I am a theoretical cosmologist, and I am interested in the three major unknown actors on the cosmic stage: dark matter, dark energy, and the inflaton field.
In the standard cosmological model, each of these three substances control the dynamics of the Universe during one stage of its evolution, but despite their importance, their nature is still mysterious. Since the explanations for dark matter, dark energy, and inflation must involve new physics, I analyze how they behave in the most highly energetic environment ever realized: the early Universe.
Below, I briefly describe some of my recent and ongoing projects, with links to articles and to the more detailed descriptions provided on my Research page. For those looking for a comprehensive publication list, here is a link to my publications on the arXiv, INSPIRE and ADS .
UNC-CH students: I encourage you to contact me if you are interested in any of these topics. I have projects available for both graduate and undergraduate students.
Inflation and the Origins of Cosmic Structure
In the first moments after the Big Bang, there is strong evidence that a period of extremely rapid expansion called inflation smoothed the Universe while simultaneously seeding the inhomogeneities that would eventually become galaxies. The engine driving that expansion, dubbed the inflaton, is unknown. My projects pertaining to inflation:
Image: NASA/WMAP science team
- Using small-scale density perturbations to probe the dynamics of inflation and the transition from inflation to a radiation-dominated Universe (aka reheating).
- Investigations of alternatives to single-field inflation, including how these models may explain the strange hemispherical asymmetry observed in the cosmic microwave background.
About fifteen percent of the matter in the Universe is made of known particles. The composition of the remaining "dark matter" is a mystery. My projects pertaining to dark matter:
Dark Energy and Modified Gravity
|Currently, most of the Universe's energy is "dark energy." This energy is unlike any other energy that we know of because it is causing the Universe's expansion to accelerate, even though gravity should be slowing the expansion down. I have focused on an alternative explanation for cosmic acceleration: that general relativity is not the ultimate theory of gravity. My projects pertaining to modifed gravity:
- Exploring how modified gravity theories behave in the early Universe, when their interactions with the energetic primordial plasma can have unexpected consequences.
- Investigating how tests of general relativity in the Solar System constrain modified gravity theories.
Content last updated on October 14, 2013: new website coming soon!