37,022 research outputs found
A simple model of gauged lepton and baryon charges
We argue that simpler fermionic contents, responsible for the extension of
the standard model with gauged lepton and baryon charges, can be constructed by
assuming existence of so-called leptoquarks (j,k) with exotic electric charges
q_j=1/2, q_k=-1/2. Some new features in our model are that (i) as the natural
consequences of anomaly cancelation the right-handed neutrinos exist, and the
number of the observed fermion families is equal to the number of the
fundamental colors; (ii) although the lepton and baryon charges are conserved,
the neutrinos can obtain small masses through the type I seesaw mechanism in
similarity to the standard context, and the baryogenesis can be generated in
several cases. They all are natural results due to the spontaneous breaking of
these charges. Some constraints on the new physics via flavor changing and
related phenomenologies such as the stable scalar with anomalous electric
charge and interested processes at colliders are also discussed.Comment: 13 pages, revised versio
Question of Peccei-Quinn symmetry and quark masses in the economical 3-3-1 model
We show that there is an infinite number of U(1) symmetries like Peccei-Quinn
symmetry in the 3-3-1 model with minimal scalar sector---two scalar triplets.
Moreover, all of them are completely broken due to the model's scalars by
themselves (notice that these scalars as known have been often used to break
the gauge symmetry and generating the masses for the model's particles). There
is no any residual Peccei-Quinn symmetry. Because of the minimal scalar content
there are some quarks that are massless at tree-level, but they can get
consistent mass contributions at one-loop due to this fact. Interestingly,
axions as associated with the mentioned U(1)s breaking (including Majoron due
to lepton-charge breaking) are all gauged away because they are also the
Goldstone bosons responsible for the gauge symmetry breaking as usual.Comment: 25 pages, 4 figures, revised version, to appear in Physical Review
Algebraic approach to the Hulthen potential
In this paper the energy eigenvalues and the corresponding eigenfunctions are
calculated for Hulthen potential. Then we obtain the ladder operators and show
that these operators satisfy SU(2) commutation relation.Comment: 8 Pages, 1 Tabl
Critical domain-wall dynamics of model B
With Monte Carlo methods, we simulate the critical domain-wall dynamics of
model B, taking the two-dimensional Ising model as an example. In the
macroscopic short-time regime, a dynamic scaling form is revealed. Due to the
existence of the quasi-random walkers, the magnetization shows intrinsic
dependence on the lattice size . A new exponent which governs the
-dependence of the magnetization is measured to be .Comment: 10pages, 4 figure
Hamiltonian equation of motion and depinning phase transition in two-dimensional magnets
Based on the Hamiltonian equation of motion of the theory with
quenched disorder, we investigate the depinning phase transition of the
domain-wall motion in two-dimensional magnets. With the short-time dynamic
approach, we numerically determine the transition field, and the static and
dynamic critical exponents. The results show that the fundamental Hamiltonian
equation of motion belongs to a universality class very different from those
effective equations of motion.Comment: 6 pages, 7 figures, have been accept by EP
Improving Stochastic Estimator Techniques for Disconnected Diagrams
Disconnected diagrams are expected to be sensitive to the inclusion of
dynamical fermions. We present a feasibility study for the observation of such
effects on the nucleonic matrix elements of the axial vector current, using
SESAM full QCD vacuum configurations with Wilson fermions on
lattices, at . Starting from the standard methods developed by the
Kentucky and Tsukuba groups, we investigate the improvement from various
refinements thereof.Comment: One author added. Contribution to Lattice 1997, 3 pages LaTex, to
appear in Nucl. Phys. B (Proc. Suppl.
Optical spectroscopy study on single crystalline LaFeAsO
Millimeter-sized single crystals of LaFeAsO were grown from NaAs flux and the
in-plane optical properties were studied over a wide frequency range. A sizable
electronic correlation effect was indicated from the analysis of the
free-carrier spectral weight. With decreasing temperature from 300 K, we
observed a continuous suppression of the spectral weight near 0.6 eV. But a
spin-density-wave gap formation at lower energy scale was seen only in the
broken-symmetry state. We elaborate that both the itinerancy and local spin
interactions of Fe\emph{3d} electrons are present for the FeAs-based systems;
however, the establishment of the long-range magnetic order at low temperature
has a dominantly itinerant origin.Comment: 4 figures, 5 page
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