Search results for "loop"
showing 10 items of 608 documents
Method to examine macrobending loss in deformed optical fibre loop
2005
This paper presents the method of research and measurement of macrobending attenuation, present during alteration of geometrical system of optical fibre loop. Presentation of a measuring device, which allows to unifying measurements in (under) conditions close to those present in industrial constructions of devices. Annexed exemplary research of macrobending loss in systems deforming optical fibre loops made from various types of optical fibres.
Nonlinear Analysis of Phase-Locked Loop (PLL): Global Stability Analysis, Hidden Oscillations and Simulation Problems
2013
In the middle of last century the problem of analyzing hidden oscillations arose in automatic control. In 1956 M. Kapranov considered a two-dimensional dynamical model of phase locked-loop (PLL) and investigated its qualitative behavior. In these investigations Kapranov assumed that oscillations in PLL systems can be self-excited oscillations only. However, in 1961, N. Gubar’ revealed a gap in Kapranov’s work and showed analytically the possibility of the existence of another type of oscillations, called later by the authors hidden oscillations, in a phase-locked loop model: from a computational point of view the system considered was globally stable (all the trajectories tend to equilibria…
A Brightening Coronal Loop Observed byTRACE. I. Morphology and Evolution
2000
We analyze the transient brightening of a solar coronal loop observed, at high time cadence (30 s) and spatial resolution (05 pixel size), with the Transition Region and Coronal Explorer (TRACE) in the 171 A band on 1998 June 26. The loop, located in AR 8253, is ≈1010 cm long and inclined with respect to the vertical to the solar surface. Its geometry and shape do not change significantly during the brightening, which lasts for ~2 hr and is preceded by highly dynamic events in nearby and perhaps interacting loops. The loop footpoints brighten first; after ~10 minutes, moving brightness fronts rise initially from the northern footpoint, and after another ~7 minutes from the southern one, at …
Vanishing of certain cuts or residues of loop integrals with higher powers of the propagators
2019
Starting from two-loops, there are Feynman integrals with higher powers of the propagators. They arise from self-energy insertions on internal lines. Within the loop-tree duality approach or within methods based on numerical unitarity one needs (among other things) the residue when a raised propagator goes on-shell. We show that for renormalised quantities in the on-shell scheme these residues can be made to vanish already at the integrand level.
New constraints on R-parity violation from μ–e conversion in nuclei
1998
We derive new constraints on the products of explicitly R-parity violating couplings $\lambda$ and $\lambda'$ in MSSM from searches for \mu-e conversion in nuclei. We concentrate on the loop induced photonic coherent conversion mode. For the combinations $|\lambda\lambda|$ which in \mu-e conversion can be probed only at loop level our constraints are in many cases more stringent than the previous ones due to the enhancement of the process by large $\ln(m^2_f/m^2_{\tilde f}).$ For the combinations of $|\lambda'\lambda'|$ the tree-level \mu-e conversion constraints are usually more restrictive than the loop ones except for two cases which involve the third generation. With the expected improv…
Effect ofmconbquark chromomagnetic interaction and on-shell two-loop integrals with two masses
1999
The effect of non-zero c quark mass on b quark HQET Lagrangian, up to 1/mb level, is calculated at two loops. The results are expressed in terms of dilogarithmic functions of mc/mb. This calculation involves on-shell two-loop propagator-type diagrams with two different masses, mb and mc. A general algorithm for reducing such Feynman integrals to the basis of two nontrivial and two trivial integrals is constructed.
μ-e conversion in nuclei versus μ→e γ: an effective field theory point of view
1998
Using an effective lagrangian description we analyze possible new physics contributions to the most relevant muon number violating processes: $\mu \to e \gamma$ and $\mu$--$e$ conversion in nuclei. We identify a general class of models in which those processes are generated at one loop level and in which $\mu$--$e$ conversion is enhanced with respect to $\mu \to e \gamma$ by a large $\ln(m^2_\mu/\Lambda^2),$ where $\Lambda$ is the scale responsible for the new physics. For this wide class of models bounds on $\mu$--$e$ conversion constrain the scale of new physics more stringently than $\mu \to e \gamma$ already at present and, with the expected improvements in $\mu$--$e$ conversion experim…
De Rham–Hodge–Kodaira Operator on Loop Groups
1997
AbstractWe consider a based loop group Le(G) over a compact Lie groupG, endowed with its pinned Wiener measureν(the law of the Brownian bridge onG) and we shall calculate the Ricci curvature for differentialn-forms over Le(G). A type of Bochner–Weitzenböck formula for general differentialn-forms (or Shigekawa identity) will be established.
Integrability Conditions: Recent Results in the Theory of Integrable Models
1990
This paper reports various results achieved recently in the theory of integrable models. These are summarised in the Fig.1! At the Chester meeting [1] two of the authors were concerned [1] with the local Riemann-Hilbert problem (double-lined box in the centre of Fig.1), its limit as a non-local Riemann-Hilbert problem used to solve classical integrable models in 2+1 dimensions (two space and one time dimensions) [2,3], and the connection of this Riemann-Hilbert problem with Ueno’s [4] Riemann-Hilbert problem associated with the representation of the algebra gl(∞) in terms of Z⊗Z matrices (Z the integers) and the solution of the K-P equations in 2+1. We were also concerned [1] with the const…
Two-loop QED Corrections to Bhabha Scattering
2006
Recent developments in the calculation of the NNLO corrections to the Bhabha scattering differential cross section in pure QED are briefly reviewed and discussed.