Seminars in 2012

Seminars from April 2012 through March 2013.

EHQG-KMI Seminar

Title
Cosmological brane systems in warped spacetime
Speaker
Masato Minamitsuji (YITP, Kyoto Univ.)
Date & Time
Tuesday, February 26, 2013, 5:00 p.m.
Place
Science Symposia (ES635)
Abstract
We discuss the time-dependent brane solutions in higher-dimensional supergravity theories. We particularly focus on the dynamical extensions of the intersecting brane solutions involving three branes. We also show that in the near horizon limits, where the time dependence is negligible, these branes describe warped AdS spacetimes as in the corresponding static solutions. We finally examine the lower-dimensional cosmological dynamics obtained after compactifications of the higher-dimensional solutions and show the solutions we have found give the four-dimensional universe with power-law expansion.

EHQG Seminar

Title
Flavor Physics in the multi-Higgs-Doublet Models
Speaker
Yuji Omura (TUM)
Date & Time
Tuesday, February 19, 2013, 5:30 p.m.
Place
ES034 Lecture Room
Abstract
I introduce our multi-Higgs-Doublet models motivated by the top forward-backward asymmetry at Tevatron and the semileptonic decay of B (B→D(*)τ ν) at the BaBar experiment. In our model, extra Higgs doublets exist and extra U(1) gauge symmetry is also introduced to avoid the strong constraints from flavor physics. The Higgs scalars, charged Higgs and the U(1) gauge boson have flavor changing couplings at tree level, and they modify the Standard-Model predictions in top and B physics. I will discuss our studies including the bounds from LHC and Belle experiments, and show the favored and allowed regions by the experiments.

EHQG Seminar

Title
Precise computation of quantum electrodynamics in lepton g−2
Speaker
Masashi Hayakawa (Nagoya Univ.)
Date & Time
Tuesday, February 5, 2013, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
The primary purpose of this talk is to “upgrade” the QED contribution to the lepton g−2 by including the first result for the 5-loop QED contribution, which has been computed for about ten years. Unfortunately, even the fact is not familiar that the 4-loop QED contribution to the muon g−2, which has been computed only by one group, is the same order of magnitude as the current discrepancy between the theory and the experiment. In this talk, I also introduce you the perturbative features of the lepton g−2, and estimate rough orders of magnitude of the individual terms in a perturbative series, in order to discuss which orders of perturbation are relevant to the current and forthcoming experiments and to check the validity of our explicit computation.

EHQG Seminar

Title
Spontaneous symmetry breaking in QCD with a strong magnetic field
Speaker
Yoshimasa Hidaka (RIKEN)
Date & Time
Tuesday, January 29, 2013, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
We discuss spontaneous symmetry breaking of QCD in a strong magneticfield. In particular, we consider chiral symmetry breaking and a possibility of the vector meson condensation. In case of the former, it is known that the chiral symmetry is always spontaneously broken in a magnetic field at zero temperature, which is called the magnetic catalysis. In this talk, we propose a new effect, the magnetic inhibition, which is opposite of the magnetic catalysis. The effect of pion fluctuations suppressing the chiral condensation becomes stronger as a magnetic field increases. We give a possible explanation of the recent lattice result in which the critical temperature decreases as the magnetic field increases. In case of the latter, several models such as a Nambu-Jona-Lasinio type model imply that the charged vector meson condensation occurs in a strong magnetic field because the mass of vector meson decreases by Zeeman splitting as the magnetic field increases. However, we show that this is not the case in QCD using the Vafa-Witten theorem. We also show the result of the vector meson mass in the Lattice simulation.

EHQG Seminar

Title
The quark-antiquark potential in N=4 SYM from an open spin-chain
Speaker
Nadav Drukker (King's Coll. London)
Date & Time
Tuesday, January 22, 2013, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
Two years ago when I visited Nagoya I presented the calculation of the quark-antiquark potential in N=4 supersymmetric Yang-Mills theory and a generalization of it at weak coupling and at strong coupling (using AdS/CFT). In this talk I will review that old work and add a significant new layer to it. I will apply the tools of integrability to calculate the same quantity. I will describe a spin-chain model and a set of thermodynamic Bethe ansatz equations which describe this system and will discuss their solution.

