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11 december 2018

Approved FOM programme

Number 160.
Title Observing the big bang: the quantum universe and its imprint on the sky (OBB)
Executive organisational unit BUW
Programme management Prof.dr. A. Achúcarro
Duration 2015-2019
Cost estimate M€ 2.3

The objectives
It is generally believed that the universe expanded exponentially a fraction of a second after the Big Bang. Quantum fluctuations frozen by the expansion left a characteristic signature in the cosmos that has miraculously survived until today, giving us a unique chance to observe the quantum world at the Big Bang. We will identify and decipher these signals.

Background, relevance and implementation
The distribution of matter in the universe, both visible (galaxies, clusters, gas) and dark, originated in tiny density fluctuations in the early universe. These are visible in the cosmic microwave background radiation, and their study in the last two decades has revolutionized our understanding of how the universe began, of its evolution and composition. 

The density fluctuations originate during a burst of exponential expansion (known as inflation) in the first fraction of a second after the Big Bang. Quantum processes at this time leave subtle statistical correlations in the temperature fluctuations, and in the distribution of matter, that are still detectable today. These contain information about the quantum universe at the very beginning that cannot be obtained in any other way, but this information is difficult to extract, also because the correlations are affected by the properties of dark matter and neutrinos, and by the nature of the gravitational force. Exploiting this unique window on the Big Bang requires state of the art observations and an exquisite understanding of the physical processes that generated the correlations. The first are being pursued by various experiments worldwide, in which the Netherlands plays a leading role, and the second is the goal of this project. A team of nine scientists plus ten young researchers at the universities of Leiden, Amsterdam, Utrecht, Groningen and Nikhef will concentrate on two main challenges:

  • Characterize the initial density perturbations together with their quantum mechanical origin, that is, pin down the physics of inflation..
  • Connect late time observations to the physics of inflation. In particular, the focus will be on improving the understanding of non-linearity's due to gravity and the e ff ects of subatomic physics (primarily neutrinos and dark matter) on the formation of large scale structures.

The final evaluation will be based on the self-evaluation report initiated by the programme leader and is foreseen for 2020.