressive in using temporary workers, which suggests the role of temporary workers as an employment buffer

A model of temporary and permanent jobs and trade

This paper proposes a monopolistic competition model in which firms facing demand uncertainty use both permanent and temporary workers to evade the labor adjustment costs associated with permanent workers, and explores links between the demand for temporary and permanent workers and economic globalization. The model highlights intensified product market competition as a driving force behind the shift in demand from permanent to temporary workers. In addition, our model shows that international outsourcing effectively reduces labor adjustment costs, which decreases the demand for permanent workers. We empirically test these links using industry-level data from the Japanese manufacturing sector. We find a positive correlation between foreign outsourcing and the replacement of permanent workers with temporary workers in domestic production. Additionally, we find that industries losing their global share of value-added tend to decrease their employment of permanent workers and increase the proportions of temporary workers

Kron Reduction and Effective Resistance of Directed Graphs

In network theory, the concept of effective resistance is a distance measure on a graph that relates the global network properties to individual connections between nodes. In addition, the Kron reduction method is a standard tool for reducing or eliminating the desired nodes, which preserves the interconnection structure and the effective resistance of the original graph. Although these two graph-theoretic concepts stem from the electric network on an undirected graph, they also have a number of applications throughout a wide variety of other fields. In this study, we propose a generalization of a Kron reduction for directed graphs. Furthermore, we prove that this reduction method preserves the structure of the original graphs, such as the strong connectivity or weight balance. In addition, we generalize the effective resistance to a directed graph using Markov chain theory, which is invariant under a Kron reduction. Although the effective resistance of our proposal is asymmetric, we prove that it induces two novel graph metrics in general strongly connected directed graphs. In particular, the effective resistance captures the commute and covering times for strongly connected weight balanced directed graphs. Finally, we compare our method with existing approaches and relate the hitting probability metrics and effective resistance in a stochastic case. In addition, we show that the effective resistance in a doubly stochastic case is the same as the resistance distance in an ergodic Markov chain

Non-perturbative approach to the effective potential of the $\lambda\phi^{4} theory at finite temperature

We construct a non-perturbative method to investigate the phase structure of the scalar theory at finite temperature. The derivative of the effective potential with respect to the mass square is expressed in terms of the full propagator. Under a certain approximation this expression reduces to the partial differential equation for the effective potential. We numerically solve the partial differential equation and obtain the effective potential non-perturbatively. It is found that the phase transition is of the second order. The critical exponents calculated in this method are consistent with the results obtained in Landau approximation.Comment: 17page, Latex, 9 figure

Temporary Jobs and Globalization: Evidence from Japan

Since the 1990s, there has been a rapid increase in the proportion of temporary workers in the Japanese workforce. This paper empirically explores a linkage between the shift from permanent to temporary workers in the Japanese manufacturing sector and economic globalization, using various industry level data. We find that FDI and/or outsourcing tend to encourage the replacement of permanent workers with temporary workers in home production. In addition, we find that industries with higher exports are the most aggressive in replacing permanent workers with temporary workers. However, some other measures of global market competition such as world share of value added are not always statistically significant. Our estimation suggests that the impact of these globalization channels is sizable relative to the impact of the Worker Dispatching Act in 2004.