ABSTRACT What constitutes a BlackSwan? And under what conditions may a BlackSwan be expected to arise? As Nassim Taleb describes it, a BlackSwan is an event that displays three key properties, the two most important of which are that: (1) it is not even imagined as a possibility prior to its occurrence; and (2) it is in some way significant in its impact. It follows that whether or not an event counts (...) as a BlackSwan depends on the subjective imaginings of contemporaneous observers and their (usually implicit) criteria regarding what counts as a ?significant impact.? Since there is nothing in determinism that precludes (1) and (2), Black Swans may occur even in a perfectly deterministic world. Nevertheless, if the world is indeed characterised by randomness, free will, emergence, and the like, then it is arguably more likely to throw forth events that display the above?mentioned properties. The same goes for various specific features of an increasingly interconnected global economy, which allowed Taleb (paradoxically) to forecast what was, for most of us at least, the great BlackSwan of 2008. (shrink)
Free and weakly interacting particles are described by a second-quantized nonlinear Schrödinger equation, or relativistic versions of it. They describe Gaussian random walks with collisions. By contrast, the fields of strongly interacting particles are governed by effective actions, whose extremum yields fractional field equations. Their particle orbits perform universal Lévy walks with heavy tails, in which rare events are much more frequent than in Gaussian random walks. Such rare events are observed in exceptionally strong windgusts, monster or rogue waves, earthquakes, (...) and financial crashes. While earthquakes may destroy entire cities, the latter have the potential of devastating entire economies. (shrink)
ABSTRACT Nassim Taleb rightly points out that although people may acknowledge in the abstract that the world is uncertain, they still behave as if a large enough sample size is all that is needed to predict, and model, the future. He also rightly notes that ever?increasing quantities of information are relevant only in simple situations, such as in predicting the range of human height, but are misleading in more random arenas, such as financial markets. However, while Taleb decries the use (...) of narratives for falsely forcing the facts to fit a given story, we need narratives in order to make sense of a complex world. Further, Taleb fails to take sufficient heed of the fact that human narratives themselves become objects that act on subjects in an ever?increasing web of complexity. (shrink)
ABSTRACT We like to believe that our world is regular, that we can predict it fairly well, and that we can control the risks we run. Nassim Taleb argues that we are fooling ourselves and that the course of history is driven by rare and extreme events, which he calls Black Swans. There is much to this, but scholars?at least in political science?are less oblivious to the problem than he believes. More thought needs to be given to hard issues (...) of whether key events were anticipated, whether there were functional substitutes for events that are seen as turning points, the role of beliefs and expectations in Black Swans, and the dynamics that might explain unpredictability. (shrink)
Feminist, critical race, and postcolonial theories have established that social identities such as race and gender are mutually constitutive—i.e., that they “intersect.” I argue that “cultural appropriation” is never merely the appropriation of culture, but also of gender, sexuality, class, etc. For example, “white hipness” is the appropriation of stereotypical black masculinity by white males. Looking at recent videos from black male hip-hop artists, I develop an account of “postmillennial black hipness.” The inverse of white hipness, this (...) practice involves the appropriation, by black men, of stereotypical white gay masculinity and/or non-American, non-white femininity. I also argue that Shephard Fairey’s recent images of (mainly militant) non-Western women of color can be read as a new form of white hipness that revises the traditional logic in two ways: (1) by appropriating non-white femininity rather than masculinity, and (2) by adopting the practice of postmillennial black hipness itself. (shrink)
We hypothesize that black women experience accelerated biological aging in response to repeated or prolonged adaptation to subjective and objective stressors. Drawing on stress physiology and ethnographic, social science, and public health literature, we lay out the rationale for this hypothesis. We also perform a first population-based test of its plausibility, focusing on telomere length, a biomeasure of aging that may be shortened by stressors. Analyzing data from the Study of Women’s Health Across the Nation (SWAN), we estimate (...) that at ages 49–55, black women are 7.5 years biologically “older” than white women. Indicators of perceived stress and poverty account for 27% of this difference. Data limitations preclude assessing objective stressors and also result in imprecise estimates, limiting our ability to draw firm inferences. Further investigation of black-white differences in telomere length using large-population-based samples of broad age range and with detailed measures of environmental stressors is merited. (shrink)
