| 1. |
- Arone, Gregory Z., et al.
(författare)
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The action of Young subgroups on the partition complex
- 2021
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Ingår i: Publications mathématiques (Bures-sur-Yvette). - : Springer Science and Business Media LLC. - 0073-8301 .- 1618-1913. ; 133, s. 47-156
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Tidskriftsartikel (refereegranskat)abstract
- We study the restrictions, the strict fixed points, and the strict quotients of the partition complex |Πn|, which is the Σn-space attached to the poset of proper nontrivial partitions of the set {1,…,n}.We express the space of fixed points |Πn|G in terms of subgroup posets for general G⊂Σn and prove a formula for the restriction of |Πn| to Young subgroups Σn1×⋯×Σnk. Both results follow by applying a general method, proven with discrete Morse theory, for producing equivariant branching rules on lattices with group actions.We uncover surprising links between strict Young quotients of |Πn|, commutative monoid spaces, and the cotangent fibre in derived algebraic geometry. These connections allow us to construct a cofibre sequence relating various strict quotients |Πn|⋄∧Σn(Sℓ)∧nand give a combinatorial proof of a splitting in derived algebraic geometry.Combining all our results, we decompose strict Young quotients of |Πn| in terms of “atoms” |Πd|⋄∧Σd(Sℓ)∧d for ℓ odd and compute their homology. We thereby also generalise Goerss’ computation of the algebraic André-Quillen homology of trivial square-zero extensions from F2 to Fp for p an odd prime.
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| 2. |
- Berman, Robert, 1976, et al.
(författare)
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A variational approach to complex Monge-Ampere equations
- 2013
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Ingår i: Publications mathématiques. - : Springer Science and Business Media LLC. - 0073-8301. ; 117:1, s. 179-245
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Tidskriftsartikel (refereegranskat)abstract
- We show that degenerate complex Monge-Ampère equations in a big cohomology class of a compact Kähler manifold can be solved using a variational method, without relying on Yau’s theorem. Our formulation yields in particular a natural pluricomplex analogue of the classical logarithmic energy of a measure. We also investigate Kähler-Einstein equations on Fano manifolds. Using continuous geodesics in the closure of the space of Kähler metrics and Berndtsson’s positivity of direct images, we extend Ding-Tian’s variational characterization and Bando-Mabuchi’s uniqueness result to singular Kähler-Einstein metrics. Finally, using our variational characterization we prove the existence, uniqueness and convergence as k→∞ of k-balanced metrics in the sense of Donaldson both in the (anti)canonical case and with respect to a measure of finite pluricomplex energy.
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| 3. |
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| 4. |
- Yom-Tov, Yoram, et al.
(författare)
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Body size of the weasel Mustela nivalis and the stoat M. erminea in Sweden.
- 2010
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Ingår i: Mammalian Biology. - : Springer Science and Business Media LLC. - 1616-5047 .- 1618-1476. ; 75, s. 420-426
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Tidskriftsartikel (refereegranskat)abstract
- In this study we examined temporal and geographical variations in a sample of 124 skulls of the weasel Mustela nivalis and 146 skulls oft hestoat M. erminea, collected in Sweden between 1959-1992 and 1913-1990, respectively. We used Principal Component Analysis (PCA) to combine the effects of latitude, longitude, year of collection, mean ambient temperature and Net Primary Productivity (NPP). The first principal component (PC1) contained latitude, ambient temperature and NPP and was significantly and positively related to male (but not female) skull size of both stoats and weasels. None of the other factors or their interactions were significantly related to skull size. We conclude that ambient temperature, either directly through energy savings, or indirectly through improved food availability (increasedNPP), had a significant effect on determining body size of male stoats and weasels in Sweden. Our results support the hypothesis that male and female of these species are affected by different selection pressures and thus react differently to changing environmental conditions.
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| 5. |
- Erséus, Christer, 1951, et al.
(författare)
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The popular model annelid Enchytraeus albidus is only one species in a complex of seashore White Worms (Clitellata, Enchytraeidae)
- 2019
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Ingår i: Organisms Diversity & Evolution. - : Springer Science and Business Media LLC. - 1439-6092 .- 1618-1077. ; 19:2, s. 105-133
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Tidskriftsartikel (refereegranskat)abstract
- The white worm Enchytraeus albidus Henle, 1837 (Clitellata, Enchytraeidae) is easy to keep in laboratory cultures, and has therefore been employed as a model organism in basic and applied biological research. Its natural habitat includes terrestrial composts and wrack beds on seashores. However, the name E. albidus is currently used for a complex of morphologically similar and closely related species. We here revise the components of the E. albidus species complex based on a sample of 100 Enchytraeus specimens from 56 sites, most of which are across Europe. These samples were DNA-barcoded for the mitochon- drial COI gene. A subset of them was sequenced for the nuclear ITS2 and H3 markers. Six species were delimited with strong support by the COI and ITS2 gene trees, as well as by a multi-locus species delimitation analysis. These species are identified morphologically and described as E. albidus s. str. (with designation of a neotype); Enchytraeus moebii (Michaelsen, 1885); Enchytraeus albellus Klinth, Erséus and Rota, sp. nov., E. cf. krumbachi (Čejka, 1913), E. sp. 1 (unnamed), and Enchytraeus polatdemiri Arslan and Timm, 2018. The last-mentioned species is a soda lake specialist, whereas E. albidus s. str. is both terrestrial and marine littoral; all other species occur only in seashores. The phylogeny of this group was estimated using the multi-species coalescent model. Monophyly of the E. albidus complex was recovered. Within this complex, three groups were recovered as monophyletic, but the relationship between them is unclear. One group comprises E. albidus s. str., E. albellus, and E. moebii; the second group E. cf. krumbachi and the unnamed E. sp. 1, and the third consists of only E. polatdemiri. This study serves as a framework for genetic identification of white worms used for experimental purposes.
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