1,072 research outputs found
Cluster structures on strata of flag varieties
We introduce some new Frobenius subcategories of the module category of a
preprojective algebra of Dynkin type, and we show that they have a cluster
structure in the sense of Buan-Iyama-Reiten-Scott. These categorical cluster
structures yield cluster algebra structures in the coordinate rings of
intersections of opposed Schubert cells.Comment: 31 pages, v.2 : a comment about the relation to Muller-Speyer
conjecture on positroid varieties is added in 7.3. v.3. final version, to
appear in Advances in Mat
The Effect of Tidal Disruptions on Giant Stars in the Galactic Center
Recent observational data suggest the depletion of late-type giant stars in the inner most region of the Galactive Nucleus. Using dynamically evolving Fokker-Planck models of the Galactic Nucleus, we have followed in detail the stellar distribution as it evolves through the postmain-sequence phases. Of particular interest was the effect of stellar collisions and tidal disruptions by the central massive black hole on post main sequence stars as they expand in size. B y modeling tidal disruptions and stellar collisions, we have found that there should be a significant depletion of the giant stars in the innermost regions of the nucleus. Our models also suggest that tidal disruptions were found to have a larger effect on the depletion of giant stars than stellar collisions in this region
Cluster algebras in algebraic Lie theory
We survey some recent constructions of cluster algebra structures on
coordinate rings of unipotent subgroups and unipotent cells of Kac-Moody
groups. We also review a quantized version of these results.Comment: Invited survey; to appear in Transformation Group
Fractional smoothness and applications in finance
This overview article concerns the notion of fractional smoothness of random
variables of the form , where is a certain
diffusion process. We review the connection to the real interpolation theory,
give examples and applications of this concept. The applications in stochastic
finance mainly concern the analysis of discrete time hedging errors. We close
the review by indicating some further developments.Comment: Chapter of AMAMEF book. 20 pages
Verwendung von bentone-haltigen Trennsäulen für die Gaschromatographie von Polyphenylgemischen. EUR 1653. = Use of bentone-containing columns for gas chromatography of polyphenyl mixtures. EUR 1653.
Isotopic Composition of Solar Wind Calcium: First in Situ Measurement by CELIAS/MTOF on Board SOHO
We present first results on the Ca isotopic abundances derived from the high
resolution Mass Time-of-Flight (MTOF) spectrometer of the charge, element, and
isotope analysis system (CELIAS) experiment on board the Solar and Heliospheric
Observatory (SOHO). We obtain isotopic ratios 40Ca/42Ca = (128+-47) and
40Ca/44Ca = (50+-8), consistent with terrestrial values. This is the first in
situ determination of the solar wind calcium isotopic composition and is
important for studies of stellar modeling and solar system formation since the
present-day solar Ca isotopic abundances are unchanged from their original
isotopic composition in the solar nebula.Comment: 14 pages, 3 figure
Big Bang Nucleosynthesis with Long Lived Charged Massive Particles
We consider Big Bang Nucleosynthesis (BBN) with long lived charged massive
particles. Before decaying, the long lived charged particle recombines with a
light element to form a bound state like a hydrogen atom. This effect modifies
the nuclear reaction rates during the BBN epoch through the modifications of
the Coulomb field and the kinematics of the captured light elements, which can
change the light element abundances. It is possible that the heavier nuclei
abundances such as Li and Be decrease sizably, while the ratios ,
D/H, and He/H remain unchanged. This may solve the current discrepancy
between the BBN prediction and the observed abundance of Li. If future
collider experiments found signals of a long-lived charged particle inside the
detector, the information of its lifetime and decay properties could provide
insights to understand not only the particle physics models but also the
phenomena in the early universe in turn.Comment: 20 pages, 6 figures, published version in Physical Review
Cluster structures on quantum coordinate rings
We show that the quantum coordinate ring of the unipotent subgroup N(w) of a
symmetric Kac-Moody group G associated with a Weyl group element w has the
structure of a quantum cluster algebra. This quantum cluster structure arises
naturally from a subcategory C_w of the module category of the corresponding
preprojective algebra. An important ingredient of the proof is a system of
quantum determinantal identities which can be viewed as a q-analogue of a
T-system. In case G is a simple algebraic group of type A, D, E, we deduce from
these results that the quantum coordinate ring of an open cell of a partial
flag variety attached to G also has a cluster structure.Comment: v2: minor corrections. v3: references updated, final version to
appear in Selecta Mathematic
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