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- String_cosmology abstract "String cosmology is a relatively new field that tries to apply equations of string theory to solve the questions of early cosmology. A related area of study is brane cosmology.This approach can be dated back to a paper by Gabriele Veneziano that shows how an inflationary cosmological model can be obtained from string theory, thus opening the door to a description of pre-Big Bang scenarios.The idea is related to a property of the bosonic string in a curve background, better known as nonlinear sigma model. First calculations from this model showed as the beta function, representing the running of the metric of the model as a function of an energy scale, is proportional to the Ricci tensor giving rise to a Ricci flow. As this model has conformal invariance and this must be kept to have a sensible quantum field theory, the beta function must be zero producing immediately the Einstein field equations. While Einstein equations seem to appear somewhat out of place, nevertheless this result is surely striking showing as a background two-dimensional model could produce higher-dimensional physics. An interesting point here is that such a string theory can be formulated without a requirement of criticality at 26 dimensions for consistency as happens on a flat background. This is a serious hint that the underlying physics of Einstein equations could be described by an effective two-dimensional conformal field theory. Indeed, the fact that we have evidence for an inflationary universe is an important support to string cosmology.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. 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. Such fields are called moduli.".
- String_cosmology wikiPageExternalLink ~gasperin.
- String_cosmology wikiPageExternalLink theme3.py?level=1&index1=15204.
- String_cosmology wikiPageID "2864696".
- String_cosmology wikiPageRevisionID "605073978".
- String_cosmology hasPhotoCollection String_cosmology.
- String_cosmology subject Category:General_relativity.
- String_cosmology subject Category:Physical_cosmology.
- String_cosmology subject Category:String_theory.
- String_cosmology comment "String cosmology is a relatively new field that tries to apply equations of string theory to solve the questions of early cosmology.".
- String_cosmology label "Cosmologie cordiste".
- String_cosmology label "String cosmology".
- String_cosmology label "علم الكون الوتري".
- String_cosmology sameAs Cosmologie_cordiste.
- String_cosmology sameAs m.087pj9.
- String_cosmology sameAs Q279029.
- String_cosmology sameAs Q279029.
- String_cosmology wasDerivedFrom String_cosmology?oldid=605073978.
- String_cosmology isPrimaryTopicOf String_cosmology.