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Levy area for the free Brownian motion: existence and non-existence. (English) Zbl 1062.46055
The author shows that the Lévy area of the piecewise linear path which coincides with $$(X_s)_{0\leq s\leq 1}$$ (free Brownian motions) at the points of a subdivision $$D$$ tends to the Lévy area of the free Brownian motion when the mesh size of $$D$$ tends to $$0$$. To this end, the author proves a Burkholder-Davis-Gundy type inequality. Then he shows that there exists no multiplicative functional above the free Brownian motion, that is, in other words, there does not exist a Lévy area in the projective tensor product.

##### MSC:
 46L54 Free probability and free operator algebras
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##### References:
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