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Virial inversion and microscopic derivation of density functionals

Presented by: 
Dimitrios Tsagkarogiannis University of L'Aquila
Wednesday 19th June 2019 - 14:30 to 15:10
INI Seminar Room 2
We present a rigorous derivation of the free energy functional for
inhomogeneous systems, i.e. with a density that depends on the position,
orientation or other internal degrees of freedom. It can be viewed as an
extension of the virial inversion (developed for homogeneous systems) to
uncountably many species. The key technical tool is a combinatorial identity for
a special type of trees which allows us to implement the inversion step as well
as to prove its convergence. Applications include classical density functional
theory, Onsager's functional for liquid crystals, hard spheres of different sizes
and shapes. Furthermore, the method can be generalized in order to provide
convergence for other expansions commonly used in the liquid state theory.
The validity is always in the gas regime, but with the new method we improve
the original radius of convergence for the hard spheres as proved by Lebowitz
and Penrose and subsequent works. This is joint work with Sabine Jansen and
Tobias Kuna.
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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons