1,800 research outputs found
Non-perturbative renormalization in Light Front Dynamics with Fock space truncation
Within the framework of the Covariant formulation of Light-Front Dynamics, we
develop a general non-perturbative renormalization scheme based on the Fock
decomposition of the state vector and its truncation. The explicit dependence
of our formalism on the orientation of the light front is essential in order to
analyze the structure of the counterterms and bare parameters needed to
renormalize the theory. We present here a general strategy to determine the
dependence of these quantities on the Fock sectors. We apply our formalism to
QED for the two-body (one fermion and one boson) truncation and recover
analytically, without any perturbative expansion, the renormalization of the
electric charge according to the requirements of the Ward Identity.Comment: 7 pages, 6 figures, to appear in the proceedings of the Workshop on
Light-Cone QCD and Nonperturbative Hadron Physics, Cairns, Australia, July
7-15, 200
Ab initio nonperturbative calculation of physical observables in light-front dynamics. Application to the Yukawa model
We present a coherent and operational strategy to calculate, in a
nonperturbative way, physical observables in light-front dynamics. This
strategy is based on the decomposition of the state vector of any compound
system in Fock components, and on the covariant formulation of light-front
dynamics, together with the so-called Fock sector dependent renormalization
scheme. We apply our approach to the calculation of the electromagnetic form
factors of a fermion in the Yukawa model, in the nontrivial three-body Fock
space truncation, for rather large values of the coupling constant. We find
that, once the renormalization conditions are properly taken into account, the
form factors do not depend on the regularization scale, when the latter is much
larger than the physical masses. We then extend the Fock space by including
antifermion degrees of freedom.Comment: 22 pages, 16 figure
Systematic renormalization scheme in light-front dynamics with Fock space truncation
Within the framework of the covariant formulation of light-front dynamics, we
develop a general non-perturbative renormalization scheme based on the Fock
decomposition of the state vector and its truncation. The counterterms and bare
parameters needed to renormalize the theory depend on the Fock sectors. We
present a general strategy in order to calculate these quantities, as well as
state vectors of physical systems, in a truncated Fock space. The explicit
dependence of our formalism on the orientation of the light front plane is
essential in order to analyze the structure of the counterterms. We apply our
formalism to the two-body (one fermion and one boson) truncation in the Yukawa
model and in QED, and to the three-body truncation in a scalar model. In QED,
we recover analytically, without any perturbative expansion, the
renormalization of the electric charge, according to the requirements of the
Ward identity.Comment: 32 pages, 14 figures, submitted in Phys. Rev.
Recent developments in light-front dynamics
Recent results on relativistic few body systems, obtained in the framework of
light-front dynamics, are briefly reviewed. The following subjects are
discussed: two scalar bosons with ladder and cross ladder kernel; two fermions
with OBE kernel; relativistic scattering (elastic and inelastic); three bosons
and fermions with zero-range interaction; many-body contributions.Comment: 5 pages, 4 figures, to appear in the proceedings of the 19th European
Conference on Few-Body Problems in Physics, Groningen, The Netherlands,
August 23-27, 200
Spin zero particle propagator from a random walk in 3-D space
The propagator of a spin zero particle in coordinate space is derived
supposing that the particle propagates rectilinearly always at the speed of
light and changes its direction in some random points due to a scattering
process.The average path between two scatterings is of the order of the Compton
length.Comment: 8 pages, no figure. accepted by Phys.Lett.
Electromagnetic form factor via Minkowski and Euclidean Bethe-Salpeter amplitudes
The electromagnetic form factors calculated through Euclidean Bethe-Salpeter
amplitude and through the light-front wave function are compared with the one
found using the Bethe-Salpeter amplitude in Minkowski space. The form factor
expressed through the Euclidean Bethe-Salpeter amplitude (both within and
without static approximation) considerably differs from the Minkowski one,
whereas form factor found in the light-front approach is almost
indistinguishable from it.Comment: 3 pages, 2 figures. Contribution to the proceedings of the 20th
International Conference on Few-Body Problems in Physics (FB20), Pisa, Italy,
September 10-14, 2007. To be published in "Few-Body Systems
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