Seminars
Seminar Schedule 2013
Past Seminars |
24 Apr. (Wed.) 15:30-
"Cosmology in LARGE volume string models" PDF (local only)
Tetsutaro Higaki (KEK)
15 May (Wed.) 15:30-
"On the energy eigenstates of matrix quantum mechanics"
Yasuhiro Sekino (KEK)
Supersymmetric matrix quantum mechanics has been proposed as a non-perturbative formulation of quantum gravity. It is hoped that the dynamics of black holes, such as thermalization, can be understood by this theory (BFSS Matrix theory), but the theory has not been solved so far. In this work, as a simplified model for BFSS Matrix theory, we study matrix quantum mechanics which consists of two bosonic matrices with SU(2) gauge symmetry. We find the energy eigenstates, and discuss implications of our result.22 May (Wed.) 15:30-
"Tensor Network and Black Hole" PDF
Masafumi Ishihara (Tohoku Univ.)
29 May (Wed.) 15:30-
"Scheme dependence of instanton counting in ALE spaces" PDF
Yuto Ito (Univ. of Tokyo)
5 June (Wed.) 15:30-
"A CDT Hamiltonian from Hořava-Lifshitz gravity" PDF
Yuki Sato (KEK)
"Dynamical Triangulations" (DT) is an attempt to search for a non-trivial UV fixed point in quantum gravity; its causal extension called Causal Dynamical Triangulations (CDT) may be a candidate. On the other hand, Hořava-Lifshitz gravity (HL) has been introduced as a UV completion of quantum gravity by giving up a part of diffeomorphism symmetry. Both theories, CDT and HL, have a fundamental space-time foliation built-in; moreover, they seem to be in the same universality class. In my talk I will show that, at least in 1+1 dimensions, CDT is nothing but the projectable version of HL. I'm also planning to mention some of frequently asked questions about this approach.12 June (Wed.) 15:30- @Room 525
"Hadron interactions from lattice QCD"
Sinya Aoki (YITP)
Progress on the potential method, recently proposed to investigate hadron interactions in lattice QCD, is introduced. The strategy to extract the potential in lattice QCD is explained in detail. The method is applied to extract $NN$ potentials, hyperon potentials and potentials for other systems. Some recent applications of the method are also discussed.19 June (Wed.) 15:30-
"Cosmology meets particle physics" PDF
Fuminobu Takahashi (Tohoku Univ.)
26 June (Wed.) 15:30-
"Neutrino Mass and Proton Decay in a U(1)_R symmetric model" Keynote
Takashi Shimomura (Niigata Univ.)
We study a U(1)_R symmetric extenstion of supersymmetric standard model with supersymmetry breaking in the visible as well as hidden sectors. Specifically we study U(1)R breaking effects parametrized by the gravitino mass. A special R-charge assignment of right-handed neutrinos allows us to have neutrino Yukawa couplings with the R-charged Higgs field, which develops a tiny vacuum expectation value after the inclusion of U(1)R symmetry breaking. Even with O(1) Yukawa couplings, a suitable size of Dirac neutrino masses can be generated if the gravitino mass is very small, m3/2 = 1—10 eV. Our flipped R-charge assignment also allows a new type of dimension five operator that can induce the proton decay. It turns out that the proton stability mildly constrains the allowed range of the gravitino mass: Gravitino heavier than 10 keV can evade the proton decay constraint as well as cosmological ones. In this case, the largest neutrino Yukawa coupling is comparable to the electron Yukawa. We also calculate the mass of the pseudo goldsino and its mixing to neutralinos, and briefly discuss its implications in cosmology and Higgs phenomenology.17 July (Wed.) 15:30-
"Diphoton Decay Excess and 125 GeV Higgs Boson in Gauge-Higgs Unification" PDF (local only)
Nobuhito Maru (Osaka City Univ.)
