648 research outputs found
Action of a finite quantum group on the algebra of complex NxN matrices
Using the fact that the algebra M := M_N(C) of NxN complex matrices can be
considered as a reduced quantum plane, and that it is a module algebra for a
finite dimensional Hopf algebra quotient H of U_q(sl(2)) when q is a root of
unity, we reduce this algebra M of matrices (assuming N odd) into
indecomposable modules for H. We also show how the same finite dimensional
quantum group acts on the space of generalized differential forms defined as
the reduced Wess Zumino complex associated with the algebra M.Comment: 11 pages, LaTeX, uses diagrams.sty, to be published in "Particles,
Fields and Gravitation" (Lodz conference), AIP proceeding
Higher Coxeter graphs associated to affine su(3) modular invariants
The affine modular invariant partition functions in 2d RCFT are
associated with a set of generalized Coxeter graphs. These partition functions
fall into two classes, the block-diagonal (Type I) and the non block-diagonal
(Type II) cases, associated, from spectral properties, to the subsets of
subgroup and module graphs respectively. We introduce a modular operator
taking values on the set of vertices of the subgroup graphs. It
allows us to obtain easily the associated Type I partition functions. We also
show that all Type II partition functions are obtained by the action of
suitable twists on the set of vertices of the subgroup graphs.
These twists have to preserve the values of the modular operator .Comment: Version 2. Abstract, introduction and conclusion rewritten,
references added. 36 page
From conformal embeddings to quantum symmetries: an exceptional SU(4) example
We briefly discuss several algebraic tools that are used to describe the
quantum symmetries of Boundary Conformal Field Theories on a torus. The
starting point is a fusion category, together with an action on another
category described by a quantum graph. For known examples, the corresponding
modular invariant partition function, which is sometimes associated with a
conformal embedding, provides enough information to recover the whole
structure. We illustrate these notions with the example of the conformal
embedding of SU(4) at level 4 into Spin(15) at level 1, leading to the
exceptional quantum graph E4(SU(4)).Comment: 22 pages, 3 color figures. Version 2: We changed the color of figures
(ps files) in such a way that they are still understood when converted to
gray levels. Version 3: Several references have been adde
From modular invariants to graphs: the modular splitting method
We start with a given modular invariant M of a two dimensional su(n)_k
conformal field theory (CFT) and present a general method for solving the
Ocneanu modular splitting equation and then determine, in a step-by-step
explicit construction, 1) the generalized partition functions corresponding to
the introduction of boundary conditions and defect lines; 2) the quantum
symmetries of the higher ADE graph G associated to the initial modular
invariant M. Notice that one does not suppose here that the graph G is already
known, since it appears as a by-product of the calculations. We analyze several
su(3)_k exceptional cases at levels 5 and 9.Comment: 28 pages, 7 figures. Version 2: updated references. Typos corrected.
su(2) example has been removed to shorten the paper. Dual annular matrices
for the rejected exceptional su(3) diagram are determine
Polymer transport in random flow
The dynamics of polymers in a random smooth flow is investigated in the
framework of the Hookean dumbbell model. The analytical expression of the
time-dependent probability density function of polymer elongation is derived
explicitly for a Gaussian, rapidly changing flow. When polymers are in the
coiled state the pdf reaches a stationary state characterized by power-law
tails both for small and large arguments compared to the equilibrium length.
