The Physics Colloquium has been arranged regularly since the fall semester of 2021. The detailed schedule and talk information of this semester are as follows.
For inquiries or suggestions of future speakers, please contact the colloquium working group (Prof. Jane Lixin Dai, Prof. Tran Trung Luu, Prof. Yanjun Tu, Prof. Chenjie Wang, and Prof. Shizhong Zhang).
Cosmology, Supernovae and Black Holes through Cosmic Lenses
Speaker: Prof. Sherry Suyu
Affiliation: Technical University of Munich
Date: September 24, 2025 (Wednesday) September 26, 2025 (Friday)
Time: 4:30 p.m. 10:00 a.m.
Venue: KB132, 1/F, Knowles Building, CBA, G/F, Chow Yei Ching Building, Main Campus, HKU, The University of Hong Kong
Poster: Download
Abstract:
Strongly lensed transients such as supernovae (SNe) and tidal disruption events (TDEs) are emerging as a new probe of cosmology, SNe and black holes. When a SN is strongly lensed by a foreground galaxy, multiple images of the SN will appear around the foreground galaxy at different times. Current and upcoming surveys including Euclid and the Rubin Observatory Legacy Survey of Space and Time (LSST) will capture hundreds of strongly lensed SNe, expanding the existing sample by two orders of magnitude. These surveys will also enable the discovery of the first strongly lensed TDEs. These events offer excellent opportunities to: (1) measure the Hubble constant via lensing time delays, shedding light on the Hubble tension, (2) obtain unprecedented constraints on SN progenitors through early-phase spectra, and (3) acquire unique insights on the emission mechanisms of TDEs that are crucial for studying black holes. I will give an overview of the first discoveries of lensed SNe and their cosmological implications, and show the rates of strongly lensed TDEs from upcoming surveys.
Key Reference:
- Suyu S. H., Goobar A., Collett T., More A., Vernardos G., 2024, SSRv, 220, 13. doi:10.1007/s11214-024-01044-7
- Kelly P. L., Rodney S., Treu T., Oguri M., Chen W., Zitrin A., Birrer S., et al., 2023, Sci, 380, abh1322. doi:10.1126/science.abh1322
- Grillo C., Pagano L., Rosati P., Suyu S.~H., 2024, A&A, 684, L23. doi:10.1051/0004-6361/202449278
- Pierel J. D. R., Newman A. B., Dhawan S., Gu M., Joshi B. A., Li T., Schuldt S., et al., 2024, ApJL, 967, L37. doi:10.3847/2041-8213/ad4648
- Mamuzic E., Ryu T., Suyu S. H., Szekerczes K., Huber S., Dai L., Oguri M., 2025, A&A, 701, A142. doi:10.1051/0004-6361/202554367
Advancing Fundamental Understanding of Nature: ATLAS Searches for New Physics
Speaker: Prof. Yang Liu
Affiliation: Sun Yat sen University
Date: October 8, 2025 (Wednesday)
Time: 4:30 p.m.
Venue: KB132, 1/F, Knowles Building, Main Campus, HKU, The University of Hong Kong
Poster: Download
Abstract:
The Standard Model (SM) is the most precise and successful framework for describing the fundamental constituents of matter and their interactions. Yet observations such as dark matter and the matter–antimatter asymmetry point to New Physics beyond the SM, motivating continued searches to deepen our understanding of nature. The ATLAS experiment—a flagship detector at the CERN Large Hadron Collider (LHC) and one of the world’s largest international collaborations—operates at the highest collision energies available, offering a unique opportunity to probe such new phenomena. In this talk, I will briefly review the LHC and ATLAS’s general search strategies, then highlight recent results from New Physics searches and discuss future prospects.
