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ISSUE OF SCALE. “For such materials, there is an absence of a clear separation of scales between the microphysics and macrophysics.” https://lnkd.in/dusKMKM View in LinkedIn

KEPLER PACKING. “Trapped surfaces form late in the collapse process, only when a certain threshold density is reached, analogous to the critical packing fraction required for jammed states in granular matter. In Fig. 2, untrapped and trapped surfaces are shown, with volume expansion of constant-time (spacelike hypersurface) slices of flat Minkowski spacetime, and volume con- traction occurring for a gravitationally collapsing body.” https://lnkd.in/dusKMKM View in LinkedIn

CONFLICTING STATES. “The laws appear to have firm underpinnings in out-of-equilibrium, nonlinear physical interactions, even though jamming per se appears to be a steady state feature.” https://lnkd.in/dusKMKM View in LinkedIn

ON BLACK HOLES AND JAMMED SAND. ‘In the gravity analogue, these states are proposed to map to untrapped and trapped surfaces which occur in general relativity, most spectacularly in gravitational collapse of a star to a black hole.” https://lnkd.in/dusKMKM View in LinkedIn

THE PROBLEM. “This dichotomic behaviour is at the heart of difficulties in the extensive ongoing and past assays in theoretical analyses of the laws that govern such materials.” https://lnkd.in/dusKMKM View in LinkedIn

THE ANALYSIS. “Isotropically Jammed states: A simple representative of an isotropically jammed state in a granular substance, in contrast to an unjammed state is depicted in Fig. 1, showing that for the same total number of grains, jamming clearly entails a contraction of the spatial volume.” https://lnkd.in/dusKMKM View in LinkedIn

DUAL STATES. “Thus, in each such alignment direction, these materials behave like a solid, while, in other directions, the material may indeed ‘flow’, akin to a fluid.” (Very quantum description in macroscopic material!) https://lnkd.in/dusKMKM View in LinkedIn

ON CABBAGES AND KINGS. “Recently, an emergent continuum elasticity model, capturing the infrared behaviour of amorphous athermal materials has been proposed, based on a tensor electrostatics version of fracton gauge theory. Such a model emerges naturally from the linearized version of the analogue gravity model proposed here.” https://lnkd.in/dusKMKM View in LinkedIn

GRAIN ALIGNMENT. “Within this paradigm, spatial density fluctuations observed in a granular material like sand, are attributed to force chains - force-ordered alignments of grains which inhibit motion of test-grains along the alignment direction (friction).” https://lnkd.in/dusKMKM View in LinkedIn

COSMIC FILAMENTS. “Density perturbation equations around the ‘background’ geometrical configuration do indeed yield as a solution, a time series of density heterogeneities or filamentary structures corresponding to that observed for granular matter, thus showing unexpected similarities with galactic filaments in structure formation models of relativistic cosmology.” https://lnkd.in/dusKMKM View in LinkedIn