11,069 research outputs found
Color screening in a constituent quark model of hadronic matter
The effect of color screening on the formation of a heavy quark-antiquark
() bound state--such as the meson--is studied using a
constituent-quark model. The response of the nuclear medium to the addition of
two color charges is simulated directly in terms of its quark constituents via
a string-flip potential that allows for quark confinement within hadrons yet
enables the hadrons to separate without generating unphysical long-range
forces. Medium modifications to the properties of the heavy meson, such as its
energy and its mean-square radius, are extracted by solving Schr\"odinger's
equation for the pair in the presence of a (screened)
density-dependent potential. The density dependence of the heavy-quark
potential is in qualitative agreement with earlier studies of its temperature
dependence extracted from lattice calculations at finite temperature. In the
present model it is confirmed that abrupt changes in the properties of the
-meson in the hadronic medium ({\it plasma}), correlate strongly with
the deconfining phase transition.Comment: 7 pages, 3 figures, submitted to PRC for publication, uses revtex
Promoting scientific integrity in nursing research, Part I: Current approaches in doctoral programs
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/88194/1/ketefian-promoting_scientific_integrity1.pd
Quantum Mechanics of the Vacuum State in Two-Dimensional QCD with Adjoint Fermions
A study of two-dimensional QCD on a spatial circle with Majorana fermions in
the adjoint representation of the gauge groups SU(2) and SU(3) has been
performed. The main emphasis is put on the symmetry properties related to the
homotopically non-trivial gauge transformations and the discrete axial symmetry
of this model. Within a gauge fixed canonical framework, the delicate interplay
of topology on the one hand and Jacobians and boundary conditions arising in
the course of resolving Gauss's law on the other hand is exhibited. As a
result, a consistent description of the residual gauge symmetry (for
SU(N)) and the ``axial anomaly" emerges. For illustrative purposes, the vacuum
of the model is determined analytically in the limit of a small circle. There,
the Born-Oppenheimer approximation is justified and reduces the vacuum problem
to simple quantum mechanics. The issue of fermion condensates is addressed and
residual discrepancies with other approaches are pointed out.Comment: 44 pages; for hardcopies of figures, contact
[email protected]
Quantum Hamiltonian Reduction of the Schwinger Model
We reexamine a unitary-transformation method of extracting a physical
Hamiltonian from a gauge field theory after quantizing all degrees of freedom
including redundant variables. We show that this {\it quantum Hamiltonian
reduction} method suffers from crucial modifications arising from
regularization of composite operators. We assess the effects of regularization
in the simplest gauge field theory, the Schwinger model. Without
regularization, the quantum reduction yields the identical Hamiltonian with the
classically reduced one. On the other hand, with regularization incorporated,
the resulting Hamiltonian of the quantum reduction disagrees with that of the
classical reduction. However, we find that the discrepancy is resolved by
redefinitions of fermion currents and that the results are again consistent
with those of the classical reduction.Comment: 23 pages, LaTeX file, UT-Komaba 94-
Relationship Between Sedentary Behavior and Arterial Stiffness in Physically Active College Students
Please download pdf version here
Gauge-invariant and infrared-improved variational analysis of the Yang-Mills vacuum wave functional
We study a gauge-invariant variational framework for the Yang-Mills vacuum
wave functional. Our approach is built on gauge-averaged Gaussian trial
functionals which substantially extend previously used trial bases in the
infrared by implementing a general low-momentum expansion for the vacuum-field
dispersion (which is taken to be analytic at zero momentum). When completed by
the perturbative Yang-Mills dispersion at high momenta, this results in a
significantly enlarged trial functional space which incorporates both dynamical
mass generation and asymptotic freedom. After casting the dynamics associated
with these wave functionals into an effective action for collections of soft
vacuum-field orbits, the leading infrared improvements manifest themselves as
four-gradient interactions. Those turn out to significantly lower the minimal
vacuum energy density, thus indicating a clear overall improvement of the
vacuum description. The dimensional transmutation mechanism and the dynamically
generated mass scale remain almost quantitatively robust, however, which
ensures that our prediction for the gluon condensate is consistent with
standard values. Further results include a finite group velocity for the soft
gluonic modes due to the higher-gradient corrections and indications for a
negative differential color resistance of the Yang-Mills vacuum.Comment: 47 pages, 5 figures (vs2 contains a few minor stylistic adjustments
to match the published version
Local Magnetization in the Boundary Ising Chain at Finite Temperature
We study the local magnetization in the 2-D Ising model at its critical
temperature on a semi-infinite cylinder geometry, and with a nonzero magnetic
field applied at the circular boundary of circumference . This model
is equivalent to the semi-infinite quantum critical 1-D transverse field Ising
model at temperature , with a symmetry-breaking field
applied at the point boundary. Using conformal field theory methods
we obtain the full scaling function for the local magnetization analytically in
the continuum limit, thereby refining the previous results of Leclair, Lesage
and Saleur in Ref. \onlinecite{Leclair}. The validity of our result as the
continuum limit of the 1-D lattice model is confirmed numerically, exploiting a
modified Jordan-Wigner representation. Applications of the result are
discussed.Comment: 9 pages, 3 figure
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