标题： 单模引力的宇宙学含义 显示英文标题

标题： Cosmological Implications of Unimodular Gravity

摘要： 我们考虑一个引力和物质场的模型，该模型仅在单模一般坐标变换（GCT）下保持不变。度规的行列式被当作一个独立的场，它在单模GCT下作为标量变换。此外，我们还要求理论在一种新的全局对称性下保持不变，我们称之为广义共形不变性。我们研究了该理论的宇宙学含义。我们证明该理论对高红移超新星数据的拟合与标准大爆炸模型相同。因此，我们需要其他宇宙学观测来检验该模型的有效性。我们还考虑了一些不遵守广义共形不变性的模型。在这些模型中，我们可以在不引入标准宇宙常数项的情况下拟合超新星数据。此外，这些模型只引入了一个暗组分，因此解决了暗物质和暗能量的巧合问题。 显示英文摘要

摘要： We consider a model of gravity and matter fields which is invariant only under unimodular general coordinate transformations (GCT). The determinant of the metric is treated as a separate field which transforms as a scalar under unimodular GCT. Furthermore we also demand that the theory is invariant under a new global symmetry which we call generalized conformal invariance. We study the cosmological implications of the resulting theory. We show that this theory gives a fit to the high-z supernova data which is identical to the standard Big Bang model. Hence we require some other cosmological observations to test the validity of this model. We also consider some models which do not obey the generalized conformal invariance. In these models we can fit the supernova data without introducing the standard cosmological constant term. Furthermore these models introduce only one dark component and hence solve the coincidence problem of dark matter and dark energy.