3,585 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
Ontology of multi-agents processes of spatial decision
In the paper of Cavezzali, Girotti and Rabino presented at ERSA 2003 conference, features of multi-agent models and their potentiality for the study of territorial phenomena are discussed. Starting from this study, the present paper digs deeper mechanisms of multi-agent systems working, describing their ontology in a more complete and articulated way as possible, and investigating: the properties of the actors, the mechanisms of interaction among actors and between actors and environment. About the environment, particular attention has been paid to the consideration about the various modalities of treatment of territory (from pure physical support to active reactive/cognitive agent in relationship with the other agents). For these modalities, finally, two typical case-studies of multi-agent model are shown: simulation of pedestrian paths choice, the software “Turisti”, and a competitive dynamic of service centres location, “Wilson”.
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
- …