Nguyen Anh Ky, IPNS
On neutrino mixing models based on $A_4$-flavor symmetry
Meeting room 3, Kenkyu honkan 1F A model of neutrino mixing based on an $A_4$ flavor symmetry is suggested. Other possible models are also listed or briefly reviewed. Besides the fields in the standard model, these models also contain new fields that transform under different representations of the group $A_4$.
A model of neutrino mixing based on an $A_4$ flavor symmetry is suggested. Other possible models are also listed or briefly reviewed. Besides the fields in the standard model, these models also contain new fields that transform under different representations of the group $A_4$.
To explain the current experimental data, the present model is constructed to deviate from a tri-bimaximal model just slightly; hence, all analysis can be done on the base of the perturbation method. Numerical results have shown the model is quite consistent with the current experimental data.
A relation to physics at Belle-II is also discussed
Atsuhisa Ota, TITECH
[Cosmophysics Seminar] CMB spectral distortions as solutions to the Boltzmann equations
Meeting room 3, Kenkyu honkan 1F
We propose to re-interpret the cosmic microwave background spectral distortions as solutions to the Boltzmann equation. This approach makes it possible to solve the second order Boltzmann equation explicitly, with the spectral y distortion and the momentum independent second order temperature perturbation, while generation of μ distortion cannot be explained even at second order in this framework. We also extend our method to higher order Boltzmann equations systematically and find new type spectral distortions, assuming that the collision term is linear in the photon distribution functions, namely, in the Thomson scattering limit. As an example, we concretely construct solutions to the cubic order Boltzmann equation and show that the equations are closed with additional three parameters composed of a cubic order temperature perturbation and two cubic order spectral distortions. The linear Sunyaev-Zel’dovich effect whose momentum dependence is different from the usual y distortion is also discussed in the presence of the next leading order Kompaneets terms, and we show that higher order spectral distortions are also generated as a result of the diffusion process in a framework of higher order Boltzmann equations. The method may be applicable to a wider class of problems and has potential to give a general prescription to non-equilibrium physics.
Kei Suzuki, Tokyo Institute of Technology
Hadron spectroscopy under strong magnetic field
Meeting room 1, Kenkyu honkan 1F
Non-central heavy-ion collisions at RHIC and LHC can create a strong magnetic field comparable to the QCD scale. Under such extreme environments, hadron properties can be drastically modified. In this talk, I will show our recent theoretical results about properties of hadrons (quarkonia, heavy-light mesons and nucleons) under magnetic field, where various phenomena induced by a magnetic field, such as mass spectra, spin mixing, Landau levels, wave function deformation, and hadron formation time, will be discussed.
Holger Bech Nielsen, Bohr Inst.
The Smallness of the Higgs mass compared to Fundametal mass (Planck mass) from Multiple Point Principle
Meeting Room 1, Kenkyu Honkan 1F
Frank Krauss, IPPP, Durham
Precision simulations for LHC physics and beyond
Meeting room 1, Kenkyu honkan 1F
I review the current precision frontier for event generator simulations of LHC physics and outline possible future developments. I will also speculate about accuracy requirements for future collider experiments probing the energy frontier
Kallol Sen, IPMU, University of Tokyo
A mellin space approach to the conformal bootstrap
Meeting room 1, Kenkyu honkan 1F
We describe in more detail our approach to the conformal bootstrap which uses the Mellin representation of CFT_d four point functions and expands them in terms of crossing symmetric combinations of AdS_d+1 Witten exchange functions. We consider arbitrary external scalar operators and set up the conditions for consistency with the operator product expansion. Namely, we demand cancellation of spurious powers (of the cross ratios, in position space) which translate into spurious poles in Mellin space. We discuss two contexts in which we can immediately apply this method by imposing the simplest set of constraint equations. The first is the epsilon expansion. We mostly focus on the Wilson-Fisher fixed point as studied in an epsilon expansion about d=4. We reproduce Feynman diagram results for operator dimensions to O(ϵ^3)rather straightforwardly. This approach also yields new analytic predictions for OPE coefficients to the same order which fit nicely with recent numerical estimates for the Ising model (at ϵ=1). We will also mention some leading order results for scalar theories near three and six dimensions. The second context is a large spin expansion, in any dimension, where we are able to reproduce and go a bit beyond some of the results recently obtained using the (double) light cone expansion. We also have a preliminary discussion about numerical implementation of the above bootstrap scheme in the absence of a small parameter.
