229 research outputs found
Anomalous dimensions and ghost decoupling in a perturbative approach to the generalized chiral Schwinger model
A generalized chiral Schwinger model is studied by means of perturbative
techniques. Explicit expressions are obtained, both for bosonic and fermionic
propagators, and compared to the ones derived by means of functional
techniques. In particular a consistent recipe is proposed to describe the
ambiguity occurring in the regularization of the fermionic determinant. The
role of the gauge fixing term, which is needed to develop perturbation theory
and the behaviour of the spectrum as a function of the parameters are clarified
together with ultraviolet and infrared properties of the model.Comment: DFPD 94/TH/29, May 1994, 28 pages, Late
Ghost decoupling in 't Hooft spectrum for mesons
We show that the replacement of the ``instantaneous'' 't Hooft's potential
with the causal form suggested by equal time canonical quantization in
light-cone gauge, which entails the occurrence of negative probability states,
does not change the bound state spectrum when the difference is treated as a
single insertion in the kernel.Comment: 7 pages, revtex, no figure
Two-dimensional QCD, instanton contributions and the perturbative Wu-Mandelstam-Leibbrandt prescription
The exact Wilson loop expression for the pure Yang-Mills U(N) theory on a
sphere of radius exhibits, in the decompactification limit , the expected pure area exponentiation. This behaviour can be
understood as due to the sum over all instanton sectors. If only the zero
instanton sector is considered, in the decompactification limit one exactly
recovers the sum of the perturbative series in which the light-cone gauge
Yang-Mills propagator is prescribed according to Wu-Mandelstam-Leibbrandt. When
instantons are disregarded, no pure area exponentiation occurs, the string
tension is different and, in the large-N limit, confinement is lost.Comment: RevTex, 11 pages, two references adde
Towards the solution of noncommutative : Morita equivalence and large N-limit
In this paper we shall investigate the possibility of solving U(1) theories
on the non-commutative (NC) plane for arbitrary values of by
exploiting Morita equivalence. This duality maps the NC U(1) on the two-torus
with a rational parameter to the standard U(N) theory in the presence
of a 't Hooft flux, whose solution is completely known. Thus, assuming a smooth
dependence on , we are able to construct a series rational approximants
of the original theory, which is finally reached by taking the large limit
at fixed 't Hooft flux. As we shall see, this procedure hides some subletities
since the approach of to infinity is linked to the shrinking of the
commutative two-torus to zero-size. The volume of NC torus instead diverges and
it provides a natural cut-off for some intermediate steps of our computation.
In this limit, we shall compute both the partition function and the correlator
of two Wilson lines. A remarkable fact is that the configurations, providing a
finite action in this limit, are in correspondence with the non-commutative
solitons (fluxons) found independently by Polychronakos and by Gross and
Nekrasov, through a direct computation on the plane.Comment: 21 pages, JHEP3 preprint tex-forma
Non Perturbative Solutions and Scaling Properties of Vector, Axial--Vector Electrodynamics in Dimensions
We study by non perturbative techniques a vector, axial--vector theory
characterized by a parameter which interpolates between pure vector and chiral
Schwinger models. Main results are two windows in the space of parameters which
exhibit acceptable solutions. In the first window we find a free massive and a
free massless bosonic excitations and interacting left--right fermions endowed
with asymptotic \hbox{states}, which feel however a long range interaction. In
the second window the massless bosonic excitation is a negative norm state
which can be consistently expunged from the ``physical" Hilbert space; fermions
are confined. An intriguing feature of our model occurs in the first window
where we find that fermionic correlators scale at both short and long
distances, but with different critical exponents. The infrared limit in the
fermionic sector is nothing but a dynamically generated massless Thirring
model.Comment: 32, DFPD 93-TH-3
Definition of Chern-Simons Terms in Thermal QED_3 Revisited
We present two compact derivations of the correct definition of the
Chern-Simons term in the topologically non trivial context of thermal .
One is based on a transgression descent from a D=4 background connection, the
other on embedding the abelian model in SU(2). The results agree with earlier
cohomology conclusions and can be also used to justify a recent simple
heuristic approach. The correction to the naive Chern-Simons term, and its
behavior under large gauge transformations are displayed.Comment: 9 pages, RevTex, no figures, new derivation from non abelian
embedding adde
New supersymmetric Wilson loops in ABJ(M) theories
We present two new families of Wilson loop operators in N= 6 supersymmetric
Chern-Simons theory. The first one is defined for an arbitrary contour on the
three dimensional space and it resembles the Zarembo's construction in N=4 SYM.
The second one involves arbitrary curves on the two dimensional sphere. In both
cases one can add certain scalar and fermionic couplings to the Wilson loop so
it preserves at least two supercharges. Some previously known loops, notably
the 1/2 BPS circle, belong to this class, but we point out more special cases
which were not known before. They could provide further tests of the
gauge/gravity correspondence in the ABJ(M) case and interesting observables,
exactly computable by localizationComment: 9 pages, no figure. arXiv admin note: text overlap with
arXiv:0912.3006 by other author
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