370 research outputs found
A nilpotent symmetry of quantum gauge theories
For the Becchi-Rouet-Stora-Tyutin (BRST) invariant extended action for any
gauge theory, there exists another off-shell nilpotent symmetry. For linear
gauges, it can be elevated to a symmetry of the quantum theory and used in the
construction of the quantum effective action. Generalizations for nonlinear
gauges and actions with higher order ghost terms are also possible.Comment: RevTeX, 9 pages, several changes to include generalizations to
quartic and higher ghost terms and non-linear gauges. Abstract changed. Final
version to be publishe
Wess-Zumino Terms for Reducible Anomalous Gauge Theories
Reducible off-shell anomalous gauge theories are studied in the framework of
an extended Field-Antifield formalism by introducing new variables associated
with the anomalous gauge degrees of freedom. The Wess-Zumino term for these
theories is constructed and new gauge invariances appear. The quantum effects
due to the extra variables are considered.Comment: 31 pages, Latex file, no figures. Section added. To appear in
Nucl.Phys.
Chiral gauge theories and anomalies in the Wilson renormalization group approach
We extend the Wilson renormalization group (RG) formulation to chiral gauge
theories and show that local gauge symmetry can be implemented by a suitable
choice of the RG flow boundary conditions. Since the space-time dimension is
four, there is no ambiguity in handling the matrix \g_5 and left and right
fermions are not coupled. As a result the ultraviolet action contains all
possible globally chiral invariant interactions. Nevertheless, the correct
chiral anomaly is reproduced.Comment: 16 pages, 4 figures, LaTex, uses epsfig, amssym
Algebraic renormalization of the BF Yang-Mills Theory
We discuss the quantum equivalence, to all orders of perturbation theory,
between the Yang-Mills theory and its first order formulation through a second
rank antisymmetric tensor field. Moreover, the introduction of an additional
nonphysical vector field allows us to interpret the Yang-Mills theory as a kind
of perturbation of the topological BF model.Comment: 14 pages, some references and acknowledgments added, version to
appear in Phys.Lett.
Lower body design of the âiCubâ a human-baby like crawling robot
The development of robotic cognition and a greater understanding of human cognition form two of the current greatest challenges of science. Within the RobotCub project the goal is the development of an embodied robotic child (iCub) with the physical and ultimately cognitive abilities of a 2frac12 year old human baby. The ultimate goal of this project is to provide the cognition research community with an open human like platform for understanding of cognitive systems through the study of cognitive development. In this paper the design of the mechanisms adopted for lower body and particularly for the leg and the waist are outlined. This is accompanied by discussion on the actuator group realisation in order to meet the torque requirements while achieving the dimensional and weight specifications. Estimated performance measures of the iCub are presented
Numerical study of the scaling properties of SU(2) lattice gauge theory in Palumbo non-compact regularization
In the framework of a non-compact lattice regularization of nonabelian gauge
theories we look, in the SU(2) case, for the scaling window through the
analysis of the ratio of two masses of hadronic states. In the two-dimensional
parameter space of the theory we find the region where the ratio is constant,
and equal to the one in the Wilson regularization. In the scaling region we
calculate the lattice spacing, finding it at least 20% larger than in the
Wilson case; therefore the simulated physical volume is larger.Comment: 24 pages, 7 figure
One Loop Anomalies and Wess-Zumino Terms for General Gauge Theories
One loop anomalies and their dependence on antifields for general gauge
theories are investigated within a Pauli-Villars regularization scheme. For
on-shell theories {\it i.e.}, with open algebras or on-shell reducible
theories, the antifield dependence is cohomologically non trivial. The
associated Wess-Zumino term depends also on antifields. In the classical basis
the antifield independent part of the WZ term is expressed in terms of the
anomaly and finite gauge transformations by introducing gauge degrees of
freedom as the extra dynamical variables. The complete WZ term is reconstructed
from the antifield independent part.Comment: 15 pages, An example of non-abelian antisymmetric field is added.
Some corrections are made to refrain from using the reconstruction theorem in
the gauge fixed basi
Wilson Renormalization Group for Supersymmetric Gauge Theories and Gauge Anomalies
We extend the Wilson renormalization group (RG) to supersymmetric theories.
As this regularization scheme preserves supersymmetry, we exploit the
superspace technique. To set up the formalism we first derive the RG flow for
the massless Wess-Zumino model and deduce its perturbative expansion. We then
consider N=1 supersymmetric Yang-Mills and show that the local gauge symmetry
-broken by the regularization- can be recovered by a suitable choice of the RG
flow boundary conditions. We restrict our analysis to the first loop, the
generalization to higher loops presenting no difficulty due to the iterative
nature of the procedure. Furthermore, adding matter fields, we reproduce the
one-loop supersymmetric chiral anomaly to the second order in the vector field.Comment: 22 pages, 1 Postscript figure, uses amssym
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