3,417 research outputs found
Magnetic Monopoles, Center Vortices, Confinement and Topology of Gauge Fields
The vortex picture of confinement is studied. The deconfinement phase
transition is explained as a transition from a phase in which vortices
percolate to a phase of small vortices. Lattice results are presented in
support of this scenario. Furthermore the topological properties of magnetic
monopoles and center vortices arising, respectively, in Abelian and center
gauges are studied in continuum Yang-Mills-theory. For this purpose the
continuum analog of the maximum center gauge is constructed.Comment: talk given by H. Reinhardt on the Int. Workshop ``Hadrons 1999'',
Coimbra, 10.-15. Sept. 199
On the spectrum of QCD(1+1) with large numbers of flavours N_F and colours N_C near N_F/N_C = 0
QCD(1+1) in the limit of a large number of flavours N_F and a large number of
colours N_C is examined in the small N_F/N_C regime. Using perturbation theory
in N_F/N_C, stringent results for the leading behaviour of the spectrum
departing from N_F/N_C = 0 are obtained. These results provide benchmarks in
the light of which previous truncated treatments of QCD(1+1) at large N_F and
N_C are critically reconsidered.Comment: 6 revtex page
One-dimensional classical adjoint SU(2) Coulomb Gas
The equation of state of a one-dimensional classical nonrelativistic Coulomb
gas of particles in the adjoint representation of SU(2) is given. The problem
is solved both with and without sources in the fundamental representation at
either end of the system. The gas exhibits confining properties at low
densities and temperatures and deconfinement in the limit of high densities and
temperatures. However, there is no phase transition to a regime where the
string tension vanishes identically; true deconfinement only happens for
infinite densities and temperatures. In the low density, low temperature limit,
a new type of collective behavior is observed.Comment: 6 pages, 1 postscript figur
Is social dispersal stressful? A study in male crested macaques (Macaca nigra).
In gregarious species, dispersal events represent one of the most dramatic changes in social life and environment an animal will experience during life due to increased predation risk, aggression from unfamiliar conspecifics and the lack of social support. However, little is known about how individuals respond physiologically to dispersal and whether this process is stressful for the individuals involved. We therefore studied the physiological stress response during dispersal in the crested macaque, a primate species in which males often change groups. Over a period of 14months and 14 dispersal events in 4 groups, we determined faecal glucocorticoid metabolite (FGCM) levels during the process of immigration into a new group and examined a variety of factors (e.g. male age, rank achieved, number of males in the group) potentially affecting FGCM levels during this process. We found that FGCM levels were significantly elevated in the first few days upon immigration, after which levels returned quickly to baseline. FGCM response levels upon immigration were significantly and positively influenced by the number of males in the group. The rank a male achieved upon immigration, aggression received, as well as the proximity to other males did not significantly influence FGCM levels. Our data confirm previous findings on other species demonstrating that in crested macaques immigration into a new social group is associated with an acute endocrine stress response. However, given that stress hormone levels remained elevated only for a short period of time, we do not expect males to experience high physiological costs during immigration. Given our limited knowledge on the physiological responses to dispersal in animals, this study contributes to our understanding of dispersal more generally, and particularly inter-individual differences in the stress response and the potential physiological costs associated with these
Topological Susceptibility of Yang-Mills Center Projection Vortices
The topological susceptibility induced by center projection vortices
extracted from SU(2) lattice Yang-Mills configurations via the maximal center
gauge is measured. Two different smoothing procedures, designed to eliminate
spurious ultraviolet fluctuations of these vortices before evaluating the
topological charge, are explored. They result in consistent estimates of the
topological susceptibility carried by the physical thick vortices
characterizing the Yang-Mills vacuum in the vortex picture. This susceptibility
is comparable to the one obtained from the full lattice Yang-Mills
