Astrophysical and Cosmological Implications of Large Volume String Compactifications

Abstract

We study the spectrum, couplings and cosmological and astrophysical implications of the moduli fields for the class of Calabi-Yau IIB string compactifications for which moduli stabilisation leads to an exponentially large volume V ~ 10^{15} l_s^6 and an intermediate string scale m_s ~ 10^{11}GeV, with TeV-scale observable supersymmetry breaking. All Kähler moduli except for the overall volume are heavier than the susy breaking scale, with m ~ ln(M_P/m_{3/2}) m_{3/2} ~ (\ln(M_P/m_{3/2}))^2 m_{susy} ~ 500 TeV and, contrary to standard expectations, have matter couplings suppressed only by the string scale rather than the Planck scale. These decay to matter early in the history of the universe, with a reheat temperature T ~ 10^7 GeV, and are free from the cosmological moduli problem (CMP). The heavy moduli have a branching ratio to gravitino pairs of 10^{-30} and do not suffer from the gravitino overproduction problem. The overall volume modulus is a distinctive feature of these models and is an M_{planck}-coupled scalar of mass m ~ 1 MeV and subject to the CMP. A period of thermal inflation can help relax this problem. This field has a lifetime ~ 10^{24}s and can contribute to dark matter. It may be detected through its decays to 2γor e^+e^-. If accessible the e^+e^- decay mode dominates, with Br(χ\to 2 γ) suppressed by a factor (ln(M_P/m_{3/2}))^2. We consider the potential for detection of this field through different astrophysical sources and find that the observed gamma-ray background constrains Ω_χ <~ 10^{-4}. The decays of this field may generate the 511 keV emission line from the galactic centre observed by INTEGRAL/SPI.

31 pages, 2 figures; v2. refs added

References in corpus (7)

• Four-dimensional String Compactifications with D-Branes, Orientifolds and Fluxes
• Contraints on radiative dark-matter decay from the cosmic microwave background
• Roulette Inflation with Kähler Moduli and their Axions
• The Effects of Dark Matter Decay and Annihilation on the High-Redshift 21 cm Background
• Continuum gamma-ray emission from light dark matter positrons and electrons
• Constraining DM through 21 cm observations
• The Neutrino Suppression Scale from Large Volumes

Cited by in corpus (14)

• Non-thermal Dark Matter and the Moduli Problem in String Frameworks
• Systematics of String Loop Corrections in Type IIB Calabi-Yau Flux Compactifications
• Volume Modulus Inflation and the Gravitino Mass Problem
• Towards Realistic String Vacua From Branes At Singularities
• Continuous Global Symmetries and Hyperweak Interactions in String Compactifications
• Circumscribing Late Dark Matter Decays Model Independently
• Sparticle Spectra and LHC Signatures for Large Volume String Compactifications
• Global Fits of the Large Volume String Scenario to WMAP5 and Other Indirect Constraints Using Markov Chain Monte Carlo
• Predictions of the causal entropic principle for environmental conditions of the universe
• Neutralino Dark Matter in BMSSM Effective Theory
• Axion-Dilaton Cosmology and Dark Energy
• Sequestered Dark Matter
• Neutrino Masses, Baryon Asymmetry, Dark Matter and the Moduli Problem : A Complete Framework
• Topology from Cosmology