Contesting Knowledge, Contested Space: Language, Place, and Power in Derek Walcott’s Colonial Schoolhouse

Derek Walcott's colonial schoolhouse bears an interesting relationship to space and place: it is both a Caribbean site, and a site that disavows its locality by valorizing the metropolis and acting as a vital institution in the psychic colonization of the Caribbean peoples. The situation of the schoolhouse within the Caribbean landscape, and the presence of the Caribbean body, means that the pedagogical relationship works in two ways, and that the hegemonic/colonial discourses of the schoolhouse are inherently challenged within its walls. While the school was used as a means of colonial subjugation, as a method of privileging the metropolitan centre, and as a way of recreating that centre within the colonies, Walcott's emphasis on place complicates and ultimately rewrites colonial discourses and practices. While the school attempts to legitimize colonial space, it in fact fosters what Walter Mignolo has termed "border thinking.

Precursors, Gauge Invariance, and Quantum Error Correction in AdS/CFT

A puzzling aspect of the AdS/CFT correspondence is that a single bulk operator can be mapped to multiple different boundary operators, or precursors. By improving upon a recent model of Mintun, Polchinski, and Rosenhaus, we demonstrate explicitly how this ambiguity arises in a simple model of the field theory. In particular, we show how gauge invariance in the boundary theory manifests as a freedom in the smearing function used in the bulk-boundary mapping, and explicitly show how this freedom can be used to localize the precursor in different spatial regions. We also show how the ambiguity can be understood in terms of quantum error correction, by appealing to the entanglement present in the CFT. The concordance of these two approaches suggests that gauge invariance and entanglement in the boundary field theory are intimately connected to the reconstruction of local operators in the dual spacetime.Comment: 25 pages, 6 figure

Negative Branes, Supergroups and the Signature of Spacetime

We study the realization of supergroup gauge theories using negative branes in string theory. We show that negative branes are intimately connected with the possibility of timelike compactification and exotic spacetime signatures previously studied by Hull. Isolated negative branes dynamically generate a change in spacetime signature near their worldvolumes, and are related by string dualities to a smooth M-theory geometry with closed timelike curves. Using negative D3 branes, we show that $SU(0|N)$ supergroup theories are holographically dual to an exotic variant of type IIB string theory on $dS_{3,2} \times \bar S^5$, for which the emergent dimensions are timelike. Using branes, mirror symmetry and Nekrasov's instanton calculus, all of which agree, we derive the Seiberg-Witten curve for $\mathcal N=2 ~SU(N|M)$ gauge theories. Together with our exploration of holography and string dualities for negative branes, this suggests that supergroup gauge theories may be non-perturbatively well-defined objects, though several puzzles remain.Comment: 66 pages, 12 figures. V2: additional references, minor typo correction

Sub-AdS Scale Locality in AdS3_3/CFT2_2

We investigate sub-AdS scale locality in a weakly coupled toy model of the AdS$_3$/CFT$_2$ correspondence. We find that this simple model has the correct density of states at low and high energies to be dual to Einstein gravity coupled to matter in AdS$_3$. Bulk correlation functions also have the correct behavior at leading order in the large $N$ expansion, but non-local effects emerge at order $1/N$. Our analysis leads to the conjecture that any large $N$ CFT$_2$ that is modular invariant and has the right low-energy density of states is dual to a gravitational theory with sub-AdS scale locality.Comment: 19 page

Geometry of the infalling causal patch

The firewall paradox states that an observer falling into an old black hole must see a violation of unitarity, locality, or the equivalence principle. Motivated by this remarkable conflict, we analyze the causal structure of black hole spacetimes in order to determine whether all the necessary ingredients for the paradox fit within a single observer's causal patch. We particularly focus on the question of whether the interior partner modes of the outgoing Hawking quanta can, in principle, be measured by an infalling observer. Since the relevant modes are spread over the entire sphere, we answer a simple geometrical question: can any observer see an entire sphere behind the horizon? We find that for all static black holes in 3+1 and higher dimensions, with any value of the cosmological constant, no single observer can see both the early Hawking radiation and the interior modes. We present a detailed description of the causal patch geometry of the Schwarzschild black hole in 3+1 dimensions, where an infalling observer comes closest to being able to measure the relevant modes.Comment: 21 pages, 7 figures. Minor edits/reformatting. Consistent with version published in PR

