arXiv subjects

Enrico Priola

Publications and source records attributed to Enrico Priola.

42 records · Page 3Linked to original sources

arXiv2009

Uniqueness in Law for Stochastic Boundary Value Problems

We study existence and uniqueness of solutions for second order ordinary stochastic differential equations with Dirichlet boundary conditions on a given interval. In the first part of the paper we provide sufficient conditions to ensure pathwise uniqueness, extending some known results. In the second part we show sufficient conditions to have the weaker concept of uniqueness in law and provide a significant example. Such conditions involve a linearized equation and are of different type with respect to the ones which are usually imposed to study pathwise uniqueness. This seems to be the first paper which deals with uniqueness in law for (anticipating) stochastic boundary value problems. We mainly use functional analytic tools and some concepts of Malliavin Calculus.

math.CA↗

arXiv2009

On linear evolution equations with cylindrical Lévy noise

We study an infinite-dimensional Ornstein-Uhlenbeck process $(X_t)$ in a given Hilbert space $H$. This is driven by a cylindrical symmetric Lévy process without a Gaussian component and taking values in a Hilbert space $U$ which usually contains $H$. We give if and only if conditions under which $X_t$ takes values in $H$ for some $t>0$ or for all $t>0$. Moreover, we prove irreducibility for $(X_t)$.

math.AP↗

arXiv2009

Well-posedness of the transport equation by stochastic perturbation

We consider the linear transport equation with a globally Holder continuous and bounded vector field. While this deterministic PDE may not be well-posed, we prove that a multiplicative stochastic perturbation of Brownian type is enough to render the equation well-posed. This seems to be the first explicit example of partial differential equation that become well-posed under the influece of noise. The key tool is a differentiable stochastic flow constructed and analysed by means of a special transformation of the drift of Ito-Tanaka type.

math.AP↗

arXiv2008

Densities for Ornstein-Uhlenbeck processes with jumps

We consider an Ornstein-Uhlenbeck process with values in R^n driven by a Lévy process (Z_t) taking values in R^d with d possibly smaller than n. The Lévy noise can have a degenerate or even vanishing Gaussian component. Under a controllability condition and an assumption on the Lévy measure of (Z_t), we prove that the law of the Ornstein-Uhlenbeck process at any time t>0 has a density on R^n. Moreover, when the Lévy process is of $α$-stable type, $α\in (0,2)$, we show that such density is a $C^{\infty}$-function.

math.PR↗

arXiv2007

Global Schauder estimates for a class of degenerate Kolmogorov equations

We consider a class of possibly degenerate second order elliptic operators $\cal A$ on $\R^n$. This class includes hypoelliptic Ornstein-Uhlenbeck type operators having an additional first order term with unbounded coefficients. We establish global Schauder estimates in Hölder spaces both for elliptic equations and for parabolic Cauchy problems involving ${\cal A}$. The Hölder function spaces are defined with respect to a non-euclidean metric related to the operator $\cal A$.

math.AP↗

arXiv2005

Norm discontinuity and spectral properties of Ornstein-Uhlenbeck semigroups

Let $E$ be a real Banach space. We study the Ornstein-Uhlenbeck semigroup $P(t)$ associated with the Ornstein-Uhlenbeck operator $$ Lf(x) = \frac12 {\rm Tr} Q D^2 f(x) + .$$ Here $Q$ is a positive symmetric operator from $E^*$ to $E$ and $A$ is the generator of a $C_0$-semigroup $S(t)$ on $E$. Under the assumption that $P$ admits an invariant measure $μ$ we prove that if $S$ is eventually compact and the spectrum of its generator is nonempty, then $$\n P(t)-P(s)\n_{L^1(E,μ)} = 2$$ for all $t,s\ge 0$ with $t\not=s$. This result is new even when $E = \R^n$. We also study the behaviour of $P$ in the space $BUC(E)$. We show that if $A\not=0$ there exists $t_0>0$ such that $$\n P(t)-P(s)\n_{BUC(E)} = 2$$ for all $0\le t,s\le t_0$ with $t\not=s$. Moreover, under a nondegeneracy assumption or a strong Feller assumption, the following dichotomy holds: either $$ \n P(t)- P(s)\n_{BUC(E)} = 2$$ for all $t,s\ge 0$, \ $t\not=s$, or $S$ is the direct sum of a nilpotent semigroup and a finite-dimensional periodic semigroup. Finally we investigate the spectrum of $L$ in the spaces $L^1(E,μ)$ and $BUC(E)$.

math.FA↗