Session T19: Kavli Foundation Special Session: Emergent Physics at the Mesoscale

Mesoscopic Lawlessness

Whether physics will contribute significantly to unraveling the secrets of life, the grandest challenge of them all, depends critically on whether proteins and other mesoscale objects exhibit emergent law. By this I mean quantitative relationships among their measured properties that are always true. The jury is still out on the matter, for there is evidence both for and against, but it is spotty, on account of the difficulty of measuring 100 nm - 1000 objects without damaging them quantum mechanically. It is therefore not clear that history will repeat itself. Physics contributed mightily to 20th century materials science through its identification and mastery of powerful macroscopic emergent laws such as crystalline rigidity, superconductivity and ferromagnetism, but it cannot do the same thing in biology, regardless of how powerful computers get, unless nature cooperates. The challenge before us as physicists is therefore not to amass more and more terabytes of data and computational output but rather to search for and, with luck, find operating principles at the scale of life greater than those of chemistry, which is to say, greater than a world ruled by nothing but miraculous accidents.   

Ultracold, trapped atomic gases as material systems

Laser cooling and evaporative cooling of neutral atomic gases has led to the creation of quantum degenerate Bose and Fermi gases that constitute a new class of material systems. Many of the features of the Hamiltonians governing the behavior of these systems can be controlled and manipulated in experiments. The necessarily finite sizes of such systems are often mesoscopic in the sense that they are large enough that collective effects are important, yet small enough that the size plays a role in determining the systems' behavior. Among the experimental tools available are optical lattices, synthetic fields, and the ability to change the size and dimensionality of the system. Ultracold gases can realize some of the idealized Hamiltonians used to model condensed matter systems, creating a quantum simulation of such models, which may be calculationally intractable. Atomic gases can also provide new condensed-matter-like systems that have no analogs in real condensed matter.