Thesis

Arrow of Time: its origin in the Universe.

• Call:

  PT-CERN Call 2021/2

• Academic Year:

  2021

• Domain:

  Astroparticle Physics

• Supervisor:

  Marina Cortês

• Co-Supervisor:

  Andrew Liddle

• Institution:

  FCUL (Universidade de Lisboa)

• Host Institution:

  IA - Instituto de Astrofísica e Ciências do Espaço

• Abstract:

  Time always moves in the same direction, it always increases and never decreases: we always remember the past and never the future. This asymmetry of time is universal, from scales on Earth up to cosmological scales. We receive light that galaxies emitted long ago in the past and never receive light they emitted in the future. This time asymmetry is not reflected in the majority of physics laws which are time symmetric, they work in the same way whether time is increasing or decreasing. In fundamental physics time is symmetric, and we attribute the cosmological arrow of time to very unusual initial conditions in the beginning of the universe. These conditions are so special that their probability is of order 1 in 10^90 or less. Why the universe started in such an unlikely state is a question to which we have no answer in cosmology. In this work we investigate whether the time asymmetry may already be present in the fundamental laws, which would avoid having to attribute it to very special initial conditions at the Big Bang. We construct models that simulate such a time asymmetry, and we will run simulations with these models from both existing and new code. The goal is to infer, from the results of the simulations, what the properties of physics are if it is fundamentally time asymmetric.