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Noncommutative extensions of the Fourier transform and its logarithm

100%

Lenczewski R.

Studia Mathematica

2002

tom 152

nr 1

69-101

We introduce noncommutative extensions of the Fourier transform of probability measures and its logarithm to the algebra 𝓐(S) of complex-valued functions on the free semigroup S = FS({z,w}) on two generators. First, to given probability measures μ, ν with all moments finite, we associate states μ̂, ν̂ on the unital free *-bialgebra (ℬ,ε,Δ) on two self-adjoint generators X,X' and a projection P. Then we introduce and study cumulants which are additive under the convolution μ̂* ν̂ = μ̂ ⊗ ν̂ ∘ Δ when restricted to the "noncommutative plane" ℬ₀ = ℂ⟨X, X'⟩. We find a combinatorial formula for the Möbius function in the inversion formula and define the moment and cumulant generating functions, $M_{μ̂}{z,w}$ and $L_{μ̂}{z,w}$, respectively, as elements of 𝓐(S). When restricted to the subsemigroups FS({z}) and FS({w}), the function $L_{μ̂}{z,w}$ coincides with the logarithm of the Fourier transform and with the K-transform of μ, respectively. Moreover, $M_{μ̂}{z,w}$ is a "semigroup interpolation" between the Fourier transform and the Cauchy transform of μ. If one chooses a suitable weight function W on the semigroup S, the moment and cumulant generating functions become elements of the Banach algebra l¹(S,W).

A noncommutative limit theorem for homogeneous correlations

100%

Lenczewski R.

Studia Mathematica

1998

tom 129

nr 3

225-252

We state and prove a noncommutative limit theorem for correlations which are homogeneous with respect to order-preserving injections. The most interesting examples of central limit theorems in quantum probability (for commuting, anticommuting, and free independence and also various q-qclt's), as well as the limit theorems for the Poisson law and the free Poisson law are special cases of the theorem. In particular, the theorem contains the q-central limit theorem for non-identically distributed variables, derived in our previous work in the context of q-bialgebras and quantum groups. More importantly, new examples of limit theorems of q-Poisson type are derived for both the infinite tensor product algebra and the reduced free product, leading to new q-laws. In the first case the limit as q → 1 is studied in more detail and a connection with partial Bell polynomials is established.

Ograniczanie wyników

2 Studia Mathematica

2 Lenczewski R.

1 2002

1 1998

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Noncommutative extensions of the Fourier transform and its logarithm

A noncommutative limit theorem for homogeneous correlations