We present an estimate for a class of unbounded perturbations of the generator of an exponentially stable semigroup. When this estimate is satisfied then the perturbed operator still generates an exponentially stable semigroup. For generators of holomorhic semigroups the class of allowed perturbations contains unbounded operators of the form HA”. with (Y < 4. The estimate is given in terms of t...

A theorem of Hegerfeldt shows that if the spectrum of the Hamiltonian is bounded from below, then the propagation speed of certain probabilities does not have an upper bound. We prove a theorem analogous to Hegerfeldt’s that appertains to asymmetric time evolutions given by a semigroup of operators. As an application, we consider a characterization of relativistic quasistable states by irreduci...

With every E0–semigroup (acting on the algebra of of bounded operators on a separable infinite-dimensional Hilbert space) there is an associated Arveson system. One of the most important results about Arveson systems is that every Arveson system is the one associated with an E0–semigroup. In these notes we give a new proof of this result that is considerably simpler than the existing ones and a...

Let L=??+V be a Schrödinger operator, where the potential V belongs to reverse Hölder class. By subordinative formula, we introduce fractional heat semigroup {e?tL?}t&gt;0, 0&lt;?&lt;1, associated with L. aid of fundamental solution equation: ?tu+Lu=?tu??u+Vu=0, estimate gradient and time-fractional derivatives kernel K?,tL(·,·), respectively. This method is independent Fourier transform, can a...

and Applied Analysis 3 In 15 the asymptotic behavior of 1.1 was studied and it was proven the existence of a global attractor for the semigroup associated to 1.1 , that is, the semigroup of operators defined as S t : u0 ∈ H −→ u t ∈ H, 1.4 The main tool in proving the existence of a global attractor is to show the existence of an absorbing set inH2 I see Theorem 1.1 in 1 . Theorem 1.1 see 15 . ...

Let $S$ be a semitopological semigroup. The $wap-$ compactification of semigroup S, is a compact semitopological semigroup with certain universal properties relative to the original semigroup, and the $Lmc-$ compactification of semigroup $S$ is a universal semigroup compactification of $S$, which are denoted by $S^{wap}$ and $S^{Lmc}$ respectively. In this paper, an internal construction of ...

We prove that in a large class of Banach spaces analytic functions the unit disc ⅅ an (unbounded) operator Af = G · f′ + g f with G, generates C0-semigroup weighted composition operators if and only it C0-semigroup. Particular instances such are classical Hardy spaces. Our result generalizes previous results this context is related to cocycles flows on Likewise, for non-separable X contained Bl...

By using the technique of factoring weakly compact operators through reflexive Banach spaces we prove that a class of ordinary differential equations with Lipschitz continuous perturbations has a strong solution when the problem is governed by a closed linear operator generating a strongly continuous semigroup of compact operators.