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Spreading maps (polymorphisms), symmetries of Poisson processes, and matching summation
Yu. A. Neretin Institute for Theoretical and Experimental Physics (Russian Federation State Scientific Center)
Abstract:
The matrix of a permutation is a partial case of Markov transition matrices. In the same way, a measure preserving bijection of a space
$(A,\alpha)$ with finite measure is a partial case of Markov transition operators. A Markov transition operator also can be considered as a map (polymorphism)
$(A,\alpha)\to (A,\alpha)$,
which spreads points of
$(A,\alpha)$ into measures on
$(A,\alpha)$.
Denote by
$\mathbb R^*$ the multiplicative group of positive real numbers and by
$\mathscr M$ the semigroup of measures on
$\mathbb R^*$. In this paper, we discuss
$\mathbb R^*$-polymorphisms
and
$\curlyvee$-polymorphisms, who are analogues of the Markov transition operators (or polymorphisms) for the groups of bijections
$(A,\alpha)\to (A,\alpha)$ leaving the measure
$\alpha$ quasiinvariant; two types of the polymorphisms correspond to the cases, when
$A$ has finite and infinite measure respectively. For the case, when the space
$A$ itself is finite, the
$\mathbb R^*$-polymorphisms are some
$\mathscr M$-valued matrices.
We construct a functor from
$\curlyvee$-polymorphisms to
$\mathbb R^*$-polymorphisms, it is described in terms of summations of
$\mathscr M$-convolution products over matchings of Poisson configurations.
UDC:
517.98 Received: 30.10.2002
Language: English