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arXiv 0705.3460hep-phastro-phhep-th
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大体积弦紧化的天体物理和宇宙学意义

Astrophysical and Cosmological Implications of Large Volume String Compactifications

Joseph P. Conlon, Fernando Quevedo

摘要:

我们研究了卡-丘IIB弦紧化类的模场的谱、耦合以及宇宙学和天体物理学意义,对于这类弦紧化,模稳定化导致了一个指数级的大体积V ~ 10^{15} l_s^6和一个中间弦尺度m_s ~ 10^{11}GeV,并具有TeV尺度的可观测超对称破缺。除了总体积外,所有的凯勒模量都比超临界尺度重,m ~ ln(M_P/ m_{3/2})m_{3/2} ~(\ln(M_P/ m_{3/2}))^2 m_{susy} ~ 500 TeV,而且与标准预期相反,物质耦合只被弦尺度而不是普朗克尺度抑制。这些物质在宇宙历史的早期衰变为物质,再热温度T ~ 10^7 GeV,并且不受宇宙学模量问题(CMP)的影响。重模量与引力子对的分支比为10^{-30},并且不受引力子过度产生问题的影响。总体积模量是这些模型的一个显著特征,并且是质量m ~ 1 MeV的M_{planck}耦合标量,并且受到CMP。一段时间的热膨胀可以帮助缓解这个问题。这个场的寿命约为10^{24}s,可以贡献暗物质。它可以通过衰变到2γ或e^+e^-而被探测到。如果可以达到,则e^+e^-衰变模式占主导地位,Br(χ \to 2 γ)被因子(ln(M_P/ m_{3/2}))^2抑制。我们考虑了通过不同天体物理源探测这个场的可能性,发现观测到的γ射线背景限制Ω x <~ 10^{-4}。这个场的衰变可能产生INTEGRAL/SPI观测到的来自银河系中心的511 keV发射线。

英文摘要:

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.

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