1,490 research outputs found
N=2 Super Yang Mills Action and BRST Cohomology
The extended BRST cohomology of N=2 super Yang-Mills theory is discussed in
the framework of Algebraic Renormalization. In particular, N=2 supersymmetric
descent equations are derived from the cohomological analysis of linearized
Slavnov-Taylor operator \B. It is then shown that both off- and on-shell N=2
super Yang-Mills actions are related to a lower-dimensional gauge invariant
field polynomial Tr\f^2 by solving these descent equations. Moreover, it is
found that these off- and on-shell solutions differ only by a \B-exact term,
which can be interprated as a consequence of the fact that the cohomology of
both cases are the same.Comment: Latex, 1+13 page
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
Algebraic renormalization of supersymmetric gauge theories with dimensionful parameters
It is usually believed that there are no perturbative anomalies in
supersymmetric gauge theories beyond the well-known chiral anomaly. In this
paper we revisit this issue, because previously given arguments are incomplete.
Specifically, we rule out the existence of soft anomalies, i.e., quantum
violations of supersymmetric Ward identities proportional to a mass parameter
in a classically supersymmetric theory. We do this by combining a previously
proven theorem on the absence of hard anomalies with a spurion analysis, using
the methods of Algebraic Renormalization. We work in the on-shell component
formalism throughout. In order to deal with the nonlinearity of on-shell
supersymmetry transformations, we take the spurions to be dynamical, and show
how they nevertheless can be decoupled.Comment: Final version, typoes fixed. Revtex, 48 page
The approximate Loebl-Koml\'os-S\'os Conjecture II: The rough structure of LKS graphs
This is the second of a series of four papers in which we prove the following
relaxation of the Loebl-Komlos--Sos Conjecture: For every there
exists a number such that for every every -vertex graph
with at least vertices of degree at least
contains each tree of order as a subgraph.
In the first paper of the series, we gave a decomposition of the graph
into several parts of different characteristics; this decomposition might be
viewed as an analogue of a regular partition for sparse graphs. In the present
paper, we find a combinatorial structure inside this decomposition. In the last
two papers, we refine the structure and use it for embedding the tree .Comment: 38 pages, 4 figures; new is Section 5.1.1; accepted to SIDM
The approximate Loebl-Koml\'os-S\'os Conjecture IV: Embedding techniques and the proof of the main result
This is the last paper of a series of four papers in which we prove the
following relaxation of the Loebl-Komlos-Sos Conjecture: For every
there exists a number~ such that for every every -vertex graph
with at least vertices of degree at least
contains each tree of order as a subgraph.
In the first two papers of this series, we decomposed the host graph , and
found a suitable combinatorial structure inside the decomposition. In the third
paper, we refined this structure, and proved that any graph satisfying the
conditions of the above approximate version of the Loebl-Komlos-Sos Conjecture
contains one of ten specific configurations. In this paper we embed the tree
in each of the ten configurations.Comment: 81 pages, 12 figures. A fix reflecting the change of Preconfiguration
Clubs in Paper III, additional small change
The Approximate Loebl-Koml\'os-S\'os Conjecture III: The finer structure of LKS graphs
This is the third of a series of four papers in which we prove the following
relaxation of the Loebl-Komlos-Sos Conjecture: For every there
exists a number such that for every every -vertex graph
with at least vertices of degree at least
contains each tree of order as a subgraph.
In the first paper of the series, we gave a decomposition of the graph
into several parts of different characteristics. In the second paper, we found
a combinatorial structure inside the decomposition. In this paper, we will give
a refinement of this structure. In the forthcoming fourth paper, the refined
structure will be used for embedding the tree .Comment: 59 pages, 4 figures; further comments by a referee incorporated; this
includes a subtle but important fix to Lemma 5.1; as a consequence,
Preconfiguration Clubs was change
The asymmetry of the dimension 2 gluon condensate: the zero temperature case
We provide an algebraic study of the local composite operators A_\mu
A_\nu-\delta_{\mu\nu}/d A^2 and A^2, with d=4 the spacetime dimension. We prove
that these are separately renormalizable to all orders in the Landau gauge.
This corresponds to a renormalizable decomposition of the operator A_\mu A_\nu
into its trace and traceless part. We present explicit results for the relevant
renormalization group functions to three loop order, accompanied with various
tests of these results. We then develop a formalism to determine the zero
temperature effective potential for the corresponding condensates, and recover
the already known result for \neq 0, together with <A_\mu
A_\nu-\delta_{\mu\nu}/d A^2>=0, a nontrivial check that the approach is
consistent with Lorentz symmetry. The formalism is such that it is readily
generalizable to the finite temperature case, which shall allow a future
analytical study of the electric-magnetic symmetry of the condensate,
which received strong evidence from recent lattice simulations by Chernodub and
Ilgenfritz, who related their results to 3 regions in the Yang-Mills phase
diagram.Comment: 25 page
- …