Stability in controlled L-theory

We prove a squeezing/stability theorem for delta-epsilon controlled L-groups when the control map is a fibration on a finite polyhedron. A relation with boundedly-controlled L-groups is also discussed.Comment: This is the version published by Geometry & Topology Monographs on 22 April 200

More examples of discrete co-compact group actions

We survey some results and questions about free actions of infinite groups on products of spheres and euclidean spaces, and give some new co-compact examples

Topological Equivalence of Linear Representations for Cyclic Groups, I & II

In the two parts of this paper we solve a problem of De Rham, proving that Reidemeister torsion invariants determine topological equivalence of linear G-representations, for G a finite cyclic group. Methods in controlled K-theory and surgery theory are developed to establish, and effectively calculate, a necessary and sufficient condition for non-linear similarity in terms of the vanishing of certain non-compact transfer maps. For cyclic groups of 2-power order, we obtain a complete classification of non-linear similarities.Comment: The first version of this paper appeared as MPI Preprint 1997-58, Max Planck Institut fuer Mathematik, Bonn. The final version includes many improvements in exposition and new results. It is now divided into two parts. Part I (36 pages) will appear in Annals of Mathematics, and Part II (43 pages) will appear in Forum Mat

Jensen's Operator Inequality

We establish what we consider to be the definitive versions of Jensen's operator inequality and Jensen's trace inequality for functions defined on an interval. This is accomplished by the introduction of genuine non-commutative convex combinations of operators, as opposed to the contractions used in earlier versions of the theory. As a consequence, we no longer need to impose conditions on the interval of definition. We show how this relates to the pinching inequality of Davis, and how Jensen's trace inequlity generalizes to C*-algebras..Comment: 12 p

Predatory Trading

This paper studies predatory trading: trading that induces and/or exploits other investors' need to reduce their positions. We show that if one trader needs to sell, others also sell and subsequently buy back the asset. This leads to price overshooting and a reduced liquidation value for the distressed trader. Hence, the market is illiquid when liquidity is most needed. Further, a trader profits from triggering another trader's crisis, and the crisis can spill over across traders and across markets.

Jurisdictional and Interstate Commerce Problems in the Imposition of Excess on Sales

I denne rapport argumenterer forfatterne for, at der i beskæftigelsespolitikken er behov for at flytte det strategiske fokus fra 'flexicurity' til 'mobication' ('mobility through education'), som indebærer, at man sætter kompetenceudvikling i centrum. Det er forfatternes vurdering, at 'flexicurity' fortsat udgør et vigtigt fundament for fleksibiliteten og sikkerheden for først og fremmest de ledige på arbejdsmarkedet, men at der er behov for en langt mere offensiv satsning på livslang uddannelse af hele arbejdsstyrken, hvis man skal sikre arbejdskraftens konkurrencedygtighed fremover. 'Mobication' sigter netop mod at styrke arbejdskraftens muligheder for at tilpasse sig og bevæge sig i forhold til de skiftende behov på et arbejdsmarked i en stadigt mere konkurrencepræget verdensøkonomi

Hypergeometric resummation of self-consistent sunset diagrams for electron-boson quantum many-body systems out of equilibrium

A newly developed hypergeometric resummation technique [H. Mera et al., Phys. Rev. Lett. 115, 143001 (2015)] provides an easy-to-use recipe to obtain conserving approximations within the self-consistent nonequilibrium many-body perturbation theory. We demonstrate the usefulness of this technique by calculating the phonon-limited electronic current in a model of a single-molecule junction within the self-consistent Born approximation for the electron-phonon interacting system, where the perturbation expansion for the nonequilibrium Green function in powers of the free bosonic propagator typically consists of a series of non-crossing \sunset" diagrams. Hypergeometric resummation preserves conservation laws and it is shown to provide substantial convergence acceleration relative to more standard approaches to self-consistency. This result strongly suggests that the convergence of the self-consistent \sunset" series is limited by a branch-cut singularity, which is accurately described by Gauss hypergeometric functions. Our results showcase an alternative approach to conservation laws and self-consistency where expectation values obtained from conserving perturbation expansions are \summed" to their self-consistent value by analytic continuation functions able to mimic the convergence-limiting singularity structure.Comment: 13 pages, 6 figure