1,100 research outputs found
Symmetry aspects of fermions coupled to torsion and electromagnetic fields
We study and explore the symmetry properties of fermions coupled to dynamical
torsion and electromagnetic fields. The stability of the theory upon radiative
corrections as well as the presence of anomalies are investigated.Comment: 9 pages, LaTe
Constructive algebraic renormalization of the abelian Higgs-Kibble model
We propose an algorithm, based on Algebraic Renormalization, that allows the
restoration of Slavnov-Taylor invariance at every order of perturbation
expansion for an anomaly-free BRS invariant gauge theory. The counterterms are
explicitly constructed in terms of a set of one-particle-irreducible Feynman
amplitudes evaluated at zero momentum (and derivatives of them). The approach
is here discussed in the case of the abelian Higgs-Kibble model, where the zero
momentum limit can be safely performed. The normalization conditions are
imposed by means of the Slavnov-Taylor invariants and are chosen in order to
simplify the calculation of the counterterms. In particular within this model
all counterterms involving BRS external sources (anti-fields) can be put to
zero with the exception of the fermion sector.Comment: Jul, 1998, 31 page
Observables in Topological Yang-Mills Theories
Using topological Yang-Mills theory as example, we discuss the definition and
determination of observables in topological field theories (of Witten-type)
within the superspace formulation proposed by Horne. This approach to the
equivariant cohomology leads to a set of bi-descent equations involving the
BRST and supersymmetry operators as well as the exterior derivative. This
allows us to determine superspace expressions for all observables, and thereby
to recover the Donaldson-Witten polynomials when choosing a Wess-Zumino-type
gauge.Comment: 39 pages, Late
On the symmetries of BF models and their relation with gravity
The perturbative finiteness of various topological models (e.g. BF models)
has its origin in an extra symmetry of the gauge-fixed action, the so-called
vector supersymmetry. Since an invariance of this type also exists for gravity
and since gravity is closely related to certain BF models, vector supersymmetry
should also be useful for tackling various aspects of quantum gravity. With
this motivation and goal in mind, we first extend vector supersymmetry of BF
models to generic manifolds by incorporating it into the BRST symmetry within
the Batalin-Vilkovisky framework. Thereafter, we address the relationship
between gravity and BF models, in particular for three-dimensional space-time.Comment: 29 page
A Completely Invariant SUSY Transform of Supersymmetric QED
We study the SUSY breaking of the covariant gauge-fixing term in SUSY QED and
observe that this corresponds to a breaking of the Lorentz gauge condition by
SUSY. Reasoning by analogy with SUSY's violation of the Wess-Zumino gauge, we
argue that the SUSY transformation, already modified to preserve Wess-Zumino
gauge, should be further modified by another gauge transformation which
restores the Lorentz gauge condition. We derive this modification and use the
resulting transformation to derive a Ward identitiy relating the photon and
photino propagators without using ghost fields. Our transformation also
fulfills the SUSY algebra, modulo terms that vanish in Lorentz gauge
Let's Twist Again: N=2 Super Yang Mills Theory Coupled To Matter
We give the twisted version of N=2 Super Yang Mills theory coupled to matter,
including quantum fields, supersymmetry transformations, action and algebraic
structure. We show that the whole action, coupled to matter, can be written as
the variation of a nilpotent operator, modulo field equations. An extended
Slavnov-Taylor identity, collecting gauge symmetry and supersymmetry, is
written, which allows to define the web of algebraic constraints, in view of
the algebraic renormalization and of the extension of the non-renormalization
theorems holding for N=2 SYM theory without matter.Comment: 28 pages, final version to be published on CQ
Gribov no-pole condition, Zwanziger horizon function, Kugo-Ojima confinement criterion, boundary conditions, BRST breaking and all that
We aim to offer a kind of unifying view on two popular topics in the studies
of nonperturbative aspects of Yang-Mills theories in the Landau gauge: the
so-called Gribov-Zwanziger approach and the Kugo-Ojima confinement criterion.
Borrowing results from statistical thermodynamics, we show that imposing the
Kugo-Ojima confinement criterion as a boundary condition leads to a modified
yet renormalizable partition function. We verify that the resulting partition
function is equivalent with the one obtained by Gribov and Zwanziger, which
restricts the domain of integration in the path integral within the first
Gribov horizon. The construction of an action implementing a boundary condition
allows one to discuss the symmetries of the system in the presence of the
boundary. In particular, the conventional BRST symmetry is softly broken.Comment: 5 pages. v2 matches version to appear in PhysRevD (RC
The gluon and ghost propagators in Euclidean Yang-Mills theory in the maximal Abelian gauge: taking into account the effects of the Gribov copies and of the dimension two condensates
The infrared behavior of the gluon and ghost propagators is studied in SU(2)
Euclidean Yang-Mills theory in the maximal Abelian gauge within the
Gribov-Zwanziger framework. The nonperturbative effects associated with the
Gribov copies and with the dimension two condensates are simultaneously encoded
into a local and renormalizable Lagrangian. The resulting behavior turns out to
be in good agreement with the lattice data.Comment: final version, to appear in Physical Review
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