short linear map

Short linear maps


The short linear maps are the morphisms of the category Ban of Banach spaces (or its full subcategory Hilb of Hilbert spaces), at least if one wishes to recover isometric isomorphisms as the abstract isomorphisms of this category.


Given Banach spaces VV and WW, a short linear map form VV to WW is a (total) function f:VWf\colon V \to W that is both short and linear, equivalently a bounded linear operator whose norm is at most 11. These are also called contractive (or weakly contractive) linear maps; they may also be called short (or contractive or weakly contractive) operators (with linearity usually assumed but sometimes mentioned), or even simply (weak) contractions.

On Hilbert spaces

Short linear maps from a Hilbert space to itself (that is endomorphisms in Hilb) are discussed (as simply ‘contractions’) in operator theory?; see Wikipedia.

Created on August 16, 2012 19:33:23 by Toby Bartels (