Donal O’Connell (Edinburgh)“Quantum Amplitudes and Classical Gravity” ABSTRACT:Scattering amplitudes in quantum field theory have received a lot of attention in recent years. We have learned that amplitudes provide a surprising link, known as the double copy, between Einstein gravity and Yang-Mills theory. I will explain why the double copy persists at the classical level, and discuss the resulting two-way flow … Read More

Sterile neutrino is a very simple dark matter candidate. In the minimal incarnation, the original Dodelson-Widrow mechanism that explains its relic abundance is in strong tension with indirect detection constraints. I present the self interacting neutrino scenario, mediated by a Majoron-like scalar or vector boson, as a novel solution to the above tension. It opens up new & wide parameter … Read More

I will discuss the on-shell formulation of effective theories, focusing on extensions of the electroweak sector. I will describe a systematic construction of bases for general massive 4-point amplitudes, utilizing the relations between massive and massless spinor amplitudes via (un)bolding. We will also see how properties of Higgsed gauge theories emerge from on-shell massive amplitudes.

Particle Theory Seminar | Sebastian Baum (Stanford): Paleo-Detectors – Digging for Dark Matter and Neutrinos Paleo-Detectors are natural minerals which record damage tracks from nuclear recoils over geological timescales. Minerals commonly found on Earth are as old as a billion years. Modern microscopy techniques may allow to reconstruct these damage tracks with nanometer scale spatial resolution. Thus, paleo-detectors would constitute … Read More

If even a relatively small number of primordial black holes (PBH) were created in the early universe, they will constitute an increasingly large fraction of the total energy density as space expands. It is thus well-motivated to consider scenarios in which the early universe was dominated by short lived PBH (M < 10^9 grams, t 10^11 GeV) to avoid overproduction. … Read More

Noble-alkali comagnetometers offer the exciting possibility of detecting the anomalous magnetic fields sourced by ultralight axion-like particles. I will discuss an on-going reanalysis of data from a helium-potassium comagnetometer at Princeton, which is expected to yield world-leading sensitivity to axion-neutron couplings in the mass range from to eV. This analysis requires a careful treatment of the stochastic fluctuations of the … Read More

Abstract: The quantum chromodynamics axion is a well-motivated dark matter candidate that may also solve the strong CP problem related to the absence of the neutron electric dipole moment. Multiple experimental efforts are currently racing to try to discover this particle in the laboratory. In this talk I will show that astrophysical observations are also a promising path towards detecting … Read More

Spacetime wormholes Low-energy quantum gravity has recently shown itself to be surprisingly powerful. Gravity provides geometric descriptions of quantum phenomena, with no reference to a UV completion such as string theory. In particular, the information content of an evaporating black hole and its Hawking radiation can be calculated, shedding new light on the black hole information problem. A common theme … Read More