Over the last decade, string theory has provided a well-motivated framework to address the microscopic nature of inflation and its sensitivity to quantum gravity effects.

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However the post-inflationary epoch has been relatively little explored so far. The main cosmological challenges to be addressed include pre- and re-heating, the origin of the matter-antimatter asymmetry, the nature of dark matter, dark radiation and dark energy.

String theory -- with its unified description of gravity and particle physics -- provides a promising framework to address these connections between cosmology and particle physics. Ultimately, post-inflationary physics will strongly constrain string models of the early Universe and could have implications for a wide range of experiments and observations, from the CMB to dark matter detection, from gravity waves to colliders.

The workshop will bring together experts in string theory, cosmology and astroparticle physics who will focus on post-inflationary string cosmology with plenty of time for informal discussions and collaboration. Update your browser to view this website correctly.

## Simons Summer Workshop: Cosmology and String Theory July 15 – August 9, | SCGP

Update my browser now. Download current event:. In the evolution of the universe, after the inflationary phase, the expansion observed today sets in that is well described by Friedmann equations. A smooth transition is expected between these two different phases. String cosmology appears to have difficulties in explaining this transition. This is known in literature as the graceful exit problem. An inflationary cosmology implies the presence of a scalar field that drives inflation.

In string cosmology, this arises from the so-called dilaton field. This is a scalar term entering into the description of the bosonic string that produces a scalar field term into the effective theory at low energies.

## String Cosmology

The corresponding equations resemble those of a Brans—Dicke theory. Analysis has been worked out from a critical number of dimension 26 down to four. In general one gets Friedmann equations in an arbitrary number of dimensions. The other way round is to assume that a certain number of dimensions is compactified producing an effective four-dimensional theory to work with.

Such a theory is a typical Kaluza—Klein theory with a set of scalar fields arising from compactified dimensions.

### Description

Such fields are called moduli. This section presents some of the relevant equations entering into string cosmology. The starting point is the Polyakov action , which can be written as:. A further antisymmetric field could be added.

## Groningen string cosmology

This is generally considered when one wants this action generating a potential for inflation. The above string action has a conformal invariance. Inflation from strings - Bento, M. B IFM On string theory and black holes - Witten, Edward Phys. Some global aspects of string compactifications - Elitzur, S. Classical solutions of two-dimensional string theory - Mandal, Gautam et al.

Dual Models for Nonhadrons - Scherk, Joel et al. B81 CALT B , Erratum: Nucl. B