280 research outputs found
Light Front Quantisation of Gauge Theories in a Finite Volume
We discuss the light-front formulation of SU(2) Yang-Mills theory on a torus.
The gauge choice we use allows for an exact and unambiguous solution of Gauss's
law.Comment: 4 pages, Latex; talk presented at QCD 94, Montpellier, France, July
7-13, and at the Fourth International Workshop on Light Cone Quantization and
Non- Perturbative Dynamics, Polana Zgorzelisko, Poland, August 15-25, TPR
94-2
Corrections to Laser Electron Thomson Scattering
Contribution to 2012 Annual Report, Central Laser Facility (CLF), Rutherford-Appleton Laboratory, UKWe discuss classical and quantum corrections to Thomson scattering between an electron and a laser. For radiation reaction, nonlinear, and quantum effects we identify characteristic dimensionless parameters in terms of which we determine the leading order correction terms
The Light-Cone Wave Function of the Pion
The light-cone wave function of the pion is calculated within the
Nambu-Jona-Lasinio model. The result is used to derive the pion electromagnetic
form factor, charge radius, structure function, pi-gamma transition form factor
and distribution amplitude.Comment: 6 pages, 1 figure, elsart.sty; talk given at 10th International
Light-Cone Meeting on Nonperturbative QCD and Hadron Phenomenology,
Heidelberg, Germany, June 200
The Vacuum Structure of Light-Front -Theory
We discuss the vacuum structure of -theory in 1+1 dimensions
quantised on the light-front . To this end, one has to solve a
non-linear, operator-valued constraint equation. It expresses that mode of the
field operator having longitudinal light-front momentum equal to zero, as a
function of all the other modes in the theory. We analyse whether this zero
mode can lead to a non-vanishing vacuum expectation value of the field
and thus to spontaneous symmetry breaking. In perturbation theory, we get no
symmetry breaking. If we solve the constraint, however, non-perturbatively,
within a mean-field type Fock ansatz, the situation changes: while the vacuum
state itself remains trivial, we find a non-vanishing vacuum expectation value
above a critical coupling. Exactly the same result is obtained within a
light-front Tamm-Dancoff approximation, if the renormalisation is done in the
correct way.Comment: 28 pages LaTeX, 1 Postscript figur
Exact Classical and Quantum Dynamics in Background Electromagnetic Fields
Analytic results for (Q)ED processes in external fields are limited to a few
special cases, such as plane waves. However, the strong focussing of intense
laser fields implies a need to go beyond the plane wave model. By exploiting
Poincar\'e symmetry and superintegrability we show how to construct, and solve
without approximation, new models of laser-particle interactions. We illustrate
the method with a model of a radially polarised (TM) laser beam, for which we
exactly determine the classical orbits and quantum wave functions. Including in
this way the effects of transverse field structure should improve predictions
and analyses for experiments at intense laser facilities.Comment: 6 pages, 3 pdf figure
A novel approach to light-front perturbation theory
We suggest a possible algorithm to calculate one-loop n-point functions
within a variant of light-front perturbation theory. The key ingredients are
the covariant Passarino-Veltman scheme and a surprising integration formula
that localises Feynman integrals at vanishing longitudinal momentum. The
resulting expressions are generalisations of Weinberg's infinite-momentum
results and are manifestly Lorentz invariant. For n = 2 and 3 we explicitly
show how to relate those to light-front integrals with standard energy
denominators. All expressions are rendered finite by means of transverse
dimensional regularisation.Comment: 10 pages, 5 figure
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