1,777 research outputs found
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 . 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 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 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() process on the free parameters of
topcolor-assisted techicolor(TC2) models, we study the contributions of the
neutral top-pion to the processes (or ), (or ), , and via the
flavor changing () couplings and discuss the
possibility of searching for the 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 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 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 the SUSY-QCD
corrections increase the leading-order (LO) total cross sections significantly
for large tan (), 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
and rapidity Y of W-boson, and the invariant mass .Comment: 24 pages, 10 figures; minor changes in references; two figures and
the corresponding disccusions added; a version to appear in PR
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