configurations. The topological properties of the SU(2) Yang-Mills vacuum can
thus be accounted for in terms of its vortex content.Comment: 12 revtex pages, 6 ps figures included using eps
Signals of confinement in Green functions of SU(2) Yang-Mills theory
The vortex picture of confinement is employed to explore the signals of
confinement in Yang-Mills Green functions. By using SU(2) lattice gauge theory,
it has been well established that the removal of the center vortices from the
lattice configurations results in the loss of confinement. The running coupling
constant, the gluon and the ghost form factors are studied in Landau gauge for
both cases, the full and the vortex removed theory. In the latter case, a
strong suppression of the running coupling constant and the gluon form factor
at low momenta is observed. At the same time, the singularity of the ghost form
factor at vanishing momentum disappears. This observation establishes an
intimate correlation between the ghost singularity and confinement. The result
also shows that a removal of the vortices generates a theory for which
Zwanziger's horizon condition for confinement is no longer satisfied.Comment: 4 pages, 4 figure
The intrinsic strangeness and charm of the nucleon using improved staggered fermions
We calculate the intrinsic strangeness of the nucleon, - ,
using the MILC library of improved staggered gauge configurations using the
Asqtad and HISQ actions. Additionally, we present a preliminary calculation of
the intrinsic charm of the nucleon using the HISQ action with dynamical charm.
The calculation is done with a method which incorporates features of both
commonly-used methods, the direct evaluation of the three-point function and
the application of the Feynman- Hellman theorem. We present an improvement on
this method that further reduces the statistical error, and check the result
from this hybrid method against the other two methods and find that they are
consistent. The values for and found here, together with
perturbative results for heavy quarks, show that dark matter scattering through
Higgs-like exchange receives roughly equal contributions from all heavy quark
flavors.Comment: 17 pages, 14 figure
Singular gauge potentials and the gluon condensate at zero temperature
We consider a new cooling procedure which separates gluon degrees of freedom
from singular center vortices in SU(2) LGT in a gauge invariant way. Restricted
by a cooling scale fixing the residual SO(3) gluonic action
relative to the string tension, the procedure is RG invariant. In the limit
a pure Z(2) vortex texture is left. This {\it minimal} vortex
content does not contribute to the string tension. It reproduces, however, the
lowest glueball states. With an action density scaling like with ,
it defines a finite contribution to the action density at T=0 in the continuum
limit. We propose to interpret this a mass dimension 4 condensate related to
the gluon condensate. Similarly, this vortex texture is revealed in the Landau
gauge.Comment: 3 pages, 4 figures, Contribution to ''Lattice 2001'' (confinement) to
appear in the Proceedings (Nucl. Phys. B Proc. Suppl.
Magnetic Monopoles, Center Vortices and Topology of Gauge Fields
The topological properties of magnetic monopoles and center vortices arising,
respectively, in Abelian and center gauges are studied in continuum Yang-Mills
Theory. For this purpose the continuum analog of the maximum center gauge is
constructed.Comment: talk presented at LATTICE99(topology) at Pisa, Italy, 3 page
Vortex structures in pure SU(3) lattice gauge theory
The structures of confining vortices which underlie pure SU(3) Yang-Mills
theory are studied by means of lattice gauge theory. Vortices and Z_3 monopoles
are defined as dynamical degrees of freedom of the Z_3 gauge theory which
emerges by center gauge fixing and by subsequent center projection. It is
observed for the first time for the case of SU(3) that these degrees of freedom
are sensible in the continuum limit: the planar vortex density and the monopole
density properly scales with the lattice spacing. By contrast to earlier
findings concerning the gauge group SU(2), the effective vortex theory only
reproduces 62% of the full string tension. On the other hand, however, the
removal of the vortices from the lattice configurations yields ensembles with
vanishing string tension. SU(3) vortex matter which originates from Laplacian
center gauge fixing is also discussed. Although these vortices recover the full
string tension, they lack a direct interpretation as physical degrees of
freedom in the continuum limit.Comment: 25 pages, 13 ps figures, improved presentation, results unchange
- …