13,169 research outputs found
Tarski monoids: Matui's spatial realization theorem
We introduce a class of inverse monoids, called Tarski monoids, that can be
regarded as non-commutative generalizations of the unique countable, atomless
Boolean algebra. These inverse monoids are related to a class of etale
topological groupoids under a non-commutative generalization of classical Stone
duality and, significantly, they arise naturally in the theory of dynamical
systems as developed by Matui. We are thereby able to reinterpret a theorem of
Matui on a class of \'etale groupoids as an equivalent theorem about a class of
Tarski monoids: two simple Tarski monoids are isomorphic if and only if their
groups of units are isomorphic. The inverse monoids in question may also be
viewed as countably infinite generalizations of finite symmetric inverse
monoids. Their groups of units therefore generalize the finite symmetric groups
and include amongst their number the classical Thompson groups.Comment: arXiv admin note: text overlap with arXiv:1407.147
Assessment in Scotland
Assessment practice will follow and reinforce the curriculum and promote high quality learning and teaching approaches. Assessment of children's and young people's progress and achievement during their broad general education to the end of S3 will be based on teachers' assessment of their knowledge and understanding, skills, attributes and capabilities, as described in the experiences and outcomes across the curriculum
Minimal kernels of Dirac operators along maps
Let be a closed spin manifold and let be a closed manifold. For maps
and Riemannian metrics on and on , we consider
the Dirac operator of the twisted Dirac bundle . To this Dirac operator one can associate an index
in . If is -dimensional, one gets a lower bound for
the dimension of the kernel of out of this index. We investigate
the question whether this lower bound is obtained for generic tupels
A Note on Positive Energy Theorem for Spaces with Asymptotic SUSY Compactification
We extend the positive mass theorem proved previously by the author to the
Lorentzian setting. This includes the original higher dimensional positive
energy theorem whose spinor proof was given by Witten in dimension four and by
Xiao Zhang in dimension five
The Energy-Momentum tensor on manifolds
On manifolds, we study the Energy-Momentum tensor associated with a
spinor field. First, we give a spinorial Gauss type formula for oriented
hypersurfaces of a manifold. Using the notion of generalized
cylinders, we derive the variationnal formula for the Dirac operator under
metric deformation and point out that the Energy-Momentum tensor appears
naturally as the second fundamental form of an isometric immersion. Finally, we
show that generalized Killing spinors for Codazzi Energy-Momentum
tensor are restrictions of parallel spinors.Comment: To appear in IJGMMP (International Journal of Geometric Methods in
Modern Physics), 22 page
Safety hazards associated with the charging of lithium/sulfur dioxide cells
A continuing research program to assess the responses of spirally wound, lithium/sulfur dioxide cells to charging as functions of charging current, temperature, and cell condition prior to charging is described. Partially discharged cells that are charged at currents greater than one ampere explode with the time to explosion inversely proportional to the charging current. Cells charged at currents of less than one ampere may fail in one of several modes. The data allows an empirical prediction of when certain cells will fail given a constant charging current
Renal fibrosis in feline chronic kidney disease: known mediators and mechanisms of injury
Chronic kidney disease (CKD) is a common medical condition of ageing cats. In most cases the underlying aetiology is unknown, but the most frequently reported pathological diagnosis is renal tubulointerstitial fibrosis. Renal fibrosis, characterised by extensive accumulation of extra-cellular matrix within the interstitium, is thought to be the final common pathway for all kidney diseases and is the pathological lesion best correlated with function in both humans and cats. As a convergent pathway, renal fibrosis provides an ideal target for the treatment of CKD and knowledge of the underlying fibrotic process is essential for the future development of novel therapies. There are many mediators and mechanisms of renal fibrosis reported in the literature, of which only a few have been investigated in the cat. This article reviews the process of renal fibrosis and discusses the most commonly cited mediators and mechanisms of progressive renal injury, with particular focus on the potential significance to feline CKD
One step multiderivative methods for first order ordinary differential equations
A family of one-step multiderivative methods based on Padé approximants to the exponential function is developed.
The methods are extrapolated and analysed for use in PECE mode.
Error constants and stability intervals are calculated and the combinations compared with well known linear multi-step combinations and combinations using high accuracy Newton-Cotes quadrature formulas as correctors.
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Einstein Manifolds As Yang-Mills Instantons
It is well-known that Einstein gravity can be formulated as a gauge theory of
Lorentz group where spin connections play a role of gauge fields and Riemann
curvature tensors correspond to their field strengths. One can then pose an
interesting question: What is the Einstein equations from the gauge theory
point of view? Or equivalently, what is the gauge theory object corresponding
to Einstein manifolds? We show that the Einstein equations in four dimensions
are precisely self-duality equations in Yang-Mills gauge theory and so Einstein
manifolds correspond to Yang-Mills instantons in SO(4) = SU(2)_L x SU(2)_R
gauge theory. Specifically, we prove that any Einstein manifold with or without
a cosmological constant always arises as the sum of SU(2)_L instantons and
SU(2)_R anti-instantons. This result explains why an Einstein manifold must be
stable because two kinds of instantons belong to different gauge groups,
instantons in SU(2)_L and anti-instantons in SU(2)_R, and so they cannot decay
into a vacuum. We further illuminate the stability of Einstein manifolds by
showing that they carry nontrivial topological invariants.Comment: v4; 17 pages, published version in Mod. Phys. Lett.
Chemical analysis of charged Li/SO(sub)2 cells
The initial focus of the program was to confirm that charging can indeed result in explosions and constitute a significant safety problem. Results of this initial effort clearly demonstrated that cells do indeed explode on charge and that charging does indeed constitute a real and severe safety problem. The results of the effort to identify the chemical reactions involved in and responsible for the observed behavior are described
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