Wednesday, March 19, 200810:00 AM - 11:00 AMCNLS Conference Room (TA-3, Bldg 1690)|
Charge Correlations in a Near-critical Plasma: Simulations challenge theory
Michael E. FisherInstitute for Physical Science and Technology, University of Maryland
2008 Kac Lecture Series
Reception/ Refreshments Served 9:30am
In a classical plasma (or an electrolyte solution) the charge-charge structure factor obeys *formula* , where *formula* and *formula* are the second- and fourth-moment charge-charge correlation lengths depending on T and the overall ionic density *formula* . The vanishing of the leading term, the first Stillinger-Lovett (SL) sum rule , simply reflects bulk electroneutrality. The second SL rule , or second-moment condition, dictates that *formula* where the Debye screening length *formula* varies as *formula*, *formula* being the elementary charge.
Recent grandcanonical Monte Carlo simulations  of a fully size- and charge-symmetric 1:1 (finely discretized) hard-sphere plasma or restricted primitive model , impose electroneutrality and so satisfy SL1 automatically. However, careful finite-size scaling analyses of extensive histogram-reweighted data indicates that the second-moment condition is violated at criticality by approximately 10%, *formula*. It is also found that *formula* diverges to *formula* in a manner that seems to mirror the density-density fluctuation.
These findings contradict Generalized Debye-Hückel theory  and also the exactly soluble charge-symmetric spherical models  both of which support SL2 at criticality and the finiteness of the fourth-moment. Nevertheless, the observed behavior is strikingly similar to that of the charge-asymmetric spherical models  where SL2 fails at criticality while diverges as *formula*.
 F.H. Stillinger and R. Lovett, J. Chem. Phys. 48, 3858 (1968).
 Work with S.K. Das and Y.C. Kim (to be published).
 See, e.g., Y.C. Kim and M.E. Fisher, Phys. Rev. Lett. 92, 185703 (2004).
 B.P. Lee and M.E. Fisher, Europhys. Lett. 39, 611 (1997).
 J.-N Aqua and M.E. Fisher, Phys. Rev. Lett. 92, 135702 (2004).
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