2,590 research outputs found
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 or , 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 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 and
for the nonlinear -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
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