This essay brings Critical Whiteness Studies into liberationist Christian ethics in order to analyze white Protestant responses to the 1969 Black Manifesto, which demanded reparations from white churches. The essay's primary argument is that the absence of a sense of white moral agency among white Protestants manifested itself in behaviors and rhetoric that ensured whiteness went unacknowledged, which caused Protestant responses to the Manifesto to fail. A related argument is that white behavior and rhetoric were particularly dramatic because of (...) the call for reparations. Reparations assume that race is a material relationship in which there has been a perpetrator and a victim, rendering the acknowledgment of white agency unavoidable. This essay thus analyzes several ways in which whites can be seen turning away from white selves, turning a scrutinizing gaze instead to Black selves and, in the process, absenting white agency from the work of racial justice. (shrink)
Theorizing Black Feminisms outlines some of the crucial debates going on among Black feminists today. In doing so it brings together a collection of some of the most exciting work by Black women scholars. The book encompasses a wide range of diverse subjects and refuses to be limited by notions of disciplinary boundaries or divisions between theory and practice. Theorizing Black Feminisms combines essays on literature, sociology, history, political science, anthropology, and art. As such it will (...) be vital reading for anyone--activist, student, artist or scholar--interested in exploring the multidisciplinary possibilities for Black feminism. Most importantly, each essay in the volume begins with the assumption that Black women are not simply victims of various oppressions. Rather, they are visionary and pragmatic agents of change. Contributors: Evelyn Barbee, University of Wisconsin; Rose Brewer, University of Minnesota; Cheryl Clarke, Rutgers University; Johnnetta Cole, Spelman College; Cindy Courville, Occidental College; Beverly Guy-Sheftall, Spelman College; Marilyn Little, University of Wisconsin; Nellie McKay, University of Wisconsin; O'molara Ogundipe, Rutgers University; Christine Obbo, Wayne State University; Loretta Ross, Center for Democratic Renewal, Atlanta. (shrink)
Crane envisions the speculative conjecture that intelligent civilizations might want and be able to produce black holes in the very far future. He implicitly suggests two main purposes of this enterprise: (i) energy production and (ii) universe production. We discuss those two options. The commentary is obviously highly speculative and should be read accordingly.
The structure of the thermal equilibrium state of a weakly interacting Bose gas is of current interest. We calculate the density matrix of that state in two ways. The most effective method, in terms of yielding a simple, explicit answer, is to construct a generating function within the traditional framework of quantum statistical mechanics. The alternative method, arguably more interesting, is to construct the thermal state as a vector state in an artificial system with twice as many degrees of freedom. (...) It is well known that this construction has an actual physical realization in the quantum thermodynamics of black holes, where the added degrees of freedom correspond to the second sheet of the Kruskal manifold and the thermal vector state is a state of the Unruh or the Hartle–Hawking type. What is unusual about the present work is that the Bogolubov transformation used to construct the thermal state combines in a rather symmetrical way with Bogolubov's original transformation of the same form, used to implement the interaction of the nonideal gas in linear approximation. In addition to providing a density matrix, the method makes it possible to calculate efficiently certain expectation values directly in terms of the thermal vector state of the doubled system. (shrink)
