**Theory Seminar**

KEK 素粒子原子核研究所・理論セミナー

TITLE： | An approximate large-N solution of the U(N)xU(N) model from 2PI effective action |

(in English) | |

SPEAKER： |
Gergely Fejos
(The Univ. of Tokyo) |

DATE： | March 6 (Tue.) 16:00 − 17:00 |

PLACE: | Honkan Bld. 3F, Seminar Room 322 |

（ABSTRACT）

I will briefly review the 2PI (or Phi-derivable) formalism and as an application I will present an approximate large-N solution of the U(N)xU(N) meson model. What makes a particular importance of this is that even the leading order large-N solution of the model is unknown. The present solution is based on an assumption on the mass hierarchy of the spectrum, which is proved to be valid in certain parts of the parameter space. The ground state of the system was explored and found that a U(N)xU(N) -> U(N-1) spontaneous symmetry breaking can be realized. The finite temperature study showed that the system (partially) suffers a 1st order transition. Properties of this transition will also be highlighted.