Results for "Takashi Toma"
total 3541took 0.42s
Lepton Flavor Violation in the Scotogenic ModelDec 10 2013Jan 28 2014We investigate lepton flavor violation in the scotogenic model proposed by Ma in which neutrinos acquire non-zero masses at the 1-loop level. Although some works exist in this direction, they have mainly focused on the radiative decay $\ell_\alpha \to ... More Radiative Lepton Model and Dark Matter with Global $U(1)'$ SymmetryJan 27 2014Mar 12 2014We propose a radiative lepton model, in which the charged lepton masses are generated at one-loop level, and the neutrino masses are induced at two-loop level. On the other hand, tau mass is derived at tree level since it is too heavy to generate radiatively. ... More A new mechanism of sterile neutrino dark matter productionFeb 08 2018We consider a scenario where the dark matter candidate is a sterile neutrino with sizable self-interactions, described by a dimension-six operator, and with negligible interactions with the Standard Model. The relic abundance is set by the freeze-out ... More Evading Direct Dark Matter Detection in Higgs Portal ModelsNov 29 2016Many models of Higgs portal Dark Matter (DM) find themselves under pressure from increasingly tight direct detection constraints. In the framework of gauge field DM, we study how such bounds can be relaxed while retaining the thermal WIMP paradigm. When ... More Multicomponent Dark Matter from Gauge SymmetryNov 01 2016Nov 11 2016The composition of Dark Matter (DM) remains an important open question. The current data do not distinguish between single- and multi-component DM, while in theory constructions it is often assumed that DM is composed of a single field. In this work, ... More X-ray lines and self-interacting dark matterJun 05 2015Dec 03 2015We study the correlation between a monochromatic signal from annihilating dark matter and its self-interacting cross section. We apply our argument to a complex scalar dark sector, where the pseudo-scalar plays the role of a warm dark matter candidate ... More Electron electric dipole moment in Inverse Seesaw modelsMay 24 2016Aug 01 2016We consider the contribution of sterile neutrinos to the electric dipole moment of charged leptons in the most minimal realisation of the Inverse Seesaw mechanism, in which the Standard Model is extended by two right-handed neutrinos and two sterile fermion ... More Electric Dipole Moments of Charged Leptons with Sterile FermionsNov 10 2015Mar 04 2016We address the impact of sterile fermions on charged lepton electric dipole moments. Any experimental signal of these observables calls for scenarios of physics beyond the Standard Model providing new sources of CP violation. In this work, we consider ... More Multicomponent dark matter particles in a two-loop neutrino modelMar 29 2013Jul 08 2013We construct a loop induced seesaw model in a TeV scale theory with gauged U(1)_{B-L} symmetry. Light neutrino masses are generated at two-loop level and right-handed neutrinos also obtain their masses by one-loop effect. Multi-component Dark Matters ... More Inert Extension of the Zee-Babu ModelAug 05 2014We propose a two-loop induced Zee-Babu type neutrino mass model at the TeV scale. Although there is no dark matter candidate in the original Zee-Babu model, that is contained in our model by introducing an unbroken discrete $Z_2$ symmetry. The discrepancy ... More Signals of dark matter in a supersymmetric two dark matter modelDec 17 2010Jun 16 2011Supersymmetric radiative neutrino mass models have often two dark matter candidates. One is the usual lightest neutralino with odd R parity and the other is a new neutral particle whose stability is guaranteed by a discrete symmetry that forbids tree-level ... More Light Dark Matter Candidate in B-L Gauged Radiative Inverse SeesawOct 08 2012Mar 19 2013We study a radiative inverse seesaw model with local B-L symmetry, in which we extend the neutrino mass structure that is generated through a kind of inverse seesaw framework to the more generic one than our previous work. We focus on a real part of bosonic ... More A Possible Origin of Bimodal Distribution of Gamma-Ray BurstsJul 01 2004Jan 16 2005We study the distribution of the durations of gamma-ray bursts (GRBs) in the unified model of short and long GRBs recently proposed by Yamazaki, Ioka, and Nakamura. Monte Carlo simulations show clear bimodal distributions, with