 Sz.-Nagy's dilation theorem

Sz.-Nagy's dilation theorem is a result in operator theory, particularly in the study of contraction operators on Hilbert spaces. It provides a framework for understanding certain types of linear operators by representing them in a higher-dimensional space. The primary aim of the theorem is to "dilate" a given operator into a unitary operator, which preserves the properties of the original operator while allowing for a more thorough analysis.