Theoretical Physics
Overview
One of the most remarkable aspects of nature is that it presents us with seemingly infinite variety of interesting phenomena, with characteristic length, time, and energy scales ranging over 60 orders of magnitude. The research activities of theoretical physicists at CMU span this entire range, and seek to address some of the most challenging open problems in particle physics, condensed matter physics, biological physics, gravitation and cosmology.
Many interesting questions in theoretical physics often arise when the interactions among the constituents of a physical system generate novel, emergent phenomena. How do quarks and their strong interactions determine the properties of protons, neutrons, and other hadrons? How do the components of biological systems influence their collective dynamic and mechanical properties? How do the thermal, electronic, and mechanical properties of condensed matter systems arise from the properties of the atoms they are made of, and the way these atoms are arranged? What are the properties of gravitational radiation emitted when two black holes form a binary inspiral? How does the matter and energy content of the universe give rise to the rich large scale structure we observe in our universe? These are only some of the questions that the theory group at CMU tackles using statistical mechanics, quantum mechanics, (quantum) field theory, and a variety of analytic and computational methods.
Markus Deserno uses theoretical and computational approaches – continuum elasticity theory and field theory as well as coarse-grained simulations – to study molecular-scale and mesoscale phenomena in biophysics. This allows him to study larger systems on longer time scales than in atomistic simulations and access a new arena for physical questions, many of which have biological significance. Specifically, Deserno investigates lipid membranes, proteins, viruses, or DNA on length scales larger than atomic resolution but smaller than a typical cell. On these scales, many fundamental physical concepts make a big impact on biology – among them thermal fluctuations, cooperativity, self-assembly, or elasticity. For instance, due to their surfactant-like nature individual lipid molecules in an aqueous environment spontaneously aggregate into membranes, which are laterally many orders of magnitude larger than their thickness. These quasi-two-dimensional fluid surfaces resist bending, a continuum elastic concept, but since the associated moduli are only about one order of magnitude bigger than thermal energy, membranes exhibit large thermal undulations that affect their properties.
