Stochastic quantum inflation for a canonical scalar field with linear self-interaction potential

We apply Starobinsky's formalism of stochastic inflation to the case of a minimally coupled scalar field with linear self-interaction potential. We solve the corresponding Fokker-Planck equation exactly, and obtain analytical expressions for the stochastic expectation values.Comment: 5 pages, no figure

Strange stars in f(R)f(R) theories of gravity in the Palatini formalism

In the present work we study strange stars in $f(R)$ theories of gravity in the Palatini formalism. We consider two concrete well-known cases, namely the $R+R^2/(6 M^2)$ model as well as the $R-\mu^4/R$ model for two different values of the mass parameter $M$ or $\mu$. We integrate the modified Tolman-Oppenheimer-Volkoff equations numerically, and we show the mass-radius diagram for each model separately. The standard case corresponding to the General Relativity is also shown in the same figure for comparison. Our numerical results show that the interior solution can be vastly different depending on the model and/or the value of the parameter of each model. In addition, our findings imply that i) for the cosmologically interesting values of the mass scales $M,\mu$ the effect of modified gravity on strange stars is negligible, while ii) for the values predicting an observable effect, the modified gravity models discussed here would be ruled out by their cosmological effects.Comment: 10 pages, 2 figure

Gravitino dark matter with neutralino NLSP in the constrained NMSSM

The gravitino dark matter with neutralino NLSP hypothesis is investigated in the framework of NMSSM. We have considered both the thermal and non-thermal gravitino production mechanisms, and we have taken into account all the collider and cosmological constraints. The maximum allowed reheating temperature after inflation, as well as the maximum allowed gravitino mass are determined.Comment: Proceedings of the 16th International Symposium on Particles, Strings and Cosmology (PASCOS 2010), Valencia (Spain), July 19-23, 201