2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/185674We describe the spontaneous partial breaking of $N=1 D=10$ supersymmetry to $N=(1,0) d=6$ and its dimensionally-reduced versions in the framework of the nonlinear realizations method. The basic Goldstone superfield is $N=(1,0) d=6$ hypermultiplet superfield satisfying a nonlinear generalization of the standard hypermultiplet constraint. We interpret the generalized constraint as the manifestly worldvolume supersymmetric form of equations of motion of the Type I super 5-brane in D=10. The related issues we address are a possible existence of brane extension of off-shell hypermultiplet actions, the possibility to utilize vector $N=(1,0) d=6$ supermultiplet as the Goldstone one, and the description of 1/4 breaking of $N=1 D=11$ supersymmetry.14 pages, LaTeX, Extended and corrected version to appear in Physics Letters B, PACS: 11.17.+y,11.30.PbHigh Energy Physics - Theorytext