Unconditional Orthonormal Systems

Martin Defant, Marius Junge

Research output: Contribution to journalArticlepeer-review


We show that a Banach space X is isomorphic to a Hilbert space if and only if the trigonometric system is unconditional in L2 (II, X). If the unconditionally constant is equal to one then X is even isometric to a Hilbert space.

Original languageEnglish (US)
Pages (from-to)233-240
Number of pages8
JournalMathematische Nachrichten
Issue number1
StatePublished - 1992
Externally publishedYes

ASJC Scopus subject areas

  • Mathematics(all)


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