I will present recent results from and future plans of the Axion Dark Matter eXperiment (ADMX). Recent results include a first pass axion search of the 800-1020 MHz frequency range at half DFSZ sensitivity for 100% axion dark matter density, the demonstration of a traveling wave parametric amplifier (TWPA) for higher-frequency wide-band operation, and a multi-mode candidate identification...
Originally proposed as a solution to the strong CP problem, the axion is also well motivated as a candidate for dark matter. In the less-explored axion mass range below 1 ueV axions behave as long-wavelength dark matter, the search for which requires novel approaches and techniques. With ABRACADABRA-10cm we demonstrate the ability to search for GUT-scale axions in the range of 0.3 to 8 neV...
I present Dark Matter Radio (DMRadio), a multi-faceted program to probe axion dark matter below 1 ueV using an electromagnetic lumped-element resonator. I describe the detection concept and design principles and discuss present experimental status. DMRadio-50L, under construction, will probe axion-like particles in the 20 peV-20 neV mass range. It will serve as a testbed for sensors evading...
In this talk, I will discuss a range of approaches to better understand ultralight and light scalar dark matter candidates, including axion-like particles. I will discuss results from PySiUltraLight, a modification of the PyUltraLight code that includes self-interaction terms to model the dynamical evolution of axion fields. I will discuss work that shows that the self-interaction should not...
Axion couplings to photons could induce photon-axion conversion in the presence of magnetic fields in the Universe. This conversion could impact various cosmic distance measurements, such as luminosity distances to type Ia supernovae and angular distances to galaxy clusters, in different ways. In this talk we consider different combinations of the most up-to-date distance measurements to...
Axion quasiparticles may exist in certain condensed matter systems. I will discuss the physics of axion quasiparticles, and how they may be used to detect axion dark matter via three-way mixing between the photon, axion and axion quasiparticle. I will introduce the proposed TOORAD experiment for TOpolOgical Resonant Axion Detection.
Axions couple extremely weakly to regular matter, making them challenging to probe in the laboratory. However, axions should be produced in the hot and dense environments of compact stars, providing these stars with an additional cooling channel that leads to well-known constraints on the axion’s couplings to matter. These constraints are indirect, and although compact stars are predicted to...
Conventional approaches to probing axions and axion-like particles (ALPs)typically rely on a coupling to photons. However, if this coupling is extremely weak, ALPs become invisible and are effectively decoupled from the Standard Model. We show that such invisible axions, which are viable candidates for dark matter, can produce a stochastic gravitational wave background in the early universe...
In this talk I discuss the gravitational wave signals of dynamical axion models. In particular, I focus on models which solve the strong CP problem and include the confinement of a QCD-like gauge group at the TeV scale. Interestingly, the amplitude of the gravitational wave spectrum depends on the mass of the dynamical axion. The resulting spectra may be observed at future mid-range...
In the monopole background, multi-fermion operators exhibit condensation. The phases of the operators are "axions" in the sense that they are topologically coupled to the electromagnetic field. We propose that an ``excited'' closed axion string is the fermion itself. We use this picture to solve a long-standing puzzle in the scattering process of a monopole and a massless fermion. It has been...
Axion models are phenomenologically relevant QFTs that exhibit higher group global symmetries. Higher groups describe the case when different types of higher form symmetries combine together in a non-trivial structure. In this talk, we will discuss how the emergence of these higher groups can be used to infer non-trivial constraints on the RG flows of theories that flow to axion-Yang-Mills in the IR.
Axions are conspicuous in particle physics; their role in physics beyond the Standard Model and cosmology cannot be overestimated. Despite the fact that they have been around for more than 40 years, recent formal developments have brought in new lessons on the interplay between axions and strong dynamics. In this talk, I discuss a new class of generalized 't Hooft anomalies that was recently...
Cosmic birefringence is predicted if an axion-like particle (ALP) moves after the recombination epoch. We show that this naturally happens if the ALP is coupled to the dark matter density because it then acquires a large effective mass after the matter-radiation equality. We give a simple model to realize this scenario, where dark matter is made of hidden monopoles, which give the ALP such a...
We study new signatures associated with electromagnetic properties of axion strings. We focus
on charge deposition onto axion strings from electromagnetic fields and
the subsequent novel neutralizing
mechanisms due to bound state formation. While early universe
signatures appear unlikely, there are a plethora of late time
signatures. Axion strings passing through galaxies obtain an...
Black hole superradiance is a powerful probe of light, weakly-coupled hidden sector particles. Particles with a Compton wavelength comparable to the black hole’s radius lead to an instability, extracting mass and angular momentum from the black hole. Many ultralight candidates, such as axions, generically have self-interactions that can influence the evolution of the superradiant instability. ...
We propose a paradigm where the QCD axion’s unexplored cosmological evolution, a rotation in the field space, gives rise to dark matter, the baryon asymmetry, and/or gravitational waves. The rotation is initiated by explicit Peccei-Quinn (PQ) symmetry breaking effective in the early Universe. The abundance of axion dark matter is determined by the rotational speed via what we call kinetic...
Parity solutions to the strong CP problem are a compelling alternative to approaches based on Peccei-Quinn symmetry, particularly given the expected violation of global symmetries in a theory of quantum gravity. The most natural of these solutions break parity at a low scale, giving rise to a host of experimentally accessible signals. We assess the status of the simplest parity-based solution...