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New approach to cosmological bulk viscosity

  1. Jul 3, 2015 #1

    Abstract: We examine the cosmological consequences of an alternative to the standard expression for bulk viscosity, one which was proposed to avoid the propagation of superluminal signals without the necessity of extending the space of variables of the theory. The Friedmann equation is derived for this case, along with an expression for the effective pressure. We find solutions for the evolution of the density of a viscous component, which differs markedly from the case of conventional Eckart theory; our model evolves toward late-time phantom-like behavior with a future singularity. Entropy production is addressed, and some similarities and differences to approaches based on the Mueller-Israel-Stewart theory are discussed.

    So is the Big Rip is achieving consensus now?
  2. jcsd
  3. Jul 3, 2015 #2

    George Jones

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    No. This is just a single paper by three authors.

    If I have understood it correctly, this paper's Big Rip scenario is different than the original Big Rip scenario,


    In both scenarios the curvature tensor (tidal force) blows up at a finite cosmological time due to infinite energy density, but in the original Big Rip, the scale factor of the universe also blows up at finite time, while in this paper the energy density blows up at a finite time and scale factor (see equation (18)).
  4. Jul 4, 2015 #3
    Expanding on my inquiry a little, my question has two parts.

    Firstly, as the paper suggests, do we have good reason to believe this model supercedes previous models of bulk viscosity in that it is more representative of the evolution of our universe?

    Secondly, how significant is the problem of modelling bulk viscosity well? Is it widely considered to be a very important problem to solve with respect to modelling our universe? Is it believed that there are greater deficiencies in the existing models which should to be solved, in order to give us a realistic understanding of the future evolution of our universe?
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