The Command and Control of Canadian and American Maritime Air Power in the Northwest Atlantic, 1941-1943

Operational, organizational, doctrinal, and cultural differences hampered effective command and control of Canadian and American maritime air power defending shipping against U-boats off the east coast during the Second World War. The American desire to implement US unity of command over both nations’ maritime air forces clashed with the Canadian preference for simple cooperation. Canadian airmen resisted several American attempts to impose unity of command until the operational situation in the Battle of the Atlantic revealed inefficiencies in coordination which necessitated all maritime air power in the Northwest Atlantic be centralized under Canadian operational control in the spring of 1943

Scalar Curvature Estimates by Parallel Alternating Torsion

We generalize Llarull's scalar curvature comparison to Riemannian manifolds admitting metric connections with parallel and alternating torsion and having a nonnegative curvature operator on 2-vectors. As a byproduct, we show that Euler number and signature of such manifolds are determined by their global holonomy representation. Our result holds in particular for all quotients of compact Lie groups of equal rank, equipped with a normal homogeneous metric. We also correct a mistake in the treatment of odd-dimensional spaces in arXiv:math/0010199 and arXiv:0705.0500Comment: 17 page

Torsion Invariants for Families

We give an overview over the higher torsion invariants of Bismut-Lott, Igusa-Klein and Dwyer-Weiss-Williams, including some more or less recent developments.Comment: LaTeX, 40 pages; v2: references added, BL = IK announced; v3: reference to DWW = IK adde

Kreck-Stolz invariants for quaternionic line bundles

We generalise the Kreck-Stolz invariants s 2 s_2 and s 3 s_3 by defining a new invariant, the t t -invariant, for quaternionic line bundles  E E over closed spin-manifolds M M of dimension 4 k − 1 4k-1 with  H 3 ( M ; Q ) = 0 H^3(M; \mathbb Q) = 0 such that  c 2 ( E ) ∈ H 4 ( M ) c_2(E)\in H^4(M) is torsion. The t t -invariant classifies closed smooth oriented 2 2 -connected rational homology 7 7 -spheres up to almost-diffeomorphism, that is, diffeomorphism up to a connected sum with an exotic sphere. It also detects exotic homeomorphisms between such manifolds. The t t -invariant also gives information about quaternionic line bundles over a fixed manifold, and we use it to give a new proof of a theorem of Feder and Gitler about the values of the second Chern classes of quaternionic line bundles over H P k \mathbb H P^k . The t t -invariant for S 4 k − 1 S^{4k-1} is closely related to the Adams e e -invariant on the ( 4 k − 5 ) (4k-5) -stem.</p

Vafa-Witten Estimates for Compact Symmetric Spaces

We give an optimal upper bound for the first eigenvalue of the untwisted Dirac operator on a compact symmetric space G/H with rk G-rk H\le 1 with respect to arbitrary Riemannian metrics. We also prove a rigidity statement.Comment: LaTeX, 11 pages. V2: Rigidity statement added, minor changes. To appea

Blood Donations and Incentives: Evidence from a Field Experiment

There is a longstanding concern that material incentives might undermine prosocial motivation, leading to a decrease in blood donations rather than an increase. This paper provides an empirical test of how material incentives affect blood donations in a large-scale field experiment spanning three months and involving more than 10,000 previous donors. We examine two types of incentive: a lottery ticket and a free cholesterol test. Lottery tickets significantly increase donations, in particular among less motivated donors. The cholesterol test leads to no discernable impact on usable blood donations. If anything, it creates a small negative selection effect in terms of donations that must be discarded.prosocial behavior, blood donations, material incentives, field experiment

An analytic invariant of G_2 manifolds

The first and third authors have constructed a defect invariant $\nu(M,\phi)$ in Z/48 for $G_2$-structures on a closed 7-manifold. We describe the nu-invariant using $\eta$-invariants and Mathai-Quillen currents on M and show that it can be refined to an integer-valued invariant $\bar\nu(M,g)$ for $G_2$-holonomy metrics. As an example, we determine the $\bar\nu$-invariants of twisted and extra twisted connected sums a la Kovalev, Corti-Haskins-Nordstr\"om-Pacini, and Nordstr\"om. In particular, we exhibit examples of 7-manifolds where the moduli space of $G_2$-holonomy metrics has at least two connected components. In one of these examples, the underlying $G_2$-structures are homotopic, in another one, they are not.Comment: pdfLaTeX, 26 pages, 2 figures (tikz). v2: 28 pages, 2 figures. Reorganised the contents for clarity. Comments welcome