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arXiv 1604.04837gr-qcastro-ph.COhep-th
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麦克斯韦张量导数中含二次项的矢量暗能量模型

Vector dark energy models with quadratic terms in the Maxwell tensor derivatives

Zahra Haghani, Tiberiu Harko, Hamid Reza Sepangi, Shahab Shahidi

摘要:

我们考虑一个矢量张量引力模型,其麦克斯韦张量导数中的二次项称为波普-波多尔斯基项。得到了该模型的引力场方程和描述矢量场演化的方程,并研究了它们的牛顿极限。研究了Bopp-Podolsky型暗能量项在Bianchi I型均匀和各向异性两种几何模型中的宇宙学意义,分别对应于场的自相互作用势的存在和不存在.通过对宇宙演化方程进行数值积分,得到了两种情况下的哈勃函数、物质能量密度、剪切标量、平均各向异性参数和减速参数以及场势的时间演化.在矢量型暗能量的麦克斯韦张量导数中的二次项的存在下,根据模型参数的数值,Bianchi I型宇宙经历了复杂的动力学演化,尘埃宇宙结束于各向同性相。矢量场的自相互作用势的存在大大缩短了宇宙完全各向同性所需的时间间隔。

英文摘要:

We consider a vector-tensor gravitational model with terms quadratic in the Maxwell tensor derivatives, called the Bopp-Podolsky term. The gravitational field equations of the model and the equations describing the evolution of the vector field are obtained and their Newtonian limit is investigated. The cosmological implications of a Bopp-Podolsky type dark energy term are investigated for a Bianchi type I homogeneous and anisotropic geometry for two models, corresponding to the absence and presence of the self-interacting potential of the field, respectively. The time evolutions of the Hubble function, of the matter energy density, of the shear scalar, of the mean anisotropy parameter, and of the deceleration parameter, respectively, as well as the field potentials are obtained for both cases by numerically integrating the cosmological evolution equations. In the presence of the vector type dark energy with quadratic terms in the Maxwell tensor derivatives, depending on the numerical values of the model parameters, the Bianchi type I Universe experiences a complex dynamical evolution, with the dust Universes ending in an isotropic phase. The presence of the self-interacting potential of the vector field significantly shortens the time interval necessary for the full isotropization of the Universe.

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