BPS states of curves in Calabi--Yau 3--folds

The Gopakumar-Vafa conjecture is defined and studied for the local geometry of a curve in a Calabi-Yau 3-fold. The integrality predicted in Gromov-Witten theory by the Gopakumar-Vafa BPS count is verified in a natural series of cases in this local geometry. The method involves Gromov-Witten computations, Mobius inversion, and a combinatorial analysis of the numbers of etale covers of a curve.Comment: Published by Geometry and Topology at http://www.maths.warwick.ac.uk/gt/GTVol5/paper9.abs.html Version 3 is GT version 2 and has corrections to eq (2) on p 295, to 1st eq in Prop 2.1 and the tables on p 39

Icebergs in the Clouds: the Other Risks of Cloud Computing

Cloud computing is appealing from management and efficiency perspectives, but brings risks both known and unknown. Well-known and hotly-debated information security risks, due to software vulnerabilities, insider attacks, and side-channels for example, may be only the "tip of the iceberg." As diverse, independently developed cloud services share ever more fluidly and aggressively multiplexed hardware resource pools, unpredictable interactions between load-balancing and other reactive mechanisms could lead to dynamic instabilities or "meltdowns." Non-transparent layering structures, where alternative cloud services may appear independent but share deep, hidden resource dependencies, may create unexpected and potentially catastrophic failure correlations, reminiscent of financial industry crashes. Finally, cloud computing exacerbates already-difficult digital preservation challenges, because only the provider of a cloud-based application or service can archive a "live," functional copy of a cloud artifact and its data for long-term cultural preservation. This paper explores these largely unrecognized risks, making the case that we should study them before our socioeconomic fabric becomes inextricably dependent on a convenient but potentially unstable computing model.Comment: 6 pages, 3 figure

Has the Silence Been Broken? Catholic Theological Ethics and Racial Justice

This survey discusses the emerging contours of a distinctive Catholic ethical approach to race, racism, and racial justice. Among its features are the adoption of a more structural and cultural understanding of human sinfulness, engaged intellectual reflection, concern about malformed white identity, an intentional dialogue with African American scholarship and culture, and the cultivation of spiritual practices and disciplines. The “Note” concludes with a discussion of the global challenges of racialization and the future challenges for Catholic ethical reflection on racism

Plugging Side-Channel Leaks with Timing Information Flow Control

The cloud model's dependence on massive parallelism and resource sharing exacerbates the security challenge of timing side-channels. Timing Information Flow Control (TIFC) is a novel adaptation of IFC techniques that may offer a way to reason about, and ultimately control, the flow of sensitive information through systems via timing channels. With TIFC, objects such as files, messages, and processes carry not just content labels describing the ownership of the object's "bits," but also timing labels describing information contained in timing events affecting the object, such as process creation/termination or message reception. With two system design tools-deterministic execution and pacing queues-TIFC enables the construction of "timing-hardened" cloud infrastructure that permits statistical multiplexing, while aggregating and rate-limiting timing information leakage between hosted computations.Comment: 5 pages, 3 figure

Distilling one-qubit magic states into Toffoli states

For certain quantum architectures and algorithms, most of the required resources are consumed during the distillation of one-qubit magic states for use in performing Toffoli gates. I show that the overhead for magic-state distillation can be reduced by merging distillation with the implementation of Toffoli gates. The resulting routine distills 8 one-qubit magic states directly to a Toffoli state, which can be used without further magic to perform a Toffoli gate.Comment: 8 pages, 11 figures, 1 table, v2: corrected several careless errors, apologie

Obligation Without Rule: Bartleby, Agamben, and the Second-Person Standpoint

In Herman Melville’s Bartleby, the Scrivener, the narrator finds himself involved in a moral relation with the title character whose sense he finds difficult to articulate. I argue that we can make sense of this relation, up to a certain point, in terms of the influential account of obligation that Stephen Darwall advances in The Second-Person Standpoint. But I also argue that there is a dimension of moral sense in the relation that is not captured by Darwall’s account, or indeed by any of the accounts of obligation that have been most prominent in the history of western philosophy from the early modern period up to the present. More specifically, I argue that what is brought out in the relation between Bartleby and the narrator is the separation of the experience of moral necessitation from the rule that would give its content. I attempt to show that this obligation without rule is a genuine moral phenomenon and that we can begin to understand it in terms of the ideas of love, singularity, and potentiality as these are developed in the work of Giorgio Agamben