Sarah Shandera

Assistant Professor of Physics

104 Davey Lab #98
University Park, PA 16802

Phone: +1 814-863-9595
Fax: +1 814-863-9608

Full list of publications    |   CV
Sarah Shandera Photo

This is an era of ‘big data’ for cosmology. From a wide range of improving observations, cosmologists try to put together a coherent story that not only details the evolution of the universe but also tries to explain why it happened the way it did. My research focuses on understanding the earliest epoch of the universe, when an interesting interplay between high energy quantum particle physics and gravity was at work. The dominant current paradigm for the physics of the very early universe is called "inflation", indicating a period of accelerated expansion. Although inflation agrees very well with data it has not been definitively tested. Intriguingly for theorists, the framework itself generates several new and very fundamental puzzles.

I work on three related directions that aim to resolve the question of whether inflation really happened, and, if it did, to uncover the underlying particle physics. My research is primarily theoretical, but in order to connect it with observations I sometimes make use of large (dark matter, “N-body”) simulations, and I collaborate with others to test models against cosmological data. In the order of narrowest to broadest, my research directions are:

Observations tell us that in recent times the universe has been expanding and cooling, and matter has been gravitationally clumping into regions dense enough to form galaxies and stars. Extrapolating this story backwards, we know that billions of years ago the universe was hot, dense and smooth up to a pattern of very small inhomogeneities in the fabric of spacetime. A good model of the primordial era (inflation, for example), must provide an origin for this structure. We use observations of the pattern of fluctuations in the cosmic microwave background (CMB), and in the matter density (eg, the galaxies) to infer the properties of the early time pattern of inhomogeneities as well as the dynamics of how they evolved. For now, new data from the CMB is coming primarily from several different ground-based instruments al looking at the polarization of the light. I am part of the group studying how to optimize the science that can be done this way in the near future ( There may also be future satellite missions, following on the successes of the WMAP and Planck satellites, to map polarization on the largest scales (

The CMB is effectively a two-dimensional surface, but we can get fully three-dimensional maps of the inhomogeneities through surveys cataloging the Large Scale Structure of the universe (galaxies and clusters of galaxies). These objects contain complementary information to what we learn from the CMB since they depend on the same early time spectrum of inhomogeneities but have evolved for a longer time. I am currently studying how the clustering of galaxies observed in eBOSS, part of the Sloan Digital Sky Survey IV (, can constrain the primordial era.

In short, this is an exciting time for cosmology because of rapid, simultaneously developments in many related areas: observations, numerical simulations necessary to understand Large Scale Structure, ideas for fundamental theory at high energy, and even new experiments in particle physics. Many puzzles on the frontier of high energy physics and gravity come together in the early universe, making cosmology a rich and dynamic area of research.