14 research outputs found
Structure of the Electric Flux in N=4 Supersymmetric Yang-Mills Theory
Correlators of Wilson loop operators with O_4=Tr(F_{\mu\nu}^2+...) are
computed in N=4 super-Yang-Mills theory using the AdS/CFT correspondence. The
results are compared with the leading order perturbative computations. As a
consequence of conformal invariance, these correlators have identical forms in
the weak and strong coupling limits for circular loops. They are essentially
different for contours not protected by conformal symmetry.Comment: 7 pages, 1 postscript figure, minor corrections and clarifying
argument
Adjoint non-Abelian Coulomb gas at large N
The non-Abelian analog of the classical Coulomb gas is discussed. The
statistical mechanics of arrays of classical particles which transform under
various representations of a non-Abelian gauge group and which interact through
non-Abelian electric fields are considered. The problem is formulated on the
lattice and, for the case of adjoint charges, it is solved in the large N
limit. The explicit solution exhibits a first order confinement-de-confinement
phase transition with computable properties. In one dimension, the solution has
a continuum limit which describes 1+1-dimensional quantum chromodynamics (QCD)
with heavy adjoint matter.Comment: 21 pages, LaTe
Nonabelian D-branes and Noncommutative Geometry
We discuss the nonabelian world-volume action which governs the dynamics of N
coincident Dp-branes. In this theory, the branes' transverse displacements are
described by matrix-valued scalar fields, and so this is a natural physical
framework for the appearance of noncommutative geometry. One example is the
dielectric effect by which Dp-branes may be polarized into a noncommutative
geometry by external fields. Another example is the appearance of
noncommutative geometries in the description of intersecting D-branes of
differing dimensions, such as D-strings ending on a D3- or D5-brane. We also
describe the related physics of giant gravitons.Comment: 21 pages, Latex, ref. adde
Wilson Loops in N=4 Supersymmetric Yang--Mills Theory
Perturbative computations of the expectation value of the Wilson loop in N=4
supersymmetric Yang-Mills theory are reported. For the two special cases of a
circular loop and a pair of anti-parallel lines, it is shown that the sum of an
infinite class of ladder-like planar diagrams, when extrapolated to strong
coupling, produces an expectation value characteristic of the results of the
AdS/CFT correspondence, . For the case of
the circular loop, the sum is obtained analytically for all values of the
coupling. In this case, the constant factor in front of also
agrees with the supergravity results. We speculate that the sum of diagrams
without internal vertices is exact and support this conjecture by showing that
the leading corrections to the ladder diagrams cancel identically in four
dimensions. We also show that, for arbitrary smooth loops, the ultraviolet
divergences cancel to order .Comment: 24 pages, LaTeX, uses feynmp, 12 postscript figure
Deconfinement Transition for Quarks on a Line
We examine the statistical mechanics of a 1-dimensional gas of both adjoint
and fundamental representation quarks which interact with each other through
1+1-dimensional U(N) gauge fields. Using large-N expansion we show that, when
the density of fundamental quarks is small, there is a first order phase
transition at a critical temperature and adjoint quark density which can be
interpreted as deconfinement. When the fundamental quark density is comparable
to the adjoint quark density, the phase transition becomes a third order one.
We formulate a way to distinguish the phases by considering the expectation
values of high winding number Polyakov loop operators.Comment: Reported problems with figures fixed; 38 pages, LaTeX, 5 figures,
epsfi
Solitons on Branes
We examine the possibility that gauge field configurations on stacks of
parallel Dp branes support topological solitons. We give an exhaustive list of
possible soliton charges for p<7. We also discuss how configurations carrying
the soliton charges can be constructed from intersecting branes.Comment: 15 pages, 2 figures; v2: two references added, version to be
published in Nucl.Phys.
Longitudinal gluons and Nambu-Goldstone bosons in a two-flavor color superconductor
In a two-flavor color superconductor, the SU(3)_c gauge symmetry is
spontaneously broken by diquark condensation. The Nambu-Goldstone excitations
of the diquark condensate mix with the gluons associated with the broken
generators of the original gauge group. It is shown how one can decouple these
modes with a particular choice of 't Hooft gauge. We then explicitly compute
the spectral density for transverse and longitudinal gluons of adjoint color 8.
The Nambu-Goldstone excitations give rise to a singularity in the real part of
the longitudinal gluon self-energy. This leads to a vanishing gluon spectral
density for energies and momenta located on the dispersion branch of the
Nambu-Goldstone excitations.Comment: 16 pages, 4 figures, minor revisions to text, one ref. adde
Fluctuation modes in color-superconductors
We investigate fluctuation effects of a gap parameter in
color-superconductors. The fluctuation modes in the super phase are described
by two scalar fields of diquarks. One of them is a Nambu-Goldstone boson and
the other is a diquark boson whose mass is about twice of the gap energy (an
extended quasi-supersymmetry). In the normal phase the fluctuation becomes a
precursory (soft) mode whose amplitude increases near the critical temperature.Comment: 6 page
Magnetic catalysis and anisotropic confinement in QCD
The expressions for dynamical masses of quarks in the chiral limit in QCD in
a strong magnetic field are obtained. A low energy effective action for the
corresponding Nambu-Goldstone bosons is derived and the values of their decay
constants as well as the velocities are calculated. The existence of a
threshold value of the number of colors , dividing the theories with
essentially different dynamics, is established. For the number of colors , an anisotropic dynamics of confinement with the confinement
scale much less than and a rich spectrum of light glueballs is
realized. For of order or larger, a conventional confinement
dynamics takes place. It is found that the threshold value grows
rapidly with the magnetic field [ for ]. In contrast to QCD with a nonzero baryon density, there are no
principal obstacles for checking these results and predictions in lattice
computer simulations.Comment: 10 pages, 1 figure. REVTeX. Minor correction. To appear in Phys. Rev.
Instanton Effects in QCD at High Baryon Density
We study instanton effects in QCD at very high baryon density. In this regime
instantons are suppressed by a large power of , where
is the QCD scale parameter and is the baryon chemical
potential. Instantons are nevertheless important because they contribute to
several physical observables that vanish to all orders in perturbative QCD. We
study, in particular, the chiral condensate and its contribution to the masses of Goldstone bosons in the CFL phase of QCD
with flavors. We find that at densities , where
is the density of nuclear matter, the result is dominated by large
instantons and subject to considerable uncertainties. We suggest that these
uncertainties can be addressed using lattice calculations of the instanton
density and the pseudoscalar diquark mass in QCD with two colors. We study the
topological susceptibility and Witten-Veneziano type mass relations in both
and QCD.Comment: 27 pages, 8 figures, minor revision