arXiv subjects

A. Sugamoto

Publications and source records attributed to A. Sugamoto.

16 recordsLinked to original sources

arXiv2022

Analytical Study of Anomalous Diffusion by Randomly Modulated Dipole

This paper derives the Fokker-Planck (FP) equation for a particle moving in potential by a randomly modulated dipole. The FP equation describes the anomalous diffusion observed in the companion paper [1] and breaks the conservation of the total probability at the singularity by the dipole. It also shows anisotropic diffusion, which is typical in fluid turbulence. We need to modify the probability density by introducing a mechanism to recover the particle. After the modification, the latent fractal dimension matches with the results of the companion paper. We hope that our model gives a new example of fractional diffusion, where the random singularity triggers fractionality.

math-ph↗

arXiv2009

Development of displacement- and frequency-noise-free interferometer in 3-D configuration for gravitational wave detection

The displacement- and frequency-noise-free interferometer (DFI) is a multiple laser interferometer array for gravitational wave detection free from both the displacement noise of optics and laser frequency noise. So far, partial experimental demonstrations of DFI have been done in 2-D table top experiments. In this paper, we report the complete demonstration of a 3-D DFI. The DFI consists of four Mach-Zehnder interferometers with four mirrors and two beamsplitters. The displacement noises both of mirrors and beamsplitters were suppressed by up to 40 dB. The non-vanishing DFI response to a gravitational wave was successfully confirmed using multiple electro-optic modulators and computing methods.

gr-qc↗

arXiv2008

BRST structure of non-linear superalgebras

In this paper we analyse the structure of the BRST charge of nonlinear superalgebras. We consider quadratic non-linear superalgebras where a commutator (in terms of (super) Poisson brackets) of the generators is a quadratic polynomial of the generators. We find the explicit form of the BRST charge up to cubic order in Faddeev-Popov ghost fields for arbitrary quadratic nonlinear superalgebras. We point out the existence of constraints on structure constants of the superalgebra when the nilpotent BRST charge is quadratic in Faddeev-Popov ghost fields. The general results are illustrated by simple examples of superalgebras.

hep-th↗

arXiv2008

Development of signal-extraction scheme for Resonant Sideband Extraction

As a future plan, an advanced gravitational-wave detector will employ an optical configuration of resonant sideband extraction (RSE), achieved with an additional mirror at the signal-detection port of the power-recycled Fabry-Perot Michelson interferometer. To control the complex coupled cavity system, one of the most important design issues is how to extract the longitudinal control signals of the cavities. We developed a new signal-extraction scheme which provides an appropriate sensing matrix. The new method uses two sets of sidebands: one of the sideband components satisfies the critical coupling ondition for the RSE interferometer and reaches the signal-extraction port, and the other sideband is completely reflected by the Michelson interferometer. They provide a diagonalized sensing matrix and enable the RSE control to be robust.

gr-qc↗

arXiv2004

Pentaquark Baryons in String Theory -- Talk at Pentaquark 04

Pentaquark baryons $Θ^{+}$ and $Ξ^{--}$ are studied in the dual gravity theory of QCD in which simple mass formulae of pentaquarks are derived in the Maldacena prototype model for supersymmetric QCD and a more realistic model for ordinary QCD. In this approach it is possible to explain the extremely narrow decay widths of pentaquarks. With the aim of constructing more reliable mass formulae, a sketch is given on spin and the hyperfine interaction in the string picture.

hep-ph↗

arXiv2002

Matrix Model on Z-Orbifold

Six dimensional compactification of the type IIA matrix model on the ${\bf Z}$-orbifold is studied. Introducing a ${\bf Z}_{3}$ symmetry properly on the three mirror images of fields in the $N$-body system of the supersymmetric D0 particles, the action of the Matrix model compactified on the ${\bf Z}$-orbifold is obtained. In this matrix model ${\cal N}=1$ supersymmetry is explicitly demonstrated.

