The MIT bag operator was introduced to describe quark confinement within hadrons. Mathematically, it corresponds to the Dirac operator in bounded domains with special (local) boundary conditions, which can be seen as a relativistic analog of the Dirichlet Laplacian. We show that many results on the Dirac operator with MIT bag boundary conditions in smooth domains (in particular, the H1-self-adjointness and the infinite mass limit) can be carried over to the case of piecewise smooth convex domains.
