Theoretical Condensed Matter and Biological Physics
Alain Karma
College of Arts & Sciences Distinguished Professor
PhD University of California at Santa Barbara, 1986
(617)373-2929
a.karma@neu.edu
Research Summary:
My main research interest lies in theoretical understanding of the emergence of nonequilibrium patterns in nonlinear systems with applications to diverse problems in materials science and biology that are both of fundamental and practical relevance. This research makes extensive uses of mathematical models and computational approaches rooted in nonequilibrium statistical physics and nonlinear dynamics.
In the materials arena, a main focus in my group has been the application of the phase-field method to microstructural pattern formation in alloys. A more recent focus is the extension of this method to stress driven processes leading to materials failure such as crack propagation and crystal decohesion. The phase-field method provides a powerful computational approach to describe the complex evolution of interfaces such as phase and grain boundaries that shape the microstructure of a material, and hence determine some of its key properties such as tensile strength and wear resistance. The power of this method rests on the spatiotemporal coarse-graining of atomistic details that renders continuum scale simulations of interface dynamics feasible. Much of the excitement in this line research has been generated by recent successes to combine atomistic and phase-field methods to make materials specific predictions on experimentally relevant length and time scales, which is becoming increasingly feasible due to the rapid advances in computer power. An ultimate practical goal of this research is to use computer simulations to optimize the properties of advanced materials.
In the biological arena, our efforts have focused on understanding basic mechanisms of “cardiac arrhythmias”, a term commonly used to describe irregular heart rhythms. Of particular interest is ventricular fibrillation, a turbulent rhythm that stops the heart from pumping and is the leading cause of sudden death among industrialized nations. Ventricular fibrillation claims about 300,000 lives per year in the US. While high risk patients can carry implantable defibrillators, reducing mortality in the wider population of patients who die suddenly and unpredictably from ventricular fibrillation has remained a major challenge. Our recent studies have focused on elucidating the origin of spatiotemporal patterns of period doubling oscillations of calcium and voltage signals in cardiac cells and tissue (networks of cardiac cells) that make the heart susceptible to the onset of life-threatening arrhythmias and fibrillation. This research has the potential to improve current means to identify high risk patients and to prevent cardiac fibrillation beyond the limitations of current therapies, either pharmacologically, or using low amplitude electrical stimuli as an alternative to a massive defibrillatory shock.
Recent Selected Publications:
- “Method for computing short-range forces between solid-liquid interfaces driving grain boundary premelting”, J. J. Hoyt, D. Olmsted, S. Jindal, M.Asta, and A. Karma, Phys. Rev. E 79, 020601 (2009).
- “Solidification microstructures and solid-state parallels: Recent developments, future directions”, M. Asta, C. Beckermann, A. Karma, W. Kurz, R. Napolitano, M. Plapp, G. Purdy, M. Rappaz, and R. Trivedi, Acta Materialia 57, 941–971 (2009).
- “Laws of crack motion and phase-field models of fracture”, V. Hakim and A. Karma, J. Mech. Phys. Solids 57, 342-368 (2009).
- “Line-defect patterns of unstable spiral waves in cardiac tissue”, J. G. Restrepo and A. Karma, Phys. Rev. E 79, 030906(R) (2009).
- “Spatiotemporal intracellular calcium dynamics during cardiac alternans”, J. G. Restrepo and A. Karma, CHAOS 19, 037115 (2009).
- “Origin of complex behaviour of spatially discordant alternans in a transgenic rabbit model of type 2 long QT syndrome”, O. Ziv, E. Morales, Y.-K. Song, X. Peng, K.E. Odening, A.E. Buxton, A. Karma, G. Koren, and B.-R. Choi, J Physiol 587, 4661-4680 (2009).
- “Off-site control of repolarization alternans in cardiac fibers”, T. Krogh-Madsen, A. Karma, M. L. Riccio, P. N. Jordan, D. J. Christini, and R. F. Gilmour, Phys. Rev E 81, 011915 (2010).
- “Phase-field crystal model for fcc ordering”, K.-A. Wu, A. Adland, and A Karma, Phys. Rev E 81, 061601 (2010).
- “Amplitude equations for polycrystalline materials with interaction between composition and stress”, R. Spatscheck and A Karma, Phys. Rev B 81, 214201 (2010).
- “Helical crack-front instability in mixed mode fracture”, A. J. Pons and A. Karma, Nature 464, 85-89 (2010).
- “Dislocation-Pairing Transitions in Hot Grain Boundaries”, D. L. Olmsted, D. Buta, A. Adland, S. M. Foiles, M. Asta, and A. Karma, Phys. Rev. Lett. 106, 046101 (2011).