Acta mathematica scientia,Series B ›› 2021, Vol. 41 ›› Issue (6): 2173-2182.doi: 10.1007/s10473-021-0622-2

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NOTES ON REAL INTERPOLATION OF OPERATOR Lp-SPACES

Marius JUNGE1, Quanhua XU2   

  1. 1. Department of Mathematics, University of Illinois, Urbana, IL 61801, USA;
    2. Institute for Advanced Study in Mathematics, Harbin Institute of Technology, Harbin 150001, China;Laboratoire de Mathématiques, Université de Bourgogne Franche-Comté, 25030 Besançon Cedex, France
  • Received:2021-04-14 Revised:2021-10-15 Online:2021-12-25 Published:2021-12-27
  • Supported by:
    Xu was partially supported by the French ANR project (ANR-19-CE40-0002) and the Natural Science Foundation of China (12031004).

Abstract: Let M be a semifinite von Neumann algebra. We equip the associated noncommutative Lp-spaces with their natural operator space structure introduced by Pisier via complex interpolation. On the other hand, for 1<p< let

Lp,p(M)=(L(M),L1(M))1p,p
be equipped with the operator space structure via real interpolation as defined by the second named author (J. Funct. Anal. 139 (1996), 500——539). We show that Lp,p(M)=Lp(M) completely isomorphically if and only if M is finite dimensional. This solves in the negative the three problems left open in the quoted work of the second author. \\ We also show that for 1<p< and 1q with pq
(L(M;q),L1(M;q))1p,p=Lp(M;q)
with equivalent norms, i.e., at the Banach space level if and only if M is isomorphic, as a Banach space, to a commutative von Neumann algebra. \\ Our third result concerns the following inequality:
(ixiq)1qLp(M)(ixir)1rLp(M)
for any finite sequence (xi)Lp+(M), where 0<r<q< and 0<p. If M is not isomorphic, as a Banach space, to a commutative von Meumann algebra, then this inequality holds if and only if pr.

Key words: operator spaces, Lp-spaces, real interpolation, column Hilbertian spaces

CLC Number: 

  • 46E30
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