无暗能量场时中微子产生的动力学暗能量
Neutrino generated dynamical dark energy with no dark energy field
摘要：
动力学暗能量（DE）现象是伴随着非相对论性费米子物质宇宙膨胀而出现的一种几何效应。这在不需要任何流体的情况下发生，例如动力学标量场（quintessence、cosmon等），与其它已知的几何DE模型相比，具有传统形式的爱因斯坦方程。这一现象是由双测度场论框架中的第一性原理引起的，在爱因斯坦框架中，费米子质量和宇宙学常数（CC）都变成了冷费米子密度n的函数。这种n依赖性在常规（实验室）条件下可以忽略不计，但它可能在宇宙学中起着重要作用。在4D引力模型中，原始作用只涉及CC和大质量费米子而没有自相互作用，对于参数空间中的不同（但很宽）区域，我们发现了两种可能的宇宙晚期从冷物质统治时代开始的场景。我们认为，驱动变量CC的费米子应该与冷中微子配置在空洞和超空洞。第一类的宇宙学动力学实际上与LambdaCDM模型一致，而第二类的动力学是一个伪撕裂方案的幻影状制度。穿越幻影分界线的发生是由于一种新型的中微子DE效应，即中微子通过具有零质量和类真空EoS P_v =-ρ_v的状态。
英文摘要：
Dynamical dark energy (DE) phenomenon emerges as a geometrical effect accompanying the cosmological expansion of nonrelativistic fermionic matter. This occurs without the need for any fluid, like e.g. dynamical scalar field (quintessence, cosmon, etc.), and with conventional form of the Einstein equations in contrast to other known geometrical DE models. The phenomenon results from first principles in the framework of the two measures field theory where, in the Einstein frame, both fermion masses and the cosmological constant (CC) turn into functions of the cold fermion density n. This n dependence becomes negligible in regular (laboratory) conditions but it may have an important role in cosmology. In the 4D gravity model where the original action involves only CC and massive fermions without selfinteraction, for different (but wide) regions in the parameter space we have found two possible classes of scenarios for the late universe starting from the cold matter domination era. We argue that the fermions which drive the variable CC should be associated with cold neutrinos disposed in voids and supervoids. The cosmological dynamics of the first class practically coincides with that of the LambdaCDM model, while the dynamics of the second class is of the phantom-like regime with a pseudo-rip scenario. Crossing the phantom divide happens due to a new type of the neutrino DE effect where neutrinos pass through the state with zero mass and with the vacuum-like EoS P_ν=-ρ_ν.
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