Showing papers by "Eleftherios Papantonopoulos published in 2001"
TL;DR: In this paper, the cosmological evolution of a type-0 string theory was studied by employing non-criticality, which may be induced by fluctuations of the D3 brane worlds.
Abstract: We study the cosmological evolution of a type-0 string theory by employing non-criticality, which may be induced by fluctuations of the D3 brane worlds. We check the consistency of the approach to O(alpha ') in the corresponding sigma-model. The ten-dimensional theory is reduced to an effective four-dimensional model, with only time dependent fields. We show that the four-dimensional universe has an inflationary phase and graceful exit from it, while the other extra dimensions are stabilized to a constant value, with the fifth dimension much larger than the others. We pay particular attention to demonstrating the role of tachyonic matter in inducing these features. The Universe asymptotes, for large times, to a non-accelerating linearly-expanding Universe with a time-dependent dilaton and a relaxing to zero vacuum energy a la quintessence.
34 citations
TL;DR: In this article, the cosmological evolution of a D3-brane universe in a type 0 string background was studied and the energy density induced on the brane because of its motion in the bulk was calculated.
Abstract: We study the cosmological evolution of a D3-brane Universe in a type 0 string background. We follow the brane-universe along the radial coordinate of the background and we calculate the energy density which is induced on the brane because of its motion in the bulk. We find that for some typical values of the parameters and for a particular range of values of the scale factor of the brane-universe, the effective energy density is dominated by a term proportional to $\frac{1}{(loga)^{4}}$ indicating a slow varying inflationary phase. For larger values of the scale factor the effective energy density takes a constant value and the brane-universe enters its usual inflationary period.
31 citations
01 Nov 2001
TL;DR: In this article, the cosmological evolution of a D3-brane universe in a type 0 string background was studied and the energy density of the brane universe was calculated.
Abstract: We study the cosmological evolution of a D3-brane Universe in a type 0 string background. We follow the brane universe along the radial coordinate of the background and we calculate the energy density which is induced on the brane because of its motion in the bulk. For constant values of tachyon and dilaton an inflationary phase is appearing. For non constant values of tachyon and dilaton and for a particular range of values of the scale factor of the brane-universe, the effective energy density is dominated by a term proportional to 1/(log α)4 indicating a slowly varying inflationary phase.
7 citations
TL;DR: In this paper, a time-dependent cosmological constant was used to solve the Einstein equations with a brane cosmology constant, and it was shown that the universe passes from a fast growing phase (inflation) to an expanding phase in a natural way.
Abstract: Motivated by brane cosmology, we solve the Einstein equations with a time-dependent cosmological constant. Assuming that at an early epoch the vacuum energy scales as 1/log t, we show that the universe passes from a fast growing phase (inflation) to an expanding phase in a natural way.
6 citations
TL;DR: In this article, a time dependent cosmological constant was used to solve the Einstein equations with a brane cosmology constant, and it was shown that the universe passes from a fast growing phase (inflation) to an expanding phase in a natural way.
Abstract: Motivated by brane cosmology we solve the Einstein equations with a time dependent cosmological constant. Assuming that at an early epoch the vacuum energy scales as $1/logt $, we show that the universe passes from a fast growing phase (inflation) to an expanding phase in a natural way.
1 citations
27 Jul 2001
TL;DR: In this paper, a model based on type-0 string theory is presented, in which our universe after the inflationary phase, passes smoothly to a flat Robertson-Walker universe.
Abstract: Inflation is now a basic ingredient of the modern cosmology. Afterreviewing the basic characteristics of inflation, we briefly discuss inflation in string and brane theories, focusing on the problem of the exit from in flation in these theories. We present a model, based on type-0 string theory, in which our universe after the inflationary phase, passes smoothly to a flat Robertson-Walker universe.