Abstract: I will get the discussion rolling on what we need the dark matter (or alternatives) for, from the point of view of observational cosmology and astrophysics. I will then compare and contrast dark matter, modified gravity theories, and oddities that don’t fit in either description. Do we need them all? Why do they fight each other? I’ll be happy to leave it at that, but here’s the context if we have time to go there. If 4D diffeomorphism invariance were to break down to 3D diffeomorphisms on the leaves of a preferred foliation something dramatic would happen to the Universe, even after full 4D diffeo symmetry is restored. The usual algebra of constraints of General Relativity would feel the symmetry breaking effects for ever after the end of the symmetry breaking phase in the form of a leftover violation of the Hamiltonian constraint. Could this be what we call “dark matter”?
Space-time symmetry breaking and the mystery of dark matter
Joao Magueijo (Imperial College London)// October 2, 2024
Abstract: I will get the discussion rolling on what we need the dark matter (or alternatives) for, from the point of view of observational cosmology and astrophysics. I will then compare and contrast dark matter, modified gravity theories, and oddities that don’t fit in either description. Do we need them all? Why do they fight each other? I’ll be happy to leave it at that, but here’s the context if we have time to go there. If 4D diffeomorphism invariance were to break down to 3D diffeomorphisms on the leaves of a preferred foliation something dramatic would happen to the Universe, even after full 4D diffeo symmetry is restored. The usual algebra of constraints of General Relativity would feel the symmetry breaking effects for ever after the end of the symmetry breaking phase in the form of a leftover violation of the Hamiltonian constraint. Could this be what we call “dark matter”?