It is a well-known fact that compact gravitating objects admit bound state configurations for massive bosonic fields. In this work we describe a new class of superradiant instabilities of axion bound states in neutron star magnetospheres. The instability arises from the mixing of axion and photon modes in the magnetic field of the neutron star which extract energy from the rotating magnetosphere. ... More

I will briefly explore the definition and limitations of the Cold Dark Matter (CDM) paradigm before introducing Generalised Dark Matter (GDM), an approach that subsumes the CDM paradigm. GDM facilitates well-defined model-independent observational constraints on the cosmological dark matter, including null tests of CDM. I will present some constraints that have been obtained using a combination of ... More

Sterile neutrinos is one of the possible physics beyond the Standard Model motivated by neutrino oscillations. Stable at cosmological time-scale sterile neutrinos may serve as dark matter. Typically, with mass in keV range, the sterile neutrinos form Warm dark matter and radiatively decay in galaxies providing X-ray telescopes with a prominent signature. Extensive searches for the sterile neu ... More

If a component of dark matter is millicharged, dark matter-baryon scattering can induce large effects in the 21-cm global signal by cooling the baryons. This can be achieved without being excluded by other cosmological, astrophysical or terrestrial constraints. We point out two important effects which have been overlooked in previous analyses. First, introducing a dark interaction between the mill ... More

In arXiv:1904.12783, we showed through numerical simulations of a minimally coupled massive Klein-Gordon scalar field that it is possible to grow "hair" on a Schwarzschild black hole if one assumes a periodically time-varying (but spatially homogeneous) background. We saw a non-trivial profile emerge on a timescale related to the mass of the black hole, both with and without backreaction of the fi ... More

I argue for the existence of topologically stable, finite mass monopoles within Born-Infeld extension of the standard model and discuss some phenomenological and cosmological implications.

At low energies, the world around us can be described very accurately using the Standard Model and \Lambda CDM. However, these are at best only ``effective'' descriptions: valid at low energies but destined to break down as experiments in particle physics and cosmology probe increasingly higher energies, ultimately requiring a new (UV complete) theory to take over. In this talk, I will review t ... More

Strong coupling in Higgs inflation at high energies hinders a joint description of inflation, reheating and low-energy dynamics. The situation may be improved with a proper UV completion of the model. A well-defined self-consistent way is to introduce an R^2-term into the action. In this modified model the strong coupling scale returns back to the Planck scale, which justifies the use of the pertu ... More

I am going to compare two simple models of dark matter (DM): a vector and a scalar DM model. Both models require the presence of two physical Higgs bosons h_1 and h_2 which come from mixed components of the standard Higgs doublet H and a complex singlet S. In the vector model, the extra U(1) symmetry is spontaneously broken by the vacuum of the complex field S. This leads to a massive gauge boson ... More

We study the consequences of (beyond) positivity of scattering amplitudes in the effective field theory description of the Higgs-Dilaton inflationary model. By requiring the EFT to be compatible with a unitary, causal, local and Lorentz invariant UV completion, we derive constraints on the Wilson coefficients of the first higher order derivative operators. We show that the values allowed by the co ... More