We analyse the Lorentz structures of weak decay matrix elements between meson states of arbitrary spin. Simplifications arise in the transition amplitudes for a heavy meson decaying into the light one via a Bethe-Salpeter approach which incorporates heavy quark symmetry. Phenomenological consequences of our results on several semileptonic, nonleptonic and flavour changing neutral current-induce...

The most general physical boundary S-matrix for the open XXZ spin chain in the non-critical regime (cosh(η) > 1) is derived starting from the bare Bethe ansazt equations. The boundary S-matrix as expected is expressed in terms of Γq-functions. In the isotropic limit corresponding results for the open XXX chain are also reproduced. e-mail: [email protected]

In this work, we employ the Bethe-Salpeter (B-S) equation to investigate the spectra of free diquarks and their B-S wave functions. We find that the B-S approach can be consistently applied to study the diqaurks with two heavy quarks or one heavy and one light quarks, but for two light-quark systems, the results are not reliable. There are a few free parameters in the whole scenario which can o...