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arXiv 2101.02645gr-qcastro-ph.COhep-th
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新二次挠率理论的非线性Hamilton分析第一部分。无曲率约束的情况

Nonlinear Hamiltonian analysis of new quadratic torsion theories Part I. Cases with curvature-free constraints

W. E. V. Barker, A. N. Lasenby, M. P. Hobson, W. J. Handley

摘要:

最近发现,当在没有物质的情况下线性化时,具有二次曲率和挠率的一般引力理论的58种情况(i)没有鬼和快子,(ii)功率计数可重整化。我们检查的八种情况下,其主要约束不依赖于曲率张量的非线性哈密顿结构。我们确认了所有这些理论在线性区域的粒子谱和么正性。我们发现定性动力学的变化,在所有八种情况下的非线性制度,建议至少有一个破碎的规范对称性,并可能激活负动能自旋宇称部门和因果行为。其中两个例子在线性水平上传播了一对无质量模式,作为引力的候选理论很有趣。然而,我们确定这些模式与矢量激发,而不是张量极化的引力子。此外,我们表明,这些理论不支持一个可行的宇宙学背景。

英文摘要:

It was recently found that, when linearised in the absence of matter, 58 cases of the general gravitational theory with quadratic curvature and torsion are (i) free from ghosts and tachyons and (ii) power-counting renormalisable. We inspect the nonlinear Hamiltonian structure of the eight cases whose primary constraints do not depend on the curvature tensor. We confirm the particle spectra and unitarity of all these theories in the linear regime. We uncover qualitative dynamical changes in the nonlinear regimes of all eight cases, suggesting at least a broken gauge symmetry, and possibly the activation of negative kinetic energy spin-parity sectors and acausal behaviour. Two of the cases propagate a pair of massless modes at the linear level, and were interesting as candidate theories of gravity. However, we identify these modes with vector excitations, rather than the tensor polarisations of the graviton. Moreover, we show that these theories do not support a viable cosmological background.

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