11 research outputs found
Bound-State Variational Wave Equation For Fermion Systems In QED
We present a formulation of the Hamiltonian variational method for QED which
enables the derivation of relativistic few-fermion wave equation that can
account, at least in principle, for interactions to any order of the coupling
constant. We derive a relativistic two-fermion wave equation using this
approach. The interaction kernel of the equation is shown to be the generalized
invariant M-matrix including all orders of Feynman diagrams. The result is
obtained rigorously from the underlying QFT for arbitrary mass ratio of the two
fermions. Our approach is based on three key points: a reformulation of QED,
the variational method, and adiabatic hypothesis. As an application we
calculate the one-loop contribution of radiative corrections to the two-fermion
binding energy for singlet states with arbitrary principal quantum number ,
and . Our calculations are carried out in the explicitly covariant
Feynman gauge.Comment: 26 page
Exact two-particle eigenstates in partially reduced QED
We consider a reformulation of QED in which covariant Green functions are
used to solve for the electromagnetic field in terms of the fermion fields. It
is shown that exact few-fermion eigenstates of the resulting Hamiltonian can be
obtained in the canonical equal-time formalism for the case where there are no
free photons. These eigenstates lead to two- and three-body Dirac-like
equations with electromagnetic interactions. Perturbative and some numerical
solutions of the two-body equations are presented for positronium and
muonium-like systems, for various strengths of the coupling.Comment: 33 pages, LaTex 2.09, 4 figures in EPS forma
Exact spinor-scalar bound states in a QFT with scalar interactions
We study two-particle systems in a model quantum field theory, in which
scalar particles and spinor particles interact via a mediating scalar field.
The Lagrangian of the model is reformulated by using covariant Green's
functions to solve for the mediating field in terms of the particle fields.
This results in a Hamiltonian in which the mediating-field propagator appears
directly in the interaction term. It is shown that exact two-particle
eigenstates of the Hamiltonian can be determined. The resulting relativistic
fermion-boson equation is shown to have Dirac and Klein-Gordon one-particle
limits. Analytic solutions for the bound state energy spectrum are obtained for
the case of massless mediating fields.Comment: 12 pages, RevTeX, 1 figur
Path Integral Variational Methods for Strongly Correlated Systems
We introduce a new approach to highly correlated systems which generalizes
the Fermi Hypernetted Chain and Correlated Basis Function techniques. While the
latter approaches can only be applied to systems for which a nonrelativistic
wave function can be defined, the new approach is based on the variation of a
trial hamiltonian within a path integral framework and thus can also be applied
to relativistic and field theoretical problems. We derive a diagrammatic scheme
for the new approach and show how a particular choice of the trial hamiltonian
corresponds exactly to the use of a Jastrow correlated ansatz for the wave
function in the Fermi Hypernetted Chain approach. We show how our new approach
can be used to find upper bounds to ground state energies in systems which the
FHNC cannot handle, including those described by an energy-dependent effective
hamiltonian. We demonstrate our approach by applying it to a quantum field
theoretical system of interacting pions and nucleons.Comment: 35 RevTeX pages, 7 separated ps figures available on reques
Solitosynthesis of Q-balls
We study the formation of Q-balls in the early universe, concentrating on
potentials with a cubic or quartic attractive interaction. Large Q-balls can
form via solitosynthesis, a process of gradual charge accretion, provided some
primordial charge assymetry and initial ``seed'' Q-balls exist. We find that
such seeds are possible in theories in which the attractive interaction is of
the form , with a light ``Higgs'' mass. Condensate formation
and fragmentation is only possible for masses in the sub-eV range;
these Q-balls may survive untill present.Comment: 9 pages, 1 figur
Collisions entre un positron et une molécule d'hydrogène avec excitation de vibrations
The elastic scattering of a positron from a hydrogen molecule has been studied in the fixed nuclei approximation, with a one centre formalism, for several internuclear separations. The adiabatic nuclear approximation has then been used to compute (rotational) vibrational excitation cross-sections.La diffusion élastique positron-molécule d'hydrogène a été étudiée dans l'approximation des noyaux fixes, avec un formalisme à un centre, pour plusieurs distances internucléaires. Puis l'approximation adiabatique nucléaire a été utilisée pour calculer des sections efficaces d'excitation de (rotation-) vibration