EHQG Seminar

Title
Radiative Emission of neutrino pair from atoms/molecules
Speaker
Minoru Tanaka (Osaka Univ.)
Date & Time
Tuesday, January 15, 2013, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
The process of collective de-excitation of atoms/molecules in a metastable level into the emission mode of a single photon plus a neutrino pair, |e〉→|g〉+γ+ν_i+‾ν_j, called radiative emission of neutrino pair (RENP), is sensitive to the absolute neutrino mass scale, the neutrino mass hierarchy, the nature (Dirac or Majorana) of massive neutrinos, and CP phases. We investigate how these neutrino properties can be determined from the measurement of the corresponding continuous photon spectrum taking the examples of Xe atom and I_2 molecule. In addition, we discuss a companion QED process, paired super-radiance (PSR), in which the neutrino pair is replaced by another photon, |e〉→|g〉+γ+γ. PSR is a novel coherent quantum process and important for several reasons: a proof-of-concept process for RENP, to determine the dynamical factor of RENP, and a background in RENP. Some numerical results of PSR in the target of para-hydrogen molecules are presented.

EHQG Seminar

Title
Cosmic R-tube, Vacuum Instability and R-axion Cosmology
Speaker
Yutaka Ookouchi (Kyoto Univ.)
Date & Time
Tuesday, December 18, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
We study general constraints on spontaneous R-symmetry breaking models. Firstly, we investigate a cosmic string associated with the R-symmetry breaking which can be viewed as a tube-like domain wall with a winding number interpolating a false vacuum and a true vacuum. Such string causes inhomogeneous decay of the false vacuum to the true vacuum via rapid expansion of the radius of the tube and hence its formation would be inconsistent with the present Universe. Secondary, we show general constraints coming from the cosmological effects of the pseudo Nambu-Goldstone bosons, R-axions. They are substantially produced in the early Universe and may cause several cosmological problems.

Special Lecture (for DC)

Title
時空の熱力学
Speaker
Satoshi Iso (KEK)
Date & Time
Wednesday, December 12–Friday, December 14, 2012
Place
ES034 Lecture Room

EHQG Seminar

Title
TeV scale mirage mediation in NMSSM
Speaker
Ken-ichi Okumura (Kyushu Univ.)
Date & Time
Tuesday, December 11, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
We study the next-to-minimal supersymmetric standard model. We consider soft supersymmetry breaking parameters, which are induced by the mirage mediation mechanism of supersymmetry breaking. We concentrate on the mirage mediation, where the so-called mirage scale is the TeV scale. In this scenario, we can realize the up-type Higgs soft mass of O(200) GeV, while other masses such as gaugino masses and stop masses are heavy such as 1 TeV or more. Cancellation between the effective mu-term and the down-type Higgs soft mass ameliorates the fine-tuning in the electroweak symmetry breaking even for μ=O(500) GeV. The mixing between the doublet and singlet Higgs bosons is suppressed by (κ/λ)/tan β. Then the lightest doublet Higgs mass naturally reaches 125 GeV lifted by the new quartic coupling. The higgsino and singlino are light and their linear combination is the lightest superparticle.

QG-KMI Seminar

Title
Cosmology with broken Null Energy Condition
Speaker
Alexander Vikman (CERN, Geneva)
Date & Time
Thursday, November 29, 2012, 5:00 p.m.
Place
Science Symposia (ES635)
Abstract
In this talk I will discuss theories where the weakest of all classical energy conditions—the Null Energy Condition (NEC)—is violated. These theories have rather peculiar unintuitive properties and therefore allow for quite exotic cosmological scenarios-bounces etc. providing new theoretical opportunities for the origin of our universe. On the other hand, for the contemporary universe, the NEC can put a bound on non-ideal parts of the Dark Energy's (DE) energy momentum tensor. This talk is based on arXiv:1109.1047 and arXiv:1209.2961.

EHQG Seminar

Title
Is “Quark-Gluon Plasma = Black Hole” in string theory?
Speaker
Takeshi Morita (KEK)
Date & Time
Tuesday, November 6, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
We study the gravity dual of four dimensional pure Yang-Mills theory through D4 branes, as proposed by Witten (holographic QCD). In this holographic QCD, it has been widely believed that the confinement phase in the pure Yang-Mills theory corresponds to the D4 soliton in gravity and the deconfinement phase corresponds to the black D4 brane. We inspect this conjecture carefully and show that the correspondence between the black D4 brane and the deconfinement phase is not correct. Instead, by using a slightly different set up, we find an alternative gravity solution called “localized soliton”, which would be properly related to the deconfinement phase. In this case, the confinement/deconfinement transition is realized as a Gregory-Laflamme type transition. We also discuss the corrected realization of the QGP phase in the Sakai-Sugimoto model.

