  We derive a microscopic theory of glassy dynamics based on the transport of
voids by micro-string motions, each of which involves particles arranged in a
line hopping simultaneously displacing one another. Disorder is modeled by a
random energy landscape quenched in the configuration space of distinguishable
particles, but transient in the physical space as expected for glassy fluids.
We study the evolution of local regions with m coupled voids. At low
temperature, energetically accessible local particle configurations can be
organized into a random tree with nodes and edges denoting configurations and
micro-string propagations respectively. Such trees defined in the configuration
space naturally describe systems defined in two- or three-dimensional physical
space. A micro-string propagation initiated by a void can facilitate similar
motions by other voids via perturbing the random energy landscape, realizing
path interactions between voids or equivalently string interactions. We obtain
explicit expressions of the particle diffusion coefficient and a particle
return probability. Under our approximation, as temperature decreases, random
trees of energetically accessible configurations exhibit a sequence of
percolation transitions in the configuration space, with local regions
containing fewer coupled voids entering the non-percolating immobile phase
first. Dynamics is dominated by coupled voids of an optimal group size, which
increases as temperature decreases. Comparison with a distinguishable-particle
lattice model (DPLM) of glass shows very good quantitative agreements using
only two adjustable parameters related to typical energy fluctuations and the
interaction range of the micro-strings.
