报告题目：Reionization optical depth and CMB-BAO tension in punctuated inflation

报 告 人：Zhiqi Huang 黄志琦 (Sun Yat-sen University)

报告时间：2025年11月27日14：00

报告地点：物理楼W260

内容摘要：Within the standard six-parameter Lambda cold dark matter (𝜦CDM) model, a 2-3𝜎 tension persists between baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) and observations of the cosmic microwave background (CMB). Although this tension has often been interpreted as evidence for dynamical dark energy or a sum of neutrino masses below the established minimum, recent studies suggest it may instead originate from an underestimation of the reionization optical depth 𝜏, particularly when inferred from large-scale CMB polarization. It has been proposed in early studies that a suppression of large-scale primordial curvature power could partially cancel the contribution of 𝜏 to the CMB low-ℓ polarization power spectrum, leading to a biased low 𝜏 measurement in standard analyses. In this work, we investigate whether punctuated inflation—which generates a suppression of primordial power on large scales through a transient fast-roll phase—can raise the inferred 𝜏 value and thereby reconcile the consistency between CMB and BAO. For simple models with step-like features in the inflaton potential, we find that the constraint on 𝜏 and the CMB-BAO tension remain nearly identical to those in the standard six-parameter 𝜦CDM model. We provide a physical explanation for this negative result.

报告人简介：Zhiqi Huang obtained his PhD from the University of Toronto, and is currently a professor at Sun Yat-sen University. His primary research interests are theoretical and observational cosmology, specifically focusing on the cosmic microwave background (CMB), early-universe physics, dark energy, and modified gravity. Prof. Huang was a core team member of the Planck collaboration and has contributed to several legacy papers in the 2015 and 2018 releases. He is currently involved in the Simons Observatory and AliCPT collaborations, with the goal of detecting primordial gravitational waves from CMB data.