Axions are hypothetical elementary particles with their small masses and tiny couplings to matter sectors, and they are known as the promising candidates for the dark matter in our Universe. Axions generically couple to the photon via the chiral anomaly effect and differentiate the phase velocities between two circularly-polarized photons, which leads to a rotation of photon's polarization...
When coupled to electromagnetism via a Chern-Simons interaction, axion-like particles (ALP) produce a rotation of the plane of linear polarization of photons known as cosmic birefringence. Recent measurements of cosmic birefringence obtained from the polarization of the cosmic microwave background (CMB) hint at the existence of an isotropic birefringence angle of $\beta\approx0.3^\circ$....
Dark matter interactions with Standard Model particles can inject energy at early times, altering the standard evolution of the early universe. In particular, this energy injection can perturb the spectrum of the cosmic microwave background (CMB) away from that of a perfect blackbody and affect processes by which the first stars form. For this study, I will discuss recent work to update the...
Unveiling the true nature of Dark Matter (DM), which manifests itself only through gravity, is one of the principal quests in physics. Leading candidates for DM are weakly interacting massive particles (WIMPs) or ultralight bosons (axions), at opposite extremes in mass scales,that have been postulated by competing theories to solve deficiencies in the Standard Model of particle physics....
In the fuzzy dark matter model, dark matter consists of “axion-like” ultra-light scalar particles with a mass of around $10^{-22}$ eV. This candidate behaves similarly to cold dark matter on large scales, but exhibits different properties on smaller (galactic) scales due to macroscopic wave effects arising from the extremely light particles’ large de Broglie wavelengths. It has both particle...
In simulations of galaxy formation, dark matter is typically modeled as a cold, collisionless particle that interacts solely through the force of gravity. This is an excellent approximation in many aspects of structure formation, but discrepancies remain between predictions and observations especially in the density profile shape of various sizes of dark matter halos. Such discrepancies may...
Cosmological and astrophysical observations provide a unique opportunity to probe the fundamental properties of dark matter. Dark matter interactions with the Standard Model of particle physics, for example, can alter predictions from the standard cosmological model, permitting robust tests of new dark matter physics. In this talk, I will describe the effects of dark matter elastic scattering...
Observational constraints have closed off all but one mass-window for primordial black holes making up all of the dark matter, and there are some specific conditions required for their production in the first place. However, they remain a tantalising dark matter candidate because they require no new beyond the standard model particles and they would additionally provide a lot of information...
Caustic crossing events of stars in galaxies lensed by galaxy clusters can lead to extreme magnification factors, $\mu > 1000$. Several stars at cosmological redshifts, $z > 1$, have already been observed by the Hubble Space Telescope, and the number is rapidly increasing with the Jame Webb Space Telescope. The probability distribution of magnification depends on the galaxy cluster and the...
The first stars in the Universe, soon to be observed with the James Webb Space Telescope (JWST) can be extremely powerful Dark Matter (DM) probes. If DM does not play a significant role in the formation of some of the first stars, then, zero metallicity Hydrogen burners (Population III stars) form. Conversely, for scenarios where DM plays a significant role during the formation of a star from...
Strong gravitational lensing by galaxies provides us with a powerful laboratory for testing dark matter models. Various particle models for dark matter give rise to different small-scale distributions of mass in the lens galaxy, which can be differentiated if the observation is sensitive enough. The sensitivity of a gravitational lens observation to the presence (or absence) of low-mass dark...
