4,148 research outputs found
Quantum corrections from a path integral over reparametrizations
We study the path integral over reparametrizations that has been proposed as
an ansatz for the Wilson loops in the large- QCD and reproduces the area law
in the classical limit of large loops. We show that a semiclassical expansion
for a rectangular loop captures the L\"uscher term associated with
dimensions and propose a modification of the ansatz which reproduces the
L\"uscher term in other dimensions, which is observed in lattice QCD. We repeat
the calculation for an outstretched ellipse advocating the emergence of an
analog of the L\"uscher term and verify this result by a direct computation of
the determinant of the Laplace operator and the conformal anomaly
On the relation between the width of the flux tube and in lattice gauge theories
Within the framework of a quantum flux tube model for the interquark
potential it is possible to predict that in (2+1) dimensions the space-like
string tension must increase with the temperature in the deconfined phase and
that the thickness of the flux tube must coincide with the inverse of the
deconfinement temperature. Both these predictions are in good agreement with
some recent numerical simulations of SU(2) and gauge models.Comment: 3 pages, uuencoded .ps file (Proceeding of Lattice '93 Conference
Nucleation of quark matter bubbles in neutron stars
The thermal nucleation of quark matter bubbles inside neutron stars is
examined for various temperatures which the star may realistically encounter
during its lifetime. It is found that for a bag constant less than a critical
value, a very large part of the star will be converted into the quark phase
within a fraction of a second. Depending on the equation of state for neutron
star matter and strange quark matter, all or some of the outer parts of the
star may subsequently be converted by a slower burning or a detonation.Comment: 13 pages, REVTeX, Phys.Rev.D (in press), IFA 93-32. 5 figures (not
included) available upon request from [email protected]
Measurement of carrier lifetime and linewidth enhancement factor for 1.5- mu m ridge-waveguide laser amplifier
Hadron Correlators and the Structure of the Quark Propagator
The structure of the quark propagator of in a confining background is
not known. We make an Ansatz for it, as hinted by a particular mechanism for
confinement, and analyze its implications in the meson and baryon correlators.
We connect the various terms in the K\"allen-Lehmann representation of the
quark propagator with appropriate combinations of hadron correlators, which may
ultimately be calculated in lattice . Furthermore, using the positivity of
the path integral measure for vector like theories, we reanalyze some mass
inequalities in our formalism. A curiosity of the analysis is that, the exotic
components of the propagator (axial and tensor), produce terms in the hadron
correlators which, if not vanishing in the gauge field integration, lead to
violations of fundamental symmetries. The non observation of these violations
implies restrictions in the space-time structure of the contributing gauge
field configurations. In this way, lattice can help us analyze the
microscopic structure of the mechanisms for confinement.Comment: 12 pp in LaTeX, preprint Univ. of Valencia, FTUV/94-16, IFIC/94-15.
To appear in Z.Phys.
On the integrability of Wilson loops in AdS_5 x S^5: Some periodic ansatze
Wilson loops are calculated within the AdS/CFT correspondence by finding a
classical solution to the string equations of motion in AdS_5 x S^5 and
evaluating its action. An important fact is that this sigma-model used to
evaluate the Wilson loops is integrable, a feature that has gained relevance
through the study of spinning strings carrying large quantum numbers and
spin-chains. We apply the same techniques used to solve the equations for
spinning strings to find the minimal surfaces describing a wide class of Wilson
loops. We focus on different cases with periodic boundary conditions on the
AdS_5 and S^5 factors and find a rich array of solutions. We examine the
different phases that appear in the problem and comment on the applicability of
integrability to the general problem.Comment: LaTex, 49 pages, 8 figure
Extragastrointestinal Symptoms and Sensory Responses During Breath Tests Distinguish Patients With Functional Gastrointestinal Disorders
Scale Free Cluster Distributions from Conserving Merging-Fragmentation Processes
We propose a dynamical scheme for the combined processes of fragmentation and
merging as a model system for cluster dynamics in nature and society displaying
scale invariant properties. The clusters merge and fragment with rates
proportional to their sizes, conserving the total mass. The total number of
clusters grows continuously but the full time-dependent distribution can be
rescaled over at least 15 decades onto a universal curve which we derive
analytically. This curve includes a scale free solution with a scaling exponent
of -3/2 for the cluster sizes.Comment: 4 pages, 3 figure
Critical Boundary Conditions for the Effective String
Gauge systems in the confining phase induce constraints at the boundaries of
the effective string, which rule out the ordinary bosonic string even with
short distance modifications. Allowing topological excitations, corresponding
to winding around the colour flux tube, produces at the quantum level a
universal free fermion string with a boundary phase nu=1/4. This coincides with
a model proposed some time ago in order to fit Monte Carlo data of 3D and 4D
Lattice gauge systems better. A universal value of the thickness of the colour
flux tube is predicted.Comment: 9 pages + 1 figur
On the Early History of Current Algebra
The history of Current Algebra is reviewed up to the appearance of the
Adler-Weisberger sum rule. Particular emphasis is given to the role current
algebra played for the historical struggle in strong interaction physics of
elementary particles between the S-matrix approach based on dispersion
relations and field theory. The question whether there are fundamental
particles or all hadrons are bound or resonant states of one another played an
important role in this struggle and is thus also regarded.Comment: 17 page
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