Spectral densities describing off-white noises

Occupation densities for SPDE's with reflection

We consider the solution (u,η) of the white-noise driven stochastic partial differential equation with reflection on the space interval [0,1] introduced by Nualart and Pardoux. First, we prove that at any fixed time t>0, the measure η([0,t]\times dθ) is absolutely continuous w.r.t. the Lebesgue measure dθon (0,1). We characterize the density as a family of additive functionals of u, and we interpret it as a renormalized local time at 0 of (u(t,θ))_{t\geq 0}. Finally we study the behaviour of ηat the boundary of [0,1]. The main technical novelty is a projection principle from the Dirichlet spac…

Existence of densities for the dynamic $Φ^4_3$ model

We apply Malliavin calculus to the $Φ^4_3$ equation on the torus and prove existence of densities for the solution of the equation evaluated at regular enough test functions. We work in the framework of regularity structures and rely on Besov-type spaces of modelled distributions in order to prove Malliavin differentiability of the solution. Our result applies to a large family of Gaussian space-time noises including white noise, in particular the noise may be degenerate as long as it is sufficiently rough on small scales.

乘性白噪声驱动的非线性SPDE界面的有效动力学

Effective dynamics of interfaces for nonlinear SPDEs driven by multiplicative white noise

本文研究乘性白噪声驱动的无穷维SPDE界面动力学，利用有限维SDE推导慢流形上的有效方程，验证SPDE与耦合系统在小随机扰动下的等价性，并在四类随机方程中展示应用。

Derivation of Fokker-Planck equations for stochastic dynamical systems under excitation of multiplicative non-Gaussian white noise

Fokker-Planck equations describe time evolution of probability densities of stochastic dynamical systems and play an important role in quantifying propagation and evolution of uncertainty. Although Fokker-Planck equations can be written explicitly for nonlinear dynamical systems excited by Gaussian white noise, they are not available in general for nonlinear dynamical systems excited by multiplicative non-Gaussian white noise. Marcus stochastic differential equations are often appropriate models in engineering and physics for stochastic dynamical systems excited by non-Gaussian white noise. In…

White-noise driven conditional McKean-Vlasov limits for systems of particles with simultaneous and random jumps

We study the convergence of $N-$particle systems described by SDEs driven by Brownian motion and Poisson random measure, where the coefficients depend on the empirical measure of the system. Every particle jumps with a jump rate depending on its position and on the empirical measure of the system. Jumps are simultaneous, that is, at each jump time, all particles of the system are affected by this jump and receive a random jump height that is centred and scaled in $N^{-1/2}.$ This particular scaling implies that the limit of the empirical measures of the system is random, describing the conditi…

Logarithmic asymptotics of the densities of SPDEs driven by spatially correlated noise

We consider the family of stochastic partial differential equations indexed by a parameter $\eps\in(0,1]$, \begin{equation*} Lu^{\eps}(t,x) = \epsσ(u^\eps(t,x))\dot{F}(t,x)+b(u^\eps(t,x)), \end{equation*} $(t,x)\in(0,T]\times\Rd$ with suitable initial conditions. In this equation, $L$ is a second-order partial differential operator with constant coefficients, $σ$ and $b$ are smooth functions and $\dot{F}$ is a Gaussian noise, white in time and with a stationary correlation in space. Let $p^\eps_{t,x}$ denote the density of the law of $u^\eps(t,x)$ at a fixed point $(t,x)\in(0,T]\times\Rd$. We …

源于具白噪声势多体量子系统的三维随机Hartree NLS

Stochastic Hartree NLS in 3d coming from a Many-Body Quantum System with White Noise Potential

本文研究T^3上具白噪声外势的defocusing Hartree NLS，建立Anderson Hamiltonian的Strichartz型估计并证明NLS的局部和整体适定性，同时将其确立为多体Bosonic系统的有效方程，证明了向BBGKY hierarchy的收敛性。