Key Reference:
- Exploration at the high-energy frontier: ATLAS Run 2 searches investigating the exotic jungle beyond the Standard Model, ATLAS Collaboration, Physics Reports, 1116, 2025, 301-385
- The quest to discover supersymmetry at the ATLAS experiment, ATLAS Collaboration, Physics Reports, 1116, 2025, 261-300
- Review of searches for vector-like quarks, vector-like leptons, and heavy neutral leptons in proton–proton collisions at √s=13 TeV at the CMS experiment, CMS Collaboration, 1115, 2025, 570-677
- Dark sector searches with the CMS experiment, CMS Collaboration, 1115, 2025, 448-569
Cold-atom quantum sensing via Bayesian quantum estimation
Speaker: Prof. Chaohong Li
Affiliation: Shenzhen University
Date: October 22, 2025 (Wednesday)
Time: 10:30 a.m.
Venue: MWT2, G/F, Meng Wah Complex, Main Campus, HKU, The University of Hong Kong
Poster: Download
Abstract:
Quantum sensors based on frequentist interferometry face a trade-off between sensitivity and dynamic range. Bayesian quantum estimation, combining Bayesian statistics with quantum metrology, can surpass the limit of conventional frequentist measurements. For cold-atom CPT clocks, our adaptive Bayesian protocol achieves Heisenberg-limited sensitivity in integration time and improves fractional frequency stability by 5.1(4) dB over conventional PID locking while enhancing robustness against technical noise [1]. In CPT magnetometry, we optimize measurement sequences to improve precision scaling from T-0.5 to T-0.85. Using Bayesian quantum estimation to optimize the interferometry sequence, we yield a 145.6 nT dynamic range (14.6 dB higher than frequentist counterpart of 5.0 nT) with a sensitivity of 6.8 ± 0.1 pT/Hz¹/² (3.3 dB improvement over the frequentist counterpart of 14.7 ± 0.4 pT/Hz¹/²) [2]. In addition to atomic clocks and magnetometers, this framework may bridge high sensitivity and broad dynamic range for other interferometry-based quantum sensors.
Key Reference:
- Chengyin Han, Zhu Ma, Yuxiang Qiu, Ruihuan Fang, Jiatao Wu, Chang Zhan, Maojie Lee, Jiahao Huang, Bo Lu, and Chaohong Lee, Atomic clock locking with Bayesian quantum pa-rameter estimation: Scheme and experiment. Physical Review Applied, 22(4): 044058 (2024).
- Zhu Ma, Chengyin Han, Zhi Tan, Haihua He, Shenzhen Shi, Xin Kang, JiaTao Wu, Jiahao Huang, Bo Lu, and Chaohong Lee, Adaptive cold-atom magnetometry mitigating the trade-off between sensitivity and dynamic range. Science Advances, 11(9): eadt3938 (2025).
TBC
Speaker: Prof. Weimin Yuan
Affiliation: NAOC
Date: November 5, 2025 (Wednesday) (Canceled)
Time: 10:30 a.m.(Canceled)
Venue: Rayson Huang Theatre, Main Campus, HKU, The University of Hong Kong
Poster: TBC
Abstract:TBC
Spin chains on metallic surfaces: model systems for heavy fermion quantum criticality
Speaker: Prof. Fakher Assaad
Affiliation: Universität Würzburg
Date: November 19, 2025 (Wednesday)
Time: 4:30 p.m.
Venue: MW103, 1/F, Meng Wah Complex, Main Campus, HKU, The University of Hong Kong
Poster: Download
Abstract:
Cobalt adatoms on metallic surfaces can be described by a simple model: a spin 3/2 Heisenberg chain with single ion anisotropy, coupled antiferromagnetically to the two dimensional conduction elections. On the basis of numerical simulations and scaling arguments we will show that this simple system allows us to explore a wealth of quantum phenomena—including the breakdown of quasiparticles, dissipation-induced quantum phase transitions, topological phases with protected edge modes, and Kondo-screened heavy Fermi liquid phases.
Key Reference:
- arXiv: 2509.11392
TBC
Speaker: Prof. Matthias Vojta
Affiliation: Technische Universität Dresden
Date: December 3, 2025 (Wednesday)
Time: 4:30 p.m.
Venue: KB132, 1/F, Knowles Building, Main Campus, HKU, The University of Hong Kong
Poster: TBC
Abstract: TBC
Key Reference: TBC