EHQG Seminar

Title
The neutral pion decay and the chiral anomaly
Speaker
Xu Feng (KEK)
Date & Time
Tuesday, October 30, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
We perform a nonperturbative calculation of the pion-to-two-photon transition form factor and the associated decay width using lattice QCD. The amplitude for a two-photon final state, which is not an eigenstate of QCD, is extracted through a Euclidean time integral of the relevant three-point function. We utilize the all-to-all quark propagator technique to carry out this integration as well as to include the disconnected quark diagram contributions. The overlap fermion formulation is employed on the lattice to ensure exact chiral symmetry on the lattice. Using the method of analytical continuation, we calculate the form factor and decay width with a comprehensive estimate of various systematic errors, except for a possible discretization effect. Our results reproduce the predication of the ABJ anomaly in the chiral limit and also agree with the PrimEx experimental measurement at the physical pion mass with a precision of a few percent.

EHQG Seminar

Title
Non-Gaussianity in isocurvature perturbations
Speaker
Toyokazu Sekiguchi (Nagoya Univ.)
Date & Time
Tuesday, October 23, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
Various models of the early Universe predict generation of isocurvature perturbations. Their amplitudes, correlations with the curvature perturbation, and scale dependences can provide us unique information of the physics at the very early stage of the Universe. In this talk, I will focus on non-Gaussianity (NG) in the isocurvature perturbations. Interestingly, as I will show, if vacuum fluctuations of light scalar fields contribute to the initial perturbations of the structure formation, some level of NG in curvature and isocurvature perturbations is inevitably induced. After discussing CMB signatures of NG in isocurvature perturbations, I will also present constraints from current observations.

EHQG Seminar

Title
Moduli Inflating Curvaton
Speaker
Chia-Min Lin (Kobe Univ.)
Date & Time
Tuesday, October 16, 2012, 5:00 p.m.
Place
ES034 Lecture Room

EHQG Seminar

Title
Holography and anomaly matching for resonances
Speaker
Naoki Yamamoto (UMD, College Park)
Date & Time
Tuesday, October 9, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
We derive a universal relation for the transverse part of triangle anomalies in a class of holographic models of QCD which may be regarded as the “anomaly matching” for resonances. We argue its consequences and possible realization in real QCD.

EHQG-KMI Seminar

Title
Modified theories of gravity and mechanisms of mass screening
Speaker
Radouane Gannouji (Tokyo Univ. of Sci.)
Date & Time
Tuesday, October 2, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
Despite the overwhelming evidence for the existence of an acceleration of the Universe, the underlying fundamental physics remains unknown. As an alternative to cosmological constant, the cosmic acceleration can result from large scale modification of gravity which necessarily include additional degrees of freedom. If these additional degrees are welcomed at large scales they should be screened at small scales where General Relativity is a perfect theory. During this talk, I will present the 3 screening mechanisms known in the literature: chameleon, symmetron and Vainshtein mechanisms. I will show the strengths and weaknesses of these models.

EHQG-KMI Seminar

Title
The Little Big Bang: The first 30 yocto seconds
Speaker
Sangyong Jeon (McGill Univ., Montreal)
Date & Time
Tuesday, July 24, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
One of the most important goals of high energy nuclear physics is to produce and study Quark-Gluon Plasma (QGP). This deconfined phase of nuclear matter naturally existed only within few microseconds after the Big Bang. Since the year 2000, the Relativistic Heavy Ion Collider (RHIC) at the Brookhaven Lab has been colliding heavy ions to re-create this hot soup of quarks and gluons with the maximum temperature exceeding 5 trillion kelvin. The Large Hadron Collider (LHC) is also producing a copious amount of data since last year with maximum temperature possibly reaching 10 trillion kelvin. The QGP created in heavy ion collisions lives incredibly short amount of time—only about 30 yocto (10^{-24}) seconds. However, within that time, it goes through an amazing array of physical phenomena including hottest temperature and largest pressure ever achieved on earth, most perfect fluid, and a phase transition (with a possible critical point) to ordinary matter to just list a few. Creating QGP demands an extraordinary skills from experimentalists as well as dedicated efforts from theorists to understand it all. In this talk, I will outline our understanding of how QGP is created in heavy ion collisions, how it evolves and how it finally transforms back to the ordinary matter using variety of theoretical tools including many-body QCD, hydrodynamics and Boltzmann equation.

EHQG Seminar

Title
SUSY extensions in light of recent Higgs searches
Speaker
Motoi Endo (Univ. Tokyo)
Date & Time
Tuesday, July 10, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
The recent LHC searches imply the Higgs mass around 125 GeV. This result tends to conflict with the muon g−2 anomaly within the framework of the minimal supersymmetric SM. In the talk, extensions of the SUSY models are discussed.

EHQG-GCOE Seminar

Title
On numerical study of supersymmetric field theories
Speaker
Hiroshi Suzuki (RIKEN)
Date & Time
Tuesday, July 3, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
It is widely believed that SUSY is a fundamentally important symmetry in particle physics beyond the standard model. However, since there does not exist SUSY invariant regularization in general, the study of non-perturbative dynamics of SUSY theories from the first principles is a non-trivial task. In this talk, I will give some overview of our studies on non-perturbative formulation SUSY field theories and its application.

