FIAS Scientific Report 2011 - Frankfurt Institute for Advanced Studies ...

The phase diagram in T -µB-Nc space
Collaborators: G. Torrieri 1 , I.N. Mishustin 1 , S. Lottini 2
1 Frankfurt Institute for Advanced Studies, 2 Institute for Theoretical Physics, Goethe University, Frankfurt
Research in this project has been devoted to exploring the QCD phase diagram in varying number of colors.
This follows from work done the year before, explaining the quantitative smallness of the critical point in the
nuclear liquid-gas phase transition by an interplay of the number of colors and the number of neighbours in a
densely packed system [1].
Such an interplay suggests that a percolation transition arises when the density and the number of colors are
varied. In [2] we have explored this transition for a general class of quark-quark propagators in a confined phase
at finite density. We show that typically percolation occurs at Nc∼ O(10) when the chemical potential is of
order ΛQCD. Fig. 1 shows the critical number of colors as a function of the parameter space of the quark-quark
propagator in such a confined but high-density system.
This paper has left a number of questions open: How does this percolation transition interplay with deconfinement
when both density and number of colors are varied? Are there phenomenological consequences of
percolation, on the lattice or in real heavy ion collisions? And what is the relationship between percolation and
the widely studied quarkyonic phase transition? Answering some of these questions will be a main target of
my research in 2012.
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Figure 1: Contour plot of the critical Nc vs coupling constant λ and propagator range rT , assuming the quarkquark
propagator is a Θ-function in momentum space (left panel) and position space (right panel). See [2] for
further details.
Related publications in 2011:
1) G. Torrieri, S. Lottini, I. Mishustin, P. Nicolini, The phase diagram in T -µ-Nc space, arXiv:1110.6219
[nucl-th].
2) S. Lottini and G. Torrieri, A percolation transition in Yang-Mills matter at finite number of colours, Phys.
Rev. Lett. 107, 152301 (2011). arXiv:1103.4824 [nucl-th].
3) G. Torrieri, Strange quark matter: Business as usual or phase transition?, arXiv:1111.6122 [nucl-th].
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