lognormal-like shapes for ... More Nonthermal dark matter models and signalsNov 03 2015Mar 04 2016Many experiments exploring weakly interacting massive particles (WIMPs) such as direct, indirect and collider searches have been carried out until now. However, a clear signal of a WIMP has not been found yet and it makes us to suspect that WIMPs are ... More Right-handed Sneutrino Dark Matter in Supersymmetric B-L ModelFeb 21 2011Jun 22 2011We show that the lightest right-handed sneutrino in TeV scale supersymmetric B-L model with inverse seesaw mechanism is a viable candidate for cold dark matter. We find that it accounts for the observed dark matter relic abundance in a wide range of parameter ... More Supersymmetry and the Supergravity LandscapeJan 01 2006In the recent times a lot of effort has been devoted to improve our knowledge about the space of string theory vacua (``the landscape'') to find statistical grounds to justify how and why the theory selects its vacuum. Particularly interesting are those ... More A Note on Lie-Lorentz DerivativesJun 18 2002Jun 18 2002The definition of ``Lie derivative'' of spinors with respect to Killing vectors is extended to all kinds of Lorentz tensors. This Lie-Lorentz derivative appears naturally in the commutator of two supersymmetry transformations generated by Killing spinors ... More Massive and Massless Black HolesAug 08 1996We review some recent work on the existence and classification of extreme black-hole-type solutions in N=8 supergravity. For the black holes considered (those that are also solutions of N=4 supergravity and of the Einstein-Maxwell-dilaton theory with ... More Massless Black Holes as Black Diholes and QuadruholesFeb 13 1996Apr 18 1996Massless black holes can be understood as bound states of a (positive mass) extreme a=\sqrt{3} black hole and a singular object with opposite (i.e. negative) mass with vanishing ADM (total) mass but non-vanishing gravitational field. Supersymmetric balance ... More Latent Tree Language ModelJul 24 2016Sep 05 2016In this paper we introduce Latent Tree Language Model (LTLM), a novel approach to language modeling that encodes syntax and semantics of a given sentence as a tree of word roles. The learning phase iteratively updates the trees by moving nodes according ... More The Pedestrian's Guide to Local TimeDec 30 2015These notes contains an introduction to the theory of Brownian and diffusion local time, as well as its relations to the Tanaka Formula, the extended Ito-Tanaka formula for convex functions, the running maximum process, and the theory of regulated stochastic ... More Numerical solution for the anisotropic Willmore flow of graphsNov 13 2011The Willmore flow is well known problem from the differential geometry. It minimizes the Willmore functional defined as integral of the mean-curvature square over given manifold. For the graph formulation, we derive modification of the Willmore flow with ... More No elliptic islands for the universal area-preserving mapDec 10 2010Jun 02 2011A renormalization approach has been used in \cite{EKW1} and \cite{EKW2} to prove the existence of a \textit{universal area-preserving map}, a map with hyperbolic orbits of all binary periods. The existence of a horseshoe, with positive Hausdorff dimension, ... More Relative commutator theory in varieties of omega-groupsMay 11 2006We introduce a new notion of commutator which depends on a choice of subvariety in any variety of omega-groups. We prove that this notion encompasses Higgins's commutator, Froehlich's central extensions and the Peiffer commutator of precrossed modules. ... More Twenty-Five Moves Suffice for Rubik's CubeMar 24 2008How many moves does it take to solve Rubik's Cube? Positions are known that require 20 moves, and it has already been shown that there are no positions that require 27 or more moves; this is a surprisingly large gap. This paper describes a program that ... More A note on the cone of mobile curvesAug 05 2009S. Boucksom, J.