# Partially Positive Semidefinite Maps on $*$-Semigroupoids and Linearisations

## TL;DR

This paper generalizes classical dilation theorems to operator-valued partially positive semidefinite maps on $*$-semigroupoids and algebroids, extending their applicability to graph-related systems and groupoid representations.

## Contribution

It introduces a unifying framework for dilation theorems on $*$-semigroupoids and algebroids, including unbounded operator representations and bounded characterizations, generalizing Stinespring's theorem.

## Key findings

- Generalization of Sz-Nagy's Dilation Theorem for $*$-semigroupoids
- Characterization of $*$-representations with bounded operators
- Extension of Stinespring's Dilation Theorem to $B^*$-algebroids

## Abstract

Motivated by Cuntz-Krieger-Toeplitz systems associated to undirected graphs and representations of groupoids, we obtain a generalisation of the Sz-Nagy's Dilation Theorem for operator valued partially positive semidefinite maps on $*$-semigroupoids with unit, with varying degrees of aggregation, firstly by $*$-representations with unbounded operators and then we characterise the existence of the corresponding $*$-representations by bounded operators. By linearisation of these constructions, we obtain similar results for operator valued partially positive semidefinite maps on $*$-algebroids with unit and then, for the special case of $B^*$-algebroids with unit, we obtain a generalisation of the Stinespring's Dilation Theorem. As an application of the generalisation of the Stinespring's Dilation Theorem, we show that some natural questions on $C^*$-algebroids are equivalent.