Minimal flux Minkowski classification

We classify Minkowski$_4$ solutions in type IIA supergravity, with N=2 supersymmetry and an SU(2) R-symmetry of a certain type. Many subcases can be reduced to relatively simple PDEs, among which we recover various intersecting brane systems, and AdS$_d$ solutions, $d=5,6,7$, and in particular the recently found general massive AdS$_7$ solutions. Imposing compactness of the internal six-manifold we obtain promising solutions with localized D-branes and O-planes.Comment: v2: Result slightly strengthened, typos corrected. v3: Published Versio

A N=2\mathcal{N}=2 Supersymmetric AdS4AdS_4 Solution in M-theory with Purely Magnetic Flux

We find a new $\mathcal{N}=2$ $AdS_4$ solution in M-theory supported by purely magnetic flux via a sequence of abelian and non-abelian T-dualities. This provides the second known example in this class besides the uplift of the Pernici and Sezgin solution to 7d gauged supergravity constructed in the eighties. We compute the free energy of the solution, and show that it scales as $N^{3/2}$. It is intriguing that even though the natural holographic interpretation is in terms of M5-branes wrapped on a special Lagrangian 3-cycle, this solution does not exhibit the expected $N^3$ behavior.Comment: 19 pages plus appendices. v2 metadata amended, reference adde

Wages, racial composition, and quality sorting in labor markets

This paper examines the relationship between wage rates and the racial composition of jobs, using large cross-sectional and longitudinal samples constructed from monthly Current Population Surveys for 1983-92. Support is found for a "quality sorting" model that posits an equilibrium in which the racial composition of jobs serves as a skill index of unmeasured labor quality. Estimation of standard wage-level equations shows that wages of both black and white workers are substantially lower in occupations with a high density of blacks. Consistent with the quality sorting hypothesis, the magnitude of the relationship is reduced sharply after accounting for occupational skill measures. Longitudinal wage-change estimates controlling for person-specific quality indicate little if any causal effect of racial composition on wages. Estimates of racial discrimination are reduced only moderately after accounting for racial composition; unexplained differentials occur within occupations or reflect inter-occupational differences uncorrelated with racial composition and occupational skill measures.

The rent's too high: Self-archive for fair online publication costs

The main contributors of scientific knowledge, researchers, generally aim to disseminate their findings far and wide. And yet, publishing companies have largely kept these findings behind a paywall. With digital publication technology markedly reducing cost, this enduring wall seems disproportionate and unjustified; moreover, it has sparked a topical exchange concerning how to modernize academic publishing. This discussion, however, seems to focus on how to compensate major publishers for providing open access through a "pay to publish" model, in turn transferring financial burdens from libraries to authors and their funders. Large publishing companies, including Elsevier, Springer Nature, Wiley, PLoS, and Frontiers, continue to earn exorbitant revenues each year, hundreds of millions of dollars of which now come from processing charges for open-access articles. A less expensive and equally accessible alternative exists: widespread self-archiving of peer-reviewed articles. All we need is awareness of this alternative and the will to employ itComment: 8 pages, 1 figure, 19 reference

Supersymmetry and non-Abelian T-duality in type II supergravity

We study the effect of T-duality on supersymmetry in the context of type II supergravity. For both U(1) Abelian and SU(2) non-Abelian T-duality, we demonstrate that the supersymmetry variations after T-duality are related to the variations before T-duality through the Kosmann spinorial Lie derivative, which vanishes when the Killing spinors are independent of the T-duality directions. As a byproduct of our analysis, we present closed expressions for SU(2) T-duality in a class of spacetimes with diagonal Bianchi IX symmetry and comment on specific examples of T-dual geometries, including a novel AdS3 geometry with large N = (0,4) superconformal symmetry.Comment: 34 pages, v2, wording improved, references updated, v3 references added, matches published version; v4 signs in section 6 changed to make consistent with earlier sections, erroneous statement about supersymmetry of AdS3 S3 S3 S1 non-Abelian T-dual corrected, reference adde