2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/199936The 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 $Γ_q$-functions. In the isotropic limit corresponding results for the open XXX chain are also reproduced.8 pages LatexHigh Energy Physics - TheoryStatistical MechanicsMathematical PhysicsExactly Solvable and Integrable Systemstext