Missing Modules, the Gnome Lie Algebra, and E10E_{10}

We study the embedding of Kac-Moody algebras into Borcherds (or generalized Kac-Moody) algebras which can be explicitly realized as Lie algebras of physical states of some completely compactified bosonic string. The extra ``missing states'' can be decomposed into irreducible highest or lowest weight ``missing modules'' w.r.t. the relevant Kac-Moody subalgebra; the corresponding lowest weights are associated with imaginary simple roots whose multiplicities can be simply understood in terms of certain polarization states of the associated string. We analyse in detail two examples where the momentum lattice of the string is given by the unique even unimodular Lorentzian lattice $II_{1,1}$ or $II_{9,1}$, respectively. The former leads to the Borcherds algebra $g_{1,1}$, which we call ``gnome Lie algebra", with maximal Kac-Moody subalgebra $A_1$. By the use of the denominator formula a complete set of imaginary simple roots can be exhibited, whereas the DDF construction provides an explicit Lie algebra basis in terms of purely longitudinal states of the compactified string in two dimensions. The second example is the Borcherds algebra $g_{9,1}$, whose maximal Kac-Moody subalgebra is the hyperbolic algebra $E_{10}$. The imaginary simple roots at level 1, which give rise to irreducible lowest weight modules for $E_{10}$, can be completely characterized; furthermore, our explicit analysis of two non-trivial level-2 root spaces leads us to conjecture that these are in fact the only imaginary simple roots for $g_{9,1}$.Comment: 31 pages, LaTeX2e, AMS packages, PSTRICK

BIRD - A Microsatellite for Hot Spot Detection

The BIRD mission of the German Aerospace Centre shall demonstrate the scientific and technological value and the technical and programmatic feasibility of a remote sensing small satellite mission under low budget constraints. The payload -a new generation of cooled infrared detectors- is adapted to the mission objective - the investigation of hot spots caused by forest fires or volcanic activities completed by the diagnosis of vegetation conditions and changes. BIRD -the Bispectral Infra-Red Detector- is a three-axis stabilised spacecraft within a volume of 0.21 m3 and a mass of 88 kg. In flight configuration with one fixed and two deployed solar panels, providing 40 W average and 200 W peak power, the spacecraft dimensions are 620x 1600x 620 mm3 • Although compatible to several launchers due to the highly compact design, the launch is scheduled for mid 2000 as a piggy-back payload. To fit in this time scale a modular design was chosen for parallel development, manufacturing and integration of all functional segments. The article gives an overview of the mission objectives and some of the main design aspects as well as shows the status of work of the space segment

E10 and a "small tension expansion" of M Theory

A formal ``small tension'' expansion of D=11 supergravity near a spacelike singularity is shown to be equivalent, at least up to 30th order in height, to a null geodesic motion in the infinite dimensional coset space E10/K(E10) where K(E10) is the maximal compact subgroup of the hyperbolic Kac-Moody group E10(R). For the proof we make use of a novel decomposition of E10 into irreducible representations of its SL(10,R) subgroup. We explicitly show how to identify the first four rungs of the E10 coset fields with the values of geometric quantities constructed from D=11 supergravity fields and their spatial gradients taken at some comoving spatial point.Comment: 4 page

(2,0) Supersymmetry and the Light-Cone Description of M5-branes

In 1007.2982 a novel system of equations which propagate in one null and four space directions were obtained as the on-shell conditions for the six-dimensional (2,0) superalgebra. In this paper we show how this system reduces to one-dimensional motion on instanton moduli space. Quantization leads to the previous light-cone proposal of the (2,0) theory, generalized to include a potential that arises on the Coulomb branch as well as couplings to background gauge and self-dual two-form fields.Comment: 15 pages, v2: minor clarifications to sections 3 and 5, references added. This version to appear in JHE

Borcherds Algebras and N=4 Topological Amplitudes

The perturbative spectrum of BPS-states in the E_8 x E_8 heterotic string theory compactified on T^2 is analysed. We show that the space of BPS-states forms a representation of a certain Borcherds algebra G which we construct explicitly using an auxiliary conformal field theory. The denominator formula of an extension G_{ext} \supset G of this algebra is then found to appear in a certain heterotic one-loop N=4 topological string amplitude. Our construction thus gives an N=4 realisation of the idea envisioned by Harvey and Moore, namely that the `algebra of BPS-states' controls the threshold corrections in the heterotic string.Comment: 39 page

The BIRD Mission

For hot spot events as forest and vegetation fires, volcanic activity or burning oil wells and coal seams a dedicated space instrumentation does not exist. Sensors being used now for the observation of these events have some drawbacks because they are not designed for the hot spot investigation. For the near future there are missions planned with a new generation of cooled infrared array sensors. The German BIRD (Bi-spectral Infrared Detection) mission will answer a lot of technological and scientific questions related to the operation of a compact bi-spectral infrared push-broom sensor on board of a micro satellite and related to the detection and investigation of fires from space. The DLR small satellite mission BIRD is dedicated to the remote sensing of hot spot events like vegetation fires, coal seam fires or active volcanoes from space and to the in-orbit verification and demonstration of new micro-satellite technologies. The total mass of the complete spacecraft is 92 k

Resumes of the Bird Mission

The DLR micro satellite BIRD (Bi-Spectral Infra Red Detection)was the Indian Polar Satellite Launch Vehicle PSLV-C3 into a 570 km ciracular sun-synchronous orbit on 22 October 2001. The BIRD mission, fully funded by the DLR, answers topical technologal and scientific questions related to the operation of a compact infra-red push-broom sensor system on board of a micro satellite and demonstrates a new spacecraft bus technologies. BIRD mission control is conducted by DLR/GSOC in Oberpfaffenhofen commanding, data reception and data processing is performed via ground stations in Weilheim and Neustrelitz (Germany). The BIRD mission is a demonstrator for small satellite projects dedicated to the hazard detection and monitoring. In the year 2003 BIRD has been used in the ESA project FUEGOSAT to demonstrate the utilisation of innovative space technologies for fire risk management

The DLR Small Satellite Mission BIRD

For hot spot events as forest and vegetation fires, volcanic activity or burning oil spills and coal seam a dedicated space instrumentation does not exist. Sensors are used now for the observation of these events have some drawbacks because they are not designed for the hot spot investigation. For the near future missions with a new generation of cooled infrared array sensors are planned. The BIRD (Bispectral Infrared Detection) mission will answer a lot of technological questions related to the operations of the infrared sensors in space. An other primary mission objective consists in the investigation of vegetation fires from space by means of these infrared sensors. New concepts of operations and new methods of the data evaluation of hot spots will be demonstrated by the BIRD mission. Last but not least new methods and knowledge in the remote sensing and evaluation of vegetation condition and changes from space will be developed within the BIRD mission. The BIRD mission is a small satellite mission with technological and scientific objectives