The Brown measure of the free multiplicative Brownian motion
Mar 26, 201964 pages
Published in:
- Probab.Theor.Related Fields 184 (2022) 1-2, 209-273,
- Probab.Theor.Related Fields 184 (2022) 209-273
- Published: Oct 1, 2022
e-Print:
- 1903.11015 [math.PR]
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Abstract: (Springer)
The free multiplicative Brownian motion is the large-N limit of the Brownian motion on in the sense of -distributions. The natural candidate for the large-N limit of the empirical distribution of eigenvalues is thus the Brown measure of . In previous work, the second and third authors showed that this Brown measure is supported in the closure of a region that appeared in the work of Biane. In the present paper, we compute the Brown measure completely. It has a continuous density on which is strictly positive and real analytic on . This density has a simple form in polar coordinates: where is an analytic function determined by the geometry of the region . We show also that the spectral measure of free unitary Brownian motion is a “shadow” of the Brown measure of , precisely mirroring the relationship between the circular and semicircular laws. We develop several new methods, based on stochastic differential equations and PDE, to prove these results.Note:
- Added references to subsequent works building on these results. Made a notational change, replacing the regularization parameter x with epsilon
- 60B20
- 46L54
- 35F21
- measure: spectral
- differential equations: stochastic
- Brownian motion
- density
- unitarity
- geometry
- Wigner
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