时间：2023.08.25
地点：中国科学院数学与系统科学研究院南楼S1013
10:00-11:00
报告人: 杨毅 教授 (台湾交通大学)
题目: Noise Subtraction using Machine Learning (ML) in Gravitational Wave Detection
摘要: The Gravitational Wave (GW) detectors are very sensitive because the GW signals is much smaller than the background noise. Reducing the background noise will improve the efficiency of the detection of the GW signals and also reduce the uncertainty of the data analysis such as Parameter Estimation (PE) of the GW signals. Machine Learning algorithm is powerful on classification, and regression problems such as anomaly detection and denoising. In this talk, I will introduce a ML algorithm, Deepclean, that is a noise subtraction method to predict the noise in the GW strain from the environmental noise recorded in the witness channels. One of the advantage of Deepclean is that the denoising process can be hardware-accelerated using GPUs so that the latency to stream out the cleaned strain is in the order of 1 second. Therefore Deepclean can be used as an online cleaning pipeline to provide improvements to the low-latency detection and the Multi-Messenger Astronomy.
11：00-12：00
报告人：凌意 研究员 （中科院高能所）
题目：引力规范对偶与全息公度模型
摘要：引力规范对偶为描述强耦合多体系统提供了强有力的工具。本报告将构建一类具有公度性质的全息模型来理解凝聚态物理中的相关问题。在具有明显周期性的格点背景下分析了系统的不稳定性，发现在一定温度下存在平移对称性自发破缺，从而实现金属绝缘转变，特别是随着格点振幅的增加，最终电荷密度波的周期与格点周期将出现公度锁定。在公度为1/2的情形下，我们计算了系统的电导率与频率之间的关系，发现在此模型中当系统从金属相转变为绝缘相时，将出现钉扎效应，但跟以往模型不同，此时的赝能隙并不是由Drude峰的偏离而形成，二是随Drude峰的快速消失而显露出来。最后，我们比较了锁定前后的电导率，发现在未锁定前，在金属绝缘转变过程中随温度下降会出现一短暂不稳定区间，期间电导率实部出现负值，而在锁定后不存在这样的现象。该模型为理解高温超导相图提供了新途径。
12:30 午餐
2:00-3:00
报告人：田雨 教授 (国科大)
题目：Bondi-Sachs坐标下的数值相对论
摘要：数值相对论是应用广泛的交叉研究领域，从黑洞和中子星碰撞的引力波产生，黑洞和其它引力体系的动力学演化过程，到规范/引力对偶体系的动力学数值模拟等等。本报告旨在介绍我们最近利用Bondi-Sachs坐标来研究黑洞体系的静态解、准正模式和动力学演化的一套较为简单高效的数值相对论形式。
3:00-4:00
报告人: 张宏宝 教授 (北京师范大学)
题 目：SL(2,C)×U(1) algebra and celestial primary conformal wave functions
报告摘要：In this talk, I will report our upcoming work on celestial primary conformal wave functions, which are believed to serve as the appropriate building blocks to formulate holographic prescription of the bulk dynamics, saying scattering amplitude in Minkowski spacetime. In particular, after a brief introduction to the relevant spinor machinery for celestial holography, I will show how the celestial primary conformal wave functions for massless particles can be understood explicitly as the representation of the bulk SL(2,C)×U(1), where SL(2,C) is the familiar Lorentz isometry algebra and U(1) corresponds to the dilatation, which can be regarded as an additional emergent symmetry. With this new observation, we can further develop the relationship between celestial conformal weights and the bulk scaling dimension. I will conclude my talk with some ideas worthy of further exploration.
4:00-5:00
报告人：张向东 教授 （华南理工大学）
题目：圈量子引力与黑洞内部结构
摘要：黑洞中奇异点的存在是经典广义相对论的一个重要结论，而这一结论也预示着经典广义相对论在极强引力场情况下失效。为解决这一问题，需要考虑引力的量子效应。圈量子引力是目前较为成功的引力量子化方案之一，近年来应用圈量子引力探讨黑洞内部结构，特别是圈量子引力对于奇异点的影响是目前研究前沿的热点问题。本报告拟综述该领域近些年的进展，并报告我们在该问题的一些进展。