English

On von Neumann algebras generated by free Poisson random weights

Operator Algebras 2025-04-07 v1

Abstract

We study a generalization of free Poisson random measure by replacing the intensity measure with a n.s.f. weight φ\varphi on a von Neumann algebra MM. We give an explicit construction of the free Poisson random weight using full Fock space over the Hilbert space L2(M,φ)L^2(M,\varphi) and study the free Poisson von Neumann algebra Γ(M,φ)\Gamma(M,\varphi) generated by this random weight. This construction can be viewed as a free Poisson type functor for left Hilbert algebras similar to Voiculescu's free Gaussian functor for Hilbert spaces. When φ(1)<\varphi(1)<\infty, we show that Γ(M,φ)\Gamma(M,\varphi) can be decomposed into free product of other algebras. For a general weight φ\varphi, we prove that Γ(M,φ) \Gamma(M,\varphi) is a factor if and only if φ(1)1 \varphi(1)\geq 1 and MC M\neq \mathbb{C} . The second quantization of subunital weight decreasing completely positive maps are studied. By considering a degenerate version of left Hilbert algebras, we are also able to treat free Araki-Woods algebras as special cases of free Poisson algebras for degenerate left Hilbert algebras. We show that the L\'{e}vy-It\^o decomposition of a jointly freely infinitely divisible family (in a tracial probability space) can in fact be interpreted as a decomposition of a degenerate left Hilbert algebra. Finally, as an application, we give a realization of any additive time-parameterized free L\'{e}vy process as unbounded operators in a full Fock space. Using this realization, we show that the filtration algebras of any additive free L\'{e}vy process are always interpolated group factors with a possible additional atom.

Keywords

Cite

@article{arxiv.2504.03087,
  title  = {On von Neumann algebras generated by free Poisson random weights},
  author = {Zhiyuan Yang},
  journal= {arXiv preprint arXiv:2504.03087},
  year   = {2025}
}

Comments

37 pages + references

R2 v1 2026-06-28T22:46:05.554Z