Assuming that the lightest neutral component in an SU (2) L gauge multiplet is the main ingredient of dark matter in the universe, we calculate the elastic scattering cross section of the dark matter with nucleon, which is an important quantity for the direct detection experiments. When the dark matter is a real scalar or a Majorana fermion which has only electroweak gauge interactions, the scattering with quarks and gluon are induced through one-and two-loop quantum processes, respectively, and both of them give rise to comparable contributions to the elastic scattering cross section. We evaluate all of the contributions at the leading order and find that there is an accidental cancellation among them. As a result, the spin-independent cross section is found to be O(10 −(46−48) ) cm 2 , which is far below the current experimental bounds.

Abstract. We propose a new approach for calculating the curvature perturbations produced during inflation in the stochastic formalism. In our formalism, the fluctuations of the efoldings are directly calculated without perturbatively expanding the inflaton field and they are connected to the curvature perturbations by the δN formalism. The result automatically includes the contributions of the higher order perturbations because we solve the equation of motion non-perturbatively. In this paper, we analytically prove that our result (the power spectrum and the nonlinearity parameter) is consistent with the standard result in single field slow-roll inflation. We also describe the algorithm for numerical calculations of the curvature perturbations in more general inflation models.

We reconsider the effective mass of a scalar field which interact with visible sector via Planck-suppressed coupling in supergravity framework. We focus on the radiation-dominated (RD) era after inflation. In this era, the effective mass is given by thermal average of interaction terms. To make our analysis clear, we rely on Kadanoff-Baym equations to evaluate the thermal average. We find that, in RD era, a scalar field acquires the effective mass of the order of H.

Hypothetical long-lived massive colored particles (MCPs or Y s) would be confined in colorless exotic strongly interacting massive particles (SIMPs) at color confinement temperature of TC ∼ 200 MeV. Two long-lived MCPs form a bound state (YȲ ) at collisions of two SIMPs. We study sensitivities of MCP annihilation to decay properties of resonances (YȲ ), and binding energies or energy levels of exotic SIMPs. The (YȲ ) formation is assumed to dominantly proceed through resonances of (YȲ ) in this paper. We make a toy model of the effective cross section for YȲ annihilation. Abundances of SIMPs are then calculated for different sets of parameters specifying properties of (YȲ ) resonances, binding energies of SIMPs, the initial abundance and the mass of MCP. Calculated relic abundances for respective SIMP species are 2 × 10 −8 -3 × 10 −4 times that of baryon. They can be much higher but cannot be much smaller than the previous estimate. The abundances can be consistent depending on parameters with the possible scenario that SIMPs bind to nuclei and subsequent exotic nuclear reactions reduce the primordial abundance of 7 Li or enhance those of 9 Be and/or B in the early Universe. A unique information on the quark-hadron phase transition in the early Universe may become available in future by elaborated studies on the annihilation process with light element abundances as observables.