▁of ▁constitu ent ▁particles ▁is ▁a ▁key ▁element ▁in ▁these ▁systems . ▁Under ▁certain ▁conditions , ▁including ▁high ▁ ▁dens ities ▁and ▁low ▁temper atures , ▁when ▁extern ally ▁driven ▁to ▁indu ce ▁flow , ▁complex ▁flu ids ▁are ▁character ized ▁by ▁irregular ▁intervals ▁of ▁solid - like ▁behavior ▁followed ▁by ▁stress ▁relax ations ▁due ▁to ▁particle ▁re arr ang ements . ▁The ▁dynamics ▁of ▁these ▁systems ▁are ▁highly ▁non linear ▁in ▁nature . ▁The ▁increase ▁in ▁stress ▁by ▁an ▁inf init es imal ▁amount ▁or ▁a ▁small ▁disp lacement ▁of ▁a ▁single ▁particle ▁can ▁result ▁in ▁the ▁difference ▁between ▁an ▁arrested ▁state ▁and ▁fluid - like ▁behavior . ▁▁ ▁Although ▁many ▁materials ▁found ▁in ▁nature ▁can ▁fit ▁into ▁the ▁class ▁of ▁complex ▁flu ids , ▁very ▁little ▁is ▁well ▁understood ▁about ▁them . ▁In cons istent ▁and ▁controvers ial ▁conclus ions ▁concerning ▁their ▁material ▁properties ▁still ▁persist . ▁The ▁careful ▁study ▁of ▁these ▁systems ▁may ▁lead ▁to ▁" new ▁physics " ▁and ▁new ▁states ▁of ▁matter . ▁For ▁example , ▁it ▁has ▁been ▁suggested ▁that ▁these ▁systems ▁can ▁jam ▁and ▁a ▁" j am ming ▁phase ▁diagram " ▁can ▁be ▁used ▁to ▁consider ▁how ▁these ▁systems ▁can ▁jam ▁and ▁un j am . ▁It ▁is ▁not ▁known ▁whether ▁further ▁research ▁will ▁demonstrate ▁these ▁find ings , ▁or ▁whether ▁such ▁a ▁theoretical ▁framework ▁will ▁prove ▁useful . ▁As ▁yet ▁this ▁large ▁body ▁of ▁theoretical ▁work ▁has ▁been ▁poor ly ▁supported ▁with ▁experiments . ▁ ▁External ▁links ▁Ste phan ▁Herm ing haus ' ▁Dynam