Few-body Phenomena in a Degenerate Fermi Gas

We will study a new area which has appeared only recently in the field of ultracold atoms. These systems are composed of gases of atoms at very low temperature (on the order of a millionth of a degree Kelvin) stored in ultrahigh vacuum which exhibit certain quantum mechanical properties.In the past couple of years experimentalists have been able to create and study systems where a few of the atoms are of different species from the others (e.g. they have a different internal state known as spin ). These atoms can be thought of as having their motional properties affected due to their interaction with the background atoms (the majority species). We can use an analogy here: imagine that the different atoms are like round spheres (such as billiard balls) moving through a viscous fluid (e.g. water). Because of the interaction between the fluid and the sphere (the drag force), we might say that the spheres have increased their mass since they have more inertia now. It turns out that in many areas of physics (condensed matter, particle physics and others) this way of thinking about the problem is very useful and leads to many insights.When we introduce the few different atoms into this background, not only will their inertia change (we say that their effective mass has changed), but also other aspects of their behaviour. For example, the way they collide with each other, or form molecules with each other.Very broadly we propose to study thereforei) How these atoms collide with each other and their interactions.ii) How these atoms propagate in the medium (e.g. their inertia, the slowing down effect of the medium on the motion of the atoms, known as damping).iii) What kinds of molecules and compounds can the atoms form in the presence of the medium which they could not before (i.e. in vacuum).iv) How best to detect and measure these effects experimentally, what techniques to use and what to look for in the data.Beyond the interest in studying atoms there is a wider one: in our specific case the background gas is of a type known as a degenerate Fermi gas . This system is a model for many systems, from electrons in metals to nuclear matter in neutron stars and therefore, the phenomena that we propose to study has close analogs in each of these other systems.

Beyond the direct impact on researchers in the same area, there are other types of impact: 1) The PDRA will be extensively trained in mathematical techniques of wide applicability outside of academia (in industry or finance for example) should he/she decide to pursue a career in those fields. 2) Other fields of physics (such as condensed matter and nuclear physics) have similar phenomena and some of the results of this proposal could bear on those problems and stimulate further research there. 3) A web site will be set up for the general public which will explain in layman's terms what the research is about, what are the interesting questions and how they relate to other areas (i.e. the background) and what are the eventual results of the proposal.