A worldsheet perspective on heterotic T-duality orbifolds

Asymmetric heterotic orbifolds are discussed from the worldsheet perspective. Starting from Buscher’s gauging of a theory of D compact bosons the duality covariant description of Tseytlin is obtained after a non-Lorentz invariant gauge fixing. A left-over of the gauge symmetry can be used to removed the doubled constant zero modes so that D physical target space coordinate remain. This can be thought of as the worldsheet realization of the strong constraint of double field theory. The extension of this description to the heterotic theory is straightforward as all results are written in terms of the invariant and the generalized metrics. An explicit method is outline how to obtain a generalized metric which is invariant under T-duality orbifold actions. It is explicitly shown how shift orbifolds lead to redefinitions of the Narain moduli. Finally, a number of higher dimensional T-folds are constructed including a novel asymmetric ℤ6 orbifold.

Spatiotemporal patterns in Golden-cheeked Warbler breeding habitat quality and quantity

The Golden-cheeked Warbler, Setophaga chrysoparia, is a migratory songbird listed as endangered under the federal Endangered Species Act that breeds exclusively in central Texas and is heavily impacted by habitat conversion. The species relies on mixed Ashe-juniper and oak woodlands for nest-building and shelter during spring and early summer months. Using land cover data spanning the last 25 years, we conducted a geospatial analysis to quantify changes and identify shifts in breeding habitat quantity and quality. Since 1985, 13% of all forests within the warbler's breeding range were disturbed, with greater incidences near San Antonio (32%) and Austin (24%) metropolitan areas. Additionally, there was a 45% decrease in high-quality habitat (i.e., intact mixed or evergreen core forests) and a decrease in patch size. Habitats within protected areas saw a less sharp decline in habitat quality and large increases in warbler sightings, but these only represent 10% of all highest-quality habitat in the breeding range. Drastic declines in habitat quality suggest that generalized metrics of conversion may underestimate true habitat loss as degradation may impact the ecological viability of remaining forests for warbler nesting. Further evidence suggests that the few protected areas within the Texas range continue to play a significant role in warbler breeding. This information will assist researchers and managers prioritizing conservation action and will inform upcoming species status determinations.

Quantifying Social Biases in NLP: A Generalization and Empirical Comparison of Extrinsic Fairness Metrics

Measuring bias is key for better understanding and addressing unfairness in NLP/ML models. This is often done via fairness metrics, which quantify the differences in a model’s behaviour across a range of demographic groups. In this work, we shed more light on the differences and similarities between the fairness metrics used in NLP. First, we unify a broad range of existing metrics under three generalized fairness metrics, revealing the connections between them. Next, we carry out an extensive empirical comparison of existing metrics and demonstrate that the observed differences in bias measurement can be systematically explained via differences in parameter choices for our generalized metrics.

Overpublication as a symptom of audit culture: A comment on Phaf (2020)

Phaf suggests that, in order to address overpublication, academics should read more and publish less. Although many academics would like to take this advice, doing so is complicated by the audit culture that marketizes and metricizes everything they do. Working from the evolutionary metaphor introduced by Phaf, we argue that the evolution of science consists not simply in adapting theory to the demands of empirical investigation, but also in adapting scientific traditions and communities to the political and institutional forces that shape them. We point specifically to the generalized metrics (e.g., impact factors) that, in audit environments, arbitrate resources, in the process engineering professional precarity and overdetermining theory building. We argue that hyper-production can be understood as an adaptation to such an audit environment. We briefly discuss some suggestions for approaching the audit through relational accounting practices that disrupt and re-inscribe calculative audits, thus creating opportunities to read more and publish less.

Systolically extremal nonpositively curved surfaces are flat with finitely many singularities

The regularity of systolically extremal surfaces is a notoriously difficult problem already discussed by Gromov in 1983, who proposed an argument toward the existence of [Formula: see text]-extremizers exploiting the theory of [Formula: see text]-regularity developed by White and others by the 1950s. We propose to study the problem of systolically extremal metrics in the context of generalized metrics of nonpositive curvature. A natural approach would be to work in the class of Alexandrov surfaces of finite total curvature, where one can exploit the tools of the completion provided in the context of Radon measures as studied by Reshetnyak and others. However the generalized metrics in this sense still don’t have enough regularity. Instead, we develop a more hands-on approach and show that, for each genus, every systolically extremal nonpositively curved surface is piecewise flat with finitely many conical singularities. This result exploits a decomposition of the surface into flat systolic bands and nonsystolic polygonal regions, as well as the combinatorial/topological estimates of Malestein–Rivin–Theran, Przytycki, Aougab–Biringer–Gaster and Greene on the number of curves meeting at most once, combined with a kite excision move. The move merges pairs of conical singularities on a surface of genus [Formula: see text] and leads to an asymptotic upper bound [Formula: see text] on the number of singularities.