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Unitary Representations of Lie Groups with Reflection Symmetry
Journal article   Open access   Peer reviewed

Unitary Representations of Lie Groups with Reflection Symmetry

Palle E.T Jorgensen and Gestur Ólafsson
Journal of functional analysis, Vol.158(1), pp.26-88
1998
DOI: 10.1006/jfan.1998.3285
url
https://doi.org/10.1006/jfan.1998.3285View
Published (Version of record) Open Access

Abstract

We consider the following class of unitary representations π of some (real) Lie group G which has a matched pair of symmetries described as follows: (i) Suppose G has a period-2 automorphism τ , and that the Hilbert space H ( π ) carries a unitary operator J such that Jπ =( π ∘ τ ) J (i.e., selfsimilarity ). (ii) An added symmetry is implied if H ( π ) further contains a closed subspace K 0 having a certain order-covariance property, and satisfying the K 0 -restricted positivity : ⦠ v | Jv ⦔⩾0, ∀ v ∈ K 0 , where ⦠· | ·⦔ is the inner product in H ( π ). From (i)–(ii), we get an induced dual representation of an associated dual group G c . All three properties, selfsimilarity, order-covariance, and positivity, are satisfied in a natural context when G is semisimple and hermitean; but when G is the ( ax + b )-group, or the Heisenberg group, positivity is incompatible with the other two axioms for the infinite-dimensional irreducible representations. We describe a class of G , containing the latter two, which admits a classification of the possible spaces K 0 ⊂ H ( π ) satisfying the axioms of selfsimilarity and order-covariance.

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