These days, more and more museums are inviting dancers to liven up the art that's on the walls and pedestals. The New Museum, on the border of SoHo and the Lower East Side, has designated a special room for live events called the South Galleries. Every day for two months, ending April 15, this gallery is home to Co-natural, a mesmerizing performance exhibition by Romanian choreographer Alexandra Pirici (pronounced Pireech). She is acclaimed in Europe and makes her U. S. debut with this exhibit. Included is a life-size hologram that really looks like another person. If you spend some time wandering around in the gallery, you start to see congruencies between the gestures of the live performers and the not-quite-live hologram. And you start to wonder about the stamina of the dancers, who are there, as moving sculpture, all day long (with a few breaks).