Robert P. Langlands

Editorial comments: This essay was first posted here on December 20, 2013. The latest version dates to May 16, 2014.

Author's comments: This note contains a few recollections of a year I spent in Turkey in 1967/68, where my office was adjacent to that of Cahit Arf, known, among other things, for the Hasse-Arf theorem and the Arf invariant. It was he who referred me---as I was first attempting to define local $\epsilon$-factors for Artin $L$-functions---to the paper of Hasse published in the Acta Salmanticensia. Hasse's paper was my first introduction to the methods that had already been introduced for calculating and comparing the $\epsilon$-factors.

Author's comments: The following three documents were composed on the receipt of the Shaw Prize in 2007. They have appeared or will appear in publications of the Shaw Foundation. The first two, a very brief autobiography and a slightly longer memoir, need no explanation. They are informal. So is the third, an attempt to explain clearly the nature of what is often referred to as the Langlands program.

Author's comments: The following brief discourse was delivered in Erlangen in October 2004, on the occasion of the award of the Karl Georg Christian von Staudt-Preis to Günter Harder. It does not do justice to his many contributions to mathematics, but does attempt to express my great admiration of him and my great respect for the passion and the tenacity with which he continues to reflect on what seem to me some of the central problems of the modern theory of numbers.

Author's comments: The article is an exercise in the reading of mathematics from earlier times.

Author's comments: The following article appeared in November 2007 in the popular scientific review, Pour la Science, but in a version slightly revised by the editors and their consultants for expository purposes and with diagrams added. I am sure the revised form is indeed easier for a layman to understand, but some assessments were added that are not mine. Rather than interfere with the editors' difficult task of turning arcane material into something meaningful to their readers, I let the revised version stand.

Portrait engraved by van Schooten the younger, editor and translator of the Latin edition of La géometrie.
Descartes said of it, "La barbe & les habits ne ressemblent aucunement."
(From the Rosenwald Collection at the Institute in Princeton)