I am working with Professor Jerry Gollub as Research Associate in nonlinear physics and fluid dynamics at the Haverford College Department of Physics since March 1998. For the 1999/2000 academic year I also have an appointment as Visiting Assistant Professor. I taught Thermal Physics in the Fall 1999 semester.
Before coming to Haverford, I completed my Ph.D. at the City College of New York, working on the dynamics of pattern formation in crystal growth of binary alloys. I received a Diplom in technical physics from the Technical University of Munich, Germany in 1995, supported by a fellowship from the 'Studienstiftung' (German National Merit Foundation).

Research Activities

My general areas of interest are nonlinear dynamics, the mechanisms of pattern formation, and phase transitions in complex materials. After studying binary alloys as a graduate student, I am focussing on granular materials in my current research. I plan to include biological materials and complex fluids in future research.

Current research at the Haverford Nonlinear Physics Laboratory with Jerry Gollub

Several experiments on the physics of granular materials are currently in progress. I designed a new cylindrical shear system, in which we measure frictional forces and image the arrangement of particles in an air-fluidized granular material that is subjected to shear. In collaboration with Lyderic Bocquet (ENS-Lyon) and Tom Lubensky (University of Pennsylvania) we have developed a locally Newtonian, continuum model of granular flow. In collaboration with Jean-Christophe Geminard, a visitor from ENS-Lyon, we are investigating friction in dry and in wet granular materials. The connection between dilation and shear in granular materials can be tested in detail in our apparatus since it permits force measurements with ms temporal and sub-µm spatial resolution. David Cooper, a Haverford senior and I found a fascinating propagating front which develops in vertically vibrated granular materials below 1g acceleration. In measurements of the velocity statistics of an excited granular medium we found non-Gaussian velocity distributions in agreement with recent theories. See the home page of the Nonlinear Physics Lab for more details on these and other projects.  

Thesis research

I investigated the origin of patterns that appear in alloys when grown from a melt. Those patterns reflect the conditions during growth of the alloy as fluctuations in the concentration of alloy components on a microscopic scale. Understanding the physics behind these patterns could prove useful in the development of new alloys and alloy processing techniques, since the strength of the alloy strongly depends on this concentration microstructure. I developed a new perturbation technique that allows measurements of the response of a growing solid to spatially perioidc perturbations.

Teaching Interests

In the Fall 99, I taught statistical physics (Physics 303a). I have been co-supervising four summer research projects in the past two summers that have resulted in two publications. Additional publications are in progress. As a recent graduate, I hope to assist students in their decisions on a career in physics. As a participant in an NSF sponsored course on career development, I have studied the diverse employment opportunities for physics Ph.D's and important strategies for success.

1. "Particle dynamics in sheared granular matter," W. Losert, L. Bocquet, T.C. Lubensky, J.P. Gollub, submitted to PRL, preprint available at: cond-mat/0004401
2. W. Losert, J.-C. Geminard, S. Nasuno, and J.P. Gollub, "Mechanisms for slow strengthening in granular materials," Phys. Rev. E, 61 4060 (2000), preprint available at cond-mat/9909330.
3. W. Losert, J.-C. Geminard, S. Nasuno, and J.P. Gollub, Friction in sheared granular material, M. Robbins, Ed., Symposium on Tribology (Materials Research Society, San Jose, CA, 1999).
4. W. Losert, D.G.W. Cooper, J. Delour, A. Kudrolli, and J.P. Gollub, "Velocity statistics in vibrated granular media," Chaos 9, 682 (1999), preprint available at cond-mat/9901203.
5. W. Losert, D.G.W. Cooper, and J.P. Gollub, "Propagating front in an excited granular layer," W. Losert, D.G.W. Cooper, and J.P. Gollub, Phys. Rev. E, 59, 5855 (1999). Preprint available at cond-mat/9812089.
6. J.-C. Geminard, W. Losert, and J.P. Gollub, "Frictional Mechanics of Wet Granular Material," Phys. Rev. E, 59, 5881 (1999). Preprint available at cond-mat/9811262.
7. W. Losert, D.A. Stillman, H.Z. Cummins, P. Kopzcynski, W.-J Rappel and A. Karma, "Selection of doublet cellular patterns in directional solidification through spatially periodic perturbations," Phys. Rev. E, 58, 7492 (1998)
8. W. Losert, O.N. Mesquita, J.M.A. Figueiredo, and H.Z. Cummins, "Direct Measurement of Dendritic Array Stability," Phys. Rev. Lett. 81, 409 (1998).
9. W. Losert, B.Q. Shi and H.Z. Cummins, "Evolution of dendritic patterns during alloy solidification: From the initial instability to the steady state," Proc. Nat. Acad. Sci. USA 95, 439 (1998).
10. W. Losert, B.Q. Shi and H.Z. Cummins, "Evolution of dendritic patterns during alloy solidification: Onset of the initial instability," Proc. Nat. Acad. Sci. USA 95, 431 (1998).
11. H.Z. Cummins, Y.H. Hwang, G. Li, W.M. Du, W. Losert, and G.Q. Shen, J. "Relaxation dynamics in orthoterphenyl: Comparing bk from extended mode-coupling theory and phenomenological analyses," J. Non-Cryst. Solids 235-237, 254 (1998).
12. W. Losert, B.Q. Shi, H.Z. Cummins, and J.A. Warren, "Spatial period-doubling instability of dendritic arrays in directional solidification," Phys. Rev. Lett. 77, 889 (1996).
13. L.M. Williams, M. Muschol, X. Qian, W. Losert, and H.Z. Cummins, "Dendritic sidebranching with periodic localized perturbations: Directional solidification of pivalic acid-coumarin152 mixtures" Phys. Rev. E 48, 489; erratum: E 48, 4862 (1993).

Please send p/reprint requests to: Wolfgang Losert

Send comments to wlosert@haverford.edu. Last updated05/25/00