| 1. |
- Allentoft, Morten E., et al.
(författare)
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Population genomics of post-glacial western Eurasia
- 2024
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 625:7994, s. 301-311
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Tidskriftsartikel (refereegranskat)abstract
- Western Eurasia witnessed several large-scale human migrations during the Holocene1–5. Here, to investigate the cross-continental effects of these migrations, we shotgun-sequenced 317 genomes—mainly from the Mesolithic and Neolithic periods—from across northern and western Eurasia. These were imputed alongside published data to obtain diploid genotypes from more than 1,600 ancient humans. Our analyses revealed a ‘great divide’ genomic boundary extending from the Black Sea to the Baltic. Mesolithic hunter-gatherers were highly genetically differentiated east and west of this zone, and the effect of the neolithization was equally disparate. Large-scale ancestry shifts occurred in the west as farming was introduced, including near-total replacement of hunter-gatherers in many areas, whereas no substantial ancestry shifts happened east of the zone during the same period. Similarly, relatedness decreased in the west from the Neolithic transition onwards, whereas, east of the Urals, relatedness remained high until around 4,000 bp, consistent with the persistence of localized groups of hunter-gatherers. The boundary dissolved when Yamnaya-related ancestry spread across western Eurasia around 5,000 bp, resulting in a second major turnover that reached most parts of Europe within a 1,000-year span. The genetic origin and fate of the Yamnaya have remained elusive, but we show that hunter-gatherers from the Middle Don region contributed ancestry to them. Yamnaya groups later admixed with individuals associated with the Globular Amphora culture before expanding into Europe. Similar turnovers occurred in western Siberia, where we report new genomic data from a ‘Neolithic steppe’ cline spanning the Siberian forest steppe to Lake Baikal. These prehistoric migrations had profound and lasting effects on the genetic diversity of Eurasian populations.
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| 2. |
- Allentoft, Morten E., et al.
(författare)
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100 ancient genomes show repeated population turnovers in Neolithic Denmark
- 2024
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Ingår i: Nature. - 0028-0836 .- 1476-4687. ; 625, s. 329-337
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Tidskriftsartikel (refereegranskat)abstract
- Major migration events in Holocene Eurasia have been characterized genetically at broad regional scales1–4. However, insights into the population dynamics in the contact zones are hampered by a lack of ancient genomic data sampled at high spatiotemporal resolution5–7. Here, to address this, we analysed shotgun-sequenced genomes from 100 skeletons spanning 7,300 years of the Mesolithic period, Neolithic period and Early Bronze Age in Denmark and integrated these with proxies for diet (13C and 15N content), mobility (87Sr/86Sr ratio) and vegetation cover (pollen). We observe that Danish Mesolithic individuals of the Maglemose, Kongemose and Ertebølle cultures form a distinct genetic cluster related to other Western European hunter-gatherers. Despite shifts in material culture they displayed genetic homogeneity from around 10,500 to 5,900 calibrated years before present, when Neolithic farmers with Anatolian-derived ancestry arrived. Although the Neolithic transition was delayed by more than a millennium relative to Central Europe, it was very abrupt and resulted in a population turnover with limited genetic contribution from local hunter-gatherers. The succeeding Neolithic population, associated with the Funnel Beaker culture, persisted for only about 1,000 years before immigrants with eastern Steppe-derived ancestry arrived. This second and equally rapid population replacement gave rise to the Single Grave culture with an ancestry profile more similar to present-day Danes. In our multiproxy dataset, these major demographic events are manifested as parallel shifts in genotype, phenotype, diet and land use.
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| 3. |
- Tengström, Emin, et al.
(författare)
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Minnen från studenttiden vid Göteborgs universitet
- 2018
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Boken ger några självbiografiska exempel på hur livet som student vid GU kunde te sig under senare halvan av 1900-talet (från 40-tal till 90-tal). Bland de teman som tas upp kan nämnas den studiesociala situationen, studentlivet i allmänhet, studierna inom ett antal ämnesområden, erfarenheterna och upplevelserna av den utbildning om erbjöds samt de dåtida ekonomiska förutsättningarna för studierna. Författare är Emin Tengström, Britta Olinder, Martin Fritz, Allan Svensson, Mats Oscarson, Britt-Mari Näsström, Peter Sjögren, Peter Tarnow och Henrik Zetterberg.
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| 4. |
- Andersson, Adam, 1979, et al.
