1,776 research outputs found
Adaptive and Adequate Lubrication for Highest Component-lifetimes in Feed Drive Axes with Ball Screws
Master integrals with 2 and 3 massive propagators for the 2-loop electroweak form factor - planar case
We compute the master integrals containing 2 and 3 massive propagators
entering the planar amplitudes of the 2-loop electroweak form factor. The
masses of the , and Higgs bosons are assumed to be degenerate. This work
is a continuation of our previous evaluation of master integrals containing at
most 1 massive propagator. The 1/\epsilon poles and the finite parts are
computed exactly in terms of a {\it new} class of 1-dimensional harmonic
polylogarithms of the variable x, with \epsilon=2-D/2 and D the pace-time
dimension. Since thresholds and pseudothresholds in s=\pm 4m^2 do appear in
addition to the old ones in s=0,\pm m^2, an extension of the basis function set
involving complex constants and radicals is introduced, together with a set of
recursion equations to reduce integrals with semi-integer powers. It is shown
that the basic properties of the harmonic polylogarithms are maintained by the
generalization. We derive small-momentum expansions |s| << m^2 of all the
6-denominator amplitudes. We also present large momentum expansions |s| >> m^2
of all the 6-denominator amplitudes which can be represented in terms of
ordinary harmonic polylogarithms. Comparison with previous results in the
literature is performed finding complete agreement.Comment: 68 pages, 7 figure
The Uehling correction to the energy levels in a pionic atom
We consider a correction to energy levels in a pionic atom induced by the
Uehling potential, i.e., by a free electron vacuum-polarization loop. The
calculation is performed for circular states (l=n-1). The result is obtained in
a closed analytic form as a function of and the pion-to-electron
mass ratio. Certain asymptotics of the result are also presented
Explicit results for all orders of the epsilon-expansion of certain massive and massless diagrams
An arbitrary term of the epsilon-expansion of dimensionally regulated
off-shell massless one-loop three-point Feynman diagram is expressed in terms
of log-sine integrals related to the polylogarithms. Using magic connection
between these diagrams and two-loop massive vacuum diagrams, the
epsilon-expansion of the latter is also obtained, for arbitrary values of the
masses. The problem of analytic continuation is also discussed.Comment: 8 pages, late
Final State Radiative Effects for the Exact O(alpha) YFS Exponentiated (Un)Stable W+W- Production At and Beyond LEP2 Energies
We present the LL final state radiative effects for the exact O(alpha) YFS
exponentiated (un)stable WW pair production at LEP2/NLC energies using Monte
Carlo event generator methods. The respective event generator, version 1.12 of
the program YFSWW3, wherein both Standard Model and anomalous triple gauge
boson couplings are allowed, generates n(\gamma) radiation both from the
initial state and from the intermediate W+ W- and generates the LL final state
W decay radiative effects. Sample Monte Carlo data are illustrated.Comment: 16 pages, 8 figures, 2 table
GroĂźe Aufmerksamkeit fĂĽr kleine Welten - Nanotechnologie und ihre Folgen - EinfĂĽhrung in den Schwerpunkt
Roadmapping als eine Erweiterung des “Methoden-Werkzeugkastens” der Technikfolgenabschätzung?
The Two Loop Crossed Ladder Vertex Diagram with Two Massive Exchanges
We compute the (three) master integrals for the crossed ladder diagram with
two exchanged quanta of equal mass. The differential equations obeyed by the
master integrals are used to generate power series expansions centered around
all the singular (plus some regular) points, which are then matched numerically
with high accuracy. The expansions allow a fast and precise numerical
calculation of the three master integrals (better than 15 digits with less than
30 terms in the whole real axis). A conspicuous relation with the equal-mass
sunrise in two dimensions is found. Comparison with a previous large momentum
expansion is made finding complete agreement.Comment: 42 pages, 1 figur
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