# E-lab Seminar

## Upcoming

Date | Wed Nov 13 2024 |
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Speaker |
Shaoping Li (Osaka University) |

Title | Neff from the dilution-resistant effect |

Abstract | The effective neutrino number is a key observable characterizing the expansion of the early universe, which can be measured by big-bang nucleosynthesis and cosmic microwave background physics. In this talk, I will introduce this important parameter and discuss the dilution-resistant effect caused by new physics coupling to neutrinos. Constraints and detection of this dilution-resistant effect will be shown. As an interesting consequence, I will show a cosmic sandwiched window of the lepton-number breaking scale. |

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Slide/Video |

Date | Tue Nov 19 2024 |
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Speaker |
Masanori Hanada (Queen Mary University of London) |

Title | Geometry from Wave Packet |

Abstract | In this talk, I will explain how matrix degrees of freedom in the matrix model or super Yang-Mills theory can describe holographic emergent geometry. A key concept is wave packet in the space of matrices (for matrix model, R^{9N^2} rather than R^9). For (3+1)-d super Yang-Mills theory, we need to consider two different notions of wave packet: wave packet in the space of matrices ("matrix wave packet"), and wave packet in the ordinary 3d space ("QFT wave packet"). By combining two notions, we obtain a "bulk wave packet". We propose that the bulk wave packet is the physical object in QFT that describes the emergent geometry from entanglement. This proposal sets a unified view on two seemingly different mechanisms of holographic emergent geometry: one based on matrix eigenvalues and the other based on quantum entanglement. References: M. Hanada, "Bulk geometry in gauge/gravity duality and color degrees of freedom,'' Phys. Rev. D \textbf{103}, no.10, 106007 (2021) [arXiv:2102.08982 [hep-th]]. V. Gautam, M. Hanada and A. Jevicki, "Operator algebra, quantum entanglement, and emergent geometry from matrix degrees of freedom,'' arXiv:2406.13364 [hep-th]. |

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Slide/Video |

Date | Tue Nov 26 2024 |
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Speaker |
Juntaro Wada (Univ. of Tokyo) |

Title | Thermal leptogenesis in the minimal gauged U(1)_{L_\mu-L_\tau} model |

Abstract | We discuss the thermal leptogenesis mechanism within the minimal gauged U(1)$_{L_\mu-L_\tau}$ model to explain the observed baryon asymmetry of the Universe (BAU). In such framework, the phases of the Pontecorvo–Maki–Nakagawa–Sakata neutrino mixing matrix and the sum of the Standard Model neutrino masses are predictable because of a restricted neutrino mass matrix structure. Additionally, in the context of thermal leptogenesis, the BAU can be computed in terms of the three remaining free variables that parameterise the right-handed neutrino masses and their Yukawa couplings to the Higgs and lepton doublets. We identify the ranges of such parameters for which the correct BAU can be reproduced. We adopt the formalism of the density matrix equations to fully account for flavour effects and consider the decays of all the three right-handed neutrinos. Our analysis reveals that thermal leptogenesis is feasible within a wide parameter space, specifically for Yukawa couplings ranging from approximate unity to $\mathcal{O}(0.03-0.05)$ and mass of the lightest right-handed neutrino $M_1\gtrsim 10^{11-12}\,\text{GeV}$, setting a leptogenesis scale in the considered model which is higher than that of the non-thermal scenario. |

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Slide/Video |

Date | Wed Dec 04 2024 |
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Speaker |
David Turton (Southampton) |

Title | TBA |

Abstract | TBA |

Remarks | |

Slide/Video |

Date | Tue Dec 17 2024 |
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Speaker |
Soichiro Shimamori (Osaka University) |

Title | Conformal field theory with composite defect |

Abstract | We explore higher-dimensional conformal field theories (CFTs) in the presence of a conformal defect that itself hosts another sub-dimensional defect. We refer to this new kind of conformal defect as the composite defect. We elaborate on the various conformal properties of the composite defect CFTs, including correlation functions, operator expansions, and conformal block expansions. As an example, we present a free O(N) vector model in the presence of a composite defect. Assuming the averaged null energy condition (ANEC) does hold even for the defect systems, we conclude that some boundary conditions can be excluded. Our investigations shed light on the rich phenomenology arising from hierarchical |

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Slide/Video |