Big Black Hole, Little Neutron Star: Magnetic Dipole Fields in the Rindler Spacetime

As a black hole and neutron star approach during inspiral, the field lines of a magnetized neutron star eventually thread the black hole event horizon and a short-lived electromagnetic circuit is established. The black hole acts as a battery that provides power to the circuit, thereby lighting up the pair just before merger. Although originally suggested as a promising electromagnetic counterpart to gravitational-wave detection, the luminous signals are promising more generally as potentially detectable phenomena, such as short gamma-ray bursts. To aid in the theoretical understanding, we present analytic solutions for the electromagnetic fields of a magnetic dipole in the presence of an event horizon. In the limit that the neutron star is very close to a Schwarzschild horizon, the Rindler limit, we can solve Maxwell's equations exactly for a magnetic dipole on an arbitrary worldline. We present these solutions here and investigate a proxy for a small segment of the neutron star orbit around a big black hole. We find that the voltage the black hole battery can provide is in the range ~10^16 statvolts with a projected luminosity of 10^42 ergs/s for an M=10M_sun black hole, a neutron star with a B-field of 10^12 G, and an orbital velocity ~0.5c at a distance of 3M from the horizon. Larger black holes provide less power for binary separations at a fixed number of gravitational radii. The black hole/neutron star system therefore has a significant power supply to light up various elements in the circuit possibly powering jets, beamed radiation, or even a hot spot on the neutron star crust.Comment: Published in Physical Review D: http://link.aps.org/doi/10.1103/PhysRevD.88.06405

A bulk inflaton from large volume extra dimensions

The universe may have extra spatial dimensions with large volume that we cannot perceive because the energy required to excite modes in the extra directions is too high. Many examples are known of such manifolds with a large volume and a large mass gap. These compactifications can help explain the weakness of four-dimensional gravity and, as we show here, they also have the capacity to produce reasonable potentials for an inflaton field. Modeling the inflaton as a bulk scalar field, it becomes very weakly coupled in four dimensions, and this enables us to build phenomenologically acceptable inflationary models with tunings at the few per mil level. We speculate on dark matter candidates and the possibility of braneless models in this setting.Comment: 21 pages, LaTeX, 2 pdf figures. v2: additional references. v3: added comments on moduli stabilizatio

THE NEW HAVEN AIRPORT: A FAILURE OF LOCAL CONTROL

One and a half million Connecticut residents live closer to Tweed-New Haven Airport than any other commercial airport. Yet travelers today can reach only two other cities from New Haven and cannot take a jet flight. No other commercial airport in New England provides air service to fewer of its surrounding residents than Tweed-New Haven. Around the area, community and business leaders cite the lack of an adequate airport as a key roadblock in the economic development of New Haven

Face the Facts, or Is the Face a Fact?: Biometric Privacy in Publicly Available Data

Recent advances in biometric technologies have caused a stir among the privacy community. Specifically, facial recognition technologies facilitated through data scraping practices have called into question the basic precepts we had around exercising biometric privacy. Yet, in spite of emerging case law on the permissibility of data scraping, comparatively little attention has been given to the privacy implications endemic to such practices. On the one hand, privacy proponents espouse the view that manipulating publicly available data from, for example, our social media profiles, derogates from users’ expectations around the kind of data they share with platforms (and the obligations such platforms have for protecting users from illicit uses of that data). On the other hand, free speech absolutists take the stance that, to the extent that biometric data is readily apparent in publicly available data, any restrictions on its secondary uses are prior restraints on speech. This Note proposes that these principles underlying privacy and free speech are compatible. Wholesale bans on biometric technologies misapprehend their legitimate uses for actually preserving privacy. Despite the overwhelming dearth of protections for biometric privacy across the United States, current battles to preserve the few regulations on these data practices illuminate the emerging frontier for privacy and free speech debates. As this Note concludes, existing regulations on biometric data practices withstand First Amendment scrutiny, and strike the appropriate balance between speech and privacy regulations

Does urban agriculture help prevent malnutrition?

Previous research has suggested that urban agriculture has a positive impact on the household food security and nutritional status of low-socioeconomic status groups in cities in Sub-Saharan Africa, but a formal test of the link between semisubsistence urban food production and nutritional status has not accompanied these claims. This paper seeks to redress this gap in the growing literature on urban agriculture through an analysis of the determinants of the nutritional status of children under five in Kampala, Uganda, where roughly one-third of all households in the sample engage in some form of urban agriculture. When controlling for other individual child, maternal, and household characteristics, these data indicate that urban agriculture has a positive, significant association with higher nutritional status of children, particularly height-for-age. Several pathways by which this relationship is manifested are suggested, and the implications of these results for urban food and nutrition policy and urban management are briefly discussed.Food policies. ,Urban agriculture. ,Food security Household. ,Children Nutrition. ,Nutritional status ,

BUILDING SOCIAL NORMS ON THE INTERNET

This Note examines how architecture, and particularly the design and coding of software on the Internet, helps shape social norms. The Note makes two points about architecture and norms. First, architectural decisions affect what norms evolve and how they evolve. By allowing or facilitating certain types of behavior and preventing others, architecture can promote the growth of norms. On the flip side, architecture not tailored to promote certain positive norms of cooperation or compliance with the wishes of the designer (or in some cases the law) may allow the growth of antisocial norms. Second, because design decisions affect behavior directly as well as indirectly through norms, software engineers must recognize the regulatory function of the code they create. Although online architecture can promote productive social norms, design decisions can also create a backlash by fostering the development of norms that work against the sort of behavior the code is written to promote. The Note begins by describing how architecture works to regulate behavior in the physical world, examines the leading theories of social norm development, and explores the intersection of architecture and norms. The latter part of the Note transposes the general theory of architecture and norms to the Internet world, first describing the particular features of the Internet-anonymity, dispersion, and the free flow of information-that make the process of norm development different in cyberspace than in physical space, and then turning to two examples, online auctions and digital music, to show how software engineers have effectively and ineffectively used code to promote the development of social norms