Tristan Smith
Swarthmore College, PA·Astronomy & Astrophysics
The standard model of cosmology, called LCDM for its two main ingredients, a cosmological constant (Lambda) driving accelerated expansion and cold dark matter, fits a remarkable range of observations with only a handful of numbers. But two cracks have appeared.
- Fields
Astronomy & Astrophysics
Physics
- Topics
cosmology
Hubble tension
sigma-8 tension
- Grants
- 1 known grant, through Aug 2027
What they work on
- Determine the theory space available to extensions of LCDM, the standard cosmological model, by identifying which model properties are required to resolve the disagreements in the measured expansion rate and matter clustering.
- Characterize the specific observational signatures such models leave in the cosmic microwave background, the afterglow of the early universe, and in large-scale structure, the distribution of matter and galaxies.
- Explore the non-linear dynamics of cosmological scalar field models, fields filling space whose strong self-interactions break simple approximations, and work out their effects on cosmological observables.
- Derive new constraints on candidate models using current and forthcoming cosmological datasets, and train undergraduate researchers through a science communication curriculum developed with the project.
More about the research
Different methods disagree about how fast the universe is expanding today, the "Hubble tension," and they also disagree about how strongly matter is clumped into structures, the "sigma-8" tension. Either the measurements have hidden problems, or the model is missing physics.
Why it matters
Measurements of the universe's expansion rate and of how matter clumps together currently disagree with the predictions of the standard cosmological model. Charting which theoretical extensions can reconcile them, and what each would look like in cosmic microwave background and galaxy-clustering data, gives observers concrete signatures to search for in upcoming surveys and could sharpen or rule out candidate explanations. Undergraduates gain research experience and formal training in science communication.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
Closest labs
Chihway Chang
University of Chicago, IL·Astronomy & Astrophysics
Measure cross-correlations between CMB lensing, galaxy positions, galaxy lensing and the thermal Sunyaev-Zel'dovich effect using DES, SPT and ACT data, to tighten constraints on the universe's properties.
Soubhik Kumar
Tufts University, MA·Physics
Use effective field theory to classify the non-Gaussian signatures, unusual statistical patterns, left by heavy beyond-Standard-Model particles produced during inflation, and build templates for searches in cosmic microwave background (CMB) surveys.
Dragan Huterer
University of Michigan, MI·Astronomy & Astrophysics
Develop a method to measure the Hubble constant by cross-correlating gravitational-wave dark sirens with galaxy distributions. Dark sirens are merger events with no detected light.
The school
Swarthmore College: 2 labs on PI Pages, $6M a year on research.
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