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Strong convergence theorems of k -strict pseudo-contractions in Hilbert spaces

Xiao Long Qin, Shin Min Kang, Mei Juan Shang (2009)

Czechoslovak Mathematical Journal

Let K be a nonempty closed convex subset of a real Hilbert space H such that K ± K K , T K H a k -strict pseudo-contraction for some 0 k < 1 such that F ( T ) = { x K x = T x } . Consider the following iterative algorithm given by x 1 K , x n + 1 = α n γ f ( x n ) + β n x n + ( ( 1 - β n ) I - α n A ) P K S x n , n 1 , where S K H is defined by S x = k x + ( 1 - k ) T x , P K is the metric projection of H onto K , A is a strongly positive linear bounded self-adjoint operator, f is a contraction. It is proved that the sequence { x n } generated by the above iterative algorithm converges strongly to a fixed point of T , which solves a variational inequality related...

Strong mixing Markov semigroups on C₁ are meager

Wojciech Bartoszek, Beata Kuna (2006)

Colloquium Mathematicae

We show that the set of those Markov semigroups on the Schatten class ₁ such that in the strong operator topology l i m t T ( t ) = Q , where Q is a one-dimensional projection, form a meager subset of all Markov semigroups.

Strong q -variation inequalities for analytic semigroups

Christian Le Merdy, Quanhua Xu (2012)

Annales de l’institut Fourier

Let T : L p ( Ω ) L p ( Ω ) be a positive contraction, with 1 &lt; p &lt; . Assume that T is analytic, that is, there exists a constant K 0 such that T n - T n - 1 K / n for any integer n 1 . Let 2 &lt; q &lt; and let v q be the space of all complex sequences with a finite strong q -variation. We show that for any x L p ( Ω ) , the sequence [ T n ( x ) ] ( λ ) n 0 belongs to v q for almost every λ Ω , with an estimate ( T n ( x ) ) n 0 L p ( v q ) C x p . If we remove the analyticity assumption, we obtain an estimate ( M n ( T ) x ) n 0 L p ( v q ) C x p , where M n ( T ) = ( n + 1 ) - 1 k = 0 n T k denotes the ergodic average of T . We also obtain similar results for strongly continuous semigroups ( T t ) t 0 of positive...

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