Seminar Information

school year

**Mar.24,2016**

T. Fujimori**Mar.2,2016**

C.Chatterjee**Feb.19,2016**

N. Sawado**Dec.12,2015**

Y. Okouchi**Nov.27,2015**

F. Takahashi

Date: | Mar.24 ,2016 16:00~ |

Room: | No.14 |

Speaker: | Toshiaki Fujimori(Keio U.) |

Title: | 2d Partition Function in Ω-background and Vortex/Instanton Correspondence |

We derive the exact vortex partition function in 2d N = (2,2) gauge theory on the Ω-background, applying the localization scheme in the Higgs phase. We show that the partition function at a finite Ω-deformation parameter ε satisfies a system of differential equations, which can be interpreted as a quantized version of the twisted F-term equations characterizing the SUSY vacua. Using the differential equations derived in this paper, we show the correspondence between the partition function of the two-dimensional vortex string worldsheet theory and the Nekrasov partition function at the root of Higgs branch of the four-dimensional N = 2 theory with two Ω-deformation parameters (ε1, ε2).

Date: | Mar.2, 2016 16:00~ |

Room: | No.13 |

Speaker: | Dr. Chandrasekhar Chatterjee (Keio Univ.) |

Title: | Non Abelian vortex in Dense QCD and low energy fermion effective action |

Quark matter at high density may exhibit color superconductivity. As magnetic flux tubes in metallic superconductors, color magnetic flux tubes as non-Abelian vortices appear in the color- flavor locked phase of high density QCD. Stable non-Abelian vortices, that are color magnetic flux tubes as well as superfluid vortices, are present in the color-flavor locked (CFL) phase of dense quark matter with di-quark condensations. We discuss the Aharanov-Bohm phases of charged particles, that is, electrons, muons and CFL mesons made of tetra quarks around a non-Abelian vortex. We also discuss the scalar (CP2 Nambu-Goldstone bosons) and fermion zero modes. These zero modes are known to be localized around a non-Abelian vortex. we determine the coupling of these bosonic and fermionic modes by using the nonlinear realization method.

Date: | Feb. 19 ,2016 |

Room: | No.13 |

Speaker: | Nobuyuki Sawado (Tokyo University of Science) |

Title: | Quantum aspects of CP^N Skyrme-Faddeev model on the collective coordinate approximation - spin statistics and fermions - |

I discuss some quantum aspects of the Skyrme-Faddeev (or the baby-Skyrme) model. The well-known Skyrme model describes properties of hadrons after a suitable quantization is performed. The collective coordinate approximation is often used to estimate the mass spectra of several hadrons. The Wess-Zumino action obeys a quantization law of which the prefactor is the number of quark colors (i.e. of the degeneracy). CP ^N Skyrme-Faddeev model possesses two-dimensional soliton solutions. For N = 1 it is believed that the quantum aspects exhibit a special property, fractional spin θ/2π (0 ? θ ? π) when the Hopf term is added in the action of the model. For the point of view of a fermionic model coupled with the baby-skyrmions, however, no ambiguity by θ appears. An analogue of the Wess-Zumino term appears in CP^N field which plays a similar role as the Hopf term and the soliton can be quantized as an anyon. As a result, one expect that the fermions may exhibit a fractional degeneracy. I would like to discuss the issues through the heat kernel expansion and also the spectral flow analysis.

Date: | Nov 27, 2015 (Fri) from 15:30 |

Room: | E316/317 |

Speaker: | Fuminobu Takahashi (Tohoku.U) |

Title: | Axion Cosmology - The Witten effect and mixings - |

After given a review on the current status of the axion cosmology, I will discuss two recent topics, one is the Witten effect, and the other is a mixing between axions. In the presence of monopoles, the theta-term of an Abelian gauge theory becomes physical, and the monopoles are known to become dyons. This is the Witten effect. I will show that the Witten effect can suppress the axion abundance as well as isocurvature perturbations. The second topic is about the mixings among axions, and I will discuss a peculiar level-crossing phenomenon.