
Taming the pion condensation in QCD at finite baryon density: a numerical test in a random matrix modelTaming the pion condensation in QCD at finite baryon density: a numerical test in a random matrix model 
"/Aoki, Sinya/"Aoki, Sinya ,
"/Hanada, Masanori/"Hanada, Masanori ,
"/Nakamura, Atsushi/"Nakamura, Atsushi
2015
(
5
)
20150514 , Springer Berlin Heidelberg
ISSN:10298479
Description
In the Monte Carlo study of QCD at finite baryon density based upon the phase reweighting method, the pion condensation in the phasequenched theory and associated zeromode prevent us from going to the lowtemperature highdensity region. We propose a method to circumvent them by a simple modification of the density of state method. We first argue that the standard version of the density of state method, which is invented to solve the overlapping problem, is effective only for a certain ‘good’ class of observables. We then modify it so as to solve the overlap problem for ‘bad’ observables as well. While, in the standard version of the density of state method, we usually constrain an observable we are interested in, we fix a different observable in our new method which has a sharp peak at some particular value characterizing the correct vacuum of the target theory. In the finitedensity QCD, such an observable is the pion condensate. The average phase becomes vanishingly small as the value of the pion condensate becomes large, hence it is enough to consider configurations with π+ ≃ 0, where the zero mode does not appear. We demonstrate an effectiveness of our method by using a toy model (the chiral random matrix theory) which captures the properties of finitedensity QCD qualitatively. We also argue how to apply our method to other theories including finitedensity QCD. Although the example we study numerically is based on the phase reweighting method, the same idea can be applied to more general reweighting methods and we show how this idea can be applied to find a possible QCD critical point.
FullText
http://repository.kulib.kyotou.ac.jp/dspace/bitstream/2433/201497/1/JHEP05%282015%29071.pdf