4 papers
On pure contractive semigroups
Shubham Rastogi, Vijaya Kumar U
We find the commutant of a pure contractive semigroup on a Hilbert space. We demonstrate that any tuple of doubly commuting pure contractive semigroups can be dilated to a tuple of…
Functions with image in a strip
Tirthankar Bhattacharyya, Anthony G. O'Farrell, Shubham Rastogi +1
We consider holomorphic functions on the unit disc whose images are contained in a strip of the complex plane. Under an additional condition, such functions are constants. We also…
Doubly commuting and dual doubly commuting semigroups of isometries
Tirthankar Bhattacharyya, Shubham Rastogi, Vijaya Kumar U
Structures of commuting semigroups of isometries under certain additional assumptions like double commutativity or dual double commutativity are found.
On factorization of the shift semigroup
Tirthankar Bhattacharyya, Shubham Rastogi, Kalyan B. Sinha +1
Let $\E$ be a finite dimensional Hilbert space. This note finds all factorizations of the right shift semigroup $§^\E=(S_t^\E)_{t\ge 0}$ on $L^2(\R_+,\E)$ into the product of c…