2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/57673One of the simplest pseudo-Hermitian models with real spectrum (viz., square-well on a real interval I of coordinates) is re-examined. A PT-symmetric complex deformation C of I is introduced and shown tractable via an innovated approach to matching conditions. The result is surprising: an arbitrarily small deformation I -> C implies a sudden collapse (i.e., the spontaneous PT-symmetry breaking) of virtually all the spectrum (i.e., up to its low-energy part).Prepared for presentation during VI-th Meeting of Math. Physicists (Czech. Phys. Soc.), March 19 - 20, 2004, Olomouc, Czech RepublicMathematical Physics81Q05; 47B50text