image: sign of the times Original Research Article

We discuss the signature of space–time in the context of the image-conjecture. In this setting, the space–time signature depends on the choice of basis for the “gravitational subalgebra” image, and Weyl transformations connect interpretations with different signatures of space–time. Also the sign of the 4-form gauge field term in the Lagrangian enters as an adjustable sign in a generalized signature. Within image, the combination of space–time signature image with conventional sign for the 4-form term, appropriate to M-theory, can be transformed to the signatures image and image of Hullʹs image- and image-theories (as well as image, image and image. Theories with other signatures organize in orbits disconnected from these theories. We argue that when taking image seriously as a symmetry algebra, one cannot discard theories with multiple time-directions as unphysical. We also briefly explore links with the image conjecture.