@article{7767,
  abstract     = {We present a model of soft active particles that leads to a rich array of collective behavior found also in dense biological swarms of bacteria and other unicellular organisms. Our model uses only local interactions, such as Vicsek-type nearest-neighbor alignment, short-range repulsion, and a local boundary term. Changing the relative strength of these interactions leads to migrating swarms, rotating swarms, and jammed swarms, as well as swarms that exhibit run-and-tumble motion, alternating between migration and either rotating or jammed states. Interestingly, although a migrating swarm moves slower than an individual particle, the diffusion constant can be up to three orders of magnitude larger, suggesting that collective motion can be highly advantageous, for example, when searching for food.},
  author       = {van Drongelen, Ruben and Pal, Anshuman and Goodrich, Carl Peter and Idema, Timon},
  issn         = {1539-3755},
  journal      = {Physical Review E},
  number       = {3},
  publisher    = {American Physical Society},
  title        = {{Collective dynamics of soft active particles}},
  doi          = {10.1103/physreve.91.032706},
  volume       = {91},
  year         = {2015},
}

@article{7768,
  abstract     = {We investigate the vibrational modes of quasi-two-dimensional disordered colloidal packings of hard colloidal spheres with short-range attractions as a function of packing fraction. Certain properties of the vibrational density of states (vDOS) are shown to correlate with the density and structure of the samples (i.e., in sparsely versus densely packed samples). Specifically, a crossover from dense glassy to sparse gel-like states is suggested by an excess of phonon modes at low frequency and by a variation in the slope of the vDOS with frequency at low frequency. This change in phonon mode distribution is demonstrated to arise largely from localized vibrations that involve individual and/or small clusters of particles with few local bonds. Conventional order parameters and void statistics did not exhibit obvious gel-glass signatures as a function of volume fraction. These mode behaviors and accompanying structural insights offer a potentially new set of indicators for identification of glass-gel transitions and for assignment of gel-like versus glass-like character to a disordered solid material.},
  author       = {Lohr, Matthew A. and Still, Tim and Ganti, Raman and Gratale, Matthew D. and Davidson, Zoey S. and Aptowicz, Kevin B. and Goodrich, Carl Peter and Sussman, Daniel M. and Yodh, A. G.},
  issn         = {1539-3755},
  journal      = {Physical Review E},
  number       = {6},
  publisher    = {American Physical Society},
  title        = {{Vibrational and structural signatures of the crossover between dense glassy and sparse gel-like attractive colloidal packings}},
  doi          = {10.1103/physreve.90.062305},
  volume       = {90},
  year         = {2014},
}

@article{7769,
  abstract     = {Athermal packings of soft repulsive spheres exhibit a sharp jamming transition in the thermodynamic limit. Upon further compression, various structural and mechanical properties display clean power-law behavior over many decades in pressure. As with any phase transition, the rounding of such behavior in finite systems close to the transition plays an important role in understanding the nature of the transition itself. The situation for jamming is surprisingly rich: the assumption that jammed packings are isotropic is only strictly true in the large-size limit, and finite-size has a profound effect on the very meaning of jamming. Here, we provide a comprehensive numerical study of finite-size effects in sphere packings above the jamming transition, focusing on stability as well as the scaling of the contact number and the elastic response.},
  author       = {Goodrich, Carl Peter and Dagois-Bohy, Simon and Tighe, Brian P. and van Hecke, Martin and Liu, Andrea J. and Nagel, Sidney R.},
  issn         = {1539-3755},
  journal      = {Physical Review E},
  number       = {2},
  publisher    = {American Physical Society},
  title        = {{Jamming in finite systems: Stability, anisotropy, fluctuations, and scaling}},
  doi          = {10.1103/physreve.90.022138},
  volume       = {90},
  year         = {2014},
}

@article{7770,
  abstract     = {Packings of frictionless athermal particles that interact only when they overlap experience a jamming transition as a function of packing density. Such packings provide the foundation for the theory of jamming. This theory rests on the observation that, despite the multitude of disordered configurations, the mechanical response to linear order depends only on the distance to the transition. We investigate the validity and utility of such measurements that invoke the harmonic approximation and show that, despite particles coming in and out of contact, there is a well-defined linear regime in the thermodynamic limit.},
  author       = {Goodrich, Carl Peter and Liu, Andrea J. and Nagel, Sidney R.},
  issn         = {1539-3755},
  journal      = {Physical Review E},
  number       = {2},
  publisher    = {American Physical Society},
  title        = {{Contact nonlinearities and linear response in jammed particulate packings}},
  doi          = {10.1103/physreve.90.022201},
  volume       = {90},
  year         = {2014},
}

@article{7772,
  abstract     = {Particle tracking and displacement covariance matrix techniques are employed to investigate the phonon dispersion relations of two-dimensional colloidal glasses composed of soft, thermoresponsive microgel particles whose temperature-sensitive size permits in situ variation of particle packing fraction. Bulk, B, and shear, G, moduli of the colloidal glasses are extracted from the dispersion relations as a function of packing fraction, and variation of the ratio G/B with packing fraction is found to agree quantitatively with predictions for jammed packings of frictional soft particles. In addition, G and B individually agree with numerical predictions for frictional particles. This remarkable level of agreement enabled us to extract an energy scale for the interparticle interaction from the individual elastic constants and to derive an approximate estimate for the interparticle friction coefficient.},
  author       = {Still, Tim and Goodrich, Carl Peter and Chen, Ke and Yunker, Peter J. and Schoenholz, Samuel and Liu, Andrea J. and Yodh, A. G.},
  issn         = {1539-3755},
  journal      = {Physical Review E},
  number       = {1},
  publisher    = {American Physical Society},
  title        = {{Phonon dispersion and elastic moduli of two-dimensional disordered colloidal packings of soft particles with frictional interactions}},
  doi          = {10.1103/physreve.89.012301},
  volume       = {89},
  year         = {2014},
}