Research Expertise and Interest


Research Description

I am a theoretical cosmologist by training but much of my recent work has been focused on how to extract fundamental properties of our universe from cosmological observations. The so called standard cosmological model of the universe has been very successful in explaining most of the cosmological observations to date. In this model the universe begins with a Big Bang followed by inflation during which the universe becomes nearly flat and the initial structures are seeded through quantum fluctuations. After its decay the universe is filled with radiation and matter, of which dark matter is itsmain component. Another component dubbed dark energy is needed to explain its acceleration in recent times and if it is in the form of cosmological constant it will dominate the expansion of the universe forever into the future. Despite the success of this model there is no shortage of theoretical alternatives, some of which differ dramatically from the standard model, such as the dark energy being dynamical in nature allowing for different scenarios of the past and future evolution of the universe, or the cyclic model of the universe which postulates the universe is going through cycles of expansion and contraction. Among the questions we can attempt to answer through observations are: what mechanism seeded the initial structures in the universe? What is the nature of dark energy? What is the future fate of the universe? What is the neutrino mass and number of neutrino families? What is the nature of dark matter?

In the News

Eight Berkeley faculty elected to National Academy of Sciences

In recognition of their outstanding achievements in original research, eight UC Berkeley faculty have been elected members of the National Academy of Sciences, one of the most distinguished scientific organizations in the country. The newly elected researchers include a neuroscientist, two physicists, two cellular biologists, a computer scientist, a chemist and an economist, and bring the total number of living UC Berkeley faculty who are members of the academy to 135.

Black holes ruled out as universe’s missing dark matter

For one brief shining moment after the 2015 detection of gravitational waves from colliding black holes, astronomers held out hope that the universe’s mysterious dark matter might consist of a plenitude of black holes sprinkled throughout the universe.

Featured in the Media

Please note: The views and opinions expressed in these articles are those of the authors and do not necessarily reflect the official policy or positions of UC Berkeley.
April 27, 2020
A new analysis using COVID-19 death data from Italy projects that the fatality rate in New York City can be no less than 0.5, or one out of every 200 infected people. The researchers, from UC Berkeley and the Lawrence Berkeley National Laboratory, also estimated, based on the predicted fatality rate, that roughly a quarter of New York City's population has been infected, and that about 26 percent of all COVID-19 deaths in New York will be among people who are younger than 65. "Our observation suggests COVID-19 kills the weakest segments of the population," says physics and astronomy professor Uros Seljak, the study's senior author. "Some of my colleagues think that we have been overly conservative, which might be true," he adds. "We have just accounted for the people who have died up until today, but people are still dying." For more on this, see our press release at Berkeley News.
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