【直播】【中科院理论物理所】北理工张向东教授、Leandros Perivolaropoulos of Ioannina U.
本次报告由中国科学院理论物理研究所主办，分别于2021年9月29日，30日15:00开始，授权蔻享学术进行网络直播。
报告一
直播二维码
报告人
张向东 教授 | 北京理工大学
时间
2021年9月29日 15:00
报告摘要
Recently, a new class of symmetry-protected topological insulators, higher-order topological insulator, has drawn research interest. Unlike conventional first-order topological insulators, two-dimensional second-order topological insulators have topologically protected corner states, and corresponding three-dimensional systems have topological gapless modes on the hinges. In some crystalline structures, the topological corner and hinge states can arise only from the nontrivial bulk topology when the lattice termination is compatible with the crystal symmetries. Recent investigations have shown that classical circuits exhibit great advantages in simulating these topological states. In this talk, we will introduce the research progress and some of our recent works for higher-order topological states based on circuits, including three-dimensional octupole insulators, four-dimensional hexadecapole insulators, higher-order topological Anderson insulators, non-Hermitian higher-order topological phases and their potential applications.
报告二
直播二维码
报告人
Leandros Perivolaropoulos | University of Ioannina
时间
2021年9月30日 15:00
报告摘要
The absolute luminosity of SnIa may be calibrated using two distinct independent calibrators: 1. The sound horizon at recombination ($z\sim 1100$) used as a standard ruler to set the scale for the LCDM H(z) and thus the SnIa absolute magnitude and luminosity (inverse distance ladder approach) 2. The locally calibrated standard candles like Cepheid stars which measure the distance to SnIa host galaxies at low redshifts ($z<0.01$, $D<40Mpc$) and thus calibrate the absolute luminosity $L$ and magnitude $M_B$ of SnIa (distance ladder approach). The two approaches lead to values of the SnIa absolute magnitude $M_B$ that are inconsistent at a level more than $4\sigma$. This inconsistency is known as a Hubble tension because the difference in the values of $M_B$ is easily translated in a difference in the values of the Hubble constant $H_0$ since $H_0$ and $M_B$ are degenerate. The two measurements of $M_B$ however are performed in different redshift ranges: The Cepheid measurement is performed for $z<0.01$ where Cepheids are detectable and the measurement using the sound horizon is performed for $z>0.01$ where the Hubble flow and the LCDM $H(z)$ are applicable. Thus, the two measurements can be made consistent if a fundamental physics transition changes the SnIa absolute luminosity ($M_B$) at a redshift $z\lesssim 0.01$. In this presentation I will summarize the independent observational evidence that indicates that such a transition may indeed have taken place focusing mainly on a new Cepheid data analysis but also on other astrophysical data. Theoretical speculation about the possible origin of such a transition will also be implemented.
中国科学院理论物理研究所专题直播&回放链接：https://www.koushare.com/topicIndex/i/itp-cas
编辑：王茹茹
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