Realizing three generations of the Standard Model fermions in the type IIB matrix model

We discuss how the Standard Model particles appear from the type IIB matrix model, which is considered to be a nonperturbative formulation of superstring theory. In particular, we are concerned with a constructive definition of the theory, in which we start with finite-N matrices and take the large-N limit afterwards. In that case, it was pointed out recently that realizing chiral fermions in the model is more difficult than it had been thought from formal arguments at N=infinity and that introduction of a matrix version of the warp factor is necessary. Based on this new insight, we show that two generations of the Standard Model fermions can be realized by considering a rather generic configuration of fuzzy S^2 and fuzzy S^2 * S^2 in the extra dimensions. We also show that three generations can be obtained by squashing one of the S^2's that appear in the configuration. Chiral fermions appear at the intersections of the fuzzy manifolds with nontrivial Yukawa couplings to the Higgs field, which can be calculated from the overlap of their wave functions.Comment: 28 pages, 11 figures; (v2) references added, typos corrected; (v3) footnote added, version to be published on JHE

The Effect of Dynamical Gauge Field on the Chiral Fermion on a boundary

We study the effect of dynamical gauge field on the Kaplan's chiral fermion on a boundary in the strong gauge coupling limit in the extra dimension. To all orders of the hopping parameter expansion, we prove exact parity invariance of the fermion propagator on the boundary. This means that the chiral property of the boundary fermion, which seems to survive even in the presence of the gauge field from a perturbative point of view, is completely destroyed by the dynamics of the gauge field.Comment: 16 pages (including 7 figures), LaTeX, UT-675, KEK-TH-39

The effectiveness of the local potential approximation in the Wegner-Houghton renormalization group

The non-perturbative Wegner-Houghton renormalization group is analyzed by the local potential approximation in O(N) scalar theories in d-dimensions $(3\leq d\leq 4)$. The leading critical exponents \nu are calculated in order to investigate the effectiveness of the local potential approximation by comparing them with the other non-perturbative methods. We show analytically that the local potential approximation gives the exact exponents up to $O(\epsilon )$ in \epsilon-expansion and the leading in 1/N-expansion. We claim that this approximation offers fairly accurate results in the whole range of the parameter space of N and d. It is a great advantage of our method that no diverging expansions appear in the procedure.Comment: 13 pages, latex, 6 figure

Lepton flavor violating signals of the neutral top-pion in future lepton colliders

The presence of the top-pions $\pi_{t}^{0,\pm}$ in the low-energy spectrum is an inevitable feature of the topcolor scenario. Taking into account the constraints of the present experimental limit of the lepton flavor violating($LFV$) process $\mu\to e\gamma$ on the free parameters of topcolor-assisted techicolor(TC2) models, we study the contributions of the neutral top-pion $\pi^{0}_{t}$ to the $LFV$ processes $\mu^{+}\mu^{-}\to\tau \mu$ (or $\tau e$), $\gamma \gamma\to\tau \mu$ (or $\tau e$), $e^{+} e^{-}\to\tau \mu$, and $e \gamma\to e \pi_{t}^{0}\to e \tau \mu(e)$ via the flavor changing ($FC$) couplings $\pi_{t}^{0}l_{i}l_{j}$ and discuss the possibility of searching for the $LFV$ signals via these processes in future lepton colliders.Comment: References added, some typos corrected. Version to be published in Phys. Rev.

Wilson Renormalization Group Equations for the Critical Dynamics of Chiral Symmetry

The critical dynamics of the chiral symmetry breaking induced by gauge interaction is examined in the Wilson renormalization group framework in comparison with the Schwinger-Dyson approach. We derive the beta functions for the four-fermi couplings in the sharp cutoff renormalzation group scheme, from which the critical couplings and the anomalous dimensions of the fermion composite operators near criticality are immediately obtained. It is also shown that the beta functions lead to the same critical behavior found by solving the so-called ladder Schwinger-Dyson equation, if we restrict the radiative corrections to a certain limited type.Comment: 13 pages, 7 epsf figure

Rapidly Converging Truncation Scheme of the Exact Renormalization Group

The truncation scheme dependence of the exact renormalization group equations is investigated for scalar field theories in three dimensions. The exponents are numerically estimated to the next-to-leading order of the derivative expansion. It is found that the convergence property in various truncations in the number of powers of the fields is remarkably improved if the expansion is made around the minimum of the effective potential. It is also shown that this truncation scheme is suitable for evaluation of infrared effective potentials. The physical interpretation of this improvement is discussed by considering O(N) symmetric scalar theories in the large-N limit.Comment: 17 pages including 13 figures, LaTeX, to appear in Prog. Theor. Phys., references adde

SUSY-QCD Corrections to W±H∓W^{\pm}H^{\mp} Associated Production at the CERN Large Hadron Collider

We calculate the SUSY-QCD corrections to the inclusive total cross sections of the associated production processes $pp\to W^{\pm}H^{\mp}+X$ in the Minimal Supersymmetric Standard Model(MSSM) at the CERN Large Hadron Collider(LHC). The SUSY-QCD corrections can increase and decrease the total cross sections depending on the choice of the SUSY parameters. When $\mu<0$ the SUSY-QCD corrections increase the leading-order (LO) total cross sections significantly for large tan$\beta$ ($\sim 40$), which can exceed 10% and have the opposite sign with respect to the QCD and the SUSY-EW corrections, and thus cancel with them to some extent. Moreover, we also investigate the effects of the SUSY-QCD on the differential distribution of cross sections in transverse momentum $p_T$ and rapidity Y of W-boson, and the invariant mass $M_{W^+H^-}$.Comment: 24 pages, 10 figures; minor changes in references; two figures and the corresponding disccusions added; a version to appear in PR