## Annals of Probability

### Regularity of laws and ergodicity of hypoelliptic SDEs driven by rough paths

#### Abstract

We consider differential equations driven by rough paths and study the regularity of the laws and their long time behavior. In particular, we focus on the case when the driving noise is a rough path valued fractional Brownian motion with Hurst parameter $H\in(\frac{1}{3},\frac{1}{2}]$. Our contribution in this work is twofold.

First, when the driving vector fields satisfy Hörmander’s celebrated “Lie bracket condition,” we derive explicit quantitative bounds on the inverse of the Malliavin matrix. En route to this, we provide a novel “deterministic” version of Norris’s lemma for differential equations driven by rough paths. This result, with the added assumption that the linearized equation has moments, will then yield that the transition laws have a smooth density with respect to Lebesgue measure.

Our second main result states that under Hörmander’s condition, the solutions to rough differential equations driven by fractional Brownian motion with $H\in(\frac{1}{3},\frac{1}{2}]$ enjoy a suitable version of the strong Feller property. Under a standard controllability condition, this implies that they admit a unique stationary solution that is physical in the sense that it does not “look into the future.”

#### Article information

Source
Ann. Probab., Volume 41, Number 4 (2013), 2544-2598.

Dates
First available in Project Euclid: 3 July 2013

https://projecteuclid.org/euclid.aop/1372859760

Digital Object Identifier
doi:10.1214/12-AOP777

Mathematical Reviews number (MathSciNet)
MR3112925

Zentralblatt MATH identifier
1288.60068

#### Citation

Hairer, Martin; Pillai, Natesh S. Regularity of laws and ergodicity of hypoelliptic SDEs driven by rough paths. Ann. Probab. 41 (2013), no. 4, 2544--2598. doi:10.1214/12-AOP777. https://projecteuclid.org/euclid.aop/1372859760

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