Write down the author's name of the book most recently published.
author's name refers to author_name; book most recently published refers to Max(publication_date)
SELECT T3.author_name FROM book AS T1 INNER JOIN book_author AS T2 ON T1.book_id = T2.book_id INNER JOIN author AS T3 ON T3.author_id = T2.author_id ORDER BY T1.publication_date DESC LIMIT 1