Times: Wednesdays, 4:45-6:00 p.m. (but sometimes 9 a.m., depending on time zone)
To receive the announcements and the invitations to the video conference, please contact Zac Picker and subscribe to the Google group firstname.lastname@example.org. All subscribers will receive an invitation to the seminar as full participants.
Seminars can also be attended in-person at room PAB 4-708 of the Physics and Astronomy Building at UCLA.
Wednesday, Nov. 1 2023 4:45 PM PST
Mehrdad Phoroutan Mehr (UC Riverside), Constraints on Dark Matter Models with Astrophysical Observations
In this talk, I will discuss the constraints on dark matter properties with compact astrophysical objects. I will first present indirect detection constraints of self-interacting dark matter models using gamma-ray measurements from the M87 galaxy. This model predicts robust dark matter self-interactions, thermalizing the inner halo. Consequently, the density profile surrounding the supermassive black hole of M87 becomes shallower compared to that in the cold dark matter model. We find that the expected signal strength is below the current gamma-ray constraints for both s- and p-wave annihilation, even in the presence of Sommerfeld enhancement. Then, I will discuss dark matter searches with exoplanets. Dark matter particles can be captured by exoplanets, leading to observable signals, such as anomalous heating and potential destruction. Lastly, I will discuss constraints on inelastic dark matter from neutron stars, direct detection experiments, and the observed relic abundance of dark matter
Wednesday, Nov. 8 2023 4:45 PM PST
Ellen Sirks (University of Sydney), TBC, cosmology or astronomy
Past seminars, 2022/2023
Wednesday, Oct. 25 2023 4:45 PM PST
Valerio De Luca (University of Pennsylvania), Superfluid dark matter around black holes
The theory of superfluid dark matter is based on sub-eV, self-interacting, bosons which may undergo Bose-Einstein condensation at the center of galaxies, thus creating a superfluid homogeneous core. We show how the superfluid density profile changes when massive black holes sit within these environments, giving rise to dark matter spikes whose slopes depend on the bosons self-interactions. Finally, we discuss the role of dynamical friction in the evolution of black hole binaries moving within the superfluid.
Wednesday Oct. 18, 2023 4:45 PM PST
Stefano Profumo (UC Santa Cruz), Rogue Worlds Meet the Dark Side
In the age of gravitational wave astronomy and direct black hole imaging, the possibility that some of the black holes in the universe have a primordial, rather than stellar, origin, and that they might be a non-negligible fraction of the cosmological dark matter, is quite intriguing. I will discuss a few ongoing projects, including (perhaps not in this exact order) (1) understanding how current and future microlensing surveys may have detected, or will soon detect, a mix of rogue planets and, potentially, light black holes of non-stellar origin, (2) what to expect if, and whether to expect that, a nearby light black hole was exploding right now, (3) how self-interacting dark matter can lead to primordial-looking late-forming black holes, and (4) whether microstructure black holes (originally proposed by Picker and Kusenko) can produce exotic forms of antimatter.
Wednesday Oct. 11, 2023 4:45 PM PST
Vincent S.H. Lee (Caltech), Probing Dark Matter with Pulsar Timing Arrays and Gravitational Wave Detectors
Pulsar timing arrays (PTAs) and gravitational wave detectors can serve as valuable tools in the detection of dark matter. Dark matter substructure within the Milky Way Galaxy can induce gravitational pulls on pulsars, leading to observable deviations in pulsar timings. We demonstrate that dark matter models predicting enhanced power on small scales are potentially within the reach of future PTA experiments, such as the Square Kilometer Array (SKA). This includes a class of post-inflationary QCD axion models known as axion miniclusters. We also discuss pipelines for searching for dark matter signals in PTA datasets and recent results from the 15-year data release of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), which has reported evidence of a stochastic gravitational background. Furthermore, dark matter particles with a mass on the kilogram scale can also produce signals in laser interferometry-based gravitational wave experiments. We discuss the signals and detection prospects from current and future gravitational wave experiments, such as LIGO and the Einstein Telescope.
Wednesday Oct. 4, 2023 4:45 PM PST
Christopher Cappiello (Queen's U, Kingston), The Morphology of Exciting Dark Matter and the Galactic 511 keV Signal
More than 50 years after it was first observed, the 511-keV gamma ray line at the Galactic Center remains unexplained, and numerous dark matter models have been proposed to account for this signal. Perhaps the simplest is the annihilation of light dark matter into electron-positron pairs, but this model faces challenges due to cosmological bounds on the required dark matter mass range. An alternative model, which avoids these constraints, is exciting dark matter (XDM). In this model, collisions between TeV-scale dark matter particles excite the dark matter to a state that can then decay back to the ground state, releasing an electron-positron pair. We study the morphology of the 511-keV signal produced by both the annihilating and exciting dark matter models, and compare the resulting flux with the most recent INTEGRAL data. We perform the first full statistical analysis of the exciting dark matter model, and find that it reproduces the observed morphology significantly better than the annihilating dark matter case.