EHQG Seminar

Title
String phenomenology: overview
Speaker
Tatsuo Kobayashi (Kyoto Univ.)
Date & Time
Tuesday, June 19, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
We give an overview of recent development in string phenomenology. We show some examples of superstring theory on 6D compact space, which lead to realistic spectra similar to the standard model. Then, we study 4D low-energy effective field theory, which is derived from such realistic string models. Discrete symmetries and their anomalies are discussed. Explicit stringy computations can provide us with important aspects on low-energy effective field theory.

EHQG Seminar

Title
Derivation of Superselection Rules and an Interpretation of Invisible Colors
Speaker
Shogo Tanimura (Nagoya Univ.)
Date & Time
Tuesday, June 12, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
In the ordinary formulation of quantum mechanics, physical observables are represented by self-adjoint operators. But, not all of self-adjoint operators in the theory correspond to physical observables in the real world. The superselection rule is a necessary condition imposed on a self-adjoint operator for being observable. Sometimes the superselection rule is regarded as a reasonable hypothesis that cannot be derived from the other principles. I introduce notions of covariant measurement and isolated conservation law. By using them I derived the superselection rules in a general scheme. As an application of this scheme I discuss why color-multiplet quantities in QCD are invisible in the macroscopic world.

EHQG Seminar

Title
cosmic acceleration: dark energy and alternatives
Speaker
Mohammad Sami (Jamia Millia Islamia)
Date & Time
Tuesday, June 5, 2012, 5:00 p.m.
Place
ES034 Lecture Room

EHQG Seminar

Title
String inspired solution to the sign problem and overlapping problem
Speaker
Masanori Hanada (KEK)
Date & Time
Tuesday, May 29, 2012, 5:00 p.m.
Place
ES034 Lecture Room

EHQG Seminar

Title
Updates on Muon g−2
Speaker
Daisuke Nomura (Tohoku Univ.)
Date & Time
Tuesday, May 22, 2012, 5:00 p.m.
Place
ES034 Lecture Room

EHQG-KMI-Tau Lepton Seminar

Title
Atomic Electric Dipole Moments as Probes of CP Violation
Speaker
Bhanu Pratap Das (IIA, Bangalore)
Date & Time
Tuesday, May 15, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
The existence of a nonzero permanent electric dipole moment (EDM) of a non-degenerate physical system physical system is a signature of the simultaneous violations of time-reversal (T) and parity (P) symmetries. T violation implies the combined charge conjugation (C) and P violation (CP violation) via the CPT theorem. Atomic EDMs are excellent probes of physics beyond the standard model, and they provide important insights into a rich variety of CP violations—leptonic, semi-leptonic, and hadronic sectors. Experimental searches are underway for the EDMs of paramagnetic (open-shell) and diamagnetic (closed-shell) atoms. The results of the experiments can be combined with those of sophisticated atomic many-body calculations to determine various CP violating coupling constants at the atomic level. These quantities can ultimately be related to the CP violation parameters at the elementary particle level and tested with the predictions of the different particle physics models. The present talk will give an introduction to atomic EDMs and touch upon on some of the ongoing searches of these EDMs as well as their future prospects.

EHQG Seminar

Title
背景時空独立な量子重力及びその宇宙論的意義
Speaker
Ken-ji Hamada (KEK)
Date & Time
Tuesday, April 24, 2012, 5:00 p.m.
Place
ES034 Lecture Room
Abstract
講演ではPlanckスケールを越えた世界を記述するために提案された背景時空独立な量子重力理論について解説します。この理論は近年私が提案した、重力場の共形因子を厳密に、その他のテンソルモードを摂動的に取り扱う繰り込み可能な量子重力理論の紫外極限に現れるもので、共形場理論(CFT)のことばを用いて定式化することが出来ます。その際、通常のCFTとは異なり、共形不変性がゲージ対称性(diffeomorphism invariance)であることから、背景時空独立性が実現します。本講演では主にそのBRST定式化を基にした物理状態等の理論構造について解説します[arXiv:1109.6109; 1203.4894又はarXiv:1202.4538]。また、繰り込み可能な量子重力が示唆する新しいインフレーション宇宙像について簡潔に解説します[arXiv:0908.0192]。

EHQG Seminar

Title
Leptophilic two Higgs doublet model at the LHC
Speaker
Koji Tsumura (Nagoya Univ.)
Date & Time
Tuesday, April 17, 2012, 5:00 p.m.
Place
ES034 Lecture Room