My latest paper in cosmology is now public! It took many years to write, as it was a single author side-project on a subject that is very different from my main field. My PhD was indeed in particle cosmology, while now I am mostly working on building physics and methods for energy saving in buildings. I am however still relatively active in theoretical physics, and this is meant to be the first article of a comeback into the field.
Here is the abstract:
In the framework of MSSM inflation, matter and gravitino production are here investigated through the decay of the fields which are coupled to the udd inflaton, a gauge invariant combination of squarks. After the end of inflation, the flat direction oscillates about the minimum of its potential, losing at each oscillation about 56\% of its energy into bursts of gauge/gaugino and scalar quanta when crossing the origin. These particles then acquire a large inflaton VEV-induced mass and decay perturbatively into the MSSM quanta and gravitinos, transferring the inflaton energy very efficiently via instant preheating.
Regarding thermalization, we show that the MSSM degrees of freedom thermalize very quickly, yet not immediately by virtue of the large vacuum expectation value of the inflaton, which breaks the SU(3)C×U(1)Y symmetry into a residual U(1). Compared to the case of LLe-type inflaton previously studied, we find an even more efficient energy transfer to the MSSM quanta, due to the enhanced particle content of the supersymmetric (SUSY) multiplet that is coupled to the flat direction. Full thermalization is achieved indeed after only O(40) oscillations.
We also compute the gravitino number density from the perturbative decay of the flat direction and of the SUSY multiplet. In agreement with the literature, the inflaton produces a negligible amount of gravitinos and does not raise any cosmological issues. On the contrary, the fields to which it is coupled are responsible for a severe gravitino overproduction problem, which is caused by their large VEV-induced effective masses. We argue that possible solutions might include non-coherent oscillations of multiple flat directions or fragmentation of the inflaton condensate with formation of Q-balls.