POLARBEAR (PB) was the first experiment deployed as part of this program and delivered in the last couple of years some of the most interesting results in the field. This single-telescope, single-frequency observatory operating with O(1000) high-sensitivity detectors is going to be progressively replaced by a more powerful Simons Array (SA), composed of three telescopes, observing in at least three frequency bands and furnished with roughly O(10,000) detectors. The experiment is scheduled to become fully operational in 2017 but its deployment will be phased so a constant stream of data will flow throughout this entire period.

CMB B-mode studies are amongst some of the most exciting, contemporary endeavors in the field of cosmology. They are broadly expected to provide a new, unique window on the physics of the very early Universe, giving a very strong evidence in favor of inflation as a correct paradigm, within which to model this phase of the Universe's evolution, but also potentially constraining some of the fundamental energy scales of physics. These are hoped to provide some essential clues for the high energy physics models.
In addition, thanks to the fact that some of the observed B-mode signal is converted from the E-mode due to the gravitational lensing of the CMB photons by the growing large scale structures, it could set unique complementary constraints on dark energy properties at the redshift z around 1-2 and on the masses of the neutrinos, with precision surpassing by a factor of at least 10 the one expected of the future laboratory experiments and sufficient to resolve the neutrino mass hierarchy problem.

The PB/SA program, thanks to its successful past and ambitious plans has positioned itself as one of the most promising world-wide efforts, which expected to maintain its leading role in reaching these exciting goals.

Two ingredients are necessary to achieve these: a powerful data set and robust data analysis techniques. In the context of this project the first ingredient will be provided by the PB/SA experimental team, developing to the cutting-edge hardware based on novel technologies. The second is in a big part a result of our group at APC, led by graduate students involved in this project. The PB/SA project at APC has resulted so far in three, highly appreciated PhD theses with the fourth one envisaged for the end of this year.

The goal of the PhD project proposed here is an analysis and scientific exploitation of the PB/SA data sets separately and in combination with other cosmological data. The specific target of the work will be techniques for a robust power spectrum estimation and cosmological parameter estimation with the goals of setting limits on both the energy scale of inflation and masses of neutrinos.

The work will involve devising and implementing algorithms relevant to such tasks, validating them on simulated data, and later applying them as part of the end-to-end data analysis pipeline to the real data sets once those are become available. The student will also have an opportunity to take part in the observational campaigns conducted from Chile.

This PhD project will be performed as part of the work of the POLARBEAR@APC group and set in the context of a broader European collaboration, involving former PB students at APC and other researchers. This provides a closely knit, friendly but efficient environment to start and conduct this kind of research within. The work will also involve a number of remote collaborations with the teams in Berkeley (University of California, Berkeley) and Japan (KEK, Tsukuba; IPMU Tokyo) as well as potentially some extended visits in both the US and Japan.

Modern cosmological data analysis is an interdisciplinary endeavor, involving elements of physics, numerical methods, statistics, and applied mathematics, amounting to a new mode of scientific research, importance of which has been steadily increasing reflecting the conversion of cosmology from a data-starved to a data-driven science. This PhD thesis is expected to help the candidate developing diverse skills eagerly sought-after in scientific and other societal contexts.

Contact: Radek Stompor  radekapc.univ-paris-diderot.fr