Periodic Report Summary - COSMIC ACCELERATION (Understanding Cosmic Acceleration: Connecting Theory and Observation)
Cosmic acceleration at early and late times are two of the biggest mysteries confronting cosmologists today. The initial conditions of the Big-Bang are thought to have been set during 'inflation', an era of almost exponential expansion in the primordial universe. Inflation also provides a mechanism to generate the primordial fluctuations, anisotropies imprinted into the Cosmic microwave background (CMB) radiation which result in the rich structure of matter today. Current cosmological data are, for the first time, precise enough to allow detailed observational tests of inflationary models. Intriguingly, several independent data sets show that the cosmological expansion may be once again accelerating. These observations lead to the conclusion that the universe is dominated by a negative-pressure component, 'dark energy', which makes up roughly three-quarters of the cosmological energy density. Theoretical models for the dark energy include Einstein's cosmological constant, a dynamical component, etc.
I proposed to develop and apply new tools to pin down the precise mechanism of inflation and the nature of dark energy. The methodology is to identify and systematically confront broad classes of models with precision cosmological data and well-motivated theoretical priors. The data will be analysed robustly so that the final constraints do not have significant unknown contributions from imprecise models or systematic errors, and the competing theories will be compared against each other using advanced model-comparison techniques to identify the simplest models that are consistent with the data. The research is certain to improve our understanding of the microphysics of inflation and dark energy if the universe corresponds to the most 'minimal' current ideas, but also flexible enough to exploit the data fully if it contains statistically significant hints of more exotic physics.
Here are some highlights of research in the second reporting period.
1) Obtained the first observational constraints on the 'multiverse' predicted by the dominant theory of quantum gravity, previously widely considered untestable. We created a ground-breaking Bayesian algorithm for non-Gaussian source detection, performing one of the first blind analyses of a full-sky dataset explicitly designed to avoid a posteriori biases. (2 journal papers).
2) Applied a robust statistical algorithm to reconstruct the power spectrum of primordial density perturbations (one of the most powerful cosmological observables) over the widest range of physical scales cosmologically accessible. (2 journal papers).
3) Developed and publicly released MODECODE, a theoretically optimal and computationally efficient software package for constraining the physics of the early universe using astrophysical data. (one journal paper).
4) Clarified a significant source of confusion in the literature on algorithms to reconstruct the largest observable scales from partial sky data (one journal paper).
5) Proposed and demonstrated powerful Bayesian statistical methods to test the fundamental cosmological assumption of statistical isotropy (two journal papers).
6) Proposed a new fast algorithm to compute the signature of primordial non-Gaussianity in inflationary models where the bispectrum has oscillatory features, a unique signature of ultra-high-energy physics. (one journal paper).
I proposed to develop and apply new tools to pin down the precise mechanism of inflation and the nature of dark energy. The methodology is to identify and systematically confront broad classes of models with precision cosmological data and well-motivated theoretical priors. The data will be analysed robustly so that the final constraints do not have significant unknown contributions from imprecise models or systematic errors, and the competing theories will be compared against each other using advanced model-comparison techniques to identify the simplest models that are consistent with the data. The research is certain to improve our understanding of the microphysics of inflation and dark energy if the universe corresponds to the most 'minimal' current ideas, but also flexible enough to exploit the data fully if it contains statistically significant hints of more exotic physics.
Here are some highlights of research in the second reporting period.
1) Obtained the first observational constraints on the 'multiverse' predicted by the dominant theory of quantum gravity, previously widely considered untestable. We created a ground-breaking Bayesian algorithm for non-Gaussian source detection, performing one of the first blind analyses of a full-sky dataset explicitly designed to avoid a posteriori biases. (2 journal papers).
2) Applied a robust statistical algorithm to reconstruct the power spectrum of primordial density perturbations (one of the most powerful cosmological observables) over the widest range of physical scales cosmologically accessible. (2 journal papers).
3) Developed and publicly released MODECODE, a theoretically optimal and computationally efficient software package for constraining the physics of the early universe using astrophysical data. (one journal paper).
4) Clarified a significant source of confusion in the literature on algorithms to reconstruct the largest observable scales from partial sky data (one journal paper).
5) Proposed and demonstrated powerful Bayesian statistical methods to test the fundamental cosmological assumption of statistical isotropy (two journal papers).
6) Proposed a new fast algorithm to compute the signature of primordial non-Gaussianity in inflationary models where the bispectrum has oscillatory features, a unique signature of ultra-high-energy physics. (one journal paper).