Model-independent energy budget of cosmological first-order phase transitions. (arXiv:2004.06995v2 [astro-ph.CO] UPDATED)

Model-independent energy budget of cosmological first-order phase transitions. (arXiv:2004.06995v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Giese_F/0/1/0/all/0/1">Felix Giese</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Konstandin_T/0/1/0/all/0/1">Thomas Konstandin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vis_J/0/1/0/all/0/1">Jorinde van de Vis</a>

We study the energy budget of a first-order cosmological phase transition,
which is an important factor in the prediction of the resulting gravitational
wave spectrum. Formerly, this analysis was based mostly on simplified models as
for example the bag equation of state. Here, we present a model-independent
approach that is exact up to the temperature dependence of the speed of sound
in the broken phase. We find that the only relevant quantities that enter in
the hydrodynamic analysis are the speed of sound in the broken phase and a
linear combination of the energy and pressure differences between the two
phases which we call pseudotrace (normalized to the enthalpy in the broken
phase). The pseudotrace quantifies the strength of the phase transition and
yields the conventional trace of the energy-momentum tensor for a relativistic
plasma (with speed of sound squared of one third). We study this approach in
several realistic models of the phase transition and also provide a code
snippet that can be used to determine the efficiency coefficient for a given
phase transition strength and speed of sound. It turns out that our approach is
accurate to the percent level for moderately strong phase transitions, while
former approaches give at best the right order of magnitude.

We study the energy budget of a first-order cosmological phase transition,
which is an important factor in the prediction of the resulting gravitational
wave spectrum. Formerly, this analysis was based mostly on simplified models as
for example the bag equation of state. Here, we present a model-independent
approach that is exact up to the temperature dependence of the speed of sound
in the broken phase. We find that the only relevant quantities that enter in
the hydrodynamic analysis are the speed of sound in the broken phase and a
linear combination of the energy and pressure differences between the two
phases which we call pseudotrace (normalized to the enthalpy in the broken
phase). The pseudotrace quantifies the strength of the phase transition and
yields the conventional trace of the energy-momentum tensor for a relativistic
plasma (with speed of sound squared of one third). We study this approach in
several realistic models of the phase transition and also provide a code
snippet that can be used to determine the efficiency coefficient for a given
phase transition strength and speed of sound. It turns out that our approach is
accurate to the percent level for moderately strong phase transitions, while
former approaches give at best the right order of magnitude.

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