Aspherical Word Labeled Oriented Graphs and Cyclically Presented Groups

A {\em word labeled oriented graph} (WLOG) is an oriented graph $\cal G$ on vertices $X=\{ x_1,\ldots ,x_k\}$, where each oriented edge is labeled by a word in $X^{\pm1}$. WLOGs give rise to presentations which generalize Wirtinger presentations of knots. WLOG presentations, where the underlying graph is a tree are of central importance in view of Whitehead's Asphericity Conjecture. We present a class of aspherical world labeled oriented graphs. This class can be used to produce highly non-injective aspherical labeled oriented trees and also aspherical cyclically presented groups.Comment: 7 pages, 3 figure

“The time loop nightmare of being a black man in the US” African American Cultural Memory in the Short Film Two Distant Strangers (2020)

This paper is concerned with African American cultural memory and the translation of historical experiences into contemporary narratives. To discuss this, I will analyze the American short film Two Distant Strangers“ (2020), which takes up contemporary discussions of the Black Lives Matter“ movement and problematizes racial profiling and police violence in the United States. Addressing the ways in which contemporary cinematic representations display traumatic memories and discuss existing memory processes, I will argue that films like Two Distant Strangers “are substantial contributions to African American cultural memory and thus capable of impacting predominant narratives about African American histor(ies) and identit(ies).

The Local Structure of Injective LOT-Complexes

Labeled oriented trees, LOT's, encode spines of ribbon discs in the 4-ball and ribbon 2-knots in the 4-sphere. The unresolved asphericity question for these spines is a major test case for Whitehead's asphericity conjecture. In this paper we give a complete description of the link of a reduced injective LOT complex. An important case is the following: If $\Gamma$ is a reduced injective LOT that does not contain boundary reduced sub-LOTs, then $lk(K(\Gamma))$ is a bi-forest. As a consequence $K(\Gamma)$ is aspherical, in fact DR, and its fundamental group is locally indicable. We also show that a general injective LOT complex is aspherical. Some of our results have already appeared in print over the last two decades and are collected here

Ribbon 2-knot groups of Coxeter type

Wirtinger presentations of deficiency 1 appear in the context of knots, long virtual knots, and ribbon 2-knots. They are encoded by (word) labeled oriented trees and, for that reason, are also called LOT presentations. These presentations are a well known and important testing ground for the validity (or failure) of Whitehead's asphericity conjecture. In this paper we define LOTs of Coxeter type and show that for every given $n$ there exists a (prime) LOT of Coxeter type with group of rank $n$. We also show that label separated Coxeter LOTs are aspherical

How Customization Affects Survey Interaction

One common trend in the world of survey data collection is the increasing use of new technological developments which can change the nature of the survey interview. A fairly recent trend is the use of machine-learning techniques to customize questions for respondents. This has the potential to create an individualized experience for the respondent and to improve data quality. Nevertheless, little is known so far of how customization affects the interaction in the survey interview. We introduce a tool developed by Schierholz et al. (2018) to code respondents’ occupation categories during the survey. The tool uses supervised learning algorithms to predict occupation categories based on previously entered text. We use this example to discuss theoretical and practical implications of customization for the interaction between the interviewer and the respondent. Preliminary results based on behavior coding of interviews will be presented that show that customization based on machine learning may lead to challenges in the standardized survey interview, particularly for the interviewer. For future research, we propose an experimental study to investigate differences between conversational and standardized interviewing techniques when working with customized survey instruments. In particular, we will focus on whether interviewers are able to exclude obviously inadequate response options and how this effects interview duration as well as perceived burden on the respondent and the interviewer