arXiv 1003.29962010-03-15hep-phastro-ph.COhep-th

标量场的宇宙凝聚--产生暗能量

Cosmological Condensation of Scalar Fields -- Making a dark energy

Houri Ziaeepour

备注：: 36 pages, 1 figure
发表信息：: Phys.Rev.D81:103526,2010
DOI：: 10.1103/PhysRevD.81.103526

摘要：

我们的宇宙是由量子力学及其扩展的量子场论（QFT）所统治的。然而，对一些宇宙学现象的解释，如暴胀，暗能量，对称性破缺，和相变需要经典标量场的存在。虽然在实验室中标量场的凝聚过程已经相当好地理解了，但将结果扩展到宇宙学背景并不是微不足道的。在这里，我们研究凝聚的形成-一个经典的标量场-在宇宙再加热后。我们假设一个由重粒子衰变产生的光量子标量场，为了简单起见，我们假设它是另一个标量。我们表明，在辐射支配时期，在一定的条件下，单独的重粒子的衰变是足够的凝聚的生产。这个过程非常类似于预热--暴胀结束时的指数粒子产生。在宇宙膨胀较快的物质支配时期，除非存在自相互作用，否则光靠衰变不能保持场的增长趋势，凝聚态的振幅迅速减小。这个问题对于暗能量尤其重要。我们表明，自相互作用的量子校正在这个过程中起着至关重要的作用。值得注意的是，他们诱导一个有效的行动，其中包括逆幂律条款，因此可以导致跟踪行为，即使当经典的自相互作用是一个简单的幂律3或4阶。这消除了拉格朗日量中不可重正化项的必要性。如果暗能量是量子标量场的凝聚，这些结果表明，它的存在与量子物理在最大可观测尺度上的作用密切相关。

英文摘要：

Our Universe is ruled by quantum mechanics and its extension Quantum Field Theory (QFT). However, the explanations for a number of cosmological phenomena such as inflation, dark energy, symmetry breakings, and phase transitions need the presence of classical scalar fields. Although the process of condensation of scalar fields in the lab is fairly well understood, the extension of results to a cosmological context is not trivial. Here we investigate the formation of a condensate - a classical scalar field - after reheating of the Universe. We assume a light quantum scalar field produced by the decay of a heavy particle, which for simplicity is assumed to be another scalar. We show that during radiation domination epoch under certain conditions, the decay of the heavy particle alone is sufficient for the production of a condensate. This process is very similar to preheating - the exponential particle production at the end of inflation. During matter domination epoch when the expansion of the Universe is faster, the decay alone can not keep the growing trend of the field and the amplitude of the condensate decreases rapidly, unless there is a self interaction. This issue is particularly important for dark energy. We show that quantum corrections of the self-interaction play a crucial role in this process. Notably, they induce an effective action which includes inverse power-law terms, and therefore can lead to a tracking behaviour even when the classical self-interaction is a simple power-law of order 3 or 4. This removes the necessity of having nonrenormalisable terms in the Lagrangian. If dark energy is the condensate of a quantum scalar field, these results show that its presence is deeply related to the action of quantum physics at largest observable scales.

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