Title: de Sitter as an Axion Detector Abstract: Axions, scalar fields with compact field spaces, are some of the most well-motivated candidates for physics beyond the Standard Model. In this talk, I will explain how inflationary correlations are uniquely sensitive to the topology of a scalar's field space, and can thus be used to distinguish […]
Title: "Towards Dark Ages with LuSEE-Night" plus "large scale isocurvature fluctuations and the Hubble tension"
Title: Gravitational Wave Symphony from Oscillating Spectator Scalar Fields Abstract: Spectator scalar fields can be generically present in the early Universe, and are potentially dark matter candidates. We investigate the prospect of such scalars as a generic source of stochastic gravitational wave background (SGWB) due to parametric resonance during their oscillation phase. By systematically analyzing […]
High Energy Physics Theory Seminar: Yiming Chen Bloomberg 447 May 31, 2024 11:00 AM - 12:00 PM
TITLE: Impact of primordial magnetic fields on matter power spectrum ABSTRACT: Primordial magnetic fields (PMFs) offer a simple explanation for the origin of galactic magnetic fields as well as of the purportedly detected magnetic fields in cosmic voids. In the talk, I discuss how PMFs' influence on structure formation can offer a complementary method to […]
TITLE: CMB limits on decaying dark matter: going beyond the ionization threshold ABSTRACT: The temperature and polarization anisotropies of the cosmic microwave background (CMB) have been used to set constraints on decaying dark matter models down to keV masses. In this talk, I will discuss recent work to extend these limits down into the sub-keV […]
Title: Binary black hole waveforms in the small mass ratio limit Abstract: Current gravitational-wave detectors are being upgraded, and plans are developing for future detectors with greater sensitivity over broader frequency bands. As instruments improve and develop, more cycles of sources’ gravitational waveforms will be measured with greater signal to noise ratio. Such higher fidelity […]
TITLE: Studying the Extreme Universe with Imaging Atmospheric Cherenkov Telescopes, ABSTRACT: The night sky is filled with flashes of blue "Cherenkov" light, which last for just a few billionths of a second. Invisible to our eyes, these flashes result from particle cascades in the Earth's atmosphere triggered by the arrival of a high energy cosmic […]
TITLE: Revisiting the axion-electron coupling ABSTRACT: In the presence of axion dark matter, fermion spins experience an “axion wind” torque and an “axioelectric” force. We investigate new experimental probes of these effects and find that magnetized analogs of multilayer dielectric haloscopes can explore orders of magnitude of new parameter space for the axion-electron coupling. We also […]
TITLE: Ghosts on the way to a QFT for gravity ABSTRACT: Ghosts have been a stumbling block in the development of a UV complete quantum field theory for gravity. We discuss how difficulties associated with ghosts are overcome in the context of 0+1d QFT. Obtaining a probability interpretation is the key issue, and for this […]
TITLE: Quasinormal Modes from Penrose Limits ABSTRACT: In this talk, I will explain how to describe quasinormal modes with a large real frequency using Penrose limits. To do so, I first recall relevant aspects of the Penrose limit, as well as the plane wave spacetimes that arise in this limit, to subsequently tie this together with […]
Title: Quantum near extremal black holes and anomalies Abstract: The Bekenstein–Hawking formula gives a coarse-grained count of the number of microstates of a black hole, and it is remarkable that it may sometimes be reproduced from a microscopic count in string theory. However, the standard approach (which we will briefly review) typically relies on supersymmetry by counting […]