In this paper, we introduce the notion of conditionally bi-free independence in an amalgamated setting. We define operator-valued conditionally bi-multiplicative pairs of functions and construct operatorvalued conditionally bi-free moment and cumulant functions. It is demonstrated that conditionally bifree independence with amalgamation is equivalent to the vanishing of mixed operator-valued bi-free and conditionally bi-free cumulants. Furthermore, an operator-valued conditionally bi-free partial R-transform is constructed and various operator-valued conditionally bi-free limit theorems are studied.
IntroductionThe notion of conditionally free (c-free for short) independence was introduced in [3] as a generalization of the notion of free independence to two-state systems. In our previous paper [6] we introduced the notion of conditionally bi-free (c-bi-free for short) independence in order to study the non-commutative left and right actions of algebras on a reduced c-free product simultaneously. Thus conditional bi-freeness is an extension of the notion of bi-free independence [14] to two-state systems. Moreover [6] introduced c-(ℓ, r)-cumulants and demonstrated that a family of pairs of algebras in a two-state non-commutative probability space is conditionally bi-free if and only if mixed (ℓ, r)-and c-(ℓ, r)-cumulants vanish.In [13] Voiculescu generalized his own notion of free independence by replacing the scalars with an arbitrary algebra thereby obtaining the notion of free independence with amalgamation (see also [12] for the combinatorial aspects). For c-free independence, the generalization to an amalgamated setting over a pair of algebras was done by Popa in [9] (see also [8]). On the other hand, the framework for generalizing bi-free independence to an amalgamated setting was suggested by Voiculescu in [14, Section 8] and the theory was fully developed in [4].The main goal of this paper is to extend the notion of c-bi-free independence to an amalgamated setting over a pair of algebras. Furthermore, we demonstrate that the combinatorics of conditionally bi-free probability and bi-free probability with amalgamation, which are governed by the lattice of bi-non-crossing partitions, are specific instances of more general combinatorial structures.Including this introduction this paper contains nine sections which are structured as follows. Section 2 briefly reviews some of the background material pertaining to conditionally bi-free probability and bi-free probability with amalgamation from [4][5][6]. In particular, the notions bi-non-crossing partitions and diagrams, their lateral refinements and cappings, interior and exterior blocks, B-B-non-commutative probability spaces, operator-valued bi-multiplicative functions, and the operator-valued bi-free moment and cumulant functions are recalled.Section 3 introduces the structures studied within conditionally bi-free independence with amalgamation. We define the notion of a B-B-non-commutative probability space with a pair of (B, D)-valued expectations (A, E, F, ...