S. S. Pankratov, M. Baldo, M. V. Zverev
We study different scenarios of topological phase transitions in the vicinity of \pi^0 condensation point in neutron matter. The transitions occur between the Fermi liquid state and a topologically different one with two sheets of the Fermi surface. Two possibilities of a rearrangement of quasiparticle degrees of freedom are shown: the first order topological phase transition and the second order one. The order of the phase transition is found to be strongly dependent on the value of the critical wave vector of the soft \pi^0 mode. The thermodynamics of the system is also studied. It is shown that the topology of the quasiparticle momentum distribution is mainly determined by the neutron matter density, while the temperature T is essential in a narrow density region. A simple explanation of the first order topological phase transition at T=0 is given.
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http://arxiv.org/abs/1208.3888
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