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arXiv 1609.01503gr-qcastro-ph.COhep-th
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具有扩展非最小导数耦合的修正引力理论中的宇宙学模型

Cosmological models in modified gravity theories with extended nonminimal derivative couplings

Tiberiu Harko, Francisco S. N. Lobo, Emmanuel N. Saridakis, Minas Tsoukalas

摘要:

我们构建引力的修改,超越Horndeski,即理论与扩展的非最小导数耦合,其中的系数函数不仅取决于标量场,但也对它的动能。这样的理论在宇宙学背景下被证明是没有幽灵的。我们研究了早期宇宙学,并表明,德西特暴胀阶段可以实现作为一个纯粹的结果,新的引力耦合。此外,我们还研究了后期的演化,在那里我们得到了一个有效的暗能量扇区,它产生于标量场及其扩展的引力耦合。我们提取各种宇宙学观测值和分析它们的行为在小红移的三个选择的潜力,即,指数,幂律,希格斯势。我们表明,宇宙从减速到加速在最近的宇宙学过去,而有效的暗能量状态方程参数趋于宇宙学常数的值在目前。最后,尽管标量场是正则的,但有效暗能量可以是幻影状的,这是模型的一个优点。

英文摘要:

We construct gravitational modifications that go beyond Horndeski, namely theories with extended nonminimal derivative couplings, in which the coefficient functions depend not only on the scalar field but also on its kinetic energy. Such theories prove to be ghost-free in a cosmological background. We investigate the early-time cosmology and show that a de Sitter inflationary phase can be realized as a pure result of the novel gravitational couplings. Additionally, we study the late-time evolution, where we obtain an effective dark energy sector which arises from the scalar field and its extended couplings to gravity. We extract various cosmological observables and analyse their behavior at small redshifts for three choices of potentials, namely, for the exponential, the power-law, and the Higgs potential. We show that the Universe passes from deceleration to acceleration in the recent cosmological past, while the effective dark-energy equation-of-state parameter tends to the cosmological-constant value at present. Finally, the effective dark energy can be phantom-like, although the scalar field is canonical, which is an advantage of the model.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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