11,126 research outputs found
Intersecting Branes, Defect Conformal Field Theories and Tensionless Strings
The defect conformal field theory describing intersecting D3-branes at a
C^2/Z_k orbifold is used to (de)construct the theory of intersecting M5-branes,
as well as M5-branes wrapping the holomorphic curve xy=c. The possibility of a
't Hooft anomaly due to tensionless strings at the intersection is discussed.
This note is based on a talk given by Zachary Guralnik at the 35th
International Symposium Ahrenshoop on the Theory of Elementary Particles.Comment: latex, one figure, 9pages. Talk given by Z.G. at the 35th
International Symposium Ahrenshoop on the Theory of Elementary Particle
Positivity of Lyapunov exponents for a continuous matrix-valued Anderson model
We study a continuous matrix-valued Anderson-type model. Both leading
Lyapunov exponents of this model are proved to be positive and distinct for all
ernergies in except those in a discrete set, which leads to
absence of absolutely continuous spectrum in . This result is an
improvement of a previous result with Stolz. The methods, based upon a result
by Breuillard and Gelander on dense subgroups in semisimple Lie groups, and a
criterion by Goldsheid and Margulis, allow for singular Bernoulli
distributions
Characterization of Water Dissociation on -AlO: Theory and Experiment
The interaction of water with -alumina (i.e. -AlO
surfaces is important in a variety of applications and a useful model for the
interaction of water with environmentally abundant aluminosilicate phases.
Despite its significance, studies of water interaction with
-AlO surfaces other than the are extremely
limited. Here we characterize the interaction of water (DO) with a well
defined -AlO surface in UHV both
experimentally, using temperature programmed desorption and surface-specific
vibrational spectroscopy, and theoretically, using periodic-slab density
functional theory calculations. This combined approach makes it possible to
demonstrate that water adsorption occurs only at a single well defined surface
site (the so-called 1-4 configuration) and that at this site the barrier
between the molecularly and dissociatively adsorbed forms is very low: 0.06 eV.
A subset of OD stretch vibrations are parallel to this dissociation coordinate,
and thus would be expected to be shifted to low frequencies relative to an
uncoupled harmonic oscillator. To quantify this effect we solve the vibrational
Schr\"odinger equation along the dissociation coordinate and find fundamental
frequencies red-shifted by more than 1,500 cm. Within the context
of this model, at moderate temperatures, we further find that some fraction of
surface deuterons are likely delocalized: dissociatively and molecularly
absorbed states are no longer distinguishable.Comment: Paper: 22 pages, 9 figures , ESI: 6 pages, 1 figur
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