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# SPS Member Research in Computational Physics

Computational physicists are a new breed of physical scientist. Unlike theoretical physicists, they rely on more than mathematical models, but unlike experimentalists, they do not need a lab. Instead, computational physicists use programming to simulate physical systems so as to extract important observables and diagrams. The creation of such algorithms has been applied to countless physical systems, including plasma, condensed matter, astrophysics, accelerator physics, and fluid dynamics.

Below, you will find some computational research topics which SPS members are currently or have been engaged in.

## Exotic Quantum Fluids confined to Quasi-One Dimensional Nanopores

#### Adviser: Adrian Del Maestro, Ph.D.

One of the most interesting phenomena in statistical physics is phase transitions. They are with us everyday, from the water evaporating in the lake to the ice melting in your glass to the dry ice subliming to a dense fog on Halloween. However, there are more interesting phase transitions than those of water. A more interesting example is He-4, an isotope of the element helium. When cooled down to near absolute zero Kelvin, the He-4 experiences a phase transition to, not a liquid or solid or gas, but a novel state of matter known as a superfluid. Such phases of matter occupy a macroscopic quantum state, which means that they behave like a quantum object in a realm of physics usually considered classical. Interestingly, the superfluid has zero viscosity--it will flow through a microscopic tube without any friction whatsoever. Superfluidity is closely related to superconductivity, except that the former describes the flow of atoms in the liquid, while the latter describes the flow of electron charge in a solid.

Of particular interest to the Del Maestro group is superfluid He-4 confined in microscopic straws. If there is a pressure difference in the straws, the He-4 atoms will line up in a quasi-one dimensional array. When these atoms line up in such a way, the superfluid behaves as a Luttinger liquid, a special cooperative 1D quantum fluid. To describe the superfluid as it flows throw the nanopores in the straw, one must turn to computational techniques. In particular, one must utilize Path Integral Monte Carlo (PIMC) to measure important observables in the system. First developed by Richard Feynman and refined by David Ceperley, the path integral approach stochastically samples the system of interacting quantum particles at finite temperature. Using these PIMC techniques, it has been shown that there is some temperature dependence not predicted by Luttinger liquid theory, therefore pointing to a refinement of Luttinger liquid theory to account for the effects of energy band curvature.

Currently, three SPS seniors are engaged in research under Prof. Adrian Del Maestro:

Click on the links above to go to their individual profiles and learn more about their work in the Del Maestro group. Click here to go to Prof. Del Maestro's webpage.

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Last modified August 12 2014 10:00 PM