1st Beijing Physics, Astrophysics and Cosmology Workshop (B-PAC)

Tuesday 31 Mar 2026, 09:00 → 16:00 Asia/Shanghai

ICTP-AP

Andrew Miller (ICTP - AP / University Chinese Academy of Sciences), Verónica Vázquez-Aceves (PKU / KIAA)

This meeting aims to bring together Beijing-based scientists that are working on physics, astrophysics and cosmology. It hopes to foster new collaborations and create a network of physicists working in Beijing.

Topics of interest include, but are not limited to:

• Gravitational waves
• Dark matter
• Neutron stars
• Black holes
• Primordial black holes
• Particle physics

 

We welcome participation from all members of the community, and especially from early-career scientists. This meeting will feature two presentations, lunch and a discussion session. We have invited:

1. Pau Amaro Seoane (Universitat Politècnica de València)
2. Mai Qiao (ICTP-AP)

 

To confirm your attendance, please register at the link.

 

 

09:30 → 10:00 Registration

10:00 → 10:05 Welcome

10:05 → 11:00 A forest of gravitational waves in our Galactic Centre

The Galactic Centre contains populations of stellar-mass and
substellar-mass compact objects orbiting the central black hole,
classified as early extreme-mass ratio inspirals (E-EMRIs) and extremely
large mass ratio inspirals (XMRIs). These systems constitute asymmetric
binaries, characterized by mass ratios exceeding 10,0000 to 1. This mass
differential causes the secondary body to approximate a test particle,
completing tens of thousands or millions of orbital cycles prior to
coalescence. This high cycle count delineates the spacetime geometry and
multipolar structure of the central black hole with greater resolution
than comparable-mass supermassive black hole binaries, which undergo
rapid coalescence and exhibit fewer in-band cycles. The prolonged
orbital data can in principle also facilitate topological analysis. By
applying the Gauss-Bonnet theorem, the accumulated orbital precession
parameters relate the integrated curvature of the spacetime to its
topological invariants. The continuous gravitational wave emission from
these populations generates a non-Gaussian, non-stationary composite
signal within the frequency band of the Laser Interferometer Space
Antenna. This aggregated signal comprises an incoherent superposition of
individual waveforms from eccentric and circular orbits, which
superimposes upon the spectral signatures of other target sources,
including binaries of supermassive black holes and verification
binaries. Spectral analysis indicates that sources with minimal
frequency drift constitute an unresolved stochastic background, while
systems with measurable frequency evolution produce distinct spectral
components. Extracting targeted signals from this composite data
requires time-frequency domain modeling and non-Poissonian statistical
subtraction protocols.

Speaker: Prof. Pau Amaro Seoane (Universitat Politècnica de València)

11:00 → 11:30 Break

11:30 → 12:30 Probing New Physics through Gravitational Wave Detection and Dark Matter Direct Detection

Numerous astrophysical observations indicate the existence of dark matter via gravitational effects, yet its nature remains elusive. Experiments exploring non-gravitational interactions between dark matter and Standard Model (SM) particles include indirect, direct, and collider detection. Meanwhile, gravitational-wave (GW) observations of compact binary coalescences since GW150914 also offer valuable opportunities to both probe the early Universe and DM interactions. This talk covers three diverse topics: ultralight DM (ULDM) searches with LIGO data, correlated noise in stochastic gravitational-wave background (SGWB) studies, and MeV-scale light DM detection strategies. Specifically, we discuss ULDM detection using new LIGO data via the cross-correlation, Band-Sampled Data excess power (BSD), and Logarithmic Power Spectral Density (LPSD) methods. Regarding correlated noise, we address strategies to estimate its impact on SGWB research by monitoring magnetic field couplings with GW strain channels. Finally, for light DM, we present constraints on effective operators via cosmic-ray boosted DM (CRDM) with LZ data and analyze potential diurnal modulation effects in underground ionization signals caused by the Earth attenuation.

Speaker: Dr Mai Qiao (ICTP - AP / University Chinese Academy of Sciences)

12:30 → 14:00 Lunch

14:00 → 15:00 Discussion

Conveners: Andrew Miller (ICTP - AP / University Chinese Academy of Sciences), Veronica Vazquez-Aceves