Extension operator for the MIT bag model (Q782427)

The authors consider a bounded domain of the three-dimensional Euclidean space, whose boundary has a suitable regularity property. They consider the Dirac operator with so-called MIT conditions, which are a natural class of boundary conditions. An extension operator from the boundary to the interior is constructed, in the spirit of a more classical one regarding Sobolev spaces. The proof consists in defining it first for the half-space, and then using localization techniques. Self-adjointness of the Dirac operator in the naturally-associated functional space is also shown.