2,535 research outputs found
Gauge theory on nonassociative spaces
We show how to do gauge theory on the octonions and other nonassociative
algebras such as `fuzzy ' models proposed in string theory. We use the
theory of quasialgebras obtained by cochain twist introduced previously. The
gauge theory in this case is twisting-equivalent to usual gauge theory on the
underlying classical space. We give a general U(1)-Yang-Mills example for any
quasi-algebra and a full description of the moduli space of flat connections in
this theory for the cube and hence for the octonions. We also obtain
further results about the octonions themselves; an explicit Moyal-product
description of them as a nonassociative quantisation of functions on the cube,
and a characterisation of their cochain twist as invariant under Fourier
transform.Comment: 24 pages latex, two .eps figure
Braided Cyclic Cocycles and Non-Associative Geometry
We use monoidal category methods to study the noncommutative geometry of
nonassociative algebras obtained by a Drinfeld-type cochain twist. These are
the so-called quasialgebras and include the octonions as braided-commutative
but nonassociative coordinate rings, as well as quasialgebra versions
\CC_{q}(G) of the standard q-deformation quantum groups. We introduce the
notion of ribbon algebras in the category, which are algebras equipped with a
suitable generalised automorphism , and obtain the required
generalisation of cyclic cohomology. We show that this \emph{braided cyclic
cocohomology} is invariant under a cochain twist. We also extend to our
generalisation the relation between cyclic cohomology and differential calculus
on the ribbon quasialgebra. The paper includes differential calculus and cyclic
cocycles on the octonions as a finite nonassociative geometry, as well as the
algebraic noncommutative torus as an associative example.Comment: 36 pages latex, 9 figure
Braided Matrix Structure of the Sklyanin Algebra and of the Quantum Lorentz Group
Braided groups and braided matrices are novel algebraic structures living in
braided or quasitensor categories. As such they are a generalization of
super-groups and super-matrices to the case of braid statistics. Here we
construct braided group versions of the standard quantum groups . They
have the same FRT generators but a matrix braided-coproduct \und\Delta
L=L\und\tens L where , and are self-dual. As an application, the
degenerate Sklyanin algebra is shown to be isomorphic to the braided matrices
; it is a braided-commutative bialgebra in a braided category. As a
second application, we show that the quantum double D(\usl) (also known as
the `quantum Lorentz group') is the semidirect product as an algebra of two
copies of \usl, and also a semidirect product as a coalgebra if we use braid
statistics. We find various results of this type for the doubles of general
quantum groups and their semi-classical limits as doubles of the Lie algebras
of Poisson Lie groups.Comment: 45 pages. Revised (= much expanded introduction
Continuous-wave, multimilliwatt, mid-infrared source tunable across 6.4–7.5  μm based on orientation-patterned GaAs
We report a continuous-wave (cw) source of tunable mid-infrared radiation providing tens of milliwatt of output
power in the 6460–7517 nm spectral range. The source is based on difference-frequency generation (DFG) in orientation-patterned
(OP)-GaAs pumped by a Tm-fiber laser at 2010 nm and a 1064 nm-Yb-fiber-pumped cw optical
parametric oscillator. Using a 25.7-mm-long OP-GaAs crystal, we have generated up to 51.1 mW of output power at
6790 nm, with >40 mW and >20 mW across 32% and 80% of the mid-infrared tuning range, respectively, which is to
the best of our knowledge the highest tunable cw power generated in OP-GaAs in this spectral range. The DFG
output at maximum power exhibits passive power stability better than 2.3% rms over more than 1 h and a frequency
stability of 1.8 GHz over more than 1 min, in high spatial beam quality. The system and crystal performance at high
pump powers have been studiedPostprint (published version
Optical emission near a high-impedance mirror
Solid state light emitters rely on metallic contacts with high
sheet-conductivity for effective charge injection. Unfortunately, such contacts
also support surface plasmon polariton (SPP) excitations that dissipate optical
energy into the metal and limit the external quantum efficiency. Here, inspired
by the concept of radio-frequency (RF) high-impedance surfaces and their use in
conformal antennas we illustrate how electrodes can be nanopatterned to
simultaneously provide a high DC electrical conductivity and high-impedance at
optical frequencies. Such electrodes do not support SPPs across the visible
spectrum and greatly suppress dissipative losses while facilitating a desirable
Lambertian emission profile. We verify this concept by studying the emission
enhancement and photoluminescence lifetime for a dye emitter layer deposited on
the electrodes
Differential and Twistor Geometry of the Quantum Hopf Fibration
We study a quantum version of the SU(2) Hopf fibration and its
associated twistor geometry. Our quantum sphere arises as the unit
sphere inside a q-deformed quaternion space . The resulting
four-sphere is a quantum analogue of the quaternionic projective space
. The quantum fibration is endowed with compatible non-universal
differential calculi. By investigating the quantum symmetries of the fibration,
we obtain the geometry of the corresponding twistor space and
use it to study a system of anti-self-duality equations on , for which
we find an `instanton' solution coming from the natural projection defining the
tautological bundle over .Comment: v2: 38 pages; completely rewritten. The crucial difference with
respect to the first version is that in the present one the quantum
four-sphere, the base space of the fibration, is NOT a quantum homogeneous
space. This has important consequences and led to very drastic changes to the
paper. To appear in CM
Quantum statistics and noncommutative black holes
We study the behaviour of a scalar field coupled to a noncommutative black
hole which is described by a -cylinder Hopf algebra. We introduce a new
class of realizations of this algebra which has a smooth limit as the
deformation parameter vanishes. The twisted flip operator is independent of the
choice of realization within this class. We demonstrate that the -matrix is
quasi-triangular up to the first order in the deformation parameter. Our
results indicate how a scalar field might behave in the vicinity of a black
hole at the Planck scale.Comment: 8 pages, no figures, revtex4; in v2 some points are explained in more
detail, few typos corrected and one reference adde
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