A work of art that exists solely in the mind of the viewer and an invisiblefilm are some of the artworks on show (or not?) at the Hayward Gallery’ssummer show, Invisible. Conceived against a backdrop of art institutions competing to mount ever larger and more spectacular exhibitions, Invisible is a much-needed tonic for our thinking about art and the roles that the audience plays in expanding its potential meanings. It brings together artworks from the past six decades that place an emphasis on conceptual and communicative possibilities of art, while bypassing the requirements of visibility and materiality. Features artists including Robert Barry, James Lee Byars, Maurizio Cattelan, Jay Chung, Song Dong, Tom Friedman, Carsten Höller, Tehching Hsieh, Yves Klein, Roman Ondák, Mario Garcia Torres, and Andy Warhol. http://www.southbankcentre.co.uk/invisible