  The concept of mechanical screening is widely applied in solid-state systems.
Examples include nucleation of defects in crystalline materials, scars and
pleats in curved crystals, wrinkles in strongly confined thin sheets, and
cell-rearrangements in biological tissue. Available theories of such screening
usually contain a crucial ingredient, which is the existence of an ordered
reference state, with respect to which screening elements nucleate to release
stresses. In contradistinction, amorphous materials in which a unique reference
state does not exist, nevertheless exhibits plastic events that act as
screening geometric charges with significant implications on the mechanical
response. In a recent paper [Phys. Rev. E 104, 024904] it was proposed that
mechanical strains in amorphous solids can be either weakly or strongly
screened by the formation of low or high density of plastic events. At low
densities the screening effect is reminiscent of the role of dipoles in
dielectrics, in only renormalizing the elastic moduli. The effect of high
density screening has no immediate electrostatic analog and is expected to
change qualitatively the mechanical response, as seen for example in the
displacement field. On the basis of experiments and simulations, we show that
in granular matter, strong screening results in significant deviation from
elasticity theory. The theoretical analysis, which accounts for an emergent
inherent length scale, the experimental measurements and the numerical
simulations of frictional granular amorphous assemblies are in agreement with
each other, and provide a strong support for the novel continuum theory.
