The Kaczmarz algorithm of successive projections suggests the following concept. A sequence $\left(e_k\right)$ of unit vectors in a Hilbert space is said to be effective if for each vector x in the space the sequence (xₙ) converges to x where (xₙ) is defined inductively: x₀ = 0 and $xₙ=x_{n-1}+\alpha ₙeₙ$, where $\alpha ₙ=⟨x-x_{n-1},eₙ⟩$. We prove the effectivity of some sequences in Hilbert spaces. We generalize the concept of effectivity to sequences of vectors in Banach spaces and we prove some results for this more general concept.

We consider the parabolic Anderson model, the Cauchy problem for the heat equation with random potential in ℤd. We use i.i.d. potentials ξ:ℤd→ℝ in the third universality class, namely the class of almost bounded potentials, in the classification of van der Hofstad, König and Mörters [Commun. Math. Phys.267 (2006) 307–353]. This class consists of potentials whose logarithmic moment generating function is regularly varying with parameter γ=1, but do not belong to the class of so-called double-exponentially...

En este trabajo consideramos ecuaciones integrales estocásticas tipo Ito, que son construidas con integral estocástica de Cabaña, sobre espacios de Hilbert separables y respecto de operadores de Wiener. Se estudian las propiedades de regularidad del proceso solución, analizando su comportamiento respecto de la variación de los coeficientes de la ecuación y de las condiciones iniciales.

 Abstract. The main result of the present paper deals with the existence of solutions of random functional-differential inclusions of the form ẋ(t, ω) ∈ G(t, ω, x(·, ω), ẋ(·, ω)) with G taking as its values nonempty compact and convex subsets of n-dimensional Euclidean space $R^n$.

Let $(\Omega ,\Sigma )$ be a measurable space and $C$ a nonempty bounded closed convex separable subset of $p$-uniformly convex Banach space $E$ for some $p>1$. We prove random fixed point theorems for a class of mappings $T\Omega \times C\to C$ satisfying: for each $x,y\in C$, $\omega \in \Omega$ and integer $n\ge 1$, $$\parallel T^n(\omega ,x)-T^n(\omega ,y)\parallel \le a\left(\omega \right)·\parallel x-y\parallel +b\left(\omega \right)\{\parallel x-T^n(\omega ,x)\parallel +\parallel y-T^n(\omega ,y)\parallel \}+c\left(\omega \right)\{\parallel x-T^n(\omega ,y)\parallel +\parallel y-T^n(\omega ,x)\parallel \},$$ where $a,b,c\Omega \to [0,\infty )$ are functions satisfying certain conditions and $T^n(\omega ,x)$ is the value at $x$ of the $n$-th iterate of the mapping $T(\omega ,·)$. Further we establish for these mappings some random fixed point theorems in a Hilbert space, in $L^p$ spaces, in Hardy spaces $H^p$ and in Sobolev spaces $H^{k,p}$...