Observational tests of past and present inflation

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Cosmological observations favor a universe with two periods of accelerated expansion in its history. One, known as Inflation, is thought to have happened in the distant past and helps explain the observed large scale features of the universe. The other period of acceleration is ongoing and, according to our current model, requires 70% of the universe density to be in the form of Dark Energy.  Both phenomena are still lacking a satisfactory description in terms of a fundamental theory.  The proposed research will contribute to developing models of Inflation and Dark Energy and ways of testing them with observations. It will help train students in a rapidly developing field, and further strengthen Canada's position as a leader in fundamental research.The Brane Inflation scenario is a working example of how inflation can be realized within the framework of String Theory -- a leading candidate for a fundamental theory of all particle interactions. What may help to distinguish Brane Inflation from other inflationary models is the special type of cosmic strings that form in brane-anti-brane collisions. I will study the non-trivial properties of these string networks and identify their observable features, such as the signatures they would induce in the cosmic microwave background radiation.The cosmic acceleration could be caused by some type of repulsive Dark Energy or be a manifestation of Gravity obeying different laws on largest scales. My work will include developing tests of Dark Energy that will maximally utilize the information contained in the data. I will also study some of the interesting models of modified gravity with the focus on their predictions for the clustering of cosmic matter. Future telescopes will be able to track the evolution of cosmic structures back in time. My research involves understanding the capabilities of planned and proposed observations and making detailed forecasts of the extent to which they will help us be distinguish between different theories.