## Journal of the Mathematical Society of Japan

### Homogenisation on homogeneous spaces

Xue-Mei LI

#### Abstract

Motivated by collapsing of Riemannian manifolds and inhomogeneous scaling of left invariant Riemannian metrics on a real Lie group $G$ with a sub-group $H$, we introduce a family of interpolation equations on $G$ with a parameter $\epsilon>0$, interpolating hypo-elliptic diffusions on $H$ and translates of exponential maps on $G$ and examine the dynamics as $\epsilon\to 0$. When $H$ is compact, we use the reductive homogeneous structure of Nomizu to extract a converging family of stochastic processes (converging on the time scale $1/\epsilon$), proving the convergence of the stochastic dynamics on the orbit spaces $G/H$ and their parallel translations, providing also an estimate on the rate of the convergence in the Wasserstein distance. Their limits are not necessarily Brownian motions and are classified algebraically by a Peter–Weyl’s theorem for real Lie groups and geometrically using a weak notion of the naturally reductive property; the classifications allow to conclude the Markov property of the limit process. This can be considered as “taking the adiabatic limit” of the differential operators $\mathcal{L}^\epsilon=(1/\epsilon) \sum_k (A_k)^2+(1/\epsilon) A_0+Y_0$ where $Y_0, A_k$ are left invariant vector fields and $\{A_k\}$ generate the Lie-algebra of $H$.

#### Article information

Source
J. Math. Soc. Japan, Volume 70, Number 2 (2018), 519-572.

Dates
First available in Project Euclid: 18 April 2018

https://projecteuclid.org/euclid.jmsj/1524038666

Digital Object Identifier
doi:10.2969/jmsj/07027546

Mathematical Reviews number (MathSciNet)
MR3787732

Zentralblatt MATH identifier
06902434

#### Citation

LI, Xue-Mei. Homogenisation on homogeneous spaces. J. Math. Soc. Japan 70 (2018), no. 2, 519--572. doi:10.2969/jmsj/07027546. https://projecteuclid.org/euclid.jmsj/1524038666

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