Operating just once the naive Foldy-Wouthuysen-Tani transformation on the Schrödinger equation for Qq̄ bound states described by a hamiltonian, we systematically develop a perturbation theory in 1/mQ which enables one to solve the Schrödinger equation to obtain masses and wave functions of the bound states in any order of 1/mQ. It is shown that positive energy projection with respect to the heav...

In this series of lectures, I shall begin with the current investigations on phenomenology of hadron dynamics to demonstrate the importance of solving hadronic bound states within the framework of light-front (LF) QCD. Then, I will describe the basic procedure how to formulate the canonical theory of LFQCD, including lightfront quantization of QCD, light-front gauge singularity, and light-front...

By a closer inspection of the massive Schwinger model within mass perturbation theory we find that, in addition to the n-boson bound states, a further type of hybrid bound states has to be included into the model. Further we explicitly compute the decay widths of the three-boson bound state and of the lightest hybrid bound state. )permanent address: Inst. f. theoret. Physik d. Uni Wien Boltzman...

We develop a perturbation theory that describes bound states of solitons localized in a confined area. External forces and influence of inhomogeneities are taken into account as perturbations to exact solutions of the sine-Gordon equation. We have investigated two special cases of fluxon trapped by a microresistor and decay of a breather under dissipation. Also, we have carried out numerical si...

In this paper, we develop bounds on the distribution function of the empirical mean for general ergodic Markov processes having a spectral gap. Our approach is based on the perturbation theory for linear operators, following the technique introduced by Gillman. Mathematics Subject Classification. 60F10. Received February 19, 2001. Revised September 21 and October 1, 2001.

The lowest (" vector ") and next-lowest (" scalar ") bound-state masses of the massive Schwinger model have been determined recently to a very high accuracy numerically on the lattice. Therefore, improved results for these bound-state masses from analytical calculations are of some interest. Here, we provide such improved results by employing both standard and renormal-ordered (fermion) mass pe...

We study a bound state of fractional D3/D7-branes in the ten-dimensional space IR × IR/Z2 using the boundary state formalism. We construct the boundary actions for this system and we show that higher order terms in the twisted fields are needed in order to satisfy the zero-force condition. We then find the classical background associated to the bound state and show that the gauge theory living ...

A new approach to perturbation theory for a Dirac particle in a central field * Abstract. The explicit semiclassical treatment of logarithmic perturbation theory for the bound-state problem within the framework of the Dirac equation is developed. Avoiding disadvantages of the standard approach in the description of exited states, new handy recursion formulae with the same simple form both for g...

In this report I will be showing how to use meson wave functions and masses to find the decay width difference between the two mass eigenstates of the D0 meson. Due to a large coupling at small energies in QCD, perturbation theory unfortunately does us no good. However, there does exist a model that attempts to keep as much of the QCD Lagrangian as possible. The model was developed by Gerard t’...

Within quantum mechanics model we study the problem of resummation of an asymptotic perturbation series for bound state parameters via optimization of the perturbative expansion. A possible application of the method to the positronium lifetime calculation is also briefly considered.