KICP theorists are actively investigating the following issues:
- inflationary cosmology (did the very young universe go through a phase of rapid expansion?)
- the origin of the matter/antimatter asymmetry (why is the observable universe dominated by "normal matter" and not anti-matter?)
- primordial nucleosynthesis (how did the first elements in the Universe form?)
- dark energy (why is the Universe accelerating and what is the nature of the "dark energy" that is believed to be causing this acceleration?)
dark matter (what are the dark matter particles and how do they interact?)- are there alternatives to general relativity that might explain the observed acceleration and account for the dark energy?
Of the topics listed above, one of the most pressing is the attempt to understand the observed acceleration of the universe. It has by now been well established that we do not live in a conventional Universe dominated by matter. Even when dark matter is taken into consideration the Universe is accelerating and spatially flat - two phenomena which cannot be accounted for by the current matter density. The most straightforward explanation for these measurements is the existence of a small but nonzero vacuum energy, or cosmological constant. However, this possibility raises significant problems: the vacuum energy is much smaller than it has any right to be, and seems suspiciously close to the matter density. It is therefore worth considering more dramatic possibilities.
One such possibility is that of dynamical dark energy, which would be slowly varying but not perfectly constant. Even more dramatic is the possibility that Einstein was wrong, and that ordinary general relativity might be breaking down on cosmological scales. Both possibilities are currently under investigation, both in terms of underlying models and observational signatures.
Along with dark energy, inflation is one of the foundational ideas of contemporary theoretical cosmology. One of the principal research goals of the Institute is to advance our understanding the physics of inflation and its relationship to particle physics at high energies. We would also like to understand how we can best constrain the parameters of inflation with the Cosmic Microwave Background (CMB) observations and large-scale distribution of galaxies.
We are currently investigating both fundamental issues of relevance to inflation (quantum fluctuations, entropy, effects of string theory and extra spacetime dimensions) and the construction of detailed inflationary models (scalar fields and their interactions, production of density and gravity-wave perturbations, the process of reheating into matter and radiation). An important feature of inflation is that it makes specific and testable predictions for observables such as CMB temperature and polarization; as these data become increasingly refined, we hope to be ready to interpret them in terms of models of fundamental physics.