Diquark interaction and gaps for color superconductivity

Using flow equations, we derive an effective quark-quark interaction and obtain the coupled set of gap equations for the condensates of the CFL phase of massless $N_f=3$ dense QCD. The formalism developed here enables one to consider more general case of nonzero $s$-quark mass.Comment: 3 pages, Lattice2002(nonzerot), talk presented at 20th International Symposium on Lattice Field Theory (LATTICE2002), Boston, Massachusetts, 24-29 June 200

Exotic superfluids: Breached Pairing, Mixed Phases and Stability

We review properties of gapless states. We construct a model where a stable breached pair (gapless) state is realized.Comment: 9 pages, talk presented at workshop "Continuous Advances in QCD 2004," Minneapolis, USA, May 13-16, 200

Stability Conditions in Gapless Superconductors

Gapless superconductivity can arise when pairing occurs between fermion species with different Fermi surface sizes, provided there is a sufficiently large mismatch between Fermi surfaces and/or at sufficiently large coupling constant. In gapless states, secondary Fermi surfaces appear where quasiparticle excitation energy vanishes. This work focuses on homogeneous and isotropic superfluids in the s-wave channel, with either zero (conventional superconductor), one, or two spherical Fermi surfaces. The stability conditions for these candidate phases are analyzed. It is found that gapless states with one Fermi surface are stable in the BEC region, while gapless states with two Fermi surfaces are unstable in all parameter space. The results can be applied to ultracold fermionic atom systems.Comment: 7 pages, 5 figures, Proceedings of 'Continuous Advances in QCD 2006', May 11-14, 2006, Minneapolis, M

Color superconductivity from magnetic interaction induced by flow equations

Using flow equations, we derive an effective quark-quark interaction and obtain the coupled set of gap equations for the condensates of the CFL phase of massless N_f=3 dense QCD. We find two different sources of the infrared cutoff in magnetic interaction. When the penetration depth of the magnetic field inside the superconductor is less than the coherence length of quark-quark bound state, our results for the gap agree with those of Son. In the other case, we obtain parametric enhancement of the gap on the coupling constant.Comment: 14 pages, talk presented at workshop "Continuous Advances in QCD 2002/Arkadyfest," Minneapolis, USA, 17-23 May, 200