Reduction of branes in generalized complex geometry

We show that certain submanifolds of generalized complex manifolds ("weak branes") admit a natural quotient which inherits a generalized complex structure. This is analog to quotienting coisotropic submanifolds of symplectic manifolds. In particular Gualtieri's generalized complex submanifolds ("branes") quotient to space-filling branes. Along the way we perform reductions by foliations (i.e. no group action is involved) for exact Courant algebroids - interpreting the reduced \v{S}evera class - and for Dirac structures.Comment: Final version, to apper in Journal of Symplectic Geometry. Proofs in section 5 simplified. 19 page

Comparison between a FEL amplifier and oscillator

Previous experiments with the Raman FEL, situated at the Twente University, showed that the output was influenced by the rather strong increase of the current density with time. The field emission diode has been modified to produce a more constant current pulse to simplify the analysis of the measurements. This resulted in a lower current density of the electron beam. With this new diode two set-ups are studied. In the first set-up the laser is still configured as an amplifier whereas in the second set-up the laser configuration is changed into an oscillator using a Bragg reflector with a space-variable corrugation height. For both set-ups we measured the frequency spectrum for specific values of undulator and guide magnetic fields. The relative performance of the amplifier and the oscillator configuration will be presented

Neighbourhood Abstraction in GROOVE - Tool Paper

In this paper we discuss the implementation of neighbourhood graph abstraction in the GROOVE tool set. Important classes of graph grammars may have unbounded state spaces and therefore cannot be verified with traditional model checking techniques. One way to address this problem is to perform graph abstraction, which allows us to generate a finite abstract state space that over-approximates the original one. In previous work we presented the theory of neighbourhood abstraction. In this paper, we present the implementation of this theory in GROOVE and illustrate its applicability with a case study that models a single-linked list

Simultaneous deformations of algebras and morphisms via derived brackets

We present a method to construct explicitly L-infinity algebras governing simultaneous deformations of various kinds of algebraic structures and of their morphisms. It is an alternative to the heavy use of the operad machinery of the existing approaches. Our method relies on Voronov's derived bracket construction.Comment: 20 pages. Final version, accepted for publication, and significantly shorter than version v1. Our previous submission arXiv:1202.2896v1 has been divided into two parts. The present paper contains the algebraic applications of the theory, while the geometric applications are the subject of the paper arXiv:1202.2896v2 ("Simultaneous deformations and Poisson geometry"