37,477 research outputs found
Parity-Violating Nuclear Force as derived from QCD Sum Rules
Parity-violating nuclear force, as may be accessed from parity violation
studies in nuclear systems, represents an area of nonleptonic weak interactions
which has been the subject of experimental investigations for several decades.
In the simple meson-exchange picture, parity-violating nuclear force may be
parameterized as arising from exchange of \pi, \rho, \omega, or other meson(s)
with strong meson-nucleon coupling at one vertex and weak parity-violating
meson-nucleon coupling at the other vertex. The QCD sum rule method allows for
a fairly complicated, but nevertheless straightforward, leading-order
loop-contribution determination of the various parity-violating MNN couplings
starting from QCD (with the nontrivial vacuum) and Glashow-Salam-Weinberg
electroweak theory. We continue our earlier investigation of parity-violating
\pi NN coupling (by Henley, Hwang, and Kisslinger) to other parity-violating
couplings. Our predictions are in reasonable overall agreement with the results
estimated on phenomenological grounds, such as in the now classic paper of
Desplanques, Donoghue, and Holstein (DDH), in the global experimental fit of
Adelberger and Haxton (AH), or the effective field theory (EFT) thinking of
Ramsey-Musolf and Page (RP).Comment: 17 pages, 5 figure
Continuous topological phase transitions between clean quantum Hall states
Continuous transitions between states with the {\em same} symmetry but
different topological orders are studied. Clean quantum Hall (QH) liquids with
neutral quasiparticles are shown to have such transitions. For clean bilayer
(nnm) states, a continous transition to other QH states (including non-Abelian
states) can be driven by increasing interlayer repulsion/tunneling. The
effective theories describing the critical points at some transitions are
derived.Comment: 4 pages, RevTeX, 2 eps figure
Quasi-adiabatic Continuation of Quantum States: The Stability of Topological Ground State Degeneracy and Emergent Gauge Invariance
We define for quantum many-body systems a quasi-adiabatic continuation of
quantum states. The continuation is valid when the Hamiltonian has a gap, or
else has a sufficiently small low-energy density of states, and thus is away
from a quantum phase transition. This continuation takes local operators into
local operators, while approximately preserving the ground state expectation
values. We apply this continuation to the problem of gauge theories coupled to
matter, and propose a new distinction, perimeter law versus "zero law" to
identify confinement. We also apply the continuation to local bosonic models
with emergent gauge theories. We show that local gauge invariance is
topological and cannot be broken by any local perturbations in the bosonic
models in either continuous or discrete gauge groups. We show that the ground
state degeneracy in emergent discrete gauge theories is a robust property of
the bosonic model, and we argue that the robustness of local gauge invariance
in the continuous case protects the gapless gauge boson.Comment: 15 pages, 6 figure
Structure and stability of quasi-two-dimensional boson-fermion mixtures with vortex-antivortex superposed states
We investigate the equilibrium properties of a quasi-two-dimensional
degenerate boson-fermion mixture (DBFM) with a bosonic vortex-antivortex
superposed state (VAVSS) using a quantum-hydrodynamic model. We show that,
depending on the choice of parameters, the DBFM with a VAVSS can exhibit rich
phase structures. For repulsive boson-fermion (BF) interaction, the
Bose-Einstein condensate (BEC) may constitute a petal-shaped "core" inside the
honeycomb-like fermionic component, or a ring-shaped joint "shell" around the
onion-like fermionic cloud, or multiple segregated "islands" embedded in the
disc-shaped Fermi gas. For attractive BF interaction just below the threshold
for collapse, an almost complete mixing between the bosonic and fermionic
components is formed, where the fermionic component tends to mimic a bosonic
VAVSS. The influence of an anharmonic trap on the density distributions of the
DBFM with a bosonic VAVSS is discussed. In addition, a stability region for
different cases of DBFM (without vortex, with a bosonic vortex, and with a
bosonic VAVSS) with specific parameters is given.Comment: 8 pages,5 figure
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