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A cyclic cosmology.

机译：循环宇宙学。

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摘要

It is speculated how dark energy in a braneworld can help reconcile an infinitely cyclic cosmology with the second law of thermodynamics. A cyclic model featuring dark energy with a phantom (w -1) equation of state leads to a turnaround at a time just before a would-be Big Rip at one end of the cycle and a bounce just before a would be crunch at the other. At the turnaround, both the volume and entropy of our universe decrease by a gigantic factor while very many independent small contracting universes are spawned. The entropy of our model decreases to nearly zero as it approaches the turnaround after which it increases by only a vanishing amount during the contracting stage, empty of matter. Shortly after the bounce, the entropy increases by a large factor during inflationary expansion. We next examine the content of the contracting universe (cu) and its entropy Scu. We find that in addition to dark energy, the universe contains zero photons on average (with the unlikely single photon, if present immediately after the turnaround, having infinitesimal energy that blue shifts eventually to produce e+e - pairs). These statements are independent of the equation of state o = p/rho of dark energy provided o -1. Thus Scu = 0 and if observations confirm o -1 the entropy problem is solved. We discuss the absence of a theoretical lower bound on &phis; = |o + 1| and then describe an anthropic fine tuning argument that renders unlikely an extremely small &phis;. The present bound &phis; 0.1 already implies a time until turnaround of ( tT -- t0) ≳ 100 Gy. The requirement that our universe satisfy a CBE-condition (Comes Back Empty) imposes a lower bound on the number Ncp of causal patches which separate at turnaround. This bound depends on the dark energy equation of state w = p/rho = -1 - &phis; with &phis; > 0. More accurate measurement of &phis; will constrain Ncp. The critical density rhoc in the model has a lower bound rhoc ≥ (109GeV) 4 or rhoc ≥ (1018GeV) 4 when the smallest bound state has size 10-15m, or 10-35m, respectively.
机译：人们推测，在一个全新的世界中，暗能量如何能够帮助调和无限循环的宇宙学与热力学第二定律。一个具有暗能量（具有幻像（w <-1）状态方程）的循环模型会在一个周期的末尾即将发生大裂口之前的某个时间发生周转，而在一个周期的紧缩之前会发生反弹。其他。在转机时，我们的宇宙的体积和熵都减少了一个巨大的因素，同时产生了许多独立的小收缩宇宙。我们的模型的熵随着它接近周转而降低到几乎为零，此后在收缩阶段它仅增加一个消失的量，没有物质。反弹后不久，在通货膨胀期间，熵增加很大。接下来，我们检查收缩宇宙（cu）的内容及其熵Scu。我们发现，除了暗能量之外，宇宙平均还包含零个光子（如果不太可能出现单个光子，如果在周转之后立即出现，则具有无限的能量，蓝色最终会转变为e + e-对）。这些陈述独立于o = -1的状态方程o =暗能量的p / rho。因此，Scu = 0，如果观察结果确认o <-1，则熵问题得到解决。我们讨论了＆phis;上没有理论上的下界。 = | o + 1 |然后描述一个人为的微调参数，该参数不太可能导致极小的φ。现在的绑定＆phis; <0.1已经意味着直到（tT-t0）＆gsim;的周转时间。 100 Gy。我们的宇宙满足CBE条件（返回空）的要求对因周转而分离的因果补丁数Ncp施加了下限。该界限取决于状态的暗能量方程w = p / rho = -1-＆phis;。与＆phis; >0。＆phis;的更准确测量将约束Ncp。当最小绑定状态的大小分别为10-15m或10-35m时，模型中的临界密度rhoc的下限为rhoc≥（109GeV）4或rhoc≥（1018GeV）4。

著录项

  • 作者

    Baum, Lauris M.;

  • 作者单位

    The University of North Carolina at Chapel Hill.;

  • 授予单位 The University of North Carolina at Chapel Hill.;
  • 学科 Physics Theory.
  • 学位 Ph.D.
  • 年度 2009
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  • 原文格式 PDF
  • 正文语种 eng
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