  Dense suspensions can exhibit an abrupt change in their viscosity in response
to increasing shear rate. The origin of this discontinuous shear thickening
(DST) has been ascribed to the transformation of lubricated contacts to
frictional, particle-on-particle contacts. Recent research on the flowing and
jamming behavior of dense suspensions has explored the intersection of ideas
from granular physics and Stokesian fluid dynamics to better understand this
transition from lubricated to frictional rheology. DST is reminiscent of
classical phase transitions, and a key question is how interactions between the
microscopic constituents give rise to a macroscopic transition. In this paper,
we extend a formalism that has proven to be successful in understanding shear
jamming of dry grains to dense suspensions. Quantitative analysis of the
collective evolution of the contact-force network accompanying the DST
transition demonstrates clear changes in the distribution of microscopic
variables, and leads to the identification of an "order parameter"
characterizing DST.