We analyze the rather unusual properties of some exact solutions in 2D dilaton gravity for which infinite quantum stresses on the Killing horizon can be compatible with regularity of the geometry. In particular, the Boulware state can support a regular horizon. We show that such solutions are contained in some well-known exactly solvable models (for example, RST). Formally, they appear to account for an additional coefficient B in the solutions (for the same Lagrangian which contains also “traditional” solutions) that gives (...) rise to the deviation of temperature T from its Hawking value T H . The Lorentzian geometry, which is a self-consistent solution of the semiclassical field equations, in such models, is smooth even at B≠0 and there is no need to put B=0 (T=T H ) to smooth it out. We show how the presence of B≠0 affects the structure of spacetime. In contrast to “usual” black holes, full fledged thermodynamic interpretation, including definite value of entropy, can be ascribed (for a rather wide class of models) to extremal horizons, not to nonextreme ones. We find also new exact solutions for “usual” black holes (with T=T H ). The properties under discussion arise in the weak-coupling regime of the effective constant of dilaton-gravity interaction. Extension of features, traced in 2D models, to 4D dilaton gravity leads, for some special models, to exceptional nonextreme black holes having no own thermal properties. (shrink)
Physical arguments stemming from the theory of black-hole thermodynamics are used to put constraints on the dynamics of closed-string tachyon condensation in Scherk–Schwarz compactifications. A geometrical interpretation of the tachyon condensation involves an effective capping of a noncontractible cycle, thus removing the very topology that supports the tachyons. A semiclassical regime is identified in which the matching between the tachyon condensation and the black-hole instability flow is possible. We formulate a generalized correspondence principle and illustrate it in several (...) different circumstances: an Euclidean interpretation of the transition from strings to black holes across the Hagedorn temperature and instabilities in the brane-antibrane system. (shrink)
We investigate quantum entanglement of gravitational configurations in 3D AdS gravity using the AdS/CFT correspondence. We derive explicit formulas for the holographic entanglement entropy (EE) of the BTZ black hole, conical singularities and regularized AdS3. The leading term in the large temperature expansion of the holographic EE of the BTZ black hole reproduces exactly its Bekenstein-Hawking entropy S BH , whereas the subleading term behaves as ln S BH . We also show that the leading term of the (...) holographic EE for the BTZ black hole can be obtained from the large temperature expansion of the partition function of a broad class of 2D CFTs on the torus. This result indicates that black hole EE is not a fundamental feature of the underlying theory of quantum gravity but emerges when the semiclassical notion of spacetime geometry is used to describe the black hole. (shrink)
Recent developments point to a breakdown in the generalized second law of thermodynamics for theories with Lorentz symmetry violation. It appears possible to construct a perpetual motion machine of the second kind in such theories, using a black hole to catalyze the conversion of heat to work. Here we describe and extend the arguments leading to that conclusion. We suggest the inference that local Lorentz symmetry may be an emergent property of the macroscopic world with origins in a microscopic (...) second law of causal horizon thermodynamics. (shrink)
An extended scale relativity theory, actively developed by one of the authors, incorporates Nottale's scale relativity principle where the Planck scale is the minimum impassible invariant scale in Nature, and the use of polyvector-valued coordinates in C-spaces (Clifford manifolds) where all lengths, areas, volumes⋅ are treated on equal footing. We study the generalization of the ordinary point-particle quantum mechanical oscillator to the p-loop (a closed p-brane) case in C-spaces. Its solution exhibits some novel features: an emergence of two explicit scales (...) delineating the asymptotic regimes (Planck scale region and a smooth region of a quantum point oscillator). In the most interesting Planck scale regime, the solution recovers in an elementary fashion some basic relations of string theory (including string tension quantization and string uncertainty relation). It is shown that the degeneracy of the first collective excited state of the p-loop oscillator yields not only the well-known Bekenstein–Hawking area-entropy linear relation but also the logarithmic corrections therein. In addition we obtain for any number of dimensions the Hawking temperature, the Schwarschild radius, and the inequalities governing the area of a black hole formed in a fusion of two black holes. One of the interesting results is a demonstration that the evaporation of a black hole is limited by the upper bound on its temperature, the Planck temperature. (shrink)
We model a black hole spacetime as a causal set and count, with a certain definition, the number of causal links crossing the horizon in proximity to a spacelike or null hypersurface Σ. We find that this number is proportional to the horizon's area on Σ, thus supporting the interpretation of the links as the “horizon atoms” that account for its entropy. The cases studied include not only equilibrium black holes but ones far from equilibrium.