In the context of gauge-Higgs unification scenario in a 5-dimensional flat spacetime, we investigate Higgs boson production via gluon fusion and its diphoton decay mode at the LHC. We show that the signal strength of the Higgs diphoton decay mode observed at ATLAS and CMS, which is considerably larger than the Standard Model expectation, can be explained by a simple gauge-Higgs unification model with color-singlet bulk fermions to which a half-periodic boundary condition is assigned. The bulk fermions also play a crucial role in reproducing the observed Higgs boson mass around 125 GeV.24 July (Wed.) 15:30-
"Phase structures of Chern-Simons matter theory on S^2 \times S^1" PDF
Tomohisa Takimi (Tata Institute of Fundamental Research)
As a new interesting class of AdS/CFT duality, 3d fundamental Chern-Simons matter theories can be dual descriptions of the Vasiliev's theory with higher spin symmetry which might be a strong clue for the quantum gravity. Analogous to the AdS/CFT correspondence between the deconfinement phase transition of large N gauge theory on spheres and the gravitational phase transition involving black-hole nucleation, we would be able to study phase structures of the Vasiliev's theory by elaborating phase structures of the Chern-Simons matter theory. Based on this motivation, I have studied phase structures of Chern-Simons matter theories with fundamental representation. In the fundamental Chern-Simons matter theories, due to the absence of the propagating degree of freedom of the gauge fields and by the topological magnetic flux, we can see new phases with saturated eigenvalue density function, which does not show up in the conventional Yang-Mills theories with the Gross-Witten-Wadia type phase transition.Special Lectures
24 Sep. (Tue.), 26 Sep. (Thu.), 27 Sep. (Fri.) @Room 525
"Gravity and Black Hole"
Akihiro Ishibashi (Kinki Univ.)
24 Sep. (Tue.)10:30-12:00, 13:30-15:00, 15:30-17:00
26 Sep. (Thu.)
10:30-12:00, 13:30-15:00, 15:30-17:00
27 Sep. (Fri.)
10:30-12:00, 13:30-15:00, 15:30-17:00
2 Oct. (Wed.) 15:30-
"Lattice QCD with Strong External Electric Fields" PDF
Arata Yamamoto (RIKEN)
We study particle generation by a strong electric field in lattice QCD. To avoid the sign problem of the Minkowskian electric field, we adopt the ‘‘isospin’’ electric charge. When a strong electric field is applied, the insulating vacuum is broken down and pairs of charged particles are produced by the Schwinger mechanism. The competition against the color confining force is also discussed.9 Oct. (Wed.) 15:30-
"Superstring theory and moduli space integration" PDF
Kantaro Ohmori (Univ. of Tokyo)
16 Oct. (Wed.) 15:30-
"Integrability of BPS equations in ABJM theory" PDF
Kazuhiro Sakai (Ritsumeikan Univ.)
I will discuss BPS equations which determine the configuration of a bound state of M2-branes and M5-branes preserving half of the supersymmetries in Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. The ABJM theory is believed to describe the low energy effective theory of M2-branes, which are the fundamental objects in M-theory. Recently we found that the BPS equations are classically integrable, showing that they admit a Lax representation. In this talk, I will explain the integrable structure of the BPS equations and how to construct solutions by making use of it. (This talk is based on the work arXiv:1308.3583 in collaboration with S. Terashima.)23 Oct. (Wed.) 15:30-
"Orbifold family unification on six dimensions"
Takashi Miura (Kobe Univ.)
We study the possibility of family unification on the basis of $SU(N)$ gauge theory on the six-dimensional space-time, $M4\times T2/Z_N$. We obtain enormous numbers of models with three families of $SU(5)$ matter multiplets and those with three families of the standard model multiplets, from a single massless Dirac fermion with a higher-dimensional representation of $SU(N)$, through the orbifold symmetry breaking mechanism.30 Oct. (Wed.) 15:30-
"Brane Refrigerator: effective temperature and effective horizon in non-equillibrium stationary system" PDF
Shin Nakamura (Nagoya Univ.)
6 Nov. (Wed.) 15:30-
"Axion Physics: From strong CP to axions out of discrete symmetries"
Jihn E. Kim (Kyung Hee Univ.)
