Dynamical Screening Effects in Correlated Electron Materials -- A Progress Report on Combined Many-Body Perturbation and Dynamical Mean Field Theory: "GW+DMFT"

We give a summary of recent progress in the field of electronic structure calculations for materials with strong electronic Coulomb correlations. The discussion focuses on developments beyond the by now well established combination of density functional and dynamical mean field theory dubbed "LDA+DMFT". It is organized around the description of dynamical screening effects in the solid. Indeed, screening in the solid gives rise to dynamical local Coulomb interactions U(w) (Aryasetiawan et al 2004 Phys. Rev. B 70 195104), and this frequency-dependence leads to effects that cannot be neglected in a truly first principles description. We review the recently introduced extension of LDA+DMFT to dynamical local Coulomb interactions "LDA+U(w)+DMFT" (Casula et al. Phys. Rev. B 85 035115 (2012), Werner et al. Nature Phys. 8 331 (2012)). A reliable description of dynamical screening effects is also a central ingredient of the "GW+DMFT" scheme (Biermann et al. Phys. Rev. Lett. 90 086402 (2003)), a combination of many-body perturbation theory in Hedin's GW approximation and dynamical mean field theory. Recently, the first GW+DMFT calculations including dynamical screening effects for real materials have been achieved, with applications to SrVO3 (Tomczak et al. Europhys. Lett. 100 67001 (2012); Phys. Rev. B 90 165138 (2014)) and adatom systems on surfaces (Hansmann et al. Phys. Rev. Lett. 110 166401 (2013)). We review these and comment on further perspectives in the field. This review is an attempt to put elements of the original works (Refs. 1-11) into the broad perspective of the development of truly first principles techniques for correlated electron materials.Comment: 40 pages, 12 figures. First published as "Highlight of the Month" (June 2013), of the Psi-k Network on "Ab initio calculation of complex processes in materials", see http://www.psi-k.org/newsletters/News_117/Highlight_117.pd

Slow theory : taking time over transnational democratic representation

The possibility for transnational democratic representation is a huge topic. This article is restricted to exploring two unconventional aspects. The first concerns 'the representative claim', extending one critical part of previous analysis of the assessment of such claims, especially by largely unelected transnational actors. The second, which strongly conditions the account of the first, concerns ‘slow theory’ as the way to approach building democratic models and, in particular, to approach transnational democratic representation

A Measure to Compare Matchings in Marriage Markets

In matching markets the number of blocking pairs is often used as a criterion to compare matchings. We argue that this criterion is lacking an economic interpretation: In many circumstances it will neither reflect the expected extent of partner changes, nor will it capture the satisfaction of the players with the matching. As an alternative, we set up two principles which single out a particularly “disruptive” subcollection of blocking pairs. We propose to take the cardinality of that subset as a measure to compare matchings. This cardinality has an economic interpretation: the subset is a justified objection against the given matching according to a bargaining set characterization of the set of stable matchings. We prove multiple properties relevant for a workable measure of comparison.Stable Marriage Problem, Matching, Blocking Pair, Instability, Matching Comparison, Decentralized Market, Bargaining Set

Frontiers of Astrophysics - Workshop Summary

We summarize recent results presented in the astrophysics session during a conference on ``Frontiers of Contemporary Physics''. We will discuss three main fields (High-Energy Astrophysics, Relativistic Astrophysics, and Cosmology), where Astrophysicists are pushing the limits of our knowledge of the physics of the universe to new frontiers. Since the highlights of early 1997 were the first detection of a redshift and the optical and X-ray afterglows of gamma-ray bursts, as well as the first well-documented flares of TeV-Blazars across a large fraction of the electromagnetic spectrum, we will concentrate on these topics. Other topics covered are black holes and relativistic jets, high-energy cosmic rays, Neutrino-Astronomy, extragalactic magnetic fields, and cosmological models.Comment: Proceedings of the Workshop "Frontiers in Contemporary Physics", Nashville, May 11-16, 1997, AIP-conference series, Ed. T. Weiler & R. Panvini, LaTex(aip2col), 13 pages, preprint also available at http://www.astro.umd.edu/~hfalcke/publications.html#frontier