285 research outputs found
A study of the Gribov copies in linear covariant gauges in Euclidean Yang-Mills theories
The Gribov copies and their consequences on the infrared behavior of the
gluon propagator are investigated in Euclidean Yang-Mills theories quantized in
linear covariant gauges. Considering small values of the gauge parameter, it
turns out that the transverse component of the gluon propagator is suppressed,
while its longitudinal part is left unchanged. A Green function, G_{tr}, which
displays infrared enhancement and which reduces to the ghost propagator in the
Landau gauge is identified. The inclusion of the dimension two gluon condensate
is also considered. In this case, the transverse component of the gluon
propagator and the Green function G_{tr} remain suppressed and enhanced,
respectively. Moreover, the longitudinal part of the gluon propagator becomes
suppressed. A comparison with the results obtained from the studies of the
Schwinger-Dyson equations and from lattice simulations is provided.Comment: 20 page
The Gribov parameter and the dimension two gluon condensate in Euclidean Yang-Mills theories in the Landau gauge
The local composite operator A^2 is added to the Zwanziger action, which
implements the restriction to the Gribov region in Euclidean Yang-Mills
theories in the Landau gauge. We prove the renormalizability of this action to
all orders of perturbation theory. This allows to study the dimension two gluon
condensate by the local composite operator formalism when the restriction
is taken into account. The effective action is evaluated at one-loop order in
the MSbar scheme. We obtain explicit values for the Gribov parameter and for
the mass parameter due to , but the expansion parameter turns out to be
rather large. Furthermore, an optimization of the perturbative expansion in
order to reduce the dependence on the renormalization scheme is performed. The
properties of the vacuum energy, with or without , are investigated. It is
shown that in the original Gribov-Zwanziger formulation (without ), the
vacuum energy is always positive at 1-loop order, independently from the
renormalization scheme and scale. With , we are unable to come to a
definite conclusion at the order considered. In the MSbar scheme, we still find
a positive vacuum energy, again with a relatively large expansion parameter,
but there are renormalization schemes in which the vacuum energy is negative,
albeit the dependence on the scheme itself appears to be strong. We recover the
well known consequences of the restriction, and this in the presence of :
an infrared suppression of the gluon propagator and an enhancement of the ghost
propagator. This behaviour is in qualitative agreement with the results
obtained from the studies of the Schwinger-Dyson equations and from lattice
simulations.Comment: 42 pages, 10 .eps figures. v2: Version accepted for publication in
Phys.Rev.D. Added references. Technical details have been collected in two
appendice
A study of the gauge invariant, nonlocal mass operator in Yang-Mills theories
The nonlocal mass operator is
considered in Yang-Mills theories in Euclidean space-time. It is shown that the
operator can be cast in local
form through the introduction of a set of additional fields. A local and
polynomial action is thus identified. Its multiplicative renormalizability is
proven by means of the algebraic renormalization in the class of linear
covariant gauges. The anomalous dimensions of the fields and of the mass
operator are computed at one loop order. A few remarks on the possible role of
this operator for the issue of the gauge invariance of the dimension two
condensates are outlined.Comment: 34 page
Post-Lie Algebras, Factorization Theorems and Isospectral-Flows
In these notes we review and further explore the Lie enveloping algebra of a
post-Lie algebra. From a Hopf algebra point of view, one of the central
results, which will be recalled in detail, is the existence of a second Hopf
algebra structure. By comparing group-like elements in suitable completions of
these two Hopf algebras, we derive a particular map which we dub post-Lie
Magnus expansion. These results are then considered in the case of
Semenov-Tian-Shansky's double Lie algebra, where a post-Lie algebra is defined
in terms of solutions of modified classical Yang-Baxter equation. In this
context, we prove a factorization theorem for group-like elements. An explicit
exponential solution of the corresponding Lie bracket flow is presented, which
is based on the aforementioned post-Lie Magnus expansion.Comment: 49 pages, no-figures, review articl
A study of the zero modes of the Faddeev-Popov operator in Euclidean Yang-Mills theories in the Landau gauge in d=2,3,4 dimensions
Examples of normalizable zero modes of the Faddeev-Popov operator in SU(2)
Euclidean Yang-Mills theories in the Landau gauge are constructed in d=2,3,4
dimensions.Comment: 18 pages. Text modifications. References added. Version accepted for
publication in the EPJ
Gaudin model and its associated Knizhnik-Zamolodchikov equation
The semiclassical limit of the algebraic Bethe Ansatz for the Izergin-Korepin
19-vertex model is used to solve the theory of Gaudin models associated with
the twisted R-matrix. We find the spectra and eigenvectors of the
independents Gaudin Hamiltonians. We also use the off-shell Bethe Ansatz
method to show how the off-shell Gaudin equation solves the associated
trigonometric system of Knizhnik-Zamolodchikov equations.Comment: 20 pages,no figure, typos corrected, LaTe
off-shell Bethe ansatz equation with boundary terms
This work is concerned with the quasi-classical limit of the boundary quantum
inverse scattering method for the vertex model with diagonal
-matrices. In this limit Gaudin's Hamiltonians with boundary terms are
presented and diagonalized. Moreover, integral representations for correlation
functions are realized to be solutions of the trigonometric
Knizhnik-Zamoldchikov equations.Comment: 38 pages, minor revison, LaTe
Molecular Genetic Characterization of the Biosynthesis Cluster of a Prenylated Isoindolinone Alkaloid Aspernidine A in Aspergillus nidulans
Aspernidine A is a prenylated isoindolinone alkaloid isolated from the model fungus Aspergillus nidulans. A genome-wide kinase knock out library of A. nidulans was examined and it was found that a mitogen-activated protein kinase gene, mpkA, deletion strain produces aspernidine A. Targeted gene deletions were performed in the kinase deletion background to identify the gene cluster for aspernidine A biosynthesis. Intermediates were isolated from mutant strains which provided information about the aspernidine A biosynthesis pathway
Dynamical gluon mass generation from <A^2> in linear covariant gauges
We construct the multiplicatively renormalizable effective potential for the
mass dimension two local composite operator A^2 in linear covariant gauges. We
show that the formation of is energetically favoured and that the gluons
acquire a dynamical mass due to this gluon condensate. We also discuss the
gauge parameter independence of the resultant vacuum energy.Comment: 21 pages. 14 .eps figures. v2: minor modifications. v3: version
accepted for publication in JHE
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