Who is this mathematician on the Fields medal? On the Fields Medal, there is a  picture  of a human portrait.
Picture is given below:

Who is this mathematician on the Fields Medal?
I think  this  portrait may be an ancient Greek  mathematician.
 A: Quotation from Wikipedia:
The medal was designed by Canadian sculptor R. Tait McKenzie.

*

*On the obverse is Archimedes and a quote attributed to 1st century AD poet Manilius, which reads in Latin: "Transire suum pectus mundoque potiri" ("Rise above oneself and grasp the world"). The date is written in Roman numerals and contains an error ("MCNXXXIII" rather than "MCMXXXIII"). In capital Greek letters the word ΑΡXIMHΔΟΥΣ, or "of Archimedes".


*On the reverse is the inscription (in Latin):
CONGREGATI
EX TOTO ORBE
MATHEMATICI
OB SCRIPTA INSIGNIA
TRIBUERE
Translation: "Mathematicians gathered from the entire world have awarded [understood but not written: 'this prize'] for outstanding writings."
In the background, there is the representation of Archimedes' tomb, with the carving illustrating his theorem On the Sphere and Cylinder, behind an olive branch. (This is the mathematical result of which Archimedes was reportedly most proud: Given a sphere and a circumscribed cylinder of the same height and diameter, the ratio between their volumes is equal to 2⁄3.)
The rim bears the name of the prizewinner.
