Jamming (physics)

This crowding of the constituent particles prevents them from flowing under an applied stress and from exploring phase space, thus making the aggregate material behave as a solid.

For example, a particularly interesting feature of the jamming transition is the difference between attractive and repulsive particle systems.

Under shear stress, the average cluster size may diverge after a finite amount of strain, leading to a jammed state.

Right at the jamming transition, the applied pressure is zero and the shear modulus is also zero, which coincides with the loss of rigidity and the unjamming of the system.

, and related to particle displacements which exactly follow the applied shear deformation; the second (negative) term is due to internal relaxations needed to keep local mechanical equilibrium in a strained disordered environment, and thus proportional to the total number of degrees of freedom, hence the dependence on space dimension d.[4] This model is relevant for compressed emulsions, where the friction between particles is negligible.

Here the cars on a road may be thought of like a granular material or a non-Newtonian fluid that is being pumped through a tube.

The notion of jamming can also be considered from a biophysical perspective to characterize the arrest of cellular motion.

[5] Cell motility is of importance in many biological processes including tissue morphogenesis, wound healing, and cancer invasion.

[6] [7] Characterizing the mechanisms that result in these "jamming" and "unjamming" phenomena can yield a more nuanced view of tissue development and aid in identifying new targets for disease therapies.

[5] [8] Identifying properties defining these cellular phase changes has been a topic of recent interest.