Michelangeli, AlessandroOttolini, Andrea2017-01-162017-01-162016-12https://openscience.sissa.it/handle/1963/35267We reconstruct the whole family of self-adjoint Hamiltonians of Ter-Martirosyan–Skornyakov type for a system of two identical fermions coupled with a third particle of different nature through an interaction of zero range. We proceed through an operator-theoretic approach based on the self-adjoint extension theory of Kreĭn, Višik, and Birman. We identify the explicit ‘Kreĭn-Višik–Birman extension parameter’ as an operator on the ‘space of charges’ for this model (the ‘Kreĭn space’) and we come to formulate a sharp conjecture on the dimensionality of its kernel. Based on our conjecture, for which we also discuss an amount of evidence, we explain the emergence of a multiplicity of extensions in a suitable regime of masses and we reproduce for the first time the previous partial constructions obtained by means of an alternative quadratic form approach.enPoint interactionsSingular perturbations of the LaplacianSelf-adjoint ex- tensionsKreĭn-Višik-Birman theoryTer-Martirosyan{Skornyakov operatorsFermionic models of zero-range interactionsPreprint