Density correlation function and dynamic transient exponents for liquid helium at and aboveT
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Authors: | Volker Dohm |
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Institution: | 1. Department of Physics and Astronomy, University of Maryland, College Park, Maryland, USA 2. Institut für Festk?rperforschung, Kernforschungsanlage Jülich GmbH, Postfach 1913, D-5170, Jülich 1, Germany
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Abstract: | The critical dynamics of liquid helium are studied by means of renormalized field theory on the basis of the symmetric planar-spin model of Halperin, Hohenberg, and Siggia. The stability problem of the dynamic fixed point is discussed in detail. Two-loop results suggest, but do not establish, the stability of the dynamic scaling fixed point. The previously found small fixed point valuew *~O(0.15) is tentatively confirmed which implies a small ratio of relaxation rates of the order parameter and the entropy. The ensuing dynamic transient exponents are calculated. The density correlation function is determined toO(ε=4?d) at and aboveT λ. Its properties in the casew *?1 provide quantitative support for the recently proposed explanation of the discrepancy between theory and light scattering experiments. A small value ofw * implies pronounced peaks of the frequency spectrum at finite frequencies at and aboveT λ. It also suppresses the temperature dependence of finite-frequency properties over an enlarged critical region as found in light scattering measurements. The quantitative relation between the value ofw *>0 and observable properties of the frequency spectrum is computed. |
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