163 research outputs found
Shear viscosity over entropy density ratio with extended quasi-particles
We consider an effective field theory description of beyond-quasi-particle
excitations aiming to associate the transport properties of the system with the
spectral density of states. Tuning various properties of the many-particle
correlations, we investigate how the robust microscopic features are translated
into the macroscopic observables like shear viscosity and entropy density. The
liquid-gas crossover is analysed using several examples. A thermal constraint
on the fluidity measure, the ratio of shear viscosity to entropy density, is
discussed.Comment: 13 pages, 7 figures, uses revtex4-1; published versio
The effect of quantum fluctuations in compact star observables
Astrophysical measurements regarding compact stars are just ahead of a big
evolution jump, since the NICER experiment deployed on ISS on 14 June 2017.
This will soon provide data that would enable the determination of compact star
radius with less than 10% error. This poses new challenges for nuclear models
aiming to explain the structure of super dense nuclear matter found in neutron
stars.
Detailed studies of the QCD phase diagram shows the importance of bosonic
quantum fluctuations in the cold dense matter equation of state. Here, we using
a demonstrative model to show the effect of bosonic quantum fluctuations on
compact star observables such as mass, radius, and compactness. We have also
calculated the difference in the value of compressibility which is caused by
quantum fluctuations.
The above mentioned quantities are calculated in mean field, one-loop and in
high order many-loop approximation. The results show that the magnitude of
these effects is ~5%, which place it into the region where forthcoming
high-accuracy measurements may detect it.Comment: 6 pages 4 figues, minor corrections were adde
FRG Approach to Nuclear Matter at Extreme Conditions
Functional renormalization group (FRG) is an exact method for taking into
account the effect of quantum fluctuations in the effective action of the
system. The FRG method applied to effective theories of nuclear matter yields
equation of state which incorporates quantum fluctuations of the fields. Using
the local potential approximation (LPA) the equation of state for Walecka-type
models of nuclear matter under extreme conditions could be determined. These
models can be tested by solving the corresponding Tolman--Oppenheimer--Volkov
(TOV) equations and investigating the properties (mass and radius) of the
corresponding compact star models. Here, we present the first steps on this
way, we obtained a Maxwell construction within the FRG-based framework using a
Walecka-type Lagrangian.Comment: 6 pages, 3 figure
Renormalization of 2PI resummation: a renormalization scheme approach
A practical method is suggested for performing renormalized 2PI resummation
at finite temperature using specific momentum dependent renormalization
schemes. In this method there is no need to solve Bethe-Salpeter equations for
2PI resummation. We examine the consistency of such schemes in the paper. The
proposed method is used to perform a two-loop renormalized 2PI resummation in
the finite temperature Phi^4 model.Comment: 14 pages revtex, 8 figure
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