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 $pp \to e^+ e^- + X$ 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 $e^+ e^-$ pair production at the LHC could be significant. The results show that the cross section of the $e^+ e^-$ pair productions via gluon-gluon collision at the LHC can be of the order of $10^2$ 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

full-FORCE: A Target-Based Method for Training Recurrent Networks

Trained recurrent networks are powerful tools for modeling dynamic neural computations. We present a target-based method for modifying the full connectivity matrix of a recurrent network to train it to perform tasks involving temporally complex input/output transformations. The method introduces a second network during training to provide suitable "target" dynamics useful for performing the task. Because it exploits the full recurrent connectivity, the method produces networks that perform tasks with fewer neurons and greater noise robustness than traditional least-squares (FORCE) approaches. In addition, we show how introducing additional input signals into the target-generating network, which act as task hints, greatly extends the range of tasks that can be learned and provides control over the complexity and nature of the dynamics of the trained, task-performing network.Comment: 20 pages, 8 figure