421 research outputs found
Noncommutative Field Theories and Gravity
We show that after the Seiberg-Witten map is performed the action for
noncommutative field theories can be regarded as a coupling to a field
dependent gravitational background. This gravitational background depends only
on the gauge field. Charged and uncharged fields couple to different
backgrounds and we find that uncharged fields couple more strongly than the
charged ones. We also show that the background is that of a gravitational plane
wave. A massless particle in this background has a velocity which differs from
the velocity of light and we find that the deviation is larger in the uncharged
case. This shows that noncommutative field theories can be seen as ordinary
theories in a gravitational background produced by the gauge field with a
charge dependent gravitational coupling.Comment: 8 pages. v2 and v3: minor corrections, added reference
On the quantum dynamics of non-commutative systems
This is a review paper concerned with the global consistency of the quantum
dynamics of non-commutative systems. Our point of departure is the theory of
constrained systems, since it provides a unified description of the classical
and quantum dynamics for the models under investigation. We then elaborate on
recently reported results concerned with the sufficient conditions for the
existence of the Born series and unitarity and turn, afterwards, into analyzing
the functional quantization of non-commutative systems. The compatibility
between the operator and the functional approaches is established in full
generality. The intricacies arising in connection with the explicit computation
of path integrals, for the systems under scrutiny, is illustrated by presenting
the detailed calculation of the Feynman kernel for the non-commutative two
dimensional harmonic oscillator.Comment: 19 pages, title changed, version to be published in Brazilian Journal
of Physic
Comment on "Attractive Forces between Electrons in 2 + 1 Dimensional QED"
It is shown that a model recently proposed for numerical calculations of
bound states in QED is in fact an improper truncation of the Aharonov-Bohm
potential.Comment: 4 page
Nonperturbative solution of the Nonconfining Schwinger Model with a generalized regularization
Nonconfining Schwinger Model [AR] is studied with a one parameter class of
kinetic energy like regularization. It may be thought of as a generalization
over the regularization considered in [AR]. Phasespace structure has been
determined in this new situation. The mass of the gauge boson acquires a
generalized expression with the bare coupling constant and the parameters
involved in the regularization. Deconfinement scenario has become transparent
at the quark-antiquark potential level.Comment: 13 pages latex fil
Gauge Dependence in the AdS/CFT Correspondence
We consider the AdS space formulation of the classical dynamics deriving from
the Stueckelberg Lagrangian. The on-shell action is shown to be free of
infrared singularities as the vector boson mass tends to zero. In this limit
the model becomes Maxwell theory formulated in an arbitrary covariant gauge.
Then we use the AdS/CFT correspondence to compute the two-point correlation
functions on the boundary. It is shown that the gauge dependence concentrates
on the contact terms.Comment: 13 pages, REVTEX, misprints in the abstract corrected. Minor changes.
Version to be publishe
The three-dimensional noncommutative Gross-Neveu model
This work is dedicated to the study of the noncommutative Gross-Neveu model.
As it is known, in the canonical Weyl-Moyal approach the model is inconsistent,
basically due to the separation of the amplitudes into planar and nonplanar
parts. We prove that if instead a coherent basis representation is used, the
model becomes renormalizable and free of the aforementioned difficulty. We also
show that, although the coherent states procedure breaks Lorentz symmetry in
odd dimensions, in the Gross-Neveu model this breaking can be kept under
control by assuming the noncommutativity parameters to be small enough. We also
make some remarks on some ordering prescriptions used in the literature.Comment: 10 pages, IOP article style; v3: revised version, accepted for
publication in J. Phys.
The Low Energy Limit of the Chern-Simons Theory Coupled to Fermions
We study the nonrelativistic limit of the theory of a quantum Chern--Simons
field minimally coupled to Dirac fermions. To get the nonrelativistic effective
Lagrangian one has to incorporate vacuum polarization and anomalous magnetic
moment effects. Besides that, an unsuspected quartic fermionic interaction may
also be induced. As a by product, the method we use to calculate loop diagrams,
separating low and high loop momenta contributions, allows to identify how a
quantum nonrelativistic theory nests in a relativistic one.Comment: 18 pages, 8 figures, Late
Chiral Bosons Through Linear Constraints
We study in detail the quantization of a model which apparently describes
chiral bosons. The model is based on the idea that the chiral condition could
be implemented through a linear constraint. We show that the space of states is
of indefinite metric. We cure this disease by introducing ghost fields in such
a way that a BRST symmetry is generated. A quartet algebra is seen to emerge.
The quartet mechanism, then, forces all physical states, but the vacuum, to
have zero norm.Comment: 9 page
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