Axions are a hypothetical class of particle predicted in a variety of settings and of utility in solving many mysteries of theoretical physics, most notably as dark matter candidates and solving the strong CP problem. I will describe recent dramatic progress in understanding what string theory predicts about the properties of axions, and the door this opens to test quantum gravity with...
One of the key predictions of the standard inflationary paradigm is the quantum mechanical generation of tensor fluctuations due to the rapid accelerated expansion of space, which later constitute a stochastic background of primordial Gravitational Waves (GWs). The amplitude of the (nearly) scale-invariant inflationary tensor power spectrum at large cosmological scales provides us with crucial...
Both single- and multi-field models of inflation might lead to enhanced scalar fluctuations on scales much smaller than those seeding the large-scale structure formation. In these scenarios, it is possible that the spike of power at high wavenumber might induce large corrections to the scalar power spectrum, e.g. in the form of loop corrections, potentially endangering the perturbativity of...
Friction and noise naturally emerge when gravitational waves propagate through unknown environments. In this talk, I will present a framework that extends effective field theories to systematically incorporate these effects. I will show how fundamental principles — such as symmetries, locality, and unitarity —place constraints on the form of dissipation and noise. Finally, I will discuss the...
The stochastic formalism of inflation allows the statistics of the curvature perturbation to be determined in a non-perturbative way, by reframing the quantum fluctuations during inflation as classical stochastic fluctuations. This is most important for the calculation of non-Gaussianity in the far tail of the perturbation probability distributions, where rare objects such as primordial black...
I describe how evolving moduli and kination epochs in the early universe can lead to a novel post-inflationary string tracker solution, in which 75% of the energy density of the universe is in the form of a gas of fundamental string loops.
