Abstract

We define and study dense Frechet subalgebras of compact quantum groups realised as smooth domains associated with a Dirac type operator with compact resolvent. Further, we construct spectral triples on compact matrix quantum groups in terms of Clebsch–Gordon coefficients and the eigenvalues of the Dirac operator {mathcal{D}}. Grotendieck’s theory of topological tensor products immediately yields a Schwartz kernel theorem for linear operators on compact quantum groups and allows us to introduce a natural class of pseudo-differential operators on them. It is also shown that regular pseudo-differential operators are closed under compositions. As a by-product, we develop elements of the distribution theory and corresponding Fourier analysis. We give applications of our construction to obtain sufficient conditions for Lp − Lq boundedness of coinvariant linear operators. We provide necessary and sufficient conditions for algebraic differential calculi on Hopf subalgebras of compact quantum groups to extend to our proposed smooth subalgebra {{C}^infty_mathcal {D}}. We check explicitly that these conditions hold true on the quantum SU2q for both its 3-dimensional and 4-dimensional calculi.

Highlights

  • In [HL36] Hardy and Littlewood proved the following generalisation of the Plancherel’s identity on the circle T, namely (1 + |m|)p−2| f (m)|p ≤ C p f p L p (T) 1 < p ≤ 2. m∈Z (1.1)The first and third authors were supported in parts by the EPSRC Grant EP/R003025/1 and by the Leverhulme Grant RPG-2017-151

  • We present a version of a Marcinkiewicz interpolation theorem for linear mappings between compact quantum group G of Kac type and the space of matrix-valued sequences that will be realised via

  • We show that every linear operator A : CD∞ → CD∞ continuous with respect to the Frechet topology can be associated with a distribution K A ‘acting’ on G × G

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Summary

Introduction

In [HL36] Hardy and Littlewood proved the following generalisation of the Plancherel’s identity on the circle T, namely (1 + |m|)p−2| f (m)|p ≤ C p f p L p. It is known that q-deformed quantum groups and homogeneous spaces do not fit into Connes axiomatic framework [Con95] if one wants to have the correct classical limit and various authors have considered modification of the axioms Another problem is that of ‘geometric realisation’ where a given spectral triple operator (understood broadly) should ideally have an interpretation as built from a spin connection and Clifford action on a spinor bundle. We analyse in Theorem 5.3 when D defined by {λπ } is an actual spectral triple in the case of compact matrix quantum group in the sense of Woronowicz [Wor87]. We want to express our gratitude to the anonymous referees for their helpful suggestions

Preliminaries
Hausdorff–Young–Paley Inequalities
Fourier Multipliers on Compact Quantum Groups
Hardy–Littlewood Inequality and Spectral Triples
Schwartz Kernels
Differential Calculi on Compact Quantum Groups
Concluding Remarks
Full Text
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