2018年度のセミナー

Date/Place May. 8th (Tue.) 15:30-16:30 / H711
Name Sugumi Kannno (Osaka Univ.)
Title Quantum entanglement between bubble universes (Slides)
Abstract In de Sitter space where the universe expands exponentially, any two of mutually separated regions eventually become causally disconnected. This is most conveniently described by spanning open universe coordinates on two open charts in de Sitter space. Recently, Maldacena and Pimentel showed that the entanglement entropy of a free massive scalar field between two open charts is non-vanishing. This result shows that two causally disconnected regions in de Sitter space are entangled. I extend the calculation of Maldacena and Pimentel to the case where a bubble wall is present between the two open charts. This can be thought of as a model of pair creation of bubble universes in de Sitter space. I will discuss the effect of the bubble wall on the entanglement entropy between the bubble universes.

 

Date/Place Apr. 24th (Tue.) 15:30-16:30 / H711
Name Chen Zhang (NCTS)
Title Simplest Little Higgs Revisited: Hidden Mass Relation, Unitarity and Naturalness (Slides)
Abstract In this talk, I will present an analysis of the scalar potential of the Simplest Little Higgs (SLH) model in an approach consistent with the spirit of continuum effective field theory (CEFT). A hidden mass relation is obtained relating the pseudo-axion mass and top partner mass, serving as a crucial test of the SLH mechanism. I also propose a strategy of analyzing the fine-tuning problem consistent with the spirit of CEFT and apply it to the SLH. The scalar potential and fine-tuning analysis strategies investigated here should also be applicable to a wide class of Little Higgs and Twin Higgs models, which may reveal interesting relations as crucial tests of the related electroweak symmetry breaking mechanism and provide a new perspective on assessing their degree of fine-tuning.

 

Date/Place Apr. 17th (Tue.) 15:30-16:30 / H711
Name Yohei Ema (KEK)
Title Flaxion and its SUSY extension (Slides)
Abstract In this talk, we propose a minimal extension of the standard model which includes only one additional complex scalar field, flavon, with flavor-dependent global U(1) symmetry. It not only explains the hierarchical flavor structure in the quark and lepton sector (including neutrino sector), but also solves the strong CP problem by identifying the CP-odd component of the flavon as the QCD axion, which we call flaxion. Furthermore, the flaxion model solves the cosmological puzzles in the standard model, i.e., origin of dark matter, baryon asymmetry of the universe, and inflation. We also discuss a supersymmetric extension of this model, paying a particular attention to dynamics of an additional scalar flat direction in the early universe.

 

Date/Place Apr. 11th (Wed.) (Informal) 12:10 / H711
Name Ryo Nagai (Tohoku University)
Title Roles of perturbative unitarity in extended Higgs scenarios (Slides)
Abstract One of the important roles of the SM Higgs boson is to keep WW scattering amplitudes perturbatively unitary in high energy limit. However, once the Higgs coupling deviates from the SM prediction, the perturbative unitarity might be broken down at the certain energy scale. In order to maintain the perturbative unitarity with anomalous higgs coupling in high energy limit, we need new particle(s) whose couplings are tuned to cancel the bad behavior of WW scattering amplitudes. The required conditions are called “unitarity sum rules”. The sum rules tell us nontrivial relationship between the properties of new particles/phenomena and the low-energy observables such as the 125GeV signal strengths (coupling strengths). In this talk, we discuss the implications of the unitarity sum rules and apply the sum rules to investigate physics beyond the standard model.

 

Date/Place Apr. 4th (Wed.) (Informal) 14:30-15:30 / H711
Name Ryoutaro Watanabe (Montreal U.)
Title Does complete set of data still prefer the B anomalies?
Abstract In this talk, I will show my ongoing work regarding new physics to accommodate the anomalies in b -> s mu mu and b -> c tau nu which have been standing on these days. So far, there are many papers for this topic and they concluded that U1 (singlet vector type of) leptoquark could explain the two simultaneously. In our work, we put a complete set of observables relevant for the above explanation and gives a fit analysis. As a result, we see what kind of patterns of LQ couplings are favored, which could be a guideline when one constructs a UV completed model to accommodate the B anomalies.

 

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