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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