The characteristic relaxation time is computed as a function of the Weissenberg
number. In the stretched state the pdf is unstationary and exhibits
multiscaling. Numerical simulations for the two-dimensional Navier-Stokes flow
confirm the relevance of theoretical results obtained for the delta-correlated
model.Comment: 28 pages, 6 figure
Molecular evidence of Late Archean archaea and the presence of a subsurface hydrothermal biosphere
Author Posting. © National Academy of Sciences of the USA, 2007. This is the author's version of the work. It is posted here by permission of National Academy of Sciences of the USA for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences 104 (2007): 14260-14265, doi:10.1073/pnas.0610903104.Highly cracked and isomerized archaeal lipids and bacterial lipids, structurally changed
by thermal stress, are present in solvent extracts of 2,707-2,685 million year old (Ma)
metasedimentary rocks from Timmins, Ontario, Canada. These lipids appear in
conventional gas chromatograms as unresolved complex mixtures (UCMs) and include
cyclic and acyclic biphytanes, C36-C39 derivatives of the biphytanes, and C31-C35
extended hopanes. Biphytane and extended hopanes are also found in high pressure
catalytic hydrogenation (HPCH) products released from solvent-extracted sediments,indicating that archaea and bacteria were present in Late Archean sedimentary
environments. Post-depositional, hydrothermal gold mineralization and graphite
precipitation occurred prior to metamorphism (~2,665 Ma). Late Archean metamorphism
significantly reduced the kerogen’s adsorptive capacity and severely restricted sediment
porosity, limiting the potential for post-Archean additions of organic matter to the
samples. Argillites exposed to hydrothermal gold mineralization have disproportionately
high concentrations of extractable archaeal and bacterial lipids relative to what is
releasable from their respective HPCH product and what is observed for argillites
deposited away from these hydrothermal settings. The addition of these lipids to the
sediments likely results from a Late Archean subsurface hydrothermal biosphere of
archaea and bacteria.This project was supported by NASA Exobiology grant #NAG5-13446 to Fabien Kenig.
SEM analysis was supported by NSF grant EAR 0318769 to Juergen Schieber. GC×GC
analysis was supported by NSF grant IIS-0430835 and the Seaver Foundation to
Christopher M. Reddy
Apple pomace powder as natural food ingredient in bakery jams
The aim of the present study was to investigate whether apple pomace powder produced by a simple drying method is suitable for replacing pectin in bakery jam products. Rheological properties of bakery jams were tested by oscillatory tests using amplitude sweep method. Apple pomace addition decreased gel strength and stability of bakery jams, while 12-month storage increased the gel strength of samples. Based on our results, dried apple pomace powder seems to be suitable to replace pectin up to 40% without changing rheological properties of bakery jams
Determination of the Michel Parameters rho, xi, and delta in tau-Lepton Decays with tau --> rho nu Tags
Using the ARGUS detector at the storage ring DORIS II, we have
measured the Michel parameters , , and for
decays in -pair events produced at
center of mass energies in the region of the resonances. Using
as spin analyzing tags, we find , , , , and . In addition, we report
the combined ARGUS results on , , and using this work
und previous measurements.Comment: 10 pages, well formatted postscript can be found at
http://pktw06.phy.tu-dresden.de/iktp/pub/desy97-194.p
Role of cellular senescence and NOX4-mediated oxidative stress in systemic sclerosis pathogenesis.
Systemic sclerosis (SSc) is a systemic autoimmune disease characterized by progressive fibrosis of skin and numerous internal organs and a severe fibroproliferative vasculopathy resulting frequently in severe disability and high mortality. Although the etiology of SSc is unknown and the detailed mechanisms responsible for the fibrotic process have not been fully elucidated, one important observation from a large US population study was the demonstration of a late onset of SSc with a peak incidence between 45 and 54 years of age in African-American females and between 65 and 74 years of age in white females. Although it is not appropriate to consider SSc as a disease of aging, the possibility that senescence changes in the cellular elements involved in its pathogenesis may play a role has not been thoroughly examined. The process of cellular senescence is extremely complex, and the mechanisms, molecular events, and signaling pathways involved have not been fully elucidated; however, there is strong evidence to support the concept that oxidative stress caused by the excessive generation of reactive oxygen species may be one important mechanism involved. On the other hand, numerous studies have implicated oxidative stress in SSc pathogenesis, thus, suggesting a plausible mechanism in which excessive oxidative stress induces cellular senescence and that the molecular events associated with this complex process play an important role in the fibrotic and fibroproliferative vasculopathy characteristic of SSc. Here, recent studies examining the role of cellular senescence and of oxidative stress in SSc pathogenesis will be reviewed
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