The "New York Post" claims that JENNIFER LOPEZ hooked up with her ex-husband MARC ANTHONY during a recent trip to the city. She'd left boyfriend Casper Smart back in L.A.

Supposedly, they spent more than two and a half hours together in his hotel. Marc was the first one to emerge...quote, "He came out really quickly, with his head down, like he didn't want to be seen."

J-Lo came out later, disheveled, but with, quote, "a smug grin on her face."