Instabilities in superconducting and superfluid matter
Final Report Abstract
We studied the chromomagnetic instability in the 2SC/g2SC phases at moderate density and at finite temperature. We calculated the Meissner masses of gluons 4-7 and 8 and showed that a large region of the phase diagram suffers from the instability (apart from the case of extremely strong coupling). Then, in order to resolve the chromomagnetic instability, we investigated the phases with gluon condensates, using the two-flavor gauged NJL model. We computed the effective potential of the gluonic/LOFF phases at finite temperature and clarified the following points: • The gluonic phase is favored over the LOFF phase in a wide range of coupling strength. • The effective potential shows a peculiar behavior (as a function of the vector condensates) that cannot be described by the Ginzburg-Landau expansion. It is particularly interesting that, in the weak-coupling regime, the gluonic/LOFF phases could be energetically more favored than the chro mo magnetically stable NQ phase. • A strong first-order phase transition takes place between the gluonic phase and the NQ p;.iase at nonzero temperature. On the other hand, the transition from the gluonic phase to the (stable) g2SC is of second order or weakly first order. Using the three-flavor model, we also explored the 2SC/g2SC and the gluonic phases in neutral three-flavor quark matter. The resulting phase diagram shows clearly that currently known phase diagrams must be significantly altered. We would like to mention that the project of finding the true ground state of neutral dense quark matter is still not complete. It is unlikely that the gluonic phase which we explored in this work is the true vacuum, because we did not investigate a LOFF phase with multiple plane waves as well as other types of gluonic phases. There is also the possibility of Bose-Einstein condensation of diquarks. In addition, although the results obtained from the (gauged) NJL models seem to be qualitatively reasonable, they are quantitatively unreliable. Therefore, a nove., technique is required to perform nonperturbative QCD calculations at the relevant densities and to obtain a plausible QCD phase diagram.
Publications
- Kiriyama, "Chromomagnetic instability and gluonic phase at nonzero temperature," proceedings of the International Workshop on Quantum Chromodynamics: QCD@Work 2007, Martina Franca, Valle d'ltria, Italy, 16-20 Jun 2007 (Siehe online unter: arXiv:0709.2985 [hep-ph)
- Kiriyama, "Chromomagnetic instability in two-flavor quark matter at nonzero temperature," Physical Review D 74, 114011 (2006).
- Kiriyama, "Chromomagnetic instability in two-flavor quark matter at nonzero temperature," Yukawa International Seminars 2006, Kyoto, Japan, 20 Nov - 6 Dec 2006.
- Kiriyama, "Meissner screening mass in two-flavor quark matter at nonzero temperature," Physical Review D 74, 074019 (2006).
- Kiriyama, D. H. Rischke, and I. A. Shovkovy, "Gluonic phase versus LOFF phase in two-flavor quark matter,1' Physics Letters B 643, 331 (2006).
