Abstract The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders
about the fundamental theory of nature at play in the extreme gravity regime, where the …

We review the landscape of QCD axion models. Theoretical constructions that extend the
window for the axion mass and couplings beyond conventional regions are highlighted and …

The dark photon is a massive hypothetical particle that interacts with the Standard Model by
kinetically mixing with the visible photon. For small values of the mixing parameter, dark …

In this paper, which is of programmatic rather than quantitative nature, we aim to further
delineate and sharpen the future potential of the LISA mission in the area of fundamental …

Ultralight bosons can affect the dynamics of spinning black holes (BHs) via superradiant
instability, which can lead to a time evolution of the supermassive BH shadow. We study …

Now that detection of gravitational-wave signals from the coalescence of extra-galactic
compact binary star mergers has become nearly routine, it is intriguing to consider other …

Black hole superradiance is a powerful probe of light, weakly coupled hidden sector
particles. Many candidate particles, such as axions, generically have self-interactions that …

Axions and other very light axion-like particles appear in many extensions of the Standard
Model, and are leading candidates to compose part or all of the missing matter of the …

We conduct frequency comparisons between a state-of-the-art strontium optical lattice clock,
a cryogenic crystalline silicon cavity, and a hydrogen maser to set new bounds on the …

Black hole (BH) shadows can be used to probe new physics in the form of ultralight particles
via the phenomenon of superradiant instability. By directly affecting the BH mass and spin …