20 research outputs found
Constructing Universal Abelian Covers of Graph Manifolds
To a rational homology sphere graph manifold one can associate a weighted
tree invariant called splice diagram. It was shown earlier that the splice
diagram determines the universal abelian cover of the manifold. We will in this
article turn the proof of this in to an algorithm to explicitly construct the
universal abelian cover from the splice diagram.Comment: 12 page
Determining When The Universal Abelian Cover of a Graph Manifold is a Rationla Homology Sphere
It was shown in my earlier article that the splice diagram of a rational
homology sphere graph manifold determines the manifolds universal abelian
cover. In this article we use the proof of this to give a condition on the
splice diagram to determine when the universal abelian cover itself is a
rational homology sphere.Comment: 13 page
Minimal surface singularities are Lipschitz normally embedded
Any germ of a complex analytic space is equipped with two natural metrics:
the {\it outer metric} induced by the hermitian metric of the ambient space and
the {\it inner metric}, which is the associated riemannian metric on the germ.
We show that minimal surface singularities are Lipschitz normally embedded
(LNE), i.e., the identity map is a bilipschitz homeomorphism between outer and
inner metrics, and that they are the only rational surface singularities with
this property.Comment: This paper is a major revision of the 2015 version. It now builds on
the paper arXiv:1806.11240 by the same authors which gives a general
characterization of Lipschitz normally embedded surface singularitie
A characterization of Lipschitz normally embedded surface singularities
Any germ of a complex analytic space is equipped with two natural metrics:
the outer metric induced by the hermitian metric of the ambient space and the
inner metric, which is the associated riemannian metric on the germ. These two
metrics are in general nonequivalent up to bilipschitz homeomorphism. We give a
necessary and sufficient condition for a normal surface singularity to be
Lipschitz normally embedded (LNE), i.e., to have bilipschitz equivalent outer
and inner metrics. In a partner paper [15] we apply it to prove that rational
surface singularities are LNE if and only if they are minimal.Comment: 30 page
Varmepumper og Lavtemperatur-fjernvarme - Rapportering fra to workshops
Denne rapport udgør et delbidrag af rapporteringen fra projektet ” Effektiv fjernvarme i fremtidens energisystem”, som under Energistyrelsens Energiforskningsprogram (EFP) udføres af et konsortium af EA-energianalyse, Systemanalyseafdelingen på Risø DTU, RAM-løse edb samt Fjernvarmens visionsudvalg nedsat under Dansk Fjernvarmeforening.Formålet med projektet er at belyse, hvordan fjernvarmens rolle i energiforsyningen kan udvikles på langt sigt gennem effektiv drift, anvendelse af ny teknologi samt dynamisk samspil med elmarkedet. En fremtidig udvikling mod et bæredygtigt energisystem vil kræve betydelige energibesparelser, herunder i rumopvarmningen. Dette vil alt andet lige mange steder føre til, at grundlaget for fjernvarmen vil ændre sig. Det er således centralt i projektet, at opstille en række scenarier for fjernvarmens fremtidige rolle i energisystemet, herunder at belyse hvad reducerede varmetab i fjernvarmenet og dynamisk anvendelse af kendte og nye energiteknologier kan betyde. Disse teknologier omfatter bl.a. varmepumper, geotermi, fjernkøling og varmelagring. Endvidere er formålet at belyse hvordan samspillet mellem elmarkedet og fjernvarmen kan effektiviseres, samt at pege på hvilke rammebetingelser der især er kritiske for fjernvarmens fortsatte udvikling og effektivisering.Som et led i analyserne i projektet er der afholdt to workshops om henholdsvis anvendelsen af varmepumper og lavtemperatur-fjernvarmenet. Denne rapport er en dokumentation af de to workshops, idet den indeholder program, deltagerliste, præsentationer og korte resumeer. I begge workshops deltog eksterne indledere parallelt med projektgruppens egne deltagere. Vi takker deltagerne for præsentationer og engageret deltagelse i diskussionerne