AMC Theatres, United Artists and Kerasotes Theatres have all announced expansion plans, including the openings of two theaters this week. AMC Theatres will debut the circuit’s first 16-screen theater in downtown Long Beach tomorrow.Dubbed the Pine Square, the theater features AMC’s HITS/Torus system. United Artists announced the opening of a 10-screen theater complex in Langhorne, Pa., which is the third theatre complex in the region opened by United Artists Theatre Circuit in the past 14 months. Illinois-based Kerasotes Theatres announced construction plans for six theaters, for a total of 38 screens in Illinois, Indiana and Missouri. In the forefront of construction plans are the Scottsdale 6 in South Bend, Ind., and the Honey Creek West 8 in Terre Haute, Ind., which are skedded to open next summer.