College of Arts and Sciences

Within the Minimal Supersymmetric Standard Model (MSSM), LHC bounds suggest that scalar superpartner masses are far above the electroweak scale. Given a high superpartner mass, nonthermal dark matter is a viable alternative to WIMP dark matter generated via freezeout. In the presence of moduli fields nonthermal dark matter production is associated with a long matter dominated phase, modifying the spectral index and primordial tensor amplitude relative to those in a thermalized primordial universe. Nonthermal dark matter can have a higher self-interaction cross-section than its thermal counterpart, enhancing astrophysical bounds on its annihilation signals. I will review recent progress in this program,

Continue reading… Supersymmetry, Non-thermal Dark Matter and Precision Cosmology

Various cosmological observations consist of prolonged integrations over small patches of sky. These include searches for B-modes in the CMB, the power spectrum of 21-cm fluctuations during the epoch of reionization and deep-field imaging by telescopes such as HST/JWST, among others. However, since these measurements are hindered by spatially-varying foreground noise, the observational sensitivity can be improved considerably by finding the region of sky cleanest of foregrounds. The best strategy thus involves a tradeoff between exploration (to find lower-foreground patches) and exploitation (through prolonged integration). But how to balance this tradeoff efficiently? This problem is akin to the multi-armed bandit (MAB) problem in probability theory,

Continue reading… Cosmic Bandits: Exploration vs. Exploitation in Cosmological Surveys – Ely Kovetz

The latest results from the PLANCK collaboration, consistent with the simplest single-field models of slow-roll inflation and with no trace of non-Gaussianity, have extinguished many hopes of seeing specific aspects of New Physics directly in the sky. One may then wonder whether the landscape of allowed inflationary models has been practically reduced to single-field effective theories. I shall argue that the answer is negative and present several inflationary models in which the turn-induced interactions between two scalar fields affect the normalization/running of the power spectrum of curvature perturbations, or smooth out its features (e.g. via particle production), actually driving the power spectrum towards phenomenologically acceptable characteristics.

Continue reading… Turning trajectories in multi-field inflation – Krzysztof Turzyński

Recent approaches to quantum gravity question the role of Lorentz invariance as a fundamental symmetry of Nature. This has implications for most of the observables in gravitational physics, also at low-energies. In this talk I will describe recent bounds on deviations from Lorentz invariance in gravity coming from binary pulsar observations and cosmological data.

Continue reading… Lorentz violation in gravity: why, how and where – Diego Blas

In general relativity, there are non-local quantum effects that come from the propagation of light particles including gravitons. I will review the effective field theory treatment which allows one to identify the reliable parts of the quantum loops. In cosmology, there are then non-local corrections to the FLRW equations. I will present some of the formalism for this and give some exploration of results.

Continue reading… Non-local quantum effects in cosmology – John Donoghue

We will explore the role that conformal symmetries may play in cosmology. First, we will discuss the symmetries underlying the statistics of the primordial perturbations which seeded the temperature anisotropies of the Cosmic Microwave Background. I will show how symmetry considerations lead us to three broad classes of theories to explain these perturbations: single-field inflation, multi-field inflation, and the conformal mechanism. We will discuss the symmetries in each case and derive their model-independent consequences. Finally, we will examine the possibility of violating the null energy condition with a well-behaved quantum field theory.

Continue reading… Cosmology from conformal symmetry – Austin Joyce

In this talk, I will discuss some general properties of effective theories of Goldstone bosons in which Lorentz symmetry is spontaneously broken. I will first introduce an extension of Goldstone theorem to systems with a finite density of charge. This very general setting is potentially applicable to contexts as diverse as early universe cosmology and QCD at finite density. Additionally, I will show how certain effective theories of Goldstones with broken Lorentz symmetry admit UV completions that do not restore any broken symmetry.

Continue reading… Goldstone bosons with spontaneously broken Lorentz symmetry – Riccardo Penco

I will show that all consistency relations for the primordial perturbations derive from a single, master identity, which follows from the Slavnov-Taylor identity for spatial diffeomorphisms. This master identity is valid at any value of momenta and therefore goes beyond the soft limit. This approach underscores the role of spatial diffeomorphism invariance at the root of cosmological consistency relations. It also offers new insights on the necessary conditions for their validity: a physical contribution to the vertex functional must satisfy certain analyticity properties in the soft limit in order for the consistency relations to hold. For standard inflationary models, this is equivalent to requiring that mode functions have constant growing-mode solutions.

Continue reading… Slavnov-Taylor Identities for Primordial Perturbations – Lasha Berezhiani

Galileons, and related theories, have deep connections to spontaneous symmetry breaking. After reviewing the origins of Galileon theories, I motivate their interpretation as Goldstone Bosons and illustrate some of their special technical properties before proceeding to discuss applications and future directions.

Continue reading… Symmetry Breaking and Galileons – Garrett Goon

CMB Lensing is a probe of the matter distribution between the surface of last scattering and today, which has been measured using CMB temperature data. Signal to noise for lensing reconstruction from CMB polarisation data is expected to be much better, since B modes on small scales should vanish in the absence of lensing. An effect of having data from an incomplete sky is leakage of E mode power in to B mode power. Upcoming data analysis from ground based CMB polarisation instruments must account for this effect. In the first part of my talk I will show results for CMB polarisation lensing reconstruction from small patches of sky,

Continue reading… CMB Lensing: reconstruction from polarisation & implications for cosmology from cross correlation with galaxies – Ruth Pearson

TBA

Continue reading… Making the connection between galaxy voids, dark matter underdensities and theory – Paul Sutter