The Description of the Collaborative Research Program's Cosmology Projects goes here.
Cosmic Calibration - Statistical Modeling of Dark Energy
Members: Tracy Holsclaw, Bruno Sanso, Herbie Lee, Katrin Heitmann, Salman Habib, David Higdon, Ujjaini Alam
The fact that the Universe is expanding has been known since the 1920's. If the Universe was filled with ordinary matter, the expansion should be decelerating. Beginning in 1998, however, observational evidence has been accumulating in favor of an accelerating expansion of the Universe. The unknown driver of the acceleration has been termed dark energy. The nature of dark energy can be investigated by studying its equation of state, that is the relationship of its pressure to its density. The equation of state can be measured via a study of the luminosity distance-redshift relation for supernovae and can be further constrained by adding baryon acoustic oscillation (BAO) and cosmic microwave background data (CMB). In this study, we employ supernovae data, BAO, and CMB data, including measurement errors, to determine whether the equation of state is constant or not. Our method is based on Bayesian analysis of a differential equation and modeling w(z) directly, where w(z) is the equation of state parameter. This is a novel approach that does not assume any parametric form for w(z). This work stems from collaboration between UCSC and Los Alamos National Laboratory (LANL) in the context of the Institute for Scalable Scientific Data Management (ISSDM) project. (The image above is of Supernovae observations and provided by Sloan Digital Sky Survey II)
How do multi streaming regions form and evolve?
Members: Uliana Popov, Alex Pang, Katrin Heitmann
In cosmology, multi-streaming regions are characterized by a high density of particles with large velocity magnitude or direction differences, or both. There is a number of potential identifiers for multi-streaming regions such as high velocity variance, high shear, sink-like behavior or high tendency to spin. The multi-streaming events are interesting to scientists because they are associated with the formation of large scale structures such as halo clusters, filaments and voids. The ability to find and track these events will help understanding the evolution of the Universe in more detail.
In this talk, we present our preliminary findings on the evolution of multi-streaming regions. We hypothesize that more than one type of multi-streaming regions exists: those that grow from smaller scale structures and tend to exist for extended periods, and those that appear briefly, as a result of two or more smaller clusters passing in close proximity to each other.