Abstract
The expansion rate of “intermediate inflation” lies between the exponential and power law expansion but corresponding accelerated expansion does not start at the onset of cosmological evolution. Present study of “intermediate inflation” reveals that it admits scaling solution and has got a natural exit form it at a later epoch of cosmic evolution, leading to late time acceleration. The corresponding scalar field responsible for such feature is also found to behave as a tracker field for gravity with canonical kinetic term.
Highlights
It is almost certain that the universe contains 70% of dark energy, which is evolving slowly in such a manner that at present the value of the equation of state parameter is w < −1/3, or more precisely, w −1, so that the universe is presently accelerating see, e.g., 1 for a recent review
This problem is known as the ”coincidence problem” when stated as ”why Λ took 15 billion years to dominate over other kinds of matter present in the universe?” A scalar field with dynamical equation of state wφ, dubbed as quintessence field 2, appears to get rid of this problem, which during “slow roll” over the potential, acquires negative pressure and acts as effective cosmological constant Λeff
It has been found that the cosmological solution in the form a a0e Atf with a0 > 0, A > 0, and 0 < f < 1 may be treated as dark energy model leading to late time cosmic acceleration, rather than intermediate inflation at early universe
Summary
It is almost certain that the universe contains 70% of dark energy, which is evolving slowly in such a manner that at present the value of the equation of state parameter is w < −1/3, or more precisely, w −1, so that the universe is presently accelerating see, e.g., 1 for a recent review. In order to comply the vacuum energy density, ρvac ≈ 1074 GeV4 calculated from quantum field theory as–ρvac ≈ m4pl/16π2 with the critical density, ρΛ ≈ 10−47 GeV4 related to the cosmological constant as–ρΛ Λm2pl/8π , it requires to set up yet another energy scale in particle physics This problem is known as the ”coincidence problem” when stated as ”why Λ took 15 billion years to dominate over other kinds of matter present in the universe?” A scalar field with dynamical equation of state wφ, dubbed as quintessence field 2 , appears to get rid of this problem, which during “slow roll” over the potential, acquires negative pressure and acts as effective cosmological constant Λeff. In a recent work it has been found that Gauss-Bonnet interaction in four dimensions with dynamic dilatonic scalar coupling leads to a solution a a0 exp Atf in the above form, where the universe starts evolving with a decelerated exponential expansion. It is found that some specific forms of the superpotential H φ 27, 28 lead to the so-called intermediate inflationary solutions
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