Tsuyoshi Houri, Kobe University
Conformal symmetry of spacetime and ladder operators of the Laplacian
Meeting room 1, Kenkyu honkan 1F
It is well known that if a spacetime admits isometry, the space of eigenfunctions for the Laplacian is given as a representation of the isometry group provided an eigenvalue is fixed. In contrast, it has been less known how conformal symmetry of spacetime is related to the Laplacian. In this talk, we first revisit a relation between conformal symmetry of the two-dimensional sphere and ladder operators for the spherical harmonics. After that, we generalise the relation in a certain class of spacetimes which includes maximally symmetric spacetimes. As an application, we discuss the horizon instability of an extreme Reissner-Nordstrom black hole.
Takahiro Hayashinaka, RESCEU
Fermionic Schwinger effect in 1+3 dimensional de Sitter spacetime
Meeting room 1, Kenkyu honkan 1F We explored Schwinger effect of spin 1/2 charged particles with static electric field in 1+3 dimensional de Sitter spacetime [1]. The vacuum expectation value of the spinor current which is induced by the produced particles in the electric field was analytically calculated. We find that the current becomes negative, namely it flows in the direction opposite to the electric field, if the electric field is weaker than a certain threshold value depending on the fermion mass, which is also known to happen in the case of scalar charged particles in 1+3 de Sitter spacetime. We also investigated the implications of the result in detail.
We explored Schwinger effect of spin 1/2 charged particles with static electric field in 1+3 dimensional de Sitter spacetime [1]. The vacuum expectation value of the spinor current which is induced by the produced particles in the electric field was analytically calculated. We find that the current becomes negative, namely it flows in the direction opposite to the electric field, if the electric field is weaker than a certain threshold value depending on the fermion mass, which is also known to happen in the case of scalar charged particles in 1+3 de Sitter spacetime. We also investigated the implications of the result in detail.
References
[1] T. Hayashinaka, T. Fujita and J. Yokoyama, JCAP 1607 (2016) 07 010, arXiv: 1603.04165
[2] only a partial list of recent works on the subject: T. M. B. Frob, J. Garriga, S. Kanno, M. Sasaki, J. Soda, T. Tanaka, and A. Vilenkin, JCAP 2014 (2014) 04 009, R. G. Cai and S. P. Kim, JHEP 09 (2014) 072, T. Kobayashi and N. Afshordi, JHEP 2014 (2014) 10 1-36, C. Stahl, E. Strobel, and S. S. Xue, Phys. Rev. D 93 (Jan, 2016) 025004, E. Bavarsad, C. Stahl, and S. S. Xue, arXiv:1602.0655, C. Stahl and S. Xue Phys.Lett. B760 (2016) 288-292, T. Hayashinaka and J. Yokoyama, JCAP 1607 (2016) 07 012, arXiv:1603.0617
Da-Shin Lee, National Dong-Hwa University
Analog Model of Quantum Phenomena in Curved Spacetime Using Cold Atomic Condensates
Meeting room 3, Kenkyu honkan 1F We explore possible analogies between quantum phenomena in curved spacetime and cold laboratory condensates whose speed of sound can be tuned by means of an external field. In the first instance, the creation of causal horizons when a system undergoes rapid changes can lead to the creation of defects e.g. cosmic strings and monopoles. We see to what extent this can be mimicked in condensates by the spontaneous creation of vortices in a field ramp. Secondly, by examining the phonon geodesics in the acoustic metric we can look for spontaneous phonon creation that mimics spontaneous particle creation in curved space-time. Also, the fluctuating nature of the phonon background suggests analogies with quantum gravity.
We explore possible analogies between quantum phenomena in curved spacetime and cold laboratory condensates whose speed of sound can be tuned by means of an external field. In the first instance, the creation of causal horizons when a system undergoes rapid changes can lead to the creation of defects e.g. cosmic strings and monopoles. We see to what extent this can be mimicked in condensates by the spontaneous creation of vortices in a field ramp. Secondly, by examining the phonon geodesics in the acoustic metric we can look for spontaneous phonon creation that mimics spontaneous particle creation in curved space-time. Also, the fluctuating nature of the phonon background suggests analogies with quantum gravity.
References:
[1] D.-S. Lee, C. Y. Lin, and R. J. Rivers: “Derivation of Hydrodynamics for the Gapless Mode in the BEC-BCS Crossover from the Exact One-Loop Effective Action,” Phys. Rev. Lett. 98, 020603 (2007).
[2] C.-Y. Lin, D.-S. Lee, and R. J. Rivers, “The role of Causality in Tunable Fermi Gas Condensates,” J. Phys. Cond. Matter 25, 04211 (2013).
[3] J.-T. Hsiang, C.-Y. Lin, D.-S. Lee, and R. J. Rivers, “Quantum Stochastic Behavior in Cold Fermi Gases: Phonon Propagation,” Phys. Rev. A 91, 051603(R) (2015).
Naoki Yoshida, Tokyo Univ.
Cosmological constraints on dark matter annihilation and decay
Meeting room 3, Kenkyu honkan 1F
