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arXiv 1403.3095hep-thastro-ph.CO
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时空对称陪集构造的不等式

Inequivalence of Coset Constructions for Spacetime Symmetries

Paolo Creminelli, Marco Serone, Gabriele Trevisan, Enrico Trincherini

摘要:

时空对称性的非线性实现可以通过对内部对称性有效的陪集构造的推广来获得。时空对称性的不同表示的物理等价性并不明显,因为它们的关系不仅涉及场的重新定义,而且涉及依赖于场的坐标变化。一个简单而相关的时空对称性是通过4D共形群的收缩而获得的,该共形群导致伽利略群。我们分析了这一组的两个非线性实现,特别是集中在非平凡的背景周围的信号的传播。光锥的孔径一般是不同的两种表示,特别是一个自由(管腔)无质量标量映射在伽利略理论,承认超光速传播。我们表明,在这个理论中,如果我们考虑在无穷远处消失的背景,没有渐近效应:轨迹的位移积分为零,可以预期,因为S-矩阵是平凡的。关于本地测量,我们表明,考虑到在一个理论中与固定源的本地耦合被映射到非本地耦合,解决了这个难题,我们表明,这种效果补偿了不同的光锥。因此,这两个理论有不同的局部性概念。这同样适用于不同的非线性实现的共形群,我们研究的特殊情况下的宇宙学有趣的背景:伽利略创世纪的情况。

英文摘要:

Non-linear realizations of spacetime symmetries can be obtained by a generalization of the coset construction valid for internal ones. The physical equivalence of different representations for spacetime symmetries is not obvious, since their relation involves not only a redefinition of the fields but also a field-dependent change of coordinates. A simple and relevant spacetime symmetry is obtained by the contraction of the 4D conformal group that leads to the Galileon group. We analyze two non-linear realizations of this group, focusing in particular on the propagation of signals around non-trivial backgrounds. The aperture of the lightcone is in general different in the two representations and in particular a free (luminal) massless scalar is mapped in a Galileon theory which admits superluminal propagation. We show that in this theory, if we consider backgrounds that vanish at infinity, there is no asymptotic effect: the displacement of the trajectory integrates to zero, as can be expected since the S-matrix is trivial. Regarding local measurements, we show that the puzzle is solved taking into account that a local coupling with fixed sources in one theory is mapped into a non-local coupling and we show that this effect compensates the different lightcone. Therefore the two theories have a different notion of locality. The same applies to the different non-linear realizations of the conformal group and we study the particular case of a cosmologically interesting background: the Galilean Genesis scenarios.

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