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The Dark Energy Imprint on the Baryon Acoustic Oscillations

Final Report Summary - DEBAO (The Dark Energy Imprint on the Baryon Acoustic Oscillations)

The project work was carried out within the central theme of the proposal - constraining cosmological models using large datasets, while adapting to the emergence of new survey datasets, particularly those from the European Space Agency's Planck Satellite. In particular we obtained limits on the curvaton model combining Baryon Acoustic Oscillation data set from the B.O.S.S. survey with those from Planck. The planned experiment BigBOSS has now been reformulated under the name DESI and continues its development as the largest wide angle, fiber fed spectroscopic survey of the coming years. Edinburgh's involvement in the United States led project has recently been enhanced by the hire of Nic Ross who is chair of the BOSS Quasar Working Group and a coordinator of the quasar science contribution to MS-DESI forecasts.

Overall ten articles have arisen from the fellowship, nine of which are already published in peer reviewed journals. At least two further papers are in progress that were initiated during the fellowship. Six of the articles, in collaboration with the Scientist in Charge Andrew Liddle, directly address the grant theme of constraining cosmological models with precision survey data. The remaining four, with international expert Lee Smolin, represent the researcher's independent research in the area of fundamental theories of gravitation. The two strands converged beautifully when the scientist in charge Andrew Liddle became involved in the final paper in the sequence with Lee Smolin, arXiv:1606.01256 bringing the separate threads of the fellowship together at its culmination.

One focus was to obtain limits on the curvaton model by combining Baryon Acoustic Oscillation data set from the B.O.S.S. survey with those from EU’s Planck satellite, which during the course of the grant became the key data set for cosmological models of inflation and dark energy. Building on work done in the first year (arXiv:1403.4591) we obtained limits on a new type of curvaton model this time. Continuing the collaboration with Sussex’s astronomer Chris Byrnes we considered the possibility that the inflaton field decays into the particles of the standard model via a curvaton channel. For this we benefited from knowledge of particle physics experts in the north american institution we visited, Perimeter Institute. We learnt that models which allow for such possible inflaton to curvaton decays are the realistic models and those that are fully consistent in a particle physics framework. This work gave origin to the article arXiv:1608.02162 which was rapidly accepted for publication, with no changes necessary.

Another follow-up on work initiated during the first year of the project was the establishment of a collaboration with Takeshi Kobayashi of CITA in Toronto, along with scientist in charge Prof A Liddle. The collaboration resulted in the article given by reference arXiv:1501.05864. In this work we derived a unified formalism to describe the hemispherical asymmetry in the cosmic microwave background generated by the mechanism proposed by Erickcek, Kamionkowski, and Carroll. This is a sophistication of the methodology used in the paper of round one in the first year, arXiv:1306.5698 and provides an analytical treatment of the phenomenology for asymmetric sky models that can be used by researchers throughout the field.

In the second year of the MC grant, the researcher continued the collaboration with Lee Smolin and extended the study of arXiv:1307.6167 to develop a time-asymmetric extension to general relativity, reference arXiv:1503.06085 below, which was part of the plans for progression of the work of the first year.

Following up on this, and extending the Canadian collaboration with Lee Smolin to scientist in charge Prof Andrew Liddle, the researcher examined means of testing the models developed in reference by use of cosmological probes, including those of the BAO scale and Planck satellite data. This is published as arXiv:1606.01256. This collaboration is part of the transfer of knowledge to the EU - which is a key objective of this grant.

A wide range of researcher training activities were undertaken during the fellowship. The most important were as follows:
* She undertook three 12-weeks module courses of "Productivity for Scientists", a program designed to allow researchers to maximize work output during their career development, by transfer of career planning strategies and time management techniques.
* She co-organised two conferences, one at Edinburgh and one at the Perimeter Institute.
* She supervised her first undergraduate student project based on the work initiated during the IIF grant with Perimeter Institute’s collaborator Lee Smolin. The student obtained an outstanding mark for their project (4.5/5).
* She introduced and organized bi-weekly Cosmology Journal Discussion meetings, held jointly at the Royal Observatory and at the University of Edinburgh's campus. This interaction between both research institutions focused on Cosmology was non-existent prior to the Fellow’s arrival. She also acted as organizer of the main Colloquia Series at the Institute for Astronomy at the Royal Observatory.

The work received substantial media attention and exposure throughout the fellowship, with the Fellow participating in many interviews in a variety of formats.