545 research outputs found
Center vortices, magnetic condensate and confinement in a simple gauge system
The confining mechanisms of 't Hooft and Mandelstam have a simple microscopic
realization in 3D Z2 gauge theory: the center vortex and the magnetic monopole
condensation are associated, in the set of configurations contributing to the
confining phase, to the presence of two kinds of infinite clusters. These
generate the area law of the large Wilson loops and the universal finite size
effects produced by the quantum fluctuations of the bosonic string describing
the infrared behavior of the flux tube.Comment: 8 pages, 4 eps figures. Contributed to NATO Advanced Research
Workshop on Confinement, Topology, and other Nonperturbative Aspects of QCD,
Stara Lesna, Slovakia, 21-27 Jan 200
The lowest modes around Gaussian solutions of tensor models and the general relativity
In the previous paper, the number distribution of the low-lying spectra
around Gaussian solutions representing various dimensional fuzzy tori of a
tensor model was numerically shown to be in accordance with the general
relativity on tori. In this paper, I perform more detailed numerical analysis
of the properties of the modes for two-dimensional fuzzy tori, and obtain
conclusive evidences for the agreement. Under a proposed correspondence between
the rank-three tensor in tensor models and the metric tensor in the general
relativity, conclusive agreement is obtained between the profiles of the
low-lying modes in a tensor model and the metric modes transverse to the
general coordinate transformation. Moreover, the low-lying modes are shown to
be well on a massless trajectory with quartic momentum dependence in the tensor
model. This is in agreement with that the lowest momentum dependence of metric
fluctuations in the general relativity will come from the R^2-term, since the
R-term is topological in two dimensions. These evidences support the idea that
the low-lying low-momentum dynamics around the Gaussian solutions of tensor
models is described by the general relativity. I also propose a renormalization
procedure for tensor models. A classical application of the procedure makes the
patterns of the low-lying spectra drastically clearer, and suggests also the
existence of massive trajectories.Comment: 31 pages, 8 figures, Added references, minor corrections, a
misleading figure replace
Separation of Cultivars of Soybeans by Chemometric Methods Using Near Infrared Spectroscopy.
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Nonlocal regularisation of noncommutative field theories
We study noncommutative field theories, which are inherently nonlocal, using
a Poincar\'e-invariant regularisation scheme which yields an effective,
nonlocal theory for energies below a cut-off scale. After discussing the
general features and the peculiar advantages of this regularisation scheme for
theories defined in noncommutative spaces, we focus our attention onto the
particular case when the noncommutativity parameter is inversely proportional
to the square of the cut-off, via a dimensionless parameter . We work out
the perturbative corrections at one-loop order for a scalar theory with quartic
interactions, where the signature of noncommutativity appears in
-dependent terms. The implications of this approach, which avoids the
problems related to UV-IR mixing, are discussed from the perspective of the
Wilson renormalisation program. Finally, we remark about the generality of the
method, arguing that it may lead to phenomenologically relevant predictions,
when applied to realistic field theories.Comment: 1+11 pages, 6 figures; v2: references added, typos corrected,
conclusions unchange
Large center vortices and confinement in 3D Z(2) gauge theory
We study the role of large clusters of center vortices in producing
confinement in 3D Z(2) gauge theory. First, we modify each configuration of a
Monte Carlo-generated ensemble in the confined phase by removing the largest
cluster of center vortices, and show that the ensemble thus obtained does not
confine. Conversely, we show that removing all of the small clusters of center
vortices and leaving the largest one only, confinement is preserved, albeit
with a string tension significantly smaller than the original one. Remarkably,
also the string corrections due to the quantum fluctuations of the confining
flux tube are preserved by this transformation.Comment: 8 pages,5 figure
On the linear increase of the flux tube thickness near the deconfinement transition
We study the flux tube thickness of a generic Lattice Gauge Theory near the
deconfining phase transition. It is well known that the effective string model
predicts a logarithmic increase of the flux tube thickness as a function of the
interquark distance for any confining LGT at zero temperature. It is perhaps
less known that this same model predicts a linear increase in the vicinity of
the deconfinement transition. We present a precise derivation of this result
and compare it with a set of high precision simulations in the case of the 3d
gauge Ising model.Comment: 20 pages, 4 figures, minor changes. Accepted for publication in JHE
Topological stability of broken symmetry on fuzzy spheres
We study the spontaneous symmetry breaking of O(3) scalar field on a fuzzy
sphere . We find that the fluctuations in the background of topological
configurations are finite. This is in contrast to the fluctuations around a
uniform configuration which diverge, due to Mermin-Wagner-Hohenberg-Coleman
theorem, leading to the decay of the condensate. Interesting implications of
enhanced topological stability of the configurations are pointed out.Comment: Version to appear in MPLA, 9 pages, 6 figure
A numerical study of confinement in compact QED
Compact U(1) lattice gauge theory in four dimensions is studied by means of
an efficient algorithm which exploits the duality transformation properties of
the model. We focus our attention onto the confining regime, considering the
interquark potential and force, and the electric field induced by two
infinitely heavy sources. We consider both the zero and finite temperature
setting, and compare the theoretical predictions derived from the effective
string model and the dual superconductor scenario to the numerical results.Comment: 31 pages, 16 eps figures; v2: references added; v3: footnote added,
summation ranges in section 4 made explicit, version published in JHE
String effects in Polyakov loop correlators
We compare the predictions of the effective string description of confinement
in finite temperature gauge theories to high precision Monte Carlo data for the
three-dimensional Z(2) gauge theory. We show that string interaction effects
become more relevant as the temperature is increased towards the deconfinement
one, and are well modeled by a Nambu-Goto string action.Comment: Lattice2002(nonzerot
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