On infinite-dimensional limit of the Steinberg representations
We present a construction of the Steinberg representation admitting an automatic pass to an infinite-dimensional limit.
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arXiv subjects
Yury A. Neretin
Publications and source records attributed to Yury A. Neretin.
On multiplication of double cosets for $\GL(\infty)$ over a finite field
We consider a group $GL(\infty)$ and its parabolic subgroup $B$ corresponding to partition $\infty=\infty+m+\infty$. Denote by $P$ the kernel of the natural homomorphism $B\to GL(m)$. We show that the space of double cosets of $GL(\infty)$ by $P$ admits a natural structure of a semigroup. In fact this semigroup acts in subspaces of $P$-fixed vectors of some unitary representations of $GL(\infty)$ over finite field.
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The space $L^2$ on semi-infinite Grassmannian over finite field
We construct a $GL$-invariant measure on a semi-infinite Grassmannian over a finite field, describe the natural group of symmetries of this measure, and decompose the space $L^2$ over the Grassmannian on irreducible representations. The spectrum is discrete, spherical functions on the Grassmannian are given in terms of the Al Salam--Carlitz orthogonal polynomials. We also construct an invariant measure on the corresponding space of flags.
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On $p$-adic colligations and 'rational maps' of Bruhat-Tits trees
Consider matrices of order $k+N$ over $p$-adic field determined up to conjugations by elements of $GL$ over $p$-adic integers. We define a product of such conjugacy classes and construct the analog of characteristic functions (transfer functions), they are maps from Bruhat-Tits trees to Bruhat-Tits buildings. We also examine categorical quotient for usual operator colligations.
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On concentration of convolutions of double cosets at infinite-dimensional limit
For infinite-dimensional groups $G\supset K$ the double cosets $K\setminus G/K$ quite often admit a structure of a semigroup; these semigroups act in $K$-fixed vectors of unitary representations of $G$. We show that such semigroups can be obtained as limits of double cosets hypergroups (or Iwahori--Hecke type algebras) on finite-dimensional (or finite) groups.
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Index hypergeometric integral transform
This is a brief overview of the index hypergeometric transform (other terms for this integral operator are: Olevskii transform, Jacobi transform, generalized Mehler--Fock transform). We discuss applications of this transform to special functions and harmonic analysis. The text is an addendum to the Russian edition of the book by G.E.Andrews, R.Askey, and R.Roy, Special Functions, Encycl. of Math. Appl. 71, Cambridge Univ. Press, 1999.
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On topologies on Lie braid groups
We discuss groups corresponding to Kohno Lie algebra of infinitesimal braids and actions of such groups. We construct homomorphisms of Lie braid groups to the group of symplectomorphisms of the space of point configurations in $R^3$ and to groups of symplectomorphisms of coadjoint orbits of SU(n).
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Hua measures on the space of $p$-adic matrices and inverse limits of Grassmannians
We construct $p$-adic counterparts of Hua measures, measures on inverse limits of $p$-adic Grassmannians, and describe natural groups of symmetries of such measures.
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Symmetries of Gaussian measures and operator colligations
Consider an infinite-dimensional linear space equipped with a Gaussian measure and the group $GL(\infty)$ of linear transformations that send the measure to equivalent one. Limit points of $GL(\infty)$ can be regarded as 'spreading' maps (polymorphisms). We show that the closure of $GL(\infty)$ in the semigroup of polymorphisms contains a certain semigroup of operator colligations and write explicit formulas for action of operator colligations by polymorphisms of the space with Gaussian measure.
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Infinite symmetric group and combinatorial descriptions of semigroups of double cosets
We show that double cosets of the infinite symmetric group with respect to some special subgroups admit natural structures of semigroups. We interpret elements of such semigroups in combinatorial terms (chips, colored graphs, two-dimensional surfaces with polygonal tiling) and describe explicitly the multiplications.
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Sphericity and multiplication of double cosets for infinite-dimensional classical groups
We construct spherical subgroups in infinite-dimensional classical groups $G$ (usually they are not symmetric and their finite-dimensional analogs are not spherical). We present a structure of a semigroup on double cosets $L\setminus G/L$ for various subgroups $L$ in $G$, moreover these semigroups act in spaces of $L$-fixed vectors in unitary representations of $G$. We also obtain semigroup envelops of groups $G$ generalizing constructions of operator colligations.
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Multi-operator colligations and multivariate characteristic functions
In the spectral theory of non-self-adjoint operators there is a well-known operation of product of operator colligations. Many similar operations appear in the theory of infinite-dimensional groups as multiplications of double cosets. We construct characteristic functions for such double cosets and get semigroups of matrix-valued functions in matrix balls.
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Spectral data for pairs of matrices of order 3 and action of the group $GL(2,Z)$
The group $GL(2,Z)$ acts in a natural way on the set of pairs of $n\times n$-matrices determined up to a simultaneous conjugation. For $n=3$ we write explicit formulas for action of generators of $GL(2,Z)$ in the terms of spectral data of matrices, i.e., spectral curves and line bundles.
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On spherical functions on the group $SU(2)\times SU(2) \times SU(2)$
We write a generating function for all spherical functions on the product of several copies of SU(2).
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