A Cosmological Tachyon Collider: Enhancing the Long-short Scale Coupling
Abstract
The squeezed limit of primordial curvature bispectrum is a powerful probe of new physics and encodes information about additional fields active during inflation such as their masses and spins. In this conventional cosmological collider setup, additional fields are stable with a positive mass squared, and hence induce a decreasing signal in the squeezed limit, making a detection challenging. In this talk, however, the speaker will introduce a cosmological tachyon collider model in which we consider a scalar field that is temporarily unstable by virtue of a transient tachyonic mass during inflation. Under appropriate IR-convergence assumptions, we find a bispectrum with an enhanced long-short scale coupling that grows in the squeezed limit parametrically faster than local non-Gaussianity. Such an ultra-squeezed non-Gaussianity signal is best-probed by cross-correlating the temperature anisotropies and mu-type distortions of the Cosmic Microwave Background. We show that the present-day Planck data already poses constraints on our model while planned future experiments such as CMB-S4 will further uncover a wide new parameter space.
About the Speaker
Dr. TONG Xi is currently a postdoctoral research associate in the Department of Applied Mathematics and Theoretical Physics in the University of Cambridge. He obtained his PhD in Physics from The Hong Kong University of Science and Technology in 2023 and his bachelor’s degree in Physics from University of Science and Technology of China in 2018. Dr. Tong’s research interest lies at the intersection of quantum field theory and classical gravity, notably primordial cosmology, black hole physics and holography. His past work encompasses topics such as cosmological collider physics, primordial non-Gaussian correlators, primordial black holes and black hole superradiance.
About the Program
For more information, please refer to the program website at http://iasprogram.ust.hk/particle_theory.
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