This study investigates the extent to which South African listed corporations voluntarily disclose information on black economic empowerment (BEE) in their annual and sustainability reports using a sample of 75 listed corporations from 2003 to 2009. BEE is a form of socio-economic affirmative action championed by the African National Congress (ANC)-led government to address historical imbalances in business participation and ownership in South Africa. We find that block ownership and institutional ownership are negatively associated with the extent of BEE (...) disclosures, whereas government ownership, board diversity (age, education, ethnicity, nationality and occupation), board size and non-executive directors are positively related to the extent of BEE disclosures. By contrast, dual board leadership structure and gender diversity are not significantly associated with BEE disclosures. Our results are robust when controlling for firm-level characteristics, fixed-effects and alternative disclosure proxies. Our results are largely consistent with the predictions of agency, legitimacy, resource dependence and stakeholder theories. (shrink)
Using quantum liquids one can simulate the behavior of the quantum vacuum in the presence of the event horizon. The condensed matter analogs demonstrate that in most cases the quantum vacuum resists formation of the horizon, and even if the horizon is formed different types of the vacuum instability develop, which are faster than the process of Hawking radiation. Nevertheless, it is possible to create the horizon on the quantum-liquid analog of the brane, where the vacuum life-time is long enough (...) to consider the horizon as the quasistationary object. Using this analogy we calculate the Bekenstein entropy of the near-extremal and extremal black holes, which comes from the fermionic microstates in the region of the horizon—the fermion zero modes. We also discuss how the cancellation of the large cosmological constant follows from the thermodynamics of the vacuum. (shrink)
This paper summarizes the findings of a three-year exploratory qualitative study of teenage childbearing in 20 low-income multigeneration black families. Teenage childbearing in these families is part of an alternative life-course strategy created in response to socioenvironmental constraints. This alternative life-course strategy is characterized by an accelerated family timetable; the separation of reproduction and marriage; an age-condensed generational family structure; and a grandparental child-rearing system. The implications of these patterns for intergenerational family roles are discussed.
The Schwarzschild solution has played a fundamental conceptual role in general relativity, and beyond, for instance, regarding event horizons, spacetime singularities and aspects of quantum field theory in curved spacetimes. However, one still encounters the existence of misconceptions and a certain ambiguity inherent in the Schwarzschild solution in the literature. By taking into account the point of view of an observer in the interior of the event horizon, one verifies that new conceptual difficulties arise. In this work, besides providing a (...) very brief pedagogical review, we further analyze the interior Schwarzschild black hole solution. Firstly, by deducing the interior metric by considering time-dependent metric coefficients, the interior region is analyzed without the prejudices inherited from the exterior geometry. We also pay close attention to several respective cosmological interpretations, and briefly address some of the difficulties associated to spacetime singularities. Secondly, we deduce the conserved quantities of null and timelike geodesics, and discuss several particular cases in some detail. Thirdly, we examine the Eddington–Finkelstein and Kruskal coordinates directly from the interior solution. In concluding, it is important to emphasize that the interior structure of realistic black holes has not been satisfactorily determined, and is still open to considerable debate. (shrink)
Previous perceptual research with black-capped and mountain chickadees has demonstrated that these species treat each other’s namesake chick-a-dee calls as belonging to separate, open-ended categories. Further, the terminal dee portion of the call has been implicated as the most prominent species marker. However, statistical classification using acoustic summary features suggests that all note-types contained within the chick-a-dee call should be sufficient for species classification. The current study seeks to better understand the note-type based mechanisms underlying species-based classification of the (...) chick-a-dee call by black-capped and mountain chickadees. In two, complimentary, operant discrimination experiments, both species were trained to discriminate the species of the signaller using either entire chick-a-dee calls, or individual note-types from chick-a-dee calls. In agreement with previous perceptual work we find that the D note had significant stimulus control over species based discrimination. However, in line with statistical classifications, we find that all note-types carry species information. We discuss reasons why the most easily discriminated note-types are likely candidates to carry species based cues. (shrink)
Although the black and white populations in the United States differ, on average, by about one standard deviation (equivalent to 15 IQ points) on current IQ tests, they differ by various amounts on different tests. The present study examines the nature of the highly variable blackwhite difference (expressed in standard score units) on the various tests. Hence, in accord with Spearman's hypothesis, the average blackwhite difference on standard IQ tests and their educational and occupational correlates.
