377 research outputs found
Gauge-Higgs Unification and Quark-Lepton Phenomenology in the Warped Spacetime
In the dynamical gauge-Higgs unification of electroweak interactions in the
Randall-Sundrum warped spacetime the Higgs boson mass is predicted in the range
120 GeV -- 290 GeV, provided that the spacetime structure is determined at the
Planck scale. Couplings of quarks and leptons to gauge bosons and their
Kaluza-Klein (KK) excited states are determined by the masses of quarks and
leptons. All quarks and leptons other than top quarks have very small couplings
to the KK excited states of gauge bosons. The universality of weak interactions
is slightly broken by magnitudes of , and for
-, - and -, respectively. Yukawa couplings become
substantially smaller than those in the standard model, by a factor |\cos
\onehalf \theta_W| where is the non-Abelian Aharonov-Bohm phase
(the Wilson line phase) associated with dynamical electroweak symmetry
breaking.Comment: 34 pages, 7 eps files, comments and a reference adde
Large Gauge Hierarchy in Gauge-Higgs Unification
We study a five dimensional SU(3) nonsupersymmetric gauge theory compactified
on and discuss the gauge hierarchy in the scenario of the
gauge-Higgs unification. Making use of calculability of the Higgs potential and
a curious feature that coefficients in the potential are given by discrete
values, we find two models, in which the large gauge hierarchy is realized,
that is, the weak scale is naturally obtained from an unique large scale such
as a grand unified theory scale or the Planck scale. The size of the Higgs mass
is also discussed in each model. One of the models we find realizes both large
gauge hierarchy and consistent Higgs mass, and shows that the Higgs mass
becomes heavier as the compactified scale becomes smaller.Comment: 21 pages, no figures, version to appear in PR
Reply to Hagen & Sudarshan's Comment
We show that the argument in Phys Rev Lett 70 (1993) 1360 is correct and
consistent, and that Hagen & Sudarshan's solution has inconsistency leading to
non-vanishing commutators of and even in physical
states. This proves that many of HS's statements in their Comment are based
merely on incorrect guess, but not on careful algebra.Comment: one page, UMN-TH-1245/9
Antiferromagnetic S=1/2 Heisenberg Chain and the Two-flavor Massless Schwinger Model
An antiferromagnetic S=1/2 Heisenberg chain is mapped to the two-flavor
massless Schwinger model at \theta=\pi. The electromagnetic coupling constant
and velocity of light in the Schwinger model are determined in terms of the
Heisenberg coupling and lattice spacing in the spin chain system.Comment: 3 pages. LaTex2
A possible minimal gauge-Higgs unification
A possible minimal model of the gauge-Higgs unification based on the higher
dimensional spacetime M^4 X (S^1/Z_2) and the bulk gauge symmetry SU(3)_C X
SU(3)_W X U(1)_X is constructed in some details. We argue that the Weinberg
angle and the electromagnetic current can be correctly identified if one
introduces the extra U(1)_X above and a bulk scalar triplet. The VEV of this
scalar as well as the orbifold boundary conditions will break the bulk gauge
symmetry down to that of the standard model. A new neutral zero-mode gauge
boson Z' exists that gains mass via this VEV. We propose a simple fermion
content that is free from all the anomalies when the extra brane-localized
chiral fermions are taken into account as well. The issues on recovering a
standard model chiral-fermion spectrum with the masses and flavor mixing are
also discussed, where we need to introduce the two other brane scalars which
also contribute to the Z' mass in the similar way as the scalar triplet. The
neutrinos can get small masses via a type I seesaw mechanism. In this model,
the mass of the Z' boson and the compactification scale are very constrained as
respectively given in the ranges: 2.7 TeV < m_Z' < 13.6 TeV and 40 TeV < 1/R <
200 TeV.Comment: 20 pages, revised versio
Dynamical Electroweak Symmetry Breaking in SO(5)xU(1) Gauge-Higgs Unification with Top and Bottom Quarks
An SO(5)xU(1) gauge-Higgs unification model in the Randall-Sundrum warped
space with top and bottom quarks is constructed. Additional fermions on the
Planck brane make exotic particles heavy by effectively changing boundary
conditions of bulk fermions from those determined by orbifold conditions. Gauge
couplings of a top quark multiplet trigger electroweak symmetry breaking by the
Hosotani mechanism, simultaneously giving a top quark the observed mass. The
bottom quark mass is generated by combination of brane interactions and the
Hosotani mechanism, where only one ratio of brane masses is relevant when the
scale of brane masses is much larger than the Kaluza-Klein scale (\sim 1.5
TeV). The Higgs mass is predicted to be 49.9 (53.5) GeV for the warp factor
10^{15} (10^{17}). The Wilson line phase turns out \pi/2 and the Higgs
couplings to W and Z vanish so that the LEP2 bound for the Higgs mass is
evaded. In the flat spacetime limit the electroweak symmetry is unbroken.Comment: 35 pages, 2 figures. A few corrections are mad
Calculable One-Loop Contributions to S and T Parameters in the Gauge-Higgs Unification
We investigate the one-loop contributions to S and T oblique parameteres in
gauge-Higgs unification. We show that these parameters are finite in five
dimensional space-time, but are divergent in more than five dimensions.
Remarkably, however, we find that a particular linear combination of S and T
parameters, S - 4 \cos \theta_{W} T, becomes finite for six dimensional
space-time, though each of these parameters is divergent. This is because, in
the Gauge-Higgs unification scenario, the operators relevant for S and T
parameters are not independent, but are included in a unique higher dimensional
gauge invariant operator. Thus the predictable linear combination is model
independent, irrespectibly of the detail of the matter content.Comment: 25 pages, 1 eps file, minor corrections, version to appear in PR
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