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BEGIN:VEVENT
UID:9d5f8b2b33c4f3feba0c87f27e0dad62
CATEGORIES:Mathematical Physics Seminar
CREATED:20210712T105918
SUMMARY:Random Close Packing as a Dynamical Phase Transition
LOCATION:zoom
DESCRIPTION: \nWednesday, July 14, 10:45AM (Zoom meeting starts at 10:30)\n“” \n“Random
Close Packing” is an ancient problem. RCP - the densest packing of spheres
poured into a jar described in Biblical times (Luke 6:38, KJV) as, “presse
d down, and shaken together, and running over” - has escaped a noncontrover
sial definition although many experiments and simulations agree to a value
?RCP ~0.64. We have found that a simple model, “Biased Random Organization
”, BRO, exhibits a dynamical phase transition between absorbing (non-overla
pping) and active states that appears to have RCP as its critical endpoint.
In Random Organization, RO, overlapping particles are each given a random
displacement < ?. In BRO some fraction of repulsive displacements are ad
ded. For 3D BRO we find ?cMAX ~ 0.64 ~ ?RCP, isostatic coordination, Z=6,
and a similar radial distribution function as found in previous RCP experi
ments and simulations. BRO, an absorbing state model, remains in the Manna
universality class. Such models are hyperuniform at critical, S(q?0) ~q?. F
or the Manna class, ?3D =0.25. At ?cMAX, we show that BRO other protocols f
or RCP have very similar S(q) with ?3D =0.25. Characterizing RCP as the hig
hest density ensemble of BRO configurations requires neither randomness, no
r hyperuniformity, nor jamming which rather become emergent properties. In
2D BRO yields a rich phase diagram with a dense hexagonal crystal, area fra
ction ~0.91, as its critical endpoint.\n
X-ALT-DESC;FMTTYPE=text/html:
Wednesday, July 14, 1
0:45AM (Zoom meeting starts at 10:30)
“”
“Random Close Packing” is an ancient problem. RCP - the dense
st packing of spheres poured into a jar described in Biblical times (Luke 6
:38, KJV) as, “pressed down, and shaken together, and running over” - has e
scaped a noncontroversial definition although many experiments and simulati
ons agree to a value ?RCP ~0.64. We have found that a simple model, “
Biased Random Organization”, BRO, exhibits a dynamical phase transition bet
ween absorbing (non-overlapping) and active states that appears to have RCP
as its critical endpoint. In Random Organization, RO, overlapping particle
s are each given a random displacement < ?. In BRO some fraction of repu
lsive displacements are added. For 3D BRO we find ?cMAX ~ 0.64 ~ ?RCP
, isostatic coordination, Z=6, and a similar radial distribution func
tion as found in previous RCP experiments and simulations. BRO, an absorbin
g state model, remains in the Manna universality class. Such models are hyp
eruniform at critical, S(q?0) ~q?. For the Manna class, ?3D =0.25. At ?cMAX
, we show that BRO other protocols for RCP have very similar S(q) with ?3D
=0.25. Characterizing RCP as the highest density ensemble of BRO configurat
ions requires neither randomness, nor hyperuniformity, nor jamming which ra
ther become emergent properties. In 2D BRO yields a rich phase diagram with
a dense hexagonal crystal, area fraction ~0.91, as its critical endpoint.<
/p>
CONTACT:Paul Chaikin – New York University
DTSTAMP:20260827T051725
DTSTART;TZID=America/New_York:20210714T104500
DTEND;TZID=America/New_York:20210714T114500
SEQUENCE:0
TRANSP:OPAQUE
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