Non-tachyonic Scherk-Schwarz compactifications, cosmology and moduli stabilization

Abstract

It is well-known that Scherk-Schwarz compactifications in string theory have a tachyon in the closed string spectrum appearing for a critical value of a compact radius. The tachyon can be removed by an appropriate orientifold projection in type II strings, giving rise to tachyon-free compactifications. We present explicit examples of this type in various dimensions, including six and four-dimensional chiral examples, with softly broken supersymmetry in the closed sector and non-BPS configurations in the open sector. These vacua are interesting frameworks for studying various cosmological issues. We discuss four-dimensional cosmological solutions and moduli stabilization triggered by nonperturbative effects like gaugino condensation on D-branes and fluxes.

36 pages, LaTeX; added references

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• Towards a Non-Supersymmetric String Phenomenology
• Internal magnetic fields and supersymmetry in orientifolds
• Spin-field Interaction Effects and Loop Dynamics in AdS/CFT Duality
• An Alternative for Moduli Stabilisation
• On exponential suppression of the cosmological constant in non-SUSY strings at two loops and beyond
• Scherk-Schwarz Breaking and Intersecting Branes
• Stability and vacuum energy in open string models with broken supersymmetry
• On interpolations from SUSY to non-SUSY strings and their properties
• Geometry of orientifold vacua and supersymmetry breaking
• Moduli Stabilization with Long Winding Strings
• A Dynamical Mechanism for Large Volumes with Consistent Couplings
• Tachyons and Misaligned Supersymmetry in Closed String Vacua