I will introduce the strong CP problem of QCD and its very light axion solution based on the Peccei-Quinn symmetry. Its SUSY extension is discussed. But the PQ global symmetry is spoiled by gravitational effects, and I suggest using discrete symmetries to obtain an approximate PQ symmetry.13 Nov. (Wed.) 15:30-
"Duality Constraints on String Theory" PDF
Hirotaka Irie (YITP)
We study an implication of p-q duality (spectral duality or T-duality) on non-perturbative completion of (p,q) minimal string theory. According to the topological recursion, spectral p-q duality is already checked for all-order perturbative analysis. Therefore the different two descriptions, (p,q) system and (q,p) system, of this string theory are equivalent for all-order perturbation theory including instanton/soliton solutions. Non-perturbative realization of this duality, on the other hand, causes a new fundamental issue. In fact, we find that not all the non-perturbative completions allow non-perturbative p-q duality; The duality rather provides a constraint on non-perturbative formulations of string theory. In particular, it prohibits some of meta-stability caused by ghost D-instantons, since there is no non-perturbative realization on the dual side in the matrix-model description. That is, we show that non-perturbative (contour) ambiguity (given by D-instanton fugacity) is restricted by string duality. Our result is the first observation that a missing piece of our understanding in non-perturbative string theory is provided by the principle of non-perturbative string duality.20 Nov. (Wed.) 13:30-
"Two-Higgs-doublet models with gauged U(1) Higgs symmetry" PDF
Yuji Omura (TUM)
It is well known that generic two-Higgs-doublet models (2HDMs) suffer from potentially large Higgs-mediated flavor-changing neutral current (FCNC) problem, unless additional symmetries are imposed on the Higgs fields thereby respecting the Natural Flavor Conservation Criterion (NFC) by Glashow and Weinberg. A common way to respect the NFC is to impose Z_2 symmetry which is softly broken by a dim-2 operator. Another new way is to introduce local U(1)_H Higgs flavor symmetry that distinguish one Higgs doublet from the other. In this talk, I introduce especially so-called type-I 2HDM and type-II 2HDM with U(1)_H gauge symmetry, and discuss Higgs physics and dark matter physics in the 2HDMs.20 Nov. (Wed.) 15:30-
"Membranes from monopole operators in ABJM theory: Large angular momentum and M-theoretic AdS4/CFT3" PDF
Hidehiko Shimada (OIQP)
In the talk, I will consider states with large angular momentum to facilitate the study of the M-theory regime of the AdS4/CFT3 correspondence (duality between M-theory on $AdS_4 \times S^7/Z_k$ and ABJM theory with gauge group $U(N)\times U(N)$ and level $k$, where $k$ is finite and $N$ is large). In particular I will discuss near-BPS operators in ABJM theory which correspond to states of membranes with large angular momenta on AdS. The talk will be based on my work with S. Kovacs(DIAS) and Y. Sato (Wits University).11 Dec. (Wed.) 15:30-
"Higgs models and physics of tau" PDF
Koji Tsumura (Kyoto Univ.)
18 Dec. (Wed.) 15:30-
"central extension of sl(2|2) algebra and its representation" PDF
Takuya Matsumoto (Utrecht Univ.)
8 Jan. (Wed.) 15:30-
"Discrete Gauge Symmetry and Aharonov-Bohm Radiation in String Theory" PDF
Yutaka Ookouchi (Kyushu Univ.)
22 Jan. (Wed.) 15:30-
"Higgs pair production as a clue to new physics"
Kunio Kaneta (Kavli IPMU)
One of the mysteries in the standard model (SM) is what kind of force makes the Higgs boson acquires a VEV. It is expected that Higgs cubic coupling is measured by Higgs pair production at the LHC and ILC, in which Higgs self-coupling plays a crucial role to probe an origin of EW symmetry breaking. The deviations from the SM in the Higgs pair production process can give us a hint of new physics beyond the SM. We consider this process from a general potential that achieves the suitable EW symmetry breaking. As an interesting example, we discuss non-perturbative Higgs model in which a runaway type of potential is used. In the model, a non-renormalizable operator plays a role to break the EW symmetry, and the cross sections of pair production can be enhanced compared to the SM. We also discuss the Higgs pair production induced by a non-canonical kinetic term of Higgs field, which will be important for searching the pair production at the ILC.Informal Lecture
12 Feb. (Wed.), 13 Feb. (Thu.)
"Inflation and Cosmology"
Fuminobu Takahashi (Tohoku Univ.)
12 Feb. (Wed.)13:30-15:00, 15:30-17:00
13 Feb. (Thu.)
10:30-12:00, 13:30-15:00 (15:30-16:30 for )
5 Feb. (Wed.) 15:30-
"Background Independent Quantum Gravity from Matrix Model"
Hyun Seok Yang (Sogang Univ.)
Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as spacetime admits a symplectic structure, in other words, a microscopic spacetime becomes noncommutative (NC). We show that the representation of NC U(1) gauge theory in a Hilbert space is equivalent to a large N gauge theory which has appeared in matrix models as a nonperturbative formulation of string/M theories. This approach for quantum gravity allows a background independent formulation where spacetime as well as matter fields is equally emergent from a universal vacuum of quantum gravity.Loading Back Numbers