1880-1975. German mathematician.
Proved the Perron-Frobenius theorem (1907): every positive square matrix has a unique largest eigenvalue with a corresponding positive eigenvector.
This theorem guarantees that Markov chains on connected graphs converge to a unique stationary distribution — the mathematical foundation of PageRank and cyberank.
Without Perron-Frobenius, there is no guarantee that the focus distribution $\pi$ converges. With it, convergence is assured under ergodicity.
Contributed extensively to continuous fractions, differential equations, and non-negative matrices.
Professor at the University of Munich for over four decades.