Let x₀ be a nonzero vector in ℂⁿ. We show that a linear map Φ: Mₙ(ℂ) → Mₙ(ℂ) preserves the local spectral radius at x₀ if and only if there is α ∈ ℂ of modulus one and an invertible matrix A ∈ Mₙ(ℂ) such that Ax₀ = x₀ and for all T ∈ Mₙ(ℂ).
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-sm188-1-4, author = {Abdellatif Bourhim and Vivien G. Miller}, title = {Linear maps on Mn(C) preserving the local spectral radius}, journal = {Studia Mathematica}, volume = {187}, year = {2008}, pages = {67-75}, zbl = {1145.47005}, language = {en}, url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-sm188-1-4} }
Abdellatif Bourhim; Vivien G. Miller. Linear maps on Mₙ(ℂ) preserving the local spectral radius. Studia Mathematica, Tome 187 (2008) pp. 67-75. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-sm188-1-4/