705 research outputs found
Instanton Distribution in Quenched and Full QCD
In order to optimize cooling as a technique to study the instanton content of
the QCD vacuum, we have studied the effects of alternative algorithms, improved
actions and boundary conditions on the evolution of single instantons and
instanton anti-instanton pairs. Using these results, we have extracted and
compared the instanton content of quenched and full QCD.Comment: 3 pages, LaTeX file + 3 figures included, uses epsfig.sty and
espcrc2.sty. Talk presented at LATTICE96(topology
Lineal Trails of D2-D2bar Superstrings
We study the superstrings suspended between a D2- and an anti-D2-brane. We
quantize the string in the presence of some general configuration of gauge
fields over the (anti-)D-brane world volumes. The interstring can move only in
a specific direction that is normal to the difference of the electric fields of
each (anti-)D-branes. Especially when the electric fields are the same, the
interstring cannot move. We obtain the condition for the tachyons to disappear
from the spectrum.Comment: 15 pages with 4 figures, referenced added, Sec. 5 on the spectrum
made cleare
Effective Potential on Fuzzy Sphere
The effective potential of quantized scalar field on fuzzy sphere is
evaluated to the two-loop level. We see that one-loop potential behaves like
that in the commutative sphere and the Coleman-Weinberg mechanism of the
radiatively symmetry breaking could be also shown in the fuzzy sphere system.
In the two-loop level, we use the heavy-mass approximation and the
high-temperature approximation to perform the evaluations. The results show
that both of the planar and nonplanar Feynman diagrams have inclinations to
restore the symmetry breaking in the tree level. However, the contributions
from planar diagrams will dominate over those from nonplanar diagrams by a
factor N^2. Thus, at heavy-mass limit or high-temperature system the quantum
field on the fuzzy sphere will behave like those on the commutative sphere. We
also see that there is a drastic reduction of the degrees of freedom in the
nonplanar diagrams when the particle wavelength is smaller than the
noncommutativity scale.Comment: Latex 18 pages, some typos correcte
30 Doradus - a Template for "Real Starbursts"?
30 Doradus is the closest massive star forming region and the best studied
template of a starburst. In this conference paper we first summarize the
properties of 30 Doradus and its stellar core, R136. We discuss the effects of
insufficient spatial resolution and cluster density profiles on dynamical mass
estimates of super star clusters, and show that their masses can be easily
overestimated by a factor of ten or more. From a very simple model, with
R136-like clusters as representative building blocks, we estimate typical
luminosities of the order 10^11 L_o for starburst galaxies.Comment: To be published in "Starbursts: From 30 Doradus to Lyman Break
Galaxies", eds. R. de Grijs & R.M. Gonzalez Delgad
Multi-layer Architecture For Storing Visual Data Based on WCF and Microsoft SQL Server Database
In this paper we present a novel architecture for storing visual data.
Effective storing, browsing and searching collections of images is one of the
most important challenges of computer science. The design of architecture for
storing such data requires a set of tools and frameworks such as SQL database
management systems and service-oriented frameworks. The proposed solution is
based on a multi-layer architecture, which allows to replace any component
without recompilation of other components. The approach contains five
components, i.e. Model, Base Engine, Concrete Engine, CBIR service and
Presentation. They were based on two well-known design patterns: Dependency
Injection and Inverse of Control. For experimental purposes we implemented the
SURF local interest point detector as a feature extractor and -means
clustering as indexer. The presented architecture is intended for content-based
retrieval systems simulation purposes as well as for real-world CBIR tasks.Comment: Accepted for the 14th International Conference on Artificial
Intelligence and Soft Computing, ICAISC, June 14-18, 2015, Zakopane, Polan
Topological Defects and Non-homogeneous Melting of Large 2D Coulomb Clusters
The configurational and melting properties of large two-dimensional clusters
of charged classical particles interacting with each other via the Coulomb
potential are investigated through the Monte Carlo simulation technique. The
particles are confined by a harmonic potential. For a large number of particles
in the cluster (N>150) the configuration is determined by two competing
effects, namely in the center a hexagonal lattice is formed, which is the
groundstate for an infinite 2D system, and the confinement which imposes its
circular symmetry on the outer edge. As a result a hexagonal Wigner lattice is
formed in the central area while at the border of the cluster the particles are
arranged in rings. In the transition region defects appear as dislocations and
disclinations at the six corners of the hexagonal-shaped inner domain. Many
different arrangements and type of defects are possible as metastable
configurations with a slightly higher energy. The particles motion is found to
be strongly related to the topological structure. Our results clearly show that
the melting of the clusters starts near the geometry induced defects, and that
three different melting temperatures can be defined corresponding to the
melting of different regions in the cluster.Comment: 7 pages, 11 figures, submitted to Phys. Rev.
Fuzzy Scalar Field Theory as a Multitrace Matrix Model
We develop an analytical approach to scalar field theory on the fuzzy sphere
based on considering a perturbative expansion of the kinetic term. This
expansion allows us to integrate out the angular degrees of freedom in the
hermitian matrices encoding the scalar field. The remaining model depends only
on the eigenvalues of the matrices and corresponds to a multitrace hermitian
matrix model. Such a model can be solved by standard techniques as e.g. the
saddle-point approximation. We evaluate the perturbative expansion up to second
order and present the one-cut solution of the saddle-point approximation in the
large N limit. We apply our approach to a model which has been proposed as an
appropriate regularization of scalar field theory on the plane within the
framework of fuzzy geometry.Comment: 1+25 pages, replaced with published version, minor improvement
Matrix dynamics of fuzzy spheres
We study the dynamics of fuzzy two-spheres in a matrix model which represents
string theory in the presence of RR flux. We analyze the stability of known
static solutions of such a theory which contain commuting matrices and SU(2)
representations. We find that irreducible as well as reducible representations
are stable. Since the latter are of higher energy, this stability poses a
puzzle. We resolve this puzzle by noting that reducible representations have
marginal directions corresponding to non-spherical deformations. We obtain new
static solutions by turning on these marginal deformations. These solutions now
have instability or tachyonic directions. We discuss condensation of these
tachyons which correspond to classical trajectories interpolating from
multiple, small fuzzy spheres to a single, large sphere. We briefly discuss
spatially independent configurations of a D3/D5 system described by the same
matrix model which now possesses a supergravity dual.Comment: 26 pages, 3 figures, uses JHEP.cls; (v2) references adde
When Is A Semiclassical Approximation Self-consistent?
A general condition for the self-consistency of a semiclassical approximation
to a given system is suggested. It is based on the eigenvalue distribution of
the relevant Hessian evaluated at the streamline configurations (configurations
that almost satisfy the classical equations of motion). The semiclassical
approximation is consistent when there exists a gap that separates small and
large eigenvalues and the spreading among the small eigenvalues is much smaller
than the gap. The idea is illustrated in the case of the double-well potential
problem in quantum mechanics. The feasibility of the present idea to test
instanton models of QCD vacuum is also briefly discussed.Comment: 15 pages in ReVTeX, 7 postscript figure
On the anatomy of multi-spin magnon and single spike string solutions
We study rigid string solutions rotating in background. For
particular values of the parameters of the solutions we find multispin
solutions corresponding to giant magnons and single spike strings. We present
an analysis of the dispersion relations in the case of three spin solutions
distributed only in and the case of one spin in and two spins in
. The possible relation of these string solutions to gauge theory
operators and spin chains are briefly discussed.Comment: 45 pages, the presentation rearranged in 3 sections, results
unchanged, references added, some typos correcte
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