Constantin Carathéodory was a mathematician whose work connected measure theory, complex analysis and the calculus of variations. He began his career as an engineer and studied mathematics while working on a dam in Egypt, before entering mathematical research. His later contributions included links between the calculus of variations and partial differential equations, as well as conformal maps and their boundary behavior.[ref]
https://mathshistory.st-andrews.ac.uk/Biographies/Caratheodory/. Biography, engineering work and principal mathematical contributions
His Caratheodory measurability criterion is a basic construction principle for measures: it selects those sets that split the outer measure of every test set additively, producing a domain on which countable additivity holds.
Portrait of Constantin Carathéodory
. Caratheodory family; photographer and date unknown, as stated in the Commons File. File records family permission as public domain and an origin-country/life-plus-70-or-shorter public-domain tag. Source usage terms, via Wikimedia Commons. Source. Articles by others on the same topic
Constantin Carathéodory (1861–1950) was a Greek mathematician known for his significant contributions to various areas of mathematics, particularly in real analysis, measure theory, and the calculus of variations. He made important advancements in the theory of functions of a real variable, the foundations of measure theory, and the development of the theory of functions of several complex variables.