Acceleration field of a Universe modeled as a mixture of scalar and matter fields

Abstract

A model of the Universe as a mixture of a scalar (inflaton or rolling tachyon from the string theory) and a matter field (classical particles) is analyzed. The particles are created at the expense of the gravitational energy through an irreversible process whereas the scalar field is supposed to interact only with itself and to be minimally coupled with the gravitational field. The irreversible processes of particle creation are related to the non-equilibrium pressure within the framework of the extended (causal or second-order) thermodynamic theory. The scalar field (inflaton or tachyon) is described by an exponential potential density added by a parameter which represents its asymptotic value and can be interpreted as the vacuum energy. This model can simulate three phases of the acceleration field of the Universe, namely,(a) an inflationary epoch with a positive acceleration followed by a decrease of the acceleration field towards zero, (b) a past decelerated period where the acceleration field decreases to a maximum negative value followed by an increase towards zero, and (c) a present accelerated epoch. For the energy densities there exist also three distinct epochs which begin with a scalar field dominated period followed by a matter field dominated epoch and coming back to a scalar field dominated phase.

9 pages, 2 figures, to be published in General Relativity and Gravitation

References in corpus (2)

• Cosmological models described by a mixture of van der Waals fluid and dark energy
• Irreversible Processes in a Universe modelled as a mixture of a Chaplygin gas and radiation

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• Pair production in a strong magnetic field: the effect of a strong background gravitational field
• Tachyonization of the $\La$CDM cosmological model
• Scenarios of cosmic string with variable cosmological constant
• Chaplygin Gas of Tachyon Nature Imposed by Symmetry and Constrained via H(z) Data
• Fermionic Tachyons as a Source of Dark Energy