Ernest Hemingway is a real author who is associated with modernists and the lost generation of the Great War. He won a Nobel prize in literature in 1954 for Old Man and the Sea, and is recognized as the greatest author of his time. His most famous works include For Whom the Bell Tolls, The Sun Also Rises, A Farewell to Arms, and The Old Man and the Sea.
He is mentioned in S in footnote 2 on page vi for first being an admirer of Straka's, and then later harshly critiquing his works. The author of the footnote seems to have more information than the public, for they imply that Hemingway only changed his mind about Straka's work after an audience with him was denied.
Later in the foreword, Caldeira mentions a telegram from Straka, inviting Caldeira to the Hotel San Sabastian in Havana, which is also the location for Hemingway's The Sun Also Rises.
Hemingway is referenced again in footnote 3 of chapter 4, page 117. In the footnote, Caldeira argues that Hemingway is quoted within the text by Straka, but by a woman, which Hemingway would have taken offense too. Caldeira postulates that Hemingway was sexist, which Jen agrees with in the margin, but Eric questions, saying Straka can be read the same way.
Hemingway is found in a photograph taken in 1937 at the Hotel Florida, in Spain, with Durand, Dos Passos, Tiago, and someone turned away from the camera. Also in the marginal notes on 186, Eric tells Jen of a rumor that Hemingway grabbed Durand's ass, and she knocked him out in a single punch. Jen says that there is nothing in Durand's journals to verify that.