## Similarity problem for certain martingale uniform algebras.(English. Russian original)Zbl 1042.46027

J. Math. Sci., New York 115, No. 2, 2141-2146 (2003); translation from Zap. Nauchn. Semin. POMI 270, 90-102 (2000).
Solving a major long-standing conjecture, G. Pisier [Taiwanese J. Math. 5, 1-17 (2001; Zbl 0999.46025)] proved that there exists a bounded, but not completely bounded, homomorphism $$\varphi:C_A\to B(H)$$, where $$C_A$$ is the disk algebra and $$B(H)$$ the algebra of all bounded operators on a Hilbert space. This article pursues the question (asked by Pisier) of whether $$C_A$$ can be replaced by other uniform algebras, and gives a very clear introduction to the problems connected with the endeavor (the conjecture whether this is possible is still open). The partial result proved in this paper requires a uniform algebra $$A$$ to possess a nontrivial bounded point derivation. If this is the case, and if $$\nu$$ is a point derivation measure for $$A$$, then one builds the so-called martingale extension algebra $$A_1 := \text{Mart} (A,\nu)$$. The author is then able to extend Pisier’s argument to prove that there exists a bounded, but not completely bounded, homomorphism from $$A_1$$ to $$B(H)$$.

### MSC:

 46J25 Representations of commutative topological algebras 47B48 Linear operators on Banach algebras 46L07 Operator spaces and completely bounded maps

Zbl 0999.46025
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