具有诱导轴模式与幻影屏障跨越的Mimetic-Metric-Torsion
Mimetic-Metric-Torsion with induced Axial mode and Phantom barrier crossing
AI总结：
扩展mimetic-metric-torsion引力理论，使mimetic标量场同时作为挠率迹和轴向模式的源，实现暗区几何统一，并证明宇宙演化中的超加速和低红移幻影屏障平滑跨越的可行性。
摘要：
我们扩展了mimetic-metric-torsion引力理论的基本形式，使得mimetic标量场不仅能作为挠率的迹模式的源，还能在几何上表现为其轴向（或伪迹）模式的源。具体而言，我们考虑将mimetic场（i）显式地耦合到著名的Riemann-Cartan作用的Holst扩展上，以及（ii）等同于相关的Barbero-Immirzi场的平方，后者被假定为一个伪标量。理论中最初普遍存在的共形对称性仍然成立，因为相关的Cartan变换不影响挠率伪迹，从而也不影响Holst项。要求理论同时保持空间宇称对称性，我们专注于宇宙学暗区的几何统一，并表明在宇宙演化过程中超加速区域始终是可行的。从观测角度来看，假设宇宙学演化轮廓非常接近$Ł$CDM，我们进一步表明在低红移处可能存在所谓的幻影屏障的平滑跨越，但仅限于一个非常受限的参数域。随后通过考察相关挠率参数的演化，确定了超加速的程度。
英文摘要：
We extend the basic formalism of mimetic-metric-torsion gravity theory, in a way that the mimetic scalar field can manifest itself geometrically as the source of not only the trace mode of torsion, but also its axial (or, pseudo-trace) mode. Specifically, we consider the mimetic field to be (i) coupled explicitly to the well-known Holst extension of the Riemann-Cartan action, and (ii) identified with the square of the associated Barbero-Immirzi field, which is presumed to be a pseudo-scalar. The conformal symmetry originally prevalent in the theory would still hold, as the associated Cartan transformations do not affect the torsion pseudo-trace, and hence the Holst term. Demanding the theory to preserve the spatial parity symmetry as well, we focus on a geometric unification of the cosmological dark sector, and show that a super-accelerating regime in the course of evolution of the universe is always feasible. From the observational perspective, assuming the cosmological evolution profile to be very close to that for $Ł$CDM, we further show that there could be a smooth crossing of the so-called phantom barrier at a low red-shift, however for a very restricted parametric domain. The extent of the super-acceleration have subsequently been ascertained by examining the evolution of the relevant torsion parameters.
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