Dual Formulation of the Lie Algebra S-expansion Procedure

The expansion of a Lie algebra entails finding a new, bigger algebra G, through a series of well-defined steps, from an original Lie algebra g. One incarnation of the method, the so-called S-expansion, involves the use of a finite abelian semigroup S to accomplish this task. In this paper we put forward a dual formulation of the S-expansion method which is based on the dual picture of a Lie algebra given by the Maurer-Cartan forms. The dual version of the method is useful in finding a generalization to the case of a gauge free differential algebra, which in turn is relevant for physical applications in, e.g., Supergravity. It also sheds new light on the puzzling relation between two Chern-Simons Lagrangians for gravity in 2+1 dimensions, namely the Einstein-Hilbert Lagrangian and the one for the so-called "exotic gravity".Comment: 12 pages, no figure

Standard General Relativity from Chern-Simons Gravity

Chern-Simons models for gravity are interesting because they provide with a truly gauge-invariant action principle in the fiber-bundle sense. So far, their main drawback has largely been the perceived remoteness from standard General Relativity, based on the presence of higher powers of the curvature in the Lagrangian (except, remarkably, for three-dimensional spacetime). Here we report on a simple model that suggests a mechanism by which standard General Relativity in five-dimensional spacetime may indeed emerge at a special critical point in the space of couplings, where additional degrees of freedom and corresponding "anomalous" Gauss-Bonnet constraints drop out from the Chern-Simons action. To achieve this result, both the Lie algebra g and the symmetric g-invariant tensor that define the Chern-Simons Lagrangian are constructed by means of the Lie algebra S-expansion method with a suitable finite abelian semigroup S. The results are generalized to arbitrary odd dimensions, and the possible extension to the case of eleven-dimensional supergravity is briefly discussed.Comment: 6 pages, no figures; v2: published versio

Reproduction, reflection, production. Imagination of the climate crisis.

Verhalen vormen een essentieel onderdeel van cultuur. Met verhalen geven we betekenis aan de wereld om ons heen. Maar ze doen meer dan bestaande ideeën bevestigen: verhalen laten ons ook nadenken over de wereld en hebben de kracht nieuwe zienswijzen te ontwikkelen en daarop te handelen. In dit artikel gaan we in op fictieve verhalen (literatuur) en verhalen gebaseerd op reële doorleefde ervaringen van klimaatverandering. Zowel literatuur als de verbinding met lokale kennis dragen bij aan het ‘’tot leven’’ brengen van de abstracte natuurwetenschappelijke kennis over de klimaatcrisis en het verbeelden, bepalen en uitvoeren van mogelijke adequate, lokale acties

Structural reduction of carbon emissions through online education in Dutch Higher Education

Dutch institutions of Higher Education have to meet stringent requirements for energy efficiency andreducing carbon emissions imposed by the national government. The commute of students and staffgreatly contributes to the carbon footprint of a Higher Education Institution. International students inDutch Higher Education also have a substantial impact on the environment due to air travel. Theirnumber increases every year. The deployment and use of ICT can contribute substantially to thereduction of energy use and carbon emissions through decreasing mobility of students and staff byincreasing virtualization and digitalization of educational processes.This exploratory study examines the opportunities of online learning as a means to reduce the impactof students’ traveling on the carbon footprint. The research methodology consists of a systematicreview of literature and a series of interviews with experts of online learning and managers of energy,ICT and/or sustainability.An obstacle for decreasing the carbon footprint of a Higher Education Institution using online learningare differences in opinion as expressed by professionals, regarding the quality of this form ofeducation. Our research shows that those in favour of face-to-face education believe, that the socialprocesses are essential for high quality education. Proponents of online learning emphasize theopportunities by focusing on the advantages for individual students – i.e. giving students more controlover their own learning process. So far, only a minority have recognized that online learning can leadto decreased mobility and a reduction of carbon emissions