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Jimmy Johansson

Publications and source records attributed to Jimmy Johansson.

5 recordsLinked to original sources
arXiv2023

A residue current associated with a twisting cochain: duality and comparison formula

Let $\mathcal{F}^\bullet$ be a complex of coherent $\mathcal{O}_X$-modules over a complex manifold $X$. We give a construction of a residue current associated with this complex that generalizes Andersson and Wulcan's construction of a residue current associated with a coherent $\mathcal{O}_X$-module $\mathcal{F}$. The main ingredients are to give a construction of a residue current associated with a twisting cochain in the sense of Toledo and Tong and to establish a comparison formula for these currents that generalizes an analogous formula given by Lärkäng.

math.CV↗
arXiv2021

An explicit isomorphism of different representations of the Ext functor using residue currents

Let $\mathcal{F}$ be a coherent $\mathcal{O}_X$-module over a complex manifold $X$, and let $G$ be a vector bundle on $X$. We describe an explicit isomorphism between two different representations of the global $\DeclareMathOperator{\Ext}{Ext}\Ext$ groups $\DeclareMathOperator{\Ext}{Ext}\Ext^k(\mathcal{F},G)$. The first representation is given by the cohomology of a twisted complex in the sense of Toledo and Tong, and the second one is obtained from the Dolbeault complex associated with $G$. A key tool that we introduce for explicitly describing this isomorphism is a residue current associated with a twisted resolution of $\mathcal{F}$.

math.CV↗
arXiv2021

Polynomial interpolation and residue currents

We show that a global holomorphic section of $\mathscr{O}(d)$ restricted to a closed complex subspace $X \subset \mathbb{P}^n$ has an interpolant if and only if it satisfies a set of moment conditions that involves a residue current associated with a locally free resolution of $\mathscr{O}_X$. When $X$ is a finite set of points in $\mathbb{C}^n \subset \mathbb{P}^n$ this can be interpreted as a set of linear conditions that a function on $X$ has to satisfy in order to have a polynomial interpolant of degree at most $d$.

math.CV↗
arXiv2020

To Explore What Isn't There -- Glyph-based Visualization for Analysis of Missing Values

This paper contributes a novel visualization method, Missingness Glyph, for analysis and exploration of missing values in data. Missing values are a common challenge in most data generating domains and may cause a range of analysis issues. Missingness in data may indicate potential problems in data collection and pre-processing, or highlight important data characteristics. While the development and improvement of statistical methods for dealing with missing data is a research area in its own right, mainly focussing on replacing missing values with estimated values, considerably less focus has been put on visualization of missing values. Nonetheless, visualization and explorative analysis has great potential to support understanding of missingness in data, and to enable gaining of novel insights into patterns of missingness in a way that statistical methods are unable to. The Missingness Glyph supports identification of relevant missingness patterns in data, and is evaluated and compared to two other visualization methods in context of the missingness patterns. The results are promising and confirms that the Missingness Glyph in several cases perform better than the alternative visualization methods.

cs.GR↗