236 research outputs found
Cosmic Necklaces from String Theory
We present the properties of a cosmic superstring network in the scenario of
flux compactification. An infinite family of strings, the (p,q)-strings, are
allowed to exist. The flux compactification leads to a string tension that is
periodic in 'p'. Monopoles, appearing here as beads on a string, are formed in
certain interactions in such networks. This allows bare strings to become
cosmic necklaces. We study network evolution in this scenario, outlining what
conditions are necessary to reach a cosmologically viable scaling solution. We
also analyze the physics of the beads on a cosmic necklace, and present general
conditions for which they will be cosmologically safe, leaving the network's
scaling undisturbed. In particular, we find that a large average loop size is
sufficient for the beads to be cosmologically safe. Finally, we argue that loop
formation will promote a scaling solution for the interbead distance in some
situations.Comment: 14 pages, 5 figures; v3, typos corrected, comments added, published
versio
The Gelaton Scenario: Equilateral non-Gaussianity from multi-field dynamics
The distinctive features of single field inflationary models with non-minimal
kinetic terms, like Dirac-Born-Infeld and k-inflation, can be captured by more
familiar multiple field inflationary systems of the type that typically arise
in low energy supergravity models. At least one heavy field, which we call the
gelaton, has an effective potential which depends on the kinetic energy of the
inflaton. Integrating out the gelaton gives rise to an effectively single field
system for which the speed of sound for the adiabatic fluctuations is reduced,
generating potentially observable equilateral non-Gaussianity, while causing
negligible isocurvature fluctuations. This mechanism is only active if there is
a relatively tight coupling between the gelaton and the inflaton, and this puts
an upper limit on the mass of the gelaton for which the inflaton-gelaton system
remains weakly coupled. This approach gives a UV-completable framework for
describing large classes of k-inflationary behavior.Comment: v3: 5 pages, very minor changes, matches version published in PR
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