*Christos Dimitriou Papakyriakopoulos, commonly known as "Papa" was born in Chalandri, Athens, Greece on June 29, 1914 and died on June 29, 1976) was one of the most promiment mathematical figures of the 20th century, specialized in geometric topology. Papakyriakopoulos came from an affluent family and went on to study Maths despite his father’s will. He was a top university student and fought in the Greek resistance. During the Greek civil war, he worked as a teacher in a village in Thessaly and went the civil war was over he returned in Athens to work as a university researcher. Soon however, his mentor was forced out of the academia due to his political beliefs and his future was hanging in peril.*

*The situation however changed in 1948, when he was invited by Ralph Fox to come as his guest at the Princeton mathematics department. Fox had been impressed by a letter from Papakyriakopoulos which purported to prove Dehn's lemma. The proof, as it turned out had flaws, but Fox's sponsorship would continue for many years and enabled Papakyriakopoulos to work on his mathematics without concern of financial support, despite the fact that the Greek authorities had marked him as a “communist”.*

*Papakyriakopoulos is best known for his proofs of Dehn's lemma, the loop theorem, and the sphere theorem, three foundational results for the study of 3-manifolds. In honor of this work, he was awarded the first Veblen Prize in Geometry in 1964. From the early sixties on, he mostly worked on the Poincar**ι** conjecture, which although he failed to prove, he gave.*

*The following unusual limerick was composed by John Milnor, shortly after learning of several graduate students' frustration at completing a project where the work of every Princeton mathematics faculty member was to be summarized in a limerick:*

*“The perfidious lemma of Dehn, Was every topologist's bane *

*'Til Christos Papakyriakopoulos proved it without any strain.”*

*The phrase "without any strain" is not meant to indicate that Papa did not expend much energy in his efforts. Rather, it refers to Papa's "tower construction", which quite nicely circumvents much of the difficulty in the cut-and-paste efforts that preceded Papa's proof.*

*He was a reclusive character, spending most of his time in his office listening to his beloved Wagner. Legend has it that in the US he lived for 25 years in the same hotel room he used when he first arrived in the country, with all of his belongings inside his original piece of luggage. He died of cancer at age 62 in Princeton, New Jersey.*