hep-th↗

arXiv2002

Generation of 4d Gauge Theory and Gravity from their 3d versions--Asymptotic Disappearance of Space and Time (ADST) Scenario--

An exotic scenario of our universe is proposed in which our universe starts from zero space-time dimensions (0d), namely, a set of discrete points, it increases the (continuous) dimensionality during the cooling down of it, and finally arrives at the present four space-time dimensions (4d). This scenario may be called asymptotic disappearance (or discretization) of space-time (ADST) scenario. The final stage of the scenario is to generate dynamically 4d from the 3d, which is shown to be possible for both gauge theory and gravity, including the standard model. To examine the validity of the scenario, 4d QED generated from its 3d version at high energy is studied, in which one spatial dimension is discretized with a lattice constant $a$. From the LEP2 experiment on $e^+ e^- \to γγ$, $a$ is constrained to satisfy $a \le 461$ GeV. Expected bound on $a$ at future $e^+ e^-$ linear collider is discussed. The finite size of $a$ modifies the dispersion relation, causing the violation of Lorentz symmetry. Then, the paradox of observing 20 TeV $γ$ rays from the active galaxy Markarian 501 may disappear, overcoming the GZK cut.

hep-th↗

arXiv2001

B -> X_s l+ l- in the vectorlike quark model

We extend the standard model by adding an extra generation of isosinglet up- and down-type quark pair which engage in weak interactions only via mixing with the three ordinary quark families. It is shown that the generalized $4\times 4$ quark mixing matrix, which is necessarily nonunitary, leads to nonvanishing flavor changing neutral currents. We then proceed to investigate various distributions and total branching ratio of the inclusive B -> X_s l+ l- (l =e,μ) rare B decays in the context of this model. It is shown that the shapes of the differential branching ratio and forward-backward asymmetry distribution are very sensitive to the value of the model parameters which are constrained by the experimental upper bound on BR(B -> X_s μ^+ μ^-). We also indicate that, for certain values of the dileptonic invariant mass, CP asymmetries up to 10% can be obtained.

hep-ph↗

arXiv2000

Chamseddine, Fröhlich, Grandjean Metric and Localized Higgs Coupling on Noncommutative Geometry

We propose a geometrized Higgs mechanism based on the gravitational sector in the Connes-Lott formulation of the standard model, which has been constructed by Chamseddine, Fr$\ddot{o}$hlic and Grandjean. The point of our idea is that Higgs-like couplings depend on the local coordinates of the four-dimensional continuum,$M_4$. The localized couplings can be calculated by the Wilson loops of the $U(1)_{EM}$ gauge field and the connection, which is defined on $Z_2\times{M_4}$.

hep-th↗

arXiv1999

Axion-Dilatonic Conformal Anomaly from Ads/CFT Correspondence

We discuss general multidimensional axion-dilatonic AdS gravity which may correspond to bosonic sector of Gibbons-Green-Perry (compactified) IIB supergravity with RR-scalar (axion). Using AdS/CFT correspondence the 4d conformal anomaly on axion-dilaton-gravitational background is found from SG side. It is shown that for IIB SG with axion such conformal anomaly coincides with the one obtained from QFT calculation in ${\cal N}=4$ super Yang-Mills theory conformally coupled with ${\cal N}=4$ conformal SG. Brief discussion on possibility to apply these results for gauged SGs is also presented.

hep-th↗

arXiv1999

Deformation of Schild String

We attempt to construct new superstring actions with a $D$-plet of Majorana fermions $ψ^{\cal B}_A$, where ${\cal B}$ is the $D$ dimensional space-time index and $A$ is the two dimensional spinor index, by deforming the Schild action. As a result, we propose three kinds of actions: the first is invariant under N=1 (the world-sheet) supersymmetry transformation and the area-preserving diffeomorphism. The second contains the Yukawa type interaction. The last possesses some non-locality because of bilinear terms of $ψ^{\cal B}_A$. The reasons why completing a Schild type superstring action with $ψ^{\cal B}_A$ is difficult are finally discussed.

