5 papers
Foguel-type operators similar to contractions
Nilanjan Das, Soma Das, Jaydeb Sarkar
Pisier's celebrated counterexample to Halmos's similarity-to-contractions problem was based on upper triangular block operator matrices involving three classical opera…
New norm estimate for composition operators
Preeti Kumari, P. Muthukumar, Jaydeb Sarkar
The classical Littlewood's theorem establishes boundedness and provides a norm estimate for composition operators on the Hardy space. In this paper, we offer an alternative proof o…
Invariant subspaces of Brownian shifts on vector-valued Hardy spaces
Nilanjan Das, Soma Das, Jaydeb Sarkar
We characterize invariant subspaces of Brownian shifts on vector-valued Hardy spaces. We also solve the unitary equivalence problem for the invariant subspaces of these shifts.
Finite-dimensional model spaces invariant under composition operators
P. Muthukumar, Jaydeb Sarkar, Batzorig Undrakh
Finite-dimensional model spaces are quotient spaces of the Hardy space on the open unit disc, determined by finite Blaschke products. Composition operators, on the other hand, act…
Invariant subspaces and the -property of Brownian Shifts
Nilanjan Das, Soma Das, Jaydeb Sarkar
We consider the restriction of Brownian shifts to their invariant subspaces and classify when they are unitarily equivalent. Additionally, we prove an asymptotic property stating t…