31,250 research outputs found
Further illustration of the use of the Frobenius-Schwinger-Dyson equations
The Frobenius-Schwinger-Dyson equations are a rather high-brow abstract
nonsense type of equations describing n-point functions of arbitrarily high
composite insertions. It is not clear how to solve or even find approximate
solutions of these equations in general, but they are worth investigating
because (a certain preferred type of) renormalization of composite insertions
has been performed in advance: it just remains to find solutions given an
action and renormalization conditions. Earlier work in this field involved only
Gaussian actions or variable transformations thereof. In this work we
illustrate the use of Frobenius-Schwinger-Dyson at a less obviously trivial
level, that of the Thirring model.Comment: 10 pages Late
Abelian and derived deformations in the presence of Z-generating geometric helices
For a Grothendieck category C which, via a Z-generating sequence (O(n))_{n in
Z}, is equivalent to the category of "quasi-coherent modules" over an
associated Z-algebra A, we show that under suitable cohomological conditions
"taking quasi-coherent modules" defines an equivalence between linear
deformations of A and abelian deformations of C. If (O(n))_{n in Z} is at the
same time a geometric helix in the derived category, we show that restricting a
(deformed) Z-algebra to a "thread" of objects defines a further equivalence
with linear deformations of the associated matrix algebra.Comment: 21 page
No Name, No Game
In an interesting contribution Joppa et al. (2011) revisit some aspects of the taxonomic impediment (Evenhuis 2007; http://www.cbd.int/gti/) and come to the conclusion that, contrary to the generally accepted idea, both the rates of species description and the number of taxonomists have increased exponentially since the 1950âs. Joppa et al. (2011) also note a marked decline in the number of species described per taxonomist which they attribute to the difficulty of finding new species in an ever declining âmissing species poolâ. Therefore, their results might be interpreted that todayâs taxonomic workforce is sufficient to describe the remaining (shallow) âpool of missing speciesâ. In this contribution, we question if this is indeed the case and propose a solution for speeding up taxonomic descriptions
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