| Abstract: Unitarity, locality, and causality are supremely constraining principles obeyed by physical scattering amplitudes. And yet the Coon amplitude appears to offer an example of a continuous one-parameter family of amplitudes, interpolating between scalar field theory and the Veneziano amplitude, that obey these cherished principles but for which no underlying physical theory is known.
I will begin my talk with a friendly overview of the properties of the Coon amplitude and of the recent literature on its possible unitarity, physical meaning, generalizations, and motivations. One important quality of the amplitude is that it possesses a branch cut. Following the recent paper 2303.02149, we will take a close look at the branch cut and discover that in fact the Coon amplitude, in its current form, violates the positivity conditions expected from unitarity. I will end the talk with a discussion of possible strategies for, and obstacles to, fixing the amplitude. Link to the Event Video |