(författare)
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Ornstein-Uhlenbeck theory in finite dimension
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The contents of these notes were presented during ten lectures, in November 2011, by Peter Sjögren in Gothenburg. The text was written by Adam Andersson who participated and is improved after the careful reading by Peter Sjögren. Ornstein-Uhlenbeck theory can be described as a model of harmonic analysis in which Lebesgue measure is everywhere replaced by a Gaussian measure. The theory has applications in quantum physics and probability theory. If one passes to infinite dimensions and places the theory in a probabilistic context, one gets the Malliavin calculus. In Chapter 1, the basic theory is developed. This concerns the Hermite polynomials, the Ornstein-Uhlenbeck operator and most importantly its semigroup. The Hermite polynomials form an orthogonal system with respect to the Gaussian measure in Euclidean space. It turns out that they are the eigenfunctions of the Ornstein-Uhlenbeck operator, and since this operator is self-adjoint and positive semidefinite, the semigroup can be defined spectrally. An explicit kernel is derived for the semigroup, known as the Mehler kernel. It will be of central importance in this text. In Chapter 2, boundary convergence for the semigroup is considered, i.e., the limiting behavior of the semigroup as the “time” tends to zero. This is done by introducing a maximal operator for the semigroup and proving that it is of weak type (1,1). This result implies almost everywhere convergence for integrable boundary functions. In Chapter 3, first-order Riesz operators related to the Ornstein- Uhlenbeck operator are treated. Explicit off-diagonal kernels for these operators are found. It is finally proved that the Riesz operators are of weak type (1,1).
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| 5. |
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| 6. |
- Bruno, Tommaso, et al.
(författare)
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On the Riesz transforms for the inverse Gauss measure
- 2021
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Ingår i: Annales Fennici Mathematici. - : Finnish Mathematical Society. - 2737-114X .- 2737-0690. ; 46:1, s. 1-16
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Tidskriftsartikel (refereegranskat)abstract
- Let $\gamma_{-1}$ be the absolutely continuous measure on $\R^n$ whose density is the reciprocal of a Gaussian function. Let further $\As$ be the natural self-adjoint Laplacian on $L^2(\gamma_{-1})$. In this paper, we prove that the Riesz transforms associated with $\As$ of order one or two are of weak type $(1,1)$, but that those of higher order are not.
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| 7. |
- Casarino, V., et al.
(författare)
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On the maximal operator of a general Ornstein-Uhlenbeck semigroup
- 2022
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Ingår i: Mathematische Zeitschrift. - : Springer Science and Business Media LLC. - 0025-5874 .- 1432-1823. ; 301, s. 2393-2413
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Tidskriftsartikel (refereegranskat)abstract
- If Q is a real, symmetric and positive definite n x n matrix, and B a real n x n matrix whose eigenvalues have negative real parts, we consider the Ornstein-Uhlenbeck semigroup on R-n with covariance Q and drift matrix B. Our main result says that the associated maximal operator is of weak type (1, 1) with respect to the invariant measure. The proof has a geometric gist and hinges on the "forbidden zones method" previously introduced by the third author.
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| 8. |
- Casarino, V., et al.
(författare)
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On the orthogonality of generalized eigenspaces for the Ornstein-Uhlenbeck operator
- 2021
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Ingår i: Archiv der Mathematik. - : Springer Science and Business Media LLC. - 0003-889X .- 1420-8938. ; 117, s. 547-556
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Tidskriftsartikel (refereegranskat)abstract
- We study the orthogonality of the generalized eigenspaces of an Ornstein-Uhlenbeck operator L in R-N, with drift given by a real matrix B whose eigenvalues have negative real parts. If B has only one eigenvalue, we prove that any two distinct generalized eigenspaces of L are orthogonal with respect to the invariant Gaussian measure. Then we show by means of two examples that if B admits distinct eigenvalues, the generalized eigenspaces of L may or may not be orthogonal.
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| 9. |
- Casarino, V., et al.
(författare)
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On the variation operator for the Ornstein-Uhlenbeck semigroup in dimension one
- 2024
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Ingår i: Annali Di Matematica Pura Ed Applicata. - 0373-3114 .- 1618-1891. ; 203:1, s. 205-219
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Tidskriftsartikel (refereegranskat)abstract
- Consider the variation seminorm of the Ornstein-Uhlenbeck semigroup Ht in dimension one, taken with respect to t. We show that this seminorm defines an operator of weak type (1, 1) for the relevant Gaussian measure. The analogous Lp estimates for 1 < p < 8 were already known.
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| 10. |
- Casarino, Valentina, et al.
(författare)
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Riesz transforms of a general Ornstein-Uhlenbeck semigroup
- 2021
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Ingår i: Calculus of Variations and Partial Differential Equations. - : Springer Science and Business Media LLC. - 1432-0835 .- 0944-2669. ; 60:4
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Tidskriftsartikel (refereegranskat)abstract
- We consider Riesz transforms of any order associated to an Ornstein-Uhlenbeck operator with covariance given by a real, symmetric and positive definite matrix, and with drift given by a real matrix whose eigenvalues have negative real parts. In this general Gaussian context, we prove that a Riesz transform is of weak type (1,1) with respect to the invariant measure if and only if its order is at most 2.
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