**Theory Seminar**

KEK 素粒子原子核研究所 理論セミナー

TITLE： | Sneaking up on dense QCD using large N methods |

(in English) | |

SPEAKER： |
Dr. Aleksey Cherman
(University of Cambridge) |

DATE： | February 8 (Wed.) 14:00 − 15:00 |

PLACE: | Kenkyu Honkan 1F, Meeting Room 1 |

（ABSTRACT）

Finite-density QCD notoriously suffers from the fermion sign problem, which makes lattice Monte Carlo simulations essentially impossible. As a result, we have little non-perturbative information on the behavior of QCD at finite baryon number density. I will discuss a recent proposal to dodge the sign problem by exploiting orbifold equivalence, a property of the large N limit of QCD. The proposal starts with the observation that if the gauge group of QCD is changed from SU(N) to SO(N), the sign problem does not appear at finite baryon number chemical potential, and the resulting theory can be studied on the lattice. Despite this seemingly drastic change, it turns out that there is a large N orbifold equivalence between the SO(N) theory and SU(N) QCD. I will argue that with some extra work, the equivalence can be made to hold at finite chemical potential, while the SO theory does not have a sign problem. This opens up the prospect of learning about QCD at finite baryon number density using lattice studies of the SO(N) theory.