A digital oscilloscope setup for the measurement of a transistor's characteristics

The measure of the characteristics of a transistor is an important step in an introductory electronics course. We propose to use a digital oscilloscope with a USB connection to perform a measurement of the characteristic curves with no additional custom circuitry. The setup is presented alongside with code that allows the importation and analysis of the results with open-source software.Comment: 4 pages, 7 figures. Data files and program files available upon request, contact info at: http://homepages.ulb.ac.be/~pdebuyl

Higher spin fields from indefinite Kac-Moody algebras

The emergence of higher spin fields in the Kac-Moody theoretic approach to M-theory is studied. This is based on work done by Schnakenburg, West and the second author. We then study the relation of higher spin fields in this approach to other results in different constructions of higher spin field dynamics. Of particular interest is the construction of space-time in the present set-up and we comment on the various existing proposals.Comment: 1+18 pages. Based on a talk presented by A. Kleinschmidt at the First Solvay Workshop on Higher-Spin Gauge Theories held in Brussels on May 12-14, 200

Dualities and signatures of G++ invariant theories

The G++ content of the formulation of gravity and M-theories as very-extended Kac-Moody invariant theories is further analysed. The different exotic phases of all the G_B++ theories, which admit exact solutions describing intersecting branes smeared in all directions but one, are derived. This is achieved by analysing for all G++ the signatures which are related to the conventional one (1,D-1) by `dualities' generated by the Weyl reflections.Comment: 26 pages, 3 figure

Self-propulsion through symmetry breaking

In addition to self-propulsion by phoretic mechanisms that arises from an asymmetric distribution of reactive species around a catalytic motor, spherical particles with a uniform distribution of catalytic activity may also propel themselves under suitable conditions. Reactive fluctuation-induced asymmetry can give rise to transient concentration gradients which may persist under certain conditions, giving rise to a bifurcation to self-propulsion. The nature of this phenomenon is analyzed in detail, and particle-level simulations are carried out to demonstrate its existence.Comment: 6 pages, 3 figures. Appeared in EPL (Europhysics Letters

Cosmological billiards and oxidation

We show how the properties of the cosmological billiards provide useful information (spacetime dimension and $p$-form spectrum) on the oxidation endpoint of the oxidation sequence of gravitational theories. We compare this approach to the other available methods: $GL(n,R)$ subgroups and the superalgebras of dualities.Comment: To appear in the Proceedings of the 27th Johns Hopkins Workshop and in the Proceedings of the 36th International Symposium Ahrenshoop; v2: minor error correcte

Driving-induced stability with long-range effects

We give a sufficient condition under which an applied rotation on medium particles stabilizes a slow probe in the rotation center. The symmetric part of the stiffness matrix thus gets a positive Lamb shift with respect to equilibrium. For illustration we take diffusive medium particles with a self-potential in the shape of a Mexican hat, high around the origin. There is a short-range attraction between the medium particles and the heavier probe, all immersed in an equilibrium thermal bath. For no or small rotation force on the medium particles, the origin is an unstable fixed point for the probe and the precise shape of the self-potential at large distances from the origin is irrelevant for the statistical force there. Above a certain rotation threshold, while the medium particles are still repelled from the origin, the probe stabilizes there and more details of the medium-density at large distance start to matter. The effect is robust around the quasi-static limit with rotation threshold only weakly depending on the temperature but the stabilization gets stronger at lower temperatures.Comment: 6 pages, 4 figure

Boundary stress tensor and asymptotically AdS3 non-Einstein spaces at the chiral point

Chiral gravity admits asymptotically AdS3 solutions that are not locally equivalent to AdS3; meaning that solutions do exist which, while obeying the strong boundary conditions usually imposed in General Relativity, happen not to be Einstein spaces. In Topologically Massive Gravity (TMG), the existence of non-Einstein solutions is particularly connected to the question about the role played by complex saddle points in the Euclidean path integral. Consequently, studying (the existence of) non-locally AdS3 solutions to chiral gravity is relevant to understand the quantum theory. Here, we discuss a special family of non-locally AdS3 solutions to chiral gravity. In particular, we show that such solutions persist when one deforms the theory by adding the higher-curvature terms of the so-called New Massive Gravity (NMG). Moreover, the addition of higher-curvature terms to the gravity action introduces new non-locally AdS3 solutions that have no analogues in TMG. Both stationary and time-dependent, axially symmetric solutions that asymptote AdS3 space without being locally equivalent to it appear. Defining the boundary stress-tensor for the full theory, we show that these non-Einstein geometries have associated vanishing conserved charges.Comment: 8 pages. v2 minor typos correcte