17,734 research outputs found
The Background Field Method as a Canonical Transformation
We construct explicitly the canonical transformation that controls the full
dependence (local and non-local) of the vertex functional of a Yang-Mills
theory on a background field. After showing that the canonical transformation
found is nothing but a direct field-theoretic generalization of the Lie
transform of classical analytical mechanics, we comment on a number of possible
applications, and in particular the non perturbative implementation of the
background field method on the lattice, the background field formulation of the
two particle irreducible formalism, and, finally, the formulation of the
Schwinger-Dyson series in the presence of topologically non-trivial
configurations.Comment: 11 pages, REVTeX. References added, some explanations extended. Final
version to appear in the journa
Effects of the R-parity violation in the minimal supersymmetric standard model on dilepton pair production at the CERN LHC
We investigate in detail the effects of the R-parity lepton number violation
in the minimal supersymmetric standard model (MSSM) on the parent process at the CERN Large Hadron Collider (LHC). The numerical
comparisons between the contributions of the R-parity violating effects to the
parent process via the Drell-Yan subprocess and the gluon-gluon fusion are
made. We find that the R-violating effects on pair production at the
LHC could be significant. The results show that the cross section of the pair productions via gluon-gluon collision at the LHC can be of the order
of fb, and this subprocess maybe competitive with the production
mechanism via the Drell-Yan subprocess. We give also quantitatively the
analysis of the effects from both the mass of sneutrino and coupling strength
of the R-parity violating interactions.Comment: 18 pages, 10 figures, accepted by Phys. Rev.
Field Decomposition and the Ground State Structure of SU(2) Yang-Mills Theory
We compute the effective potential of SU(2) Yang-Mills theory using the
background field method and the Faddeev-Niemi decomposition of the gauge
fields. In particular, we find that the potential will depend on the values of
two scalar fields in the decomposition and that its structure will give rise to
a symmetry breaking.Comment: 8 pages, 1 figure. Typos corrected and title change
Loss of Individual MicroRNAs Causes Mutant Phenotypes in Sensitized Genetic Backgrounds in \u3cem\u3eC. elegans\u3c/em\u3e
MicroRNAs (miRNAs) are small, noncoding RNAs that regulate the translation and/or stability of their mRNA targets. Previous work showed that for most miRNA genes of C. elegans, single-gene knockouts did not result in detectable mutant phenotypes. This may be due, in part, to functional redundancy between miRNAs. However, in most cases, worms carrying deletions of all members of a miRNA family do not display strong mutant phenotypes. They may function together with unrelated miRNAs or with non-miRNA genes in regulatory networks, possibly to ensure the robustness of developmental mechanisms. To test this, we examined worms lacking individual miRNAs in genetically sensitized backgrounds. These include genetic backgrounds with reduced processing and activity of all miRNAs or with reduced activity of a wide array of regulatory pathways. With these two approaches, we identified mutant phenotypes for 25 out of 31 miRNAs included in this analysis. Our findings describe biological roles for individual miRNAs and suggest that the use of sensitized genetic backgrounds provides an efficient approach for miRNA functional analysis
Trident pair production in strong laser pulses
We calculate the trident pair production amplitude in a strong laser
background. We allow for finite pulse duration, while still treating the laser
fields nonperturbatively in strong-field QED. Our approach reveals explicitly
the individual contributions of the one-step and two-step processes. We also
expose the role gauge invariance plays in the amplitudes and discuss the
relation between our results and the optical theorem.Comment: 4 pages, 1 .eps figure. Version 2: reference added, published versio
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