In this talk, I will present the first ab initio computation of white dwarf (WD) cooling due to plasmon decay in a model of gauged $U(1)_{L_\mu-L_\tau}$. In particular, I will present the full result taking into account resonance effects of the $A'$ mass with the WD plasma frequencies.
I will show how current observations of the neutrino luminosity function of early-stage WDs exclude...
As an elegant solution to the strong CP problem and promising dark matter candidate, the QCD axion is one of the best motivated particles beyond the SM. The hunt for the QCD axion, both with terrestrial experiments as well as astrophysical observables, has exploded in the last years. As of today, astrophysical observations, such as neutron star cooling and energy loss from supernovae, place...
New light scalar fields with a negative quadratic coupling to Standard Model fermions can be sourced in large, dense objects. Finite density contributions to the potential result in the displacement of the field from its vacuum value. This situation arises, for example, for a lighter-than-usual QCD axion. The sourcing of the scalar field leads to a reduction of the fermion masses, which,...
Lighter than expected QCD axions can get sourced in neutron stars, which can lead to a new ground state of nuclear matter, reminiscent of strange quark matter. The presence of such a new ground state drastically changes the stellar composition of neutron stars; in particular, in the limit where axion gradient effects can be neglected, the star ends with an extremely large energy density. This...
We revisit the dynamical generation of an arbitrarily small neutrino Yukawa coupling in the Standard Model with trans-Planckian asymptotic safety and apply the same mechanism to the gauged B − L model. We show that thanks to the presence of additional irrelevant couplings, the described neutrino-mass generation in the B − L model is potentially more in line with existing theoretical...
In an external electric or magnetic field, a gravitational wave (GW) may be converted into electromagnetic radiation. We present a coordinate-invariant framework to describe the GW signal in a detector that is based on this effect, such as cavities for axion searches. In this framework, we pay special attention to the definition of manifestly coordinate-independent expressions for the...
Theories beyond General Relativity typically contain at least one additional scalar degree of freedom, effectively mediating an additional force. While this force must be highly suppressed in low-density environments--to pass current constraints--it generically leads to deviations from General Relativity in high-density / high-curvature environments, such as neutron stars and black holes, and...
In this talk, we investigate the interplay between the observation of lepton number violating processes and the generation of the baryon asymmetry of the Universe via low-scale leptogenesis. We focus on the impact of non-standard interactions, beyond the usual Majorana mass term, on the observation of neutrinoless double beta decay and the resulting parameter space for successful leptogenesis....
Constraints on dark sector particles decaying into neutrinos typically focus on their impact on the effective number of relativistic species, $N_{eff}$, in the early Universe. However, for heavy relics with longer lifetimes, constraints mainly arise from the photo-disintegration of primordial abundances. The high-energy neutrinos injected by the decay can interact with both the thermal...
A persistent issue in electroweak baryogenesis calculations is the significant disparity in predictions yielded by different approaches, with variations spanning several orders of magnitude. In this study, we examine a system comprising two fermion flavours, proposing the existence of two sources of CP-violating. The semi-classical force and a new resonantly enhanced mixing source can be...
Analysing Baryogenesis and employing techniques from Non-Equilibrium QFT and integrating them with Functional Renormalization, we demonstrate and calculate key quantities such as the Matter-Antimatter asymmetry and thermal masses and widths. This combination also allows us to re-examine the Sakharov conditions. Moreover, we elucidate the interconnections between various common methodologies.
The cosmic microwave background (CMB) spectrum is an extraordinary tool to explore physics beyond the standard model. Due to the exquisite precision of its measurements, it constitutes a natural place to look for small effects due to the hidden universe. In particular, CMB spectral distortions can unveil the existence of dark photons which are kinetically coupled to the standard photon. In...
Domain walls are a type of topological defects that can arise in the early universe after the spontaneous breaking of a discrete symmetry. This occurs in several beyond Standard Model theories with an extended Higgs sector such as the Next-to-Two-Higgs-Doublet model (N2HDM).
In this talk I will discuss the ingredients needed for the successful generation of a matter-antimatter asymmetry in...
The possibility of a Gamma-Gamma collider extension to the Beam dump of the $17.5$ GeV European XFEL has been discussed before as a first high energy collider of its sort. It would not just be to study the concept of a gamma-gamma collider but this collider would also be without competition in the region of $5-12$ GeV for gamma-gamma physics. In this range $b\bar{b}$ and $c\bar{c}$ resonances,...
