333 research outputs found
Zero modes' fusion ring and braid group representations for the extended chiral su(2) WZNW model
The zero modes' Fock space for the extended chiral WZNW model gives
room to a realization of the Grothendieck fusion ring of representations of the
restricted quantum universal enveloping algebra (QUEA) at an even
(-th) root of unity, and of its extension by the Lusztig operators. It is
shown that expressing the Drinfeld images of canonical characters in terms of
Chebyshev polynomials of the Casimir invariant allows a streamlined
derivation of the characteristic equation of from the defining relations of
the restricted QUEA. The properties of the fusion ring of the Lusztig's
extension of the QUEA in the zero modes' Fock space are related to the braiding
properties of correlation functions of primary fields of the extended
current algebra model.Comment: 36 pages, 1 figure; version 3 - improvements in Sec. 2 and 3:
definitions of the double, as well as R- (and M-)matrix changed to fit the
zero modes' one
Quantum matrix algebra for the SU(n) WZNW model
The zero modes of the chiral SU(n) WZNW model give rise to an intertwining
quantum matrix algebra A generated by an n x n matrix a=(a^i_\alpha) (with
noncommuting entries) and by rational functions of n commuting elements
q^{p_i}. We study a generalization of the Fock space (F) representation of A
for generic q (q not a root of unity) and demonstrate that it gives rise to a
model of the quantum universal enveloping algebra U_q(sl_n), each irreducible
representation entering F with multiplicity 1. For an integer level k the
complex parameter q is an even root of unity, q^h=-1 (h=k+n) and the algebra A
has an ideal I_h such that the factor algebra A_h = A/I_h is finite
dimensional.Comment: 48 pages, LaTeX, uses amsfonts; final version to appear in J. Phys.
Extended chiral algebras in the SU(2)_0 WZNW model
We investigate the W-algebras generated by the integer dimension chiral
primary operators of the SU(2)_0 WZNW model. These have a form almost identical
to that found in the c=-2 model but have, in addition, an extended Kac-Moody
structure. Moreover on Hamiltonian reduction these SU(2)_0 W-algebras exactly
reduce to those found in c=-2. We explicitly find the free field
representations for the chiral j=2 and j=3 operators which have respectively a
fermionic doublet and bosonic triplet nature. The correlation functions of
these operators accounts for the rational solutions of the
Knizhnik-Zamolodchikov equation that we find. We explicitly compute the full
algebra of the j=2 operators and find that the associativity of the algebra is
only guaranteed if certain null vectors decouple from the theory. We conjecture
that these algebras may produce a quasi-rational conformal field theory.Comment: 18 pages LATEX. Minor corrections. Full j=2 algebra adde
Adsorption and reaction of CO on (Pd–)Al2O3 and (Pd–)ZrO2: vibrational spectroscopy of carbonate formation
γ-Alumina is widely used as an oxide support in catalysis, and palladium nanoparticles supported by alumina represent one of the most frequently used dispersed metals. The surface sites of the catalysts are often probed via FTIR spectroscopy upon CO adsorption, which may result in the formation of surface carbonate species. We have examined this process in detail utilizing FTIR to monitor carbonate formation on γ-alumina and zirconia upon exposure to isotopically labelled and unlabelled CO and CO2. The same was carried out for well-defined Pd nanoparticles supported on Al2O3 or ZrO2. A water gas shift reaction of CO with surface hydroxyls was detected, which requires surface defect sites and adjacent OH groups. Furthermore, we have studied the effect of Cl synthesis residues, leading to strongly reduced carbonate formation and changes in the OH region (isolated OH groups were partly replaced or were even absent). To corroborate this finding, samples were deliberately poisoned with Cl to an extent comparable to that of synthesis residues, as confirmed by Auger electron spectroscopy. For catalysts prepared from Cl-containing precursors a new CO band at 2164 cm−1 was observed in the carbonyl region, which was ascribed to Pd interacting with Cl. Finally, the FTIR measurements were complemented by quantification of the amount of carbonates formed via chemisorption, which provides a tool to determine the concentration of reactive defect sites on the alumina surface
Indecomposable U_q(sl_n) modules for q^h = -1 and BRS intertwiners
A class of indecomposable representations of U_q(sl_n) is considered for q an
even root of unity (q^h = -1) exhibiting a similar structure as (height h)
indecomposable lowest weight Kac-Moody modules associated with a chiral
conformal field theory. In particular, U_q(sl_n) counterparts of the
Bernard-Felder BRS operators are constructed for n=2,3. For n=2 a pair of dual
d_2(h) = h dimensional U_q(sl_2) modules gives rise to a 2h-dimensional
indecomposable representation including those studied earlier in the context of
tensor product expansions of irreducible representations. For n=3 the interplay
between the Poincare'-Birkhoff-Witt and (Lusztig) canonical bases is exploited
in the study of d_3(h) = h(h+1)(2h+1)/6 dimensional indecomposable modules and
of the corresponding intertwiners.Comment: 31 pages, LaTeX, amsfonts, amssym
Infrared Studies on Bimetallic Copper/Nickel Catalysts Supported on Zirconia and Ceria/Zirconia
Use of anticoagulants and antiplatelet agents in stable outpatients with coronary artery disease and atrial fibrillation. International CLARIFY registry
Computational investigation of CO adsorbed on Aux, Agx and (AuAg)x nanoclusters (x = 1 − 5, 147) and monometallic Au and Ag low-energy surfaces
Silver Ion Mediated Shape Control of Platinum Nanoparticles: Removal of Silver by Selective Etching Leads to Increased Catalytic Activity
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