13,371 research outputs found
Direct simulation of compressible reacting flows
A research program for direct numerical simulations of compressible reacting flows is described. Two main research subjects are proposed: the effect of pressure waves on turbulent combustion and the use of direct simulation methods to validate flamelet models for turbulent combustion. The interest of a compressible code to study turbulent combustion is emphasized through examples of reacting shear layer and combustion instabilities studies. The choice of experimental data to compare with direct simulation results is discussed. A tentative program is given and the computation cases to use are described as well as the code validation runs
Chiral-Yang-Mills theory, non commutative differential geometry, and the need for a Lie super-algebra
In Yang-Mills theory, the charges of the left and right massless Fermions are
independent of each other. We propose a new paradigm where we remove this
freedom and densify the algebraic structure of Yang-Mills theory by integrating
the scalar Higgs field into a new gauge-chiral 1-form which connects Fermions
of opposite chiralities. Using the Bianchi identity, we prove that the
corresponding covariant differential is associative if and only if we gauge a
Lie-Kac super-algebra. In this model, spontaneous symmetry breakdown naturally
occurs along an odd generator of the super-algebra and induces a representation
of the Connes-Lott non commutative differential geometry of the 2-point finite
space.Comment: 17 pages, no figur
Algebraic structure of multi-parameter quantum groups
Multi-parameter versions U_p(g) and C_p[G] of the standard quantum groups
U_q(g) and C_q[G] are considered where G is a semi-simple connected complex
algebraic group and g is the Lie algebra of G. The primitive spectrum of C_p[G]
is calculated, generalizing a result of Joseph for the standard quantum groups.
This classification is compared with the classification of symplectic leaves
for the associated Poisson structure on G.Comment: AMS Latex, 37 pages, June 1994; to appear in Advances in Mat
Extension of the osp(m|n)~ so(m-n) Correspondence to the Infinite-Dimensional Chiral Spinors and Self Dual Tensors
The spinor representations of the orthosymplectic Lie superalgebras osp(m|n)
are considered and constructed. These are infinite-dimensional irreducible
representations, of which the superdimension coincides with the dimension of
the spinor representation of so(m-n). Next, we consider the self dual tensor
representations of osp(m|n) and their generalizations: these are also
infinite-dimensional and correspond to the highest irreducible component of the
power of the spinor representation. We determine the character of
these representations, and deduce a superdimension formula. From this, it
follows that also for these representations the osp(m|n)~ so(m-n)
correspondence holds
Low temperature reflectivity study of ZnO/(Zn,Mg)O quantum wells grown on M-plane ZnO substrates
We report growth of high quality ZnO/Zn0.8Mg0.2O quantum well on M-plane
oriented ZnO substrates. The optical properties of these quantum wells are
studied by using reflectance spectroscopy. The optical spectra reveal strong
in-plane optical anisotropies, as predicted by group theory, and marked
reflectance structures, as an evidence of good interface morphologies.
Signatures ofc onfined excitons built from the spin-orbit split-off valence
band, the analog of exciton C in bulk ZnO are detected in normal incidence
reflectivity experiments using a photon polarized along the c axis of the
wurtzite lattice. Experiments performed in the context of an orthogonal photon
polarization, at 90^{\circ}; of this axis, reveal confined states analogs of A
and B bulk excitons. Envelope function calculations which include excitonic
interaction nicely account for the experimental report
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