Analogical Reasoning

This chapter from our book Legal Writing in Context aims to demystify analogical reasoning for law students

Opportunities in forage production

Non-Peer Reviewe

Einstein-Weyl structures and Bianchi metrics

We analyse in a systematic way the (non-)compact four dimensional Einstein-Weyl spaces equipped with a Bianchi metric. We show that Einstein-Weyl structures with a Class A Bianchi metric have a conformal scalar curvature of constant sign on the manifold. Moreover, we prove that most of them are conformally Einstein or conformally K\"ahler ; in the non-exact Einstein-Weyl case with a Bianchi metric of the type $VII_0, VIII$ or $IX$, we show that the distance may be taken in a diagonal form and we obtain its explicit 4-parameters expression. This extends our previous analysis, limited to the diagonal, K\"ahler Bianchi $IX$ case.Comment: Latex file, 12 pages, a minor modification, accepted for publication in Class. Quant. Gra

GOTCHA Password Hackers!

We introduce GOTCHAs (Generating panOptic Turing Tests to Tell Computers and Humans Apart) as a way of preventing automated offline dictionary attacks against user selected passwords. A GOTCHA is a randomized puzzle generation protocol, which involves interaction between a computer and a human. Informally, a GOTCHA should satisfy two key properties: (1) The puzzles are easy for the human to solve. (2) The puzzles are hard for a computer to solve even if it has the random bits used by the computer to generate the final puzzle --- unlike a CAPTCHA. Our main theorem demonstrates that GOTCHAs can be used to mitigate the threat of offline dictionary attacks against passwords by ensuring that a password cracker must receive constant feedback from a human being while mounting an attack. Finally, we provide a candidate construction of GOTCHAs based on Inkblot images. Our construction relies on the usability assumption that users can recognize the phrases that they originally used to describe each Inkblot image --- a much weaker usability assumption than previous password systems based on Inkblots which required users to recall their phrase exactly. We conduct a user study to evaluate the usability of our GOTCHA construction. We also generate a GOTCHA challenge where we encourage artificial intelligence and security researchers to try to crack several passwords protected with our scheme.Comment: 2013 ACM Workshop on Artificial Intelligence and Security (AISec

'They are all dead that i could ask': Indigenous Innovation and the Micropolitics of the Field in Twentieth-century Southern Africa

Recovering the agency, skill and innovation of archaeological field assistants from historical encounters is essential to interrogating processes of knowledge production, but is often hampered by access to appropriate archival sources and methods. We detail a field project from early twentieth-century Basutoland (modern-day Lesotho) that is unique both for its aim to salvage details of rock-art production as a dying craft and for its archive chronicling the project's intellectual journey from experiment to draft manuscripts to published work over more than three decades. We argue that critical historiographic attention to this archive offers a guide for examining the intimate dynamics of fieldwork and the effects of these micropolitics on the archaeological canon. We demonstrate how sustained attention to long processes of knowledge production can pinpoint multiple instances in which the usability of field assistants' scientific knowledge is qualified, validated, or rejected, and in this case how an African assistant is transformed into an ethnographic interlocutor. For rock-art studies especially, this represents a need for interrogating the epistemic cultures - not just the content - of foundational historical data

Lattice energy-momentum tensor with Symanzik improved actions

We define the energy-momentum tensor on lattice for the $\lambda \phi^4$ and for the nonlinear $\sigma$-model Symanzik tree-improved actions, using Ward identities or an explicit matching procedure. The resulting operators give the correct one loop scale anomaly, and in the case of the sigma model they can have applications in Monte Carlo simulations.Comment: Self extracting archive fil