English

Quasi-invariance of completely random measure

Probability 2018-03-07 v1

Abstract

Let XX be a locally compact Polish space. Let K(X)\mathbb K(X) denote the space of discrete Radon measures on XX. Let μ\mu be a completely random discrete measure on XX, i.e., μ\mu is (the distribution of) a completely random measure on XX that is concentrated on K(X)\mathbb K(X). We consider the multiplicative (current) group C0(XR+)C_0(X\to\mathbb R_+) consisting of functions on XX that take values in R+=(0,)\mathbb R_+=(0,\infty) and are equal to 1 outside a compact set. Each element θC0(XR+)\theta\in C_0(X\to\mathbb R_+) maps K(X)\mathbb K(X) onto itself; more precisely, θ\theta sends a discrete Radon measure isiδxi\sum_i s_i\delta_{x_i} to iθ(si)siδxi\sum_i \theta(s_i)s_i\delta_{x_i}. Thus, elements of C0(XR+)C_0(X\to\mathbb R_+) transform the weights of discrete Radon measures. We study conditions under which the measure μ\mu is quasi-invariant under the action of the current group C0(XR+)C_0(X\to\mathbb R_+) and consider several classes of examples. We further assume that X=RdX=\mathbb R^d and consider the group of local diffeomorphisms Diff0(X)\operatorname{Diff}_0(X). Elements of this group also map K(X)\mathbb K(X) onto itself. More precisely, a diffeomorphism φDiff0(X)\varphi\in \operatorname{Diff}_0(X) sends a discrete Radon measure isiδxi\sum_i s_i\delta_{x_i} to isiδφ(xi)\sum_i s_i\delta_{\varphi(x_i)}. Thus, diffeomorphisms from Diff0(X)\operatorname{Diff}_0(X) transform the atoms of discrete Radon measures. We study quasi-invariance of μ\mu under the action of Diff0(X)\operatorname{Diff}_0(X). We finally consider the semidirect product G:=Diff0(X)×C0(XR+)\mathfrak G:=\operatorname{Diff}_0(X)\times C_0(X\to \mathbb R_+) and study conditions of quasi-invariance and partial quasi-invariance of μ\mu under the action of G\mathfrak G.

Keywords

Cite

@article{arxiv.1803.02116,
  title  = {Quasi-invariance of completely random measure},
  author = {Habeebat O. Ibraheem and Eugene Lytvynov},
  journal= {arXiv preprint arXiv:1803.02116},
  year   = {2018}
}

Comments

The paper is to appear in Methods of Functional Analysis and Topology