hep-th↗

arXiv1997

Non-spectator contributions to B->X_s eta'

We propose a nonspectator mechanism in which eta' is produced by two gluon fusion as the underlying process to explain the inclusive B-> X_s eta' as well as the exclusive B -> K^(*) eta' decays.

hep-ph↗

arXiv1997

Non-spectator contribution: A mechanism for inclusive B-> X_s eta' and exclusive B-> K(*) eta' decays

We propose a mechanism which can explain the large BR(B-> X_s eta')~ 10^(-3) observed by CLEO. In this mechanism, eta' is produced by the fusion of two gluons, one from QCD penguin b->sg and the other one emitted by the light quark inside the B meson. The inclusive decay rate which is calculated via using the factorization assumption, can easily account for the observed branching ratio. We also estimate the exclusive branching ratio BR(B->K eta')=7.0X10^(-5) which is in good agreement with the experimental data and present our prediction for K* mode BR(B->K* eta')=3.4X10^(-5).

hep-ph↗

arXiv1997

Classicalization of Quantum Fluctuation in Inflationary Universe

We discuss the classicalization of a quantum state induced by an environment in the inflationary stage of the universe. The classicalization is necessary for the homogeneous ground sate to become classical non-homogeneous one accompanied with the statistical fluctuation, which is a plausible candidate for the seeds of structure formation. Using simple models, we show that i) the two classicalization criteria, the classical correlation and quantum decoherence, are simultaneously satisfied by the environment and that ii) the power spectrum of the resultant statistical fluctuation depends upon the detail of the classicalization process. Especially, the result ii) means that, taking account of the classicalization process, the inflationary scenario does not necessarily predict the unique spectrum which is usually believed.

gr-qc↗

arXiv1995

Quantum effects of stringy and membranic nature for the swimming of micro-organisms in a fluid

The static potential is investigated in string and membrane theories coupled to $U(1)$ gauge fields (specifically, external magnetic fields) and with antisymmetric tensor fields. The explicit dependence of the potential on the shape of the extended objects is obtained, including a careful calculation of the quantum effects. Noting the features which are common to the dynamics of strings and membranes moving in background fields and to the swimming of micro-organisms in a fluid, the latter problem is studied. The Casimir energy of a micro-organism is estimated, taking into account the quantum effects and the backreaction from the outside fluid. The static potential is investigated in string and membrane theories coupled to $U(1)$ gauge fields (specifically, external magnetic fields) and with antisymmetric tensor fields. The explicit dependence of the potential on the shape of the extended objects is obtained, including a careful calculation of the quantum effects. Noting the features which are common to the dynamics of strings and membranes moving in background fields and to the swimming of micro-organisms in a fluid, the latter problem is studied. The Casimir energy of a micro-organism is estimated, taking into account the quantum effects and the backreaction from the outside fluid.

hep-th↗

arXiv1995

Majorana neutrino versus Dirac neutrino in ${\rm e}^{+}{\rm e}^{-} \to {\rm W}^{+}{\rm W}^{-}$ through radiative corrections

Radiative corrections to ${\rm e}^{+}{\rm e}^{-}\! \rightarrow {\rm W}^{+}{\rm W}^{-}$ from Majorana neutrinos are studied in the context of the see-saw mechanism. Focusing on the effects of the fourth generation neutrinos, we calculate W-pair form factors, the differential cross sections and the forward-backward asymmetries for the polarized electrons at one-loop level. The behaviour of the form factors at the threshold of Majorana particle pair productions is found to differ from that of Dirac particle pair productions. In the cross section for unpolarized electrons, the radiative corrections, depending on the mass parameters of the see-saw mechanism, are found to be $\sim 0.5\%$ at the energy range of the LEP200 and the next generation linear colliders.

hep-ph↗