报告题目：Heavy Spinning Particles from Signs of Primordial Non-Gaussianities: Beyond the Positivity Bounds

报 告 人：周思益，香港科技大学

报告时间：2019-05-16 10:00

报告地点：物理系理科楼C302

报告摘要：Within the so-called cosmological collider program, imprints of new particles on primordial non-Gaussianities have been studied intensively. In particular, their non-analytic features in the soft limit provide a smoking gun for new particles at the inflation scale. While this approach is very powerful to probe particles of the mass near the Hubble scale, the signal is exponentially suppressed for heavy particles. To enlarge the scope of the cosmological collider, we explore a new approach to probing spins of heavy particles from signs of Wilson coefficients of the inflaton effective action and the corresponding primordial non-Gaussianities. As a first step, we focus on the regime where the de Sitter conformal symmetry is weakly broken. It is well known that the leading order effective operator $(\partial_\mu\phi\partial^\mu\phi)^2$ is universally positive as a consequence of unitarity. In contrast, we find that the sign of the six derivative operator $(\nabla_\mu\partial_\nu\phi)^2(\partial_\rho\phi)^2$ is positive for intermediate heavy scalars, whereas it is negative for intermediate heavy spinning particles, hence the sign can be used to probe spins of heavy states generating the effective operator. We also study phenomenology of primordial non-Gaussianities thereof.