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arXiv 1802.03088hep-th
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膜SUSY破裂与引力子质量

Brane SUSY Breaking and the Gravitino Mass

Noriaki Kitazawa

摘要:

具有自发破缺超对称性的超引力模型近年来得到了广泛的研究,同时也有一些值得注意的非线性极限。虽然在这些模型中引力子吸收了南武-戈德斯通费米子的自由度后变得自然有质量,但也有一些情况下自由度的简单计数并不适用,特别是因为在幺正规范中没有明确的引力子质量项。相应的模型需要非平凡的de Sitter类背景,澄清他们的Nambu-Goldstone模式的命运变得有趣。我们阐述了这样一个事实,即这些非平凡的背景可以容纳,一贯的,引力场携带的自由度是中间的无质量和大规模的领域在一个平坦的时空。例如,在一个具有德西特背景的简单超引力模型中,引力子的总自由度与平坦时空中的质量自旋为3/2的场一样多,而引力子在球极投影图像中经历零锥传播的意义上保持无质量。另一方面,在10维USp(32)I型Sugimoto模型中,“膜超对称破缺”需要更复杂的背景,引力子的自由度是有质量引力子的一半,但它又表现为无质量引力子。

英文摘要:

Supergravity models with spontaneously broken supersymmetry have been widely investigated over the years, together with some notable non-linear limits. Although in these models the gravitino becomes naturally massive absorbing the degrees of freedom of a Nambu-Goldstone fermion, there are cases in which the naive counting of degrees of freedom does not apply, in particular because of the absence of explicit gravitino mass terms in unitary gauge. The corresponding models require non-trivial de Sitter-like backgrounds, and it becomes of interest to clarify the fate of their Nambu-Goldstone modes. We elaborate on the fact that these non-trivial backgrounds can accommodate, consistently, gravitino fields carrying a number of degrees of freedom that is intermediate between those of massless and massive fields in a flat spacetime. For instance, in a simple supergravity model of this type with de Sitter background, the overall degrees of freedom of gravitino are as many as for a massive spin-3/2 field in flat spacetime, while the gravitino remains massless in the sense that it undergoes null-cone propagation in the stereographic picture. On the other hand, in the ten-dimensional USp(32) Type I Sugimoto model with "brane SUSY breaking", which requires a more complicated background, the degrees of freedom of gravitino are half as many of those of a massive one, and yet it somehow behaves again as a massless one.

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