String Cosmology and Inflation

Abstract

Following a suggestion by Gasperini and Veneziano, that String Cosmology can be reconciled with Inflation and, hence, with the Standard Big Bang, we display an analytical solution which possesses four interesting properties: (1) it is non-singular; (2) it distinguishes the dynamics of the external scale factor, $a(t)$, from that of the internal one, $b(t)$; (3) it exhibits a non-monotonic behavior of $a(t)$; and (4) it stabilizes both Newton's constant and $b(t)$ (the latter to a finite, non-vanishing value). The interest of the non-monotonic evolution of $a(t)$ consists in the fact that it contains three phases of accelerated expansion, contraction and expansion before the final decelerated expansion which eventually becomes the Standard Big Bang. The total number of e-folds of the three accelerated eras can be calculated and tuned to fit the requests of observational astronomy.

Revtex file, 21 pages, 4 figures available on request, accepted for publication on Phys. Rev. D

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• Pre-Big-Bang in String Cosmology
• Singularity-free cosmological solutions of the superstring effective action
• On Physical Equivalence between Nonlinear Gravity Theories
• Challenges for Superstring Cosmology
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• Graceful exit in quantum string cosmology
• Lectures on Cosmic Inflation and its Potential Stringy Realizations
• Non-standard primordial fluctuations and nongaussianity in string inflation
• Modulated Reheating and Large Non-Gaussianity in String Cosmology
• Singularity and exit problems in two-dimensional string cosmology
• Inflationary and Deflationary Branches in Extended Pre--Big Bang Cosmology
• Graviton Spectra in String Cosmology
• Gauss-Bonnet models with cosmological constant and non zero spatial curvature in $D=4$
• General aspects of Gauss-Bonnet models without potential in dimension four
• Exact inflationary solutions
• Multidimensional Gravity and Cosmology: Exact Solutions
• A Non-Singular Universe in String Cosmology