By a continuous degenerate semigroup we mean a strongly continuous mapping T : R+ ! L(X) having the semigroup property. Thus, T (0) is a projection which may be different from the identity. The main theorem is a Trotter-Kato type approximation result for such degenerate semigroups. It is used to study convergence of heat semigroups with respect to variable domains.
"APPROXIMATION OF DEGENERATE SEMIGROUPS." Taiwanese J. Math. 5 (2) 279 - 295, 2001. https://doi.org/10.11650/twjm/1500407337