A. Mohammadi

Hamilton-Jacobi Formalism for Tachyon Inflation

Tachyon inflation is reconsidered by using the recent observational data obtained from Planck-2013 and BICEP2. The Hamilton-Jacobi formalism is picked out as a desirable approach in this work, which allows one to easily obtain the main parameters of the model. The Hubble parameter is supposed as a power-law and exponential function of the scalar field, and each case is considered separately. The constraints on the model, which come from observational data, are explained during the work. The results show a suitable value for the tensor spectral index and an appropriate form of the potential.

Brane inflation driven by noncanonical scalar field

In this work, we are going to study the inflationary era of the Universe evolution by using second type of Randall-Sundrum model (RS-II) braneworld gravity. It is supposed that the Universe is dominated by scalar field with noncanonical kinetic terms. The kinetic term is supposed as a power-law function, and the work is performed for two typical cases. Using recent observations, the free parameters of the model are determined. It is shown that theoretical results are in acceptable agreement with observational data. Finally the time period of inflation is derived approximately, and it is found out that the inflation could occur after the five-dimensional Planck time.

Hamilton-Jacobi formalism to warm inflationary scenario

Hamilton-Jacobi formalism as a powerful method is being utilized to reconsider warm inflationary scenario, where the scalar field as the main component deriving inflation interacts with other field. Separating the context to strong and weak dissipative regimes, the goal is followed for two popular function of dissipation coefficient. Applying slow-rolling approximations, the required perturbation parameters are extracted and by comparison to the latest Planck data, the free parameters are restricted. Possibility of producing an acceptable inflation is studied where the result shows that for all cases the model could successfully suggests amplitude of scalar perturbation, scalar spectral index , its running, and the tensor-to-scalar ratio.

Quark-hadron phase transition in a chameleon Brans-Dicke model of brane gravity

In this work, the quark-hadron phase transition in a chameleon Brans-Dicke model of brane world cosmology within an effective model of QCD is investigated. Whereas, in the chameleon Brans-Dicke model of brane world cosmology, the Friedmann equation and conservation of density energy are modified, resulting in an increased expansion in the early Universe. These have important effects on quark-hadron phase transitions. We investigate the evolution of the physical quantities relevant to quantitative descriptions of the early times, namely, the energy density,

Inflationary universe in the presence of a minimal measurable length

\rho

BRANE COSMOLOGY WITH GENERALIZED CHAPLYGIN GAS IN THE BULK

, temperature,

Viscous warm inflation: Hamilton–Jacobi formalism

T

Intermediate inflation driven by DBI scalar field

, and the scale factor,

Brane Cosmology for Vacuum and Cosmological Constant Bulk

a

Constant-roll approach to non-canonical inflation

, before, during, and after the phase transition. We do this for smooth crossover formalism in which lattice QCD data is used for obtaining the matter equation of state and first order phase transition formalism. Our analyses show that the quark-hadron phase transition has occurred at approximately one nanosecond after the big bang and the general behavior of temperature is similar in both of two approaches.