While his professional research interests focus on complex analysis and discrete dynamical systems, people in the crossword world know him as the creator of challenging puzzles. In his popular crossword blog, "Rex Parker does the NYT Crossword Puzzle", Binghamton University professor Michael Sharp, writes that he considers Mr. Walden to be "one of the greatest constructors alive . or dead" and awarded him a gold medal for the Best Themeless Puzzle of 2007. Walden will be supervising the judging of the Puzzle Day tournaments and will be giving a talk about constructing and solving difficult crossword puzzles.