A naive introduction of a dependency of the mass of a black hole on the Schwarzschild time coordinate results in singular behavior of curvature invariants at the horizon, violating expectations from complementarity. If instead a temporal dependence is introduced in terms of a coordinate akin to the river time representation, the Ricci scalar is nowhere singular away from the origin. It is found that for a shrinking mass scale due to evaporation, the null radial geodesics that generate the horizon (...) are slightly displaced from the coordinate singularity. In addition, a changing horizon scale significantly alters the form of the coordinate singularity in diagonal (orthogonal) metric coordinates representing the space-time. A Penrose diagram describing the growth and evaporation of an example black hole is constructed to examine the evolution of the coordinate singularity. (shrink)
Introduction : first things : two black and blue thoughts -- Author's note I. a sewing needle inside a plastic and rubber suction cup sitting on a watch spring, or, an object for seeing nothing -- Elegy of milk, in black and blue : the bruising of La Chambre claire -- "A" is for Alice, for amnesia, for anamnesis: a fairy tale (almost blue) called La Jetée -- Happiness with a long piece of black leader : Chris (...) Marker's sans soleil -- Author's note II. She wrote me -- "Summer was inside the marble": Alain Resnais and Magurite Duras's Hiroshima mon amour. (shrink)
A simple statistical interpretation of the origin of black hole entropy is presented. It is shown that this entropy can be understood as emerging as a result of missing information about the exact state of the matter from which the black hole was formed.
According to prevailing theory, relativistic degenerate stars with masses beyond the Chandrasekhar and Oppenheimer–Volkoff (OV) limits cannot achieve hydrostatic equilibrium through either electron or neutron degeneracy pressure and must collapse to form stellar black holes. In such end states, all matter and energy within the Schwarzschild horizon descend into a central singularity. Avoidance of this fate is a hoped-for outcome of the quantization of gravity, an as-yet incomplete undertaking. Recent studies, however, suggest the possibility that known quantum processes may (...) intervene to arrest complete collapse, thereby leading to equilibrium states of macroscopic size and finite density. I describe here one such process which entails pairing (or other even-numbered association) of neutrons (or constituent quarks in the event of nucleon disruption) to form a condensate of composite bosons in equilibrium with a core of degenerate fermions. This process is analogous to, but not identical with, the formation of hadron Cooper pairs that give rise to neutron superfluidity and proton superconductivity in neutron stars. Fermion condensation to composite bosons in a star otherwise destined to collapse to a black hole facilitates hydrostatic equilibrium in at least two ways: (1) removal of fermions results in a decrease in the Fermi level which stiffens the dependence of degeneracy pressure on fermion density, and (2) phase separation into a fermionic core surrounded by a self-gravitating condensate diminishes the weight which must be balanced by fermion degeneracy pressure. The outcome is neither a black hole nor a neutron star, but a novel end state, a “fermicon star,” with unusual physical properties. (shrink)
We present a framework for analyzing black hole backreaction from the point of view of quantum open systems using influence functional formalism. We focus on the model of a black hole described by a radially perturbed quasi-static metric and Hawking radiation by a conformally coupled massless quantum scalar field. It is shown that the closed-time-path (CTP) effective action yields a non-local dissipation term as well as a stochastic noise term in the equation of motion, the Einstein–Langevin equation. Once (...) the thermal Green's function in a Schwarzschild background becomes available to the required accuracy, the strategy described here can be applied to obtain concrete results on backreaction. We also present an alternative derivation of the CTP effective action in terms of the Bogolyubov coefficients, thus making a connection with the interpretation of the noise term as measuring the difference in particle production in alternative histories. (shrink)
The Einstein-conformally coupled scalar field system is studied in the presence of a cosmological constant. We consider a massless or massive scalar field with no additional self-interaction, and spherically symmetric black hole geometries. When the cosmological constant is positive, no scalar hair can exist and the only solution is the Schwarzschild–de Sitter black hole. When the cosmological constant is negative, stable scalar field hair exists provided the mass of the scalar field is not too large.
The death of Frantz Fanon at the age of thirty-six robbed the African revolution of its leading intellectual and moral force. His death also cut short one of the most extraordinary intellectual careers in contemporary political thought. Fanon was a political psychologist whose approach to revolutionary theory was grounded in his psychiatric practice. During his years in Algeria he published clinical studies on the behaviour of violent patients, the role of culture in the development of illness and the function of (...) the psychiatric hospital as a social milieu. These papers illuminate Fanon's political theory, expose weaknesses in his concept of political consciousness and liberation, and contain a 'secret history' explaining the tide of revolutionary movements in the Third World. (shrink)