 Abstract and Introduction
 Simulation description
 Analysis
 Simulation results
 Analytical results
 Figures
 Conclusions
Abstract and Introduction
 very dense things are ephemeral
 internal pressure gradient cause spreading
 main things to worry about
 REALISTIC
 SIGNIFICANCE? – matching the PDF with the dense regions, out to ~300 over density but it’s clear that the high density things don’t last long, and the regions they are embedded in are overdense. ALSO if self gravity plays a role and you compare the things that last long enough for self gravity to cause them to remain permanently bound, is the fact that the free fall time of the region is shorter than the expansion time of the shocks of higher density
 IF there is a free fall of a bigish region  it becomes jeans instable on smaller scale but the subsequent things that become most unstable are smaller and there is a simple scaling and they become smaller in proportion to inverse of density

ORDERLY collapse with successive smaller size, and jeans isothermal things = REFERENCES to people who showed that the isothermal approximation is pretty good until the density is high, maybe 13 orders of magnitude beyond the mean density = HOPE of understanding clusters and individual stars, but what implications can WE draw from these very stylized turbulence driving at mach noubmbers comparable to those decuded from molecular clouds – CLEAR lot is not available to us.
 LARGE SCALE gravity in the galaxies in the spiral arms and SN movements – not because it has a signfiicant effect of the interior of molecular clouds, it leads to organization of larger scale overdensities. IN THAT SENSE, driving like what is done in the boxes, but once you have discrete entities, the simplest CO/H estimates and velocity estimates suggest that they are partially bound, and in general a significant fraction could be bound, because the collapse runs away on small scales.

HOW MUCH driving during the collapse? But the collapsing turbulent box and Murray et al. suggest that you can get more out of a collapse out of turbulent cloud out of maintaining turbulence, rather than collapse.
 SUMMARIZE turbulence – try to remove some of the mystery of what happens, and we found the following things – gave us these ideas we discussed before. Well correlated, connection between sizes of regions that could be bound.
Simulation description
basic simulation designdescription of driving schemetracer particle integration simulations of exponential shock evolution
Analysis
reinterpolation of the particles using PPMreinterpolation of the particles using GPI Description of the group finding method
 fof cataloging using different density thresholds
 merging together of groups with overlap
 Description of the voronoi tesselation methodology
 Description of the orientation and trajectory interpolation at the peak locations
 Description of the tracking method for timedependent shock evolution
 Potential calculation
 Bound group finding and splitting
 timedependent profiles of exponential shock simulations
 timedependent profiles of shocks from the turbulence simulations
Simulation results
 simulation visualization, density field colorized by velocity
 density profile of individual shocks
 average density profiles of all shocks, exponential profile
 density PDF reconstructed from the tracer particle groups + voronoi tesselation
 density PDF at different times reconstructed from tracers
 comparisons of potential groups and density peaks
 time evolution of the potential field, potential minima dynamical timescales vs. collapse timescales
 timedependent properties of shock populations, lifetimes, etc.
 shapes of shocks, curvature
 spatial clustering of shocks, correlation function, power spectrum?
Analytical results
 Exponential atmosphere calculation
 Model for exponential shock spreading
 Connection between shocks of different generations?
Figures
 log normal from shocks
 volumes at a given density
 densest regions – collapse
 ephemeral exist
Conclusions
 Density PDF can be described as a sum of individual shocks
 Shocks are roughly exponential atmospheres
 The densest shocks have strong pressure gradients that cause them to spread quickly
 The typical lifetime of the densest shocks is short
 The typical lifetime of potential minima is longer
 Star formation efficiency may be a combination of the conversion of binding energy into feedback energy and the competition between collapse time and survival time of dense shocks.
 Shocks are strongly spatially clustered, correlation function knows about the driving scale