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Wednesday, March 19, 2008
10:00 AM - 11:00 AM
CNLS Conference Room (TA-3, Bldg 1690)


Charge Correlations in a Near-critical Plasma: Simulations challenge theory

Michael E. Fisher
Institute 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 [1], simply reflects bulk electroneutrality. The second SL rule [1], 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 [2] of a fully size- and charge-symmetric 1:1 (finely discretized) hard-sphere plasma or restricted primitive model [3], 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 [4] and also the exactly soluble charge-symmetric spherical models [5] 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 [5] where SL2 fails at criticality while diverges as *formula*. [1] F.H. Stillinger and R. Lovett, J. Chem. Phys. 48, 3858 (1968). [2] Work with S.K. Das and Y.C. Kim (to be published). [3] See, e.g., Y.C. Kim and M.E. Fisher, Phys. Rev. Lett. 92, 185703 (2004). [4] B.P. Lee and M.E. Fisher, Europhys. Lett. 39, 611 (1997). [5] J.-N Aqua and M.E. Fisher, Phys. Rev. Lett. 92, 135702 (2004). For Additional Information Please Visit Our Website:

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