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Our lab has been involved in the investigation of granular matter since the late 1980s. Most work has been done in close collaboration with Sidney Nagel’s group.  Recent projects have investigated the unusual liquid state properties of granular matter, including the emergence of tightly collimated jets and their break-up into droplets.  Our current research effort focuses on the exploration of interparticle forces such as van der Waals and electrostatic forces, which are usually masked by gravity but can be uncovered in freely falling granular streams.  We are also exploring the connections between the shear response of dry granular matter and dense suspensions, both of which behave as frictional fluids that jam when dilation is frustrated.



   







      freely falling streams               impact              impact-induced jets                  Hele-Shaw                      packings  



For info on specific projects click on the images above or check out a longer listing under PROJECTS

For direct access to images and videos see the Gallery



The papers below are some of our review articles on granular matter and far-from-equilibrium physics:

  1. Heinrich Jaeger and Andrea J. Liu, “Far-from-equilibrium physics: an overview”. This paper gives an introduction and overview of the new directions (plus lots of references) in one of the key research areas within condensed matter physics, as highlighted in the CMMP2010 report by the Nat’l Academy of Sciences/National Research Council (see image of cover, above). The paper is based on Chapter 5 of that report. pdf file

  2. Heinrich M. Jaeger, "Sand, Jams, and Jets", Physics World 18, 34-39 (2005). This paper covers some of the more recent developments. pdf file

  3. Heinrich M. Jaeger, Troy Shinbrot, and Paul Umbanhowar, "Does the granular matter?", Frontiers of Science Symposium 1999, Proc. Nat'l Acad. Sci. 97, 12959 (2000). pdf file

  4. Heinrich M. Jaeger, Sidney R. Nagel, and Robert P. Behringer, "Granular Solids, Liquids, and Gases", Rev. Mod. Phys. 68, 1259-1273 (1996). This paper gives an overview of the emerging field of granular physics as of the mid-1990s. pdf file

Granular materials are large aggregates of particles that interact primarily via contacts with neighboring particles. In their simplest form, individual particles are macroscopic solids and (nearly) spherical, such as grains of sand, and interactions occur only when particles come in direct contact. What makes granular materials so remarkable is that the aggregate, despite its simple ingredients, exhibits an astounding range of complex, nonlinear behaviors that do not follow the classification into solid, liquid or gas states of matter we are used to for ordinary many-particle systems comprised of much more microscopic building blocks, such as molecules or atoms. Because the particles are macroscopic, thermal energies and the associated randomization are typically no longer relevant. This means that the aggregate rarely reaches the thermodynamic equilibrium and instead gets stuck in highly disordered, metastable configurations. Transitions between solid-, liquid- and gas-like aggregate states are no longer induced by simply changing an external control parameter such as temperature, but instead are driven by variables such as (local) packing density and applied stresses.  Much of this behavior can also be found in dense, amorphous aggregates comprised of more microscopic constituents, such as colloids or molecules, where the jamming transition connects with the glass transition.  As a result, granular matter has become a model system within condensed matter physics for the study of emergent many-particle phenomena far from equilibrium.