Takehiro Nabeshima, Toyama University
TeV-Scale Seesaw with Loop-Induced Dirac Mass Term and Dark Matter from U(1)_{B－L} Gauge Symmetry Breaking
Meeting room 3, Kenkyu honkan 1F
show a TeV-scale seesaw model where Majorana neutrino masses, the dark matter mass, and stability of the dark matter can be all originated from the U(1)_{B－L} gauge symmetry. Dirac mass terms for neutrinos are forbidden at the tree level by U(1)_{B－L}, and they are induced at the one-loop level by spontaneous U(1)_{B－L} breaking. The right-handed neutrinos can be naturally at the TeV-scale or below because of the induced Dirac mass terms with loop suppression. Such right- handed neutrinos would be discovered at the CERN Large Hadron Collider (LHC). On the other hand, stability of the dark matter is guaranteed without introducing an additional Z_2 symmetry by a remaining global U(1) symmetry after the U(1)_{B－L} breaking. A Dirac fermion Psi_1 or a complex neutral scalar s^0_1 is the dark matter candidate in this model. Since the dark matter (Psi_1 or s^0_ 1 ) has its own B－L charge, the invisible decay of the U(1)_{B－L} gauge boson Z′ is enhanced. Experimental constraints on the model are considered, and the collider phenomenology at the LHC as well as future linear colliders is discussed briefly.
Jun Suzuki, University of Electro-Communications
Radiation from accelerated impurities in a Bose–Einstein condensate (in Japanese)
Seminar room, Kenkyu honkan 3F
We investigate radiation spectra arising from accelerated point-like impurities in the homogeneous Bose– Einstein condensate. A general formula for the radiation spectrum is obtained in the integral form as a function of given impurity trajectory within the Bogoliubov approximation. The Planckian spectrum is obtained for a special accelerated motion, which is shown to be unphysical. Non-Planckian spectrum is found in the case of a uniformly accelerated impurity. We compare our result with similar settings discussed in other quantum systems.
Yoske Sumitomo, Hong Kong University of Science and Technology
Comments on Stability for de Sitter Vacua in String Theory
Meeting room 1, Kenkyu honkan 1F
We analyze a property of mass matrix at positive extrema in type II string theory. In IIA, off-diagonal components are not suppressed, therefore tachyonic directions are likely met in the presence of many moduli. While in a IIB model, such the suppression is achieved due to a hierarchy by non-perturbative effect and an alpha’ correction. Many moduli may help to realize small cosmological constant in the model.
Yuya Sasai, University of Helsinki
Closed string transport coefficients and the membrane paradigm
Meeting room 1, Kenkyu honkan 1F
>I discuss a correspondence between a fictitious fluid in the black hole membrane paradigm and highly excited closed string states according to the black hole correspondence principle. I calculate the membrane transport coefficients of an electric NS-NS 2-charged black hole and transport coefficients of the highly excited closed string states which possess a Kaluza-Klein number and a winding number. Comparing both the transport coefficients at the correspondence point, I show that, except for the bulk viscosity, the membrane transport coefficients are of the same order as the transport coefficients of the closed string states on the stretched horizon. Also, I show that, except for the bulk viscosity, both the dimensionless transport coefficients, which are defined by dividing the transport coefficients by the entropy density, are exactly equal if the central charge is 6.
Xerxes Tata, University of Hawaii
SUPERSYMMETRY, LHC AND DARK MATTER
Meeting room 1, Kenkyu honkan 1F
The hypothesis of weak scale supersymmetry ameliorates the gauge hierarchy problem, yields gauge couplings consistent with grand unification, and when augmented by R-parity conservation, provides natural candidates for the observed dark matter (DM). We review strategies for SUSY searches at the LHC, and project its reach in terms of sparticle masses in a relatively model-indendent manner. Assuming that the neutralino is a stable thermal relic from standard Big Bang cosmology, the measured density of cold DM selects out special regions in the parameter space of any underlying SUSY model with concomitant implications for collider physics, dark matter searches and low energy measurements. We examine the thermal neutralino relic density within the mSUGRA model as well as in various one-parameter extensions of mSUGRA (where we relax the underlying untested universality assumption) constructed to yield the measured relic density, and show that these implications, are in general, model-dependent. We nevertheless point out some relatively robust implications of the relic density determination for the LHC. Changing tracks, we describe a new bottom-up strategy for extracting neutralino mass parameters at the LHC and discuss its limitations. We conclude with an outlook for the future.
Daniel K. Brattan, Durham U
Fluid gravity at finite r
Seminar room, Kenkyu honkan 3F
The fluid/gravity correspondence provides a precise link between solutions to a class of Navier-Stokes problems and solving vacuum Einstein’s equations with a negative cosmological constant. In this talk I will attempt to demonstrate that we do not need to be at the boundary of the resultant spacetimes to extract transport coefficients. I will also discuss some tantalising hints of how the membrane paradigm may be embedded as an object in the boundary field theory.
Giacomo Cacciapaglia, IPN Lyon
The Neutrino of the Opera: faster than light, or illusion?
Lecture room 2, 4 go-kan 2F
I will briefly discuss the recent measurement of the speed of neutrinos by the OPERA collaboration, which reported an apparent faster than light propagation. The discussion will focus on some theoretical aspects of the super-luminal interpretation: energy dependence, Cherenkov emission, spectrum of the pion decay. Finally, I will present preliminary results based on a model in 5 dimensions.
Teruaki Suyama, RESCEU, Tokyo University
Dark energy from primordial inflationary quantum fluctuations
Meeting room 1, Kenkyu honkan 1F
We show that current cosmic acceleration can be explained by an almost massless scalar field experiencing quantum fluctuations during primordial inflation. Provided its mass does not exceed the Hubble parameter today, this field has been frozen during the cosmological ages to start dominating the universe only recently. By using supernovae data, completed with baryonic acoustic oscillations from galaxy surveys and cosmic microwave background anisotropies, we infer the energy scale of primordial inflation to be around a few TeV, which implies a negligible tensor-to-scalar ratio of the primordial fluctuations. Moreover, our model suggests that inflation lasted for an extremely long period. Dark energy could therefore be a natural consequence of cosmic inflation close to the electroweak energy scale.
Hikaru Kawai, Kyoto Universtiy
ベービーユニバースによる自然性問題の解消
Meeting room, 3 go-kan 1F
宇宙項がプランク質量（の４乗）に比べて１００桁以上も小さいことは、宇宙項問題といわれ、古くからの謎である。これを自然に説明する試みの一つに Coleman による baby universe のメカニズムがあるが、残念ながら、Euclid 化された量子重力に特有の問題のため、そもそも何を予言しているのか等、よくわからない点が多い。ここでは、Minkowski の量子重力にもとづいて、multiverse の波動関数を考え、それが baby universe の存在によってどのような影響を受けるかを調べる。その結果、宇宙項の値が非常に小さい値をとる確率が、圧倒的に大きいことがわかり、宇宙項問題が自然に解消していることがわかる。また、同様のメカニズムにより、Higgs mass 等の自然性問題が解決できる可能性についても議論する。
Yuho Sakatani, Kyoto University
Entropic formulation of relativistic continuum mechanics and its applications (in Japanese)
Meeting room 1, Kenkyu honkan 1F
