Cheap$kate: Free events in NYC this week

The host of MSNBC's "Hardball with Chris Matthews" will be talking about his new book, "Tip and the Gipper: When Politics Worked," an inside look at the political relationship between then-Speaker of the House Tip O'Neill and former President Ronald Reagan. Matthews, who served as a top aide to the speaker, saw up close how the political opponents worked together for the nation's benefit.

"Eat, Pray, Love" -- the travel and relationship memoir-turned-Hollywood flick starring Julia Roberts and Javier Bardem -- catapulted Elizabeth Gilbert into the literary spotlight. Now, the New York Times bestselling author returns to fiction with "The Signature of All Things," which follows scientist Alma Whittaker's life and love affair with utopian artist Ambrose Pike. Gilbert will be talking about her novel Tuesday at Barnes & Noble.

String theory and the math of hyperspaceIf you understand some of the principles of string theory or have a desire to, stop by the National Museum of Mathematics, better known as MoMath, to hear Brian Greene, professor of physics and mathematics at Columbia University, discuss how string theory connects to concepts in geometry. Be sure to register at mathencounters.org so you can ensure a spot.

The work of pioneering activists in the 1980s and 1990s changed the conversation around AIDS and brought about real change and action from world leaders. This new exhibit at the New York Public Library showcases the library's documented history of the impact and significance of these early AIDS activists. The exhibit opens Friday and runs through April 6.

Sugar Sweets FestivalSatisfy your sweet tooth this Sunday at the City Reliquary's Fourth Annual Sugar Sweets Festival. The fest features FREE events like blue-ribbon baking competitions, demos, performances by The Candy Sleepers and Caleb Curtis, raffles and the exhibit opening of Bakelicious Brooklyn, where six Brooklyn bakers share their secrets. Various treats will be on sale ranging from $1 to $4, with all proceeds going to benefit the City Reliquary. Do we have your mouths watering yet?

If you're a fan of contemporary art, then you certainly won't want to miss the latest edition of the Affordable Art Fair. The name pretty much says it all, with more than 50 national and international galleries putting up original paintings, prints, sculptures and photographs, with some works as low as $100. Regular admission is $15, but we wouldn't be good Cheap$kates if we didn't find a FREE deal: Friday evening admission won't cost you a dime. The show runs from 11 a.m. to 8 p.m. Thursday through Saturday, and until 6 p.m. on Sunday.