scholarly journals Four-loop QCD propagators and vertices with one vanishing external momentum

2017 ◽  
Vol 2017 (6) ◽  
Author(s):  
B. Ruijl ◽  
T. Ueda ◽  
J. A. M. Vermaseren ◽  
A. Vogt
Keyword(s):  
External Momentum

scholarly journals New series representations for the two-loop massive sunset diagram

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
B. Ananthanarayan ◽  
Samuel Friot ◽  
Shayan Ghosh
Keyword(s):  
Perturbation Theory ◽  
Standard Model ◽  
Analytic Continuation ◽  
Chiral Perturbation Theory ◽  
Convergent Series ◽  
Regions Of Interest ◽  
External Momentum ◽  
Chiral Perturbation ◽  
Physical Problems ◽  
Series Representations

Abstract We derive new convergent series representations for the two-loop sunset diagram with three different propagator masses $$m_1,\, m_2$$m1,m2 and $$m_3$$m3 and external momentum p by techniques of analytic continuation on a well-known triple series that corresponds to the Lauricella $$F_C^{(3)}$$FC(3) function. The convergence regions of the new series contain regions of interest to physical problems. These include some ranges of masses and squared external momentum values which make them useful from Chiral Perturbation Theory to some regions of the parameter space of the Minimal Supersymmetric Standard Model. The analytic continuation results presented for the Lauricella series could be used in other settings as well.

DAMPING OF ULTRASOFT FERMIONS IN FINITE TEMPERATURE QED

2007 ◽  
Vol 22 (12) ◽  
pp. 903-914 ◽  
Author(s):  
A. ABADA ◽  
K. BOUAKAZ ◽  
D. DEGHICHE
Keyword(s):  
Finite Temperature ◽  
Second Order ◽  
External Momentum ◽  
Hard Thermal Loop ◽  
Gauge Fixing ◽  
Covariant Gauge

We calculate the fermion damping rates to second order in powers of the external momentum in the context of QED at finite temperature using the hard-thermal-loop summation scheme. We find the coefficients of zeroth and first orders finite whereas that of second-order logarithmically infrared sensitive. The calculation is done in covariant gauge and the result is independent of gauge fixing.

scholarly journals MESON PVV INTERACTIONS ARE DETERMINED BY QUARK LOOPS

1999 ◽  
Vol 14 (27) ◽  
pp. 4331-4345 ◽  
Author(s):  
R. DELBOURGO ◽  
DONGSHENG LIU ◽  
M. D. SCADRON
Keyword(s):  
External Momentum ◽  
Coupling Constants ◽  
P Wave ◽  
Wave State ◽  
Mixing Angles ◽  
Meson Decays ◽  
Three Body ◽  
Radiative Meson Decays ◽  
Quark Loops

We show that all abnormal parity three-body meson interactions can be adequately described by quark loops, evaluated at zero external momentum, with couplings determined by U(Nf) symmetry. We focus primarily on radiative meson decays which involve one pseudoscalar. The agreement with experiment for nonrare decays is surprisingly good and requires very few parameters, namely the coupling constants gπqq and gρqq and some mixing angles. This agreement extends to some three-body decays that are dominated by pion pairs in a P-wave state.

One-loop nonlinear correction for QED

2016 ◽  
Vol 31 (27) ◽  
pp. 1650153
Author(s):  
J. S. N. Furtado ◽  
G. R. Silva
Keyword(s):  
Effective Action ◽  
External Momentum ◽  
Nonlinear Correction ◽  
Derivative Expansion

In this work, we study the generation of a nonlinear correction for QED, namely, the Euler–Heisenberg effective action. In order to achieve this, we consider two methods. The first method employed consists in make use of Feynman parametrization to solve the integrals properly, while in the second method a derivative expansion in the external momentum was considered.

scholarly journals Impacts of External Momentum Torque on Impurity Particle Transport in LHD

2017 ◽  
Vol 12 (0) ◽  
pp. 1203039-1203039 ◽  
Author(s):  
Masanori NUNAMI ◽  
Masahiko SATO ◽  
Motoki NAKATA ◽  
Shinichiro TODA ◽  
Hideo SUGAMA ◽  
...  
Keyword(s):  
Particle Transport ◽  
External Momentum ◽  
Impurity Particle

scholarly journals A NEW BASIS FOR QED BOUND STATE COMPUTATIONS

2002 ◽  
Vol 17 (28) ◽  
pp. 4113-4132 ◽  
Author(s):  
J. PESTIEAU ◽  
C. SMITH
Keyword(s):  
Light Scattering ◽  
Binding Energy ◽  
Scattering Amplitude ◽  
Bound State ◽  
External Momentum ◽  
Simple Method ◽  
Positronium Decay

A simple method to compute QED bound state properties is presented, in which binding energy effects are treated nonperturbatively. It is shown that to take the effects of all ladder Coulomb photon exchanges into account, one can simply perform the derivative of standard QED amplitudes with respect to the external momentum. For example, the derivative of the light-by-light scattering amplitude gives an amplitude for orthopositronium decay to three photons where any number of Coulomb photon exchanges between the e+e-is included.Various applications are presented. From them, it is shown that binding energy must be treated nonperturbatively in order to preserve the analyticity of positronium decay amplitudes.Interesting perspectives for quarkonium physics are briefly sketched.

scholarly journals Mechanisms for generating toroidal rotation in tokamaks without external momentum input

2010 ◽  
Vol 17 (5) ◽  
pp. 056108 ◽  
Author(s):  
W. M. Solomon ◽  
K. H. Burrell ◽  
A. M. Garofalo ◽  
S. M. Kaye ◽  
R. E. Bell ◽  
...  
Keyword(s):  
External Momentum ◽  
Toroidal Rotation
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