-P. Demailly, M. Paun and Th. Peternell proved that the cone of mobile curves ME(X) of a projective complex manifold X is dual to the cone generated by classes of effective divisors and conjectured an extension of this duality in the Kaehler ... More Bounded sets of sheaves on compact Kaehler manifoldsMar 30 2011Jun 02 2011We show that any set of quotients with fixed Chern classes of a given coherent sheaf on a compact Kaehler manifold is bounded in a sense which we define. The result is proved by adapting Grothendieck's boundedness criterium expressed via the Hilbert polynomial ... More A new approach to Sobolev spaces in metric measure spacesApr 29 2015Apr 19 2016Let $(X,d_X,\mu)$ be a metric measure space where $X$ is locally compact and separable and $\mu$ is a Borel regular measure such that $0 <\mu(B(x,r)) <\infty$ for every ball $B(x,r)$ with center $x \in X$ and radius $r>0$. We define $\mathcal{X}$ to be ... More A Note on Random Coverings of ToriJul 04 2013Apr 07 2014This note provides a generalisation of a recent result by J\"arvenp\"a\"a, J\"arvenp\"a\"a, Koivusalo, Li, and Suomala, (to appear), on the dimension of limsup-sets of random coverings of tori. The result in this note is stronger in the sense that it ... More A Unified Model for Gamma-Ray BurstsFeb 23 2005A possible unified model of short and long gamma-ray bursts (GRBs), X-ray rich GRBs, and X-ray flashes is proposed. It is assumed that the jet of a GRB consists of many emitting sub-shells (i.e., an inhomogeneous jet model). The multiplicity of the sub-shells ... More Two Loop Neutrino Model with Dark Matter and LeptogenesisMay 18 2015Jul 08 2016We study a two-loop induced radiative neutrino model at TeV scale with global $U(1)$ symmetry, in which we analyze dark matter and resonant leptogenesis. The model includes two kinds of dark matter candidates. We discuss what kind of dark matter can satisfy ... More Tail Emission of Prompt Gamma-Ray Burst JetsSep 07 2005Apr 04 2006Tail emission of the prompt gamma-ray burst (GRB) is discussed using a multiple emitting sub-shell (inhomogeneous jet, sub-jets or mini-jets) model, where the whole GRB jet consists of many emitting sub-shells. One may expect that such a jet with angular ... More A pentaquark picture of Lambda(1405)Aug 17 2007We test a pentaquark model of the negative parity hyperon Lambda(1405). We use a model where valence four quarks and one antiquark move in a potential relativistically and interact with each other and themselves through gluon and NG boson. Fall-apart ... More More on $U_q(su(1,1))$ with $q$ a Root of UnityDec 10 1993Highest weight representations of $U_q(su(1,1))$ with $q=\exp \pi i/N$ are investigated. The structures of the irreducible hieghesat weight modules are discussed in detail. The Clebsch-Gordan decomposition for the tensor product of two irreducible representations ... More Quasi-equilibrium nonadditivityApr 30 2014The possibility that a short-range interacting system exhibits nonadditivity is investigated. After the discussion on the precise definition of additivity and its consequence, we show that it is possible when the system is in a quasi-equilibrium state ... More Exactness of the mean-field dynamics in optical cavity systemsDec 30 2012Jun 20 2013Validity of the mean-field approach to open system dynamics in the optical cavity system is examined. It is rigorously shown that the mean-field approach is justified in the thermodynamic limit. The result is applicable to nonequilibrium situations, e.g. ... More Extensive increase of entropy in quantum quenchJun 23 2016Oct 25 2016In the setup of isolated quantum systems, it is proved that the thermodynamic entropy and the diagonal entropy must increase extensively in any nontrivial quantum quench. The extensive increase of the thermodynamic entropy is shown for any initial state ... More Scale-Free Networks Hidden in Chaotic Dynamical SystemsJul 22 2010In this paper, we show our discovery that state-transition networks in several chaotic dynamical systems are "scale-free networks," with a technique to understand a dynamical system as a whole, which we call the analysis for "Discretized-State Transition" ... More Strong field physics in condensed matterFeb 12 2011There are deep similarities between non-linear QFT studied in high-energy and non-equilibrium physics in condensed matter. Ideas such as the Schwinger mechanism and the Volkov state are deeply related to non-linear transport and photovoltaic Hall effect ... More Finite rank Bratteli--Vershik homeomorphisms are expansiveJun 01 2016Aug 19 2016Downarowicz and Maass (2008) have shown that every Cantor minimal homeomorphism with finite topological rank $K > 1$ is expansive. Bezuglyi, Kwiatkowski, and Medynets (2009) extended the result to non-minimal aperiodic cases. In this paper, we show that ... More