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arXiv 0802.0470hep-thhep-ph
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具有消失的单圈宇宙学常数和微扰破缺的超对称性的准现实杂化弦模型?

Quasi-realistic heterotic-string models with vanishing one-loop cosmological constant and perturbatively broken supersymmetry?

Gerald B. Cleaver, Alon E. Faraggi, Elisa Manno, Cristina Timirgaziu

摘要:

自由费米子表述中的准现实弦模型通常包含一个反常U(1),它产生了费耶特-伊利奥普洛斯D项,在弦微扰理论中的单圈水平上打破了超对称性。超对称性传统上是通过在真空上施加F-和D-平坦性来恢复的。通过对平直方向的标准分析,我们提出了一个准现实的三代弦模型,其中严格的F-和D-平直解似乎并不存在于超势的所有阶。我们推测,这一结果表明,在这个模型中的超对称平坦的F-和D-解决方案的不存在。我们提供了一些论据来支持这种情况,并讨论其潜在的影响。弦谱的玻色-费米简并意味着单圈配分函数和单圈宇宙学常数在模型中消失。如果我们的断言是正确的,这个模型可能代表了已知的第一个宇宙学常数消失和微扰破缺的超对称性的例子。我们讨论的内部自由费米子边界条件,可能对应于一个大的模型,共享这些属性的独特属性。由于非对称边界条件,这类模型的几何模量是固定的,而超对称平坦方向的缺失意味着超对称模量也是固定的,并且隐扇区非微扰效应可能会固定光子。

英文摘要:

Quasi-realistic string models in the free fermionic formulation typically contain an anomalous U(1), which gives rise to a Fayet-Iliopoulos D-term that breaks supersymmetry at the one--loop level in string perturbation theory. Supersymmetry is traditionally restored by imposing F- and D-flatness on the vacuum. By employing the standard analysis of flat directions we present a quasi--realistic three generation string model in which stringent F- and D-flat solution do not appear to exist to all orders in the superpotential. We speculate that this result is indicative of the non-existence of supersymmetric flat F- and D-solutions in this model. We provide some arguments in support of this scenario and discuss its potential implications. Bose-Fermi degeneracy of the string spectrum implies that the one--loop partition function and hence the one-loop cosmological constant vanishes in the model. If our assertion is correct, this model may represent the first known example with vanishing cosmological constant and perturbatively broken supersymmetry. We discuss the distinctive properties of the internal free fermion boundary conditions that may correspond to a large set of models that share these properties. The geometrical moduli in this class of models are fixed due to asymmetric boundary conditions, whereas absence of supersymmetric flat directions would imply that the supersymmetric moduli are fixed as well and the dilaton may be fixed by hidden sector nonperturbative effects.

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