Casting Shadows on Holographic Reconstruction

In the context of the AdS/CFT correspondence, we study several holographic probes that relate information about the bulk spacetime to CFT data. The best-known example is the relation between minimal surfaces in the bulk and entanglement entropy of a subregion in the CFT. Building on earlier work, we identify "shadows" in the bulk: regions that are not illuminated by any of the bulk probes we consider, in the sense that the bulk surfaces do not pass through these regions. We quantify the size of the shadow in the near horizon region of a black hole and in the vicinity of a sufficiently dense star. The existence of shadows motivates further study of the bulk-boundary dictionary in order to identify CFT quantities that encode information about the shadow regions in the bulk. We speculate on the interpretation of our results from a dual field theory perspective.Comment: 42 pages, 38 figure

SUGESTÃO DE MÉTODO PARA CORRELACIONAR FORÇA MUSCULAR E ELETROMIOGRAFIA

O objetivo deste trabalho é apresentar um método de estimar qualitativamente a força muscular, a partir do sinal eletromiográfico de superfície, durante contrações isométricas. Para alcançar tal objetivo, uma série de processos matemáticos são efetuados sobre o sinal eletromiográfico, incluindo técnicas com filtros de janela móvel ponderada, transformando o eletromiograma em uma curva simples, similar ao sinal de força. Para testar o modelo proposto, foram feitas 216 diferentes situações de medida de força de mordida e eletromiografia, sobre os músculos masseter e temporal, distribuídas em um projeto de experimento. O parâmetro escolhido para medir a eficiência do método foi o coeficiente de correlação entre duas curvas. O método mostrou-se mais eficiente quanto maior a força empregada.This paper introduces a method for qualitatively analysis of the muscular strength, starting from a superficial electromiographical (EMG) signai during isometric contractions. To do so, a number of mathematical processes are carried out based on the electromiographic signai, among which, using a mobile window filter techniques in order to transform the EMG signai into a simple curve, similar to the force signai. In order to test the proposed model, 216 different situations of bite force and electromyography were carried out, on the temporal and masseter muscles, distributed along the experimental project. The reference chosen to measure the efficiency of the method was the correlation coefficient between both curves. The method showed that the higher the force employed, the greater its efficiency

Synchronous parallel kinetic Monte Carlo for continuum diffusion-reaction systems

A novel parallel kinetic Monte Carlo (kMC) algorithm formulated on the basis of perfect time synchronicity is presented. The algorithm is intended as a generalization of the standard n-fold kMC method, and is trivially implemented in parallel architectures. In its present form, the algorithm is not rigorous in the sense that boundary conflicts are ignored. We demonstrate, however, that, in their absence, or if they were correctly accounted for, our algorithm solves the same master equation as the serial method. We test the validity and parallel performance of the method by solving several pure diffusion problems (i.e. with no particle interactions) with known analytical solution. We also study diffusion-reaction systems with known asymptotic behavior and find that, for large systems with interaction radii smaller than the typical diffusion length, boundary conflicts are negligible and do not affect the global kinetic evolution, which is seen to agree with the expected analytical behavior. Our method is a controlled approximation in the sense that the error incurred by ignoring boundary conflicts can be quantified intrinsically, during the course of a simulation, and decreased arbitrarily (controlled) by modifying a few problem-dependent simulation parameters

Non‐canonical autophagy functions of ATG16L1 in epithelial cells limit lethal infection by influenza A virus

Influenza A virus (IAV) and SARS-CoV-2 (COVID-19) cause pandemic infections where cytokine storm syndrome and lung inflammation lead to high mortality. Given the high social and economic cost of respiratory viruses, there is an urgent need to understand how the airways defend against virus infection. Here we use mice lacking the WD and linker domains of ATG16L1 to demonstrate that ATG16L1-dependent targeting of LC3 to single-membrane, non-autophagosome compartments - referred to as non-canonical autophagy - protects mice from lethal IAV infection. Mice with systemic loss of non-canonical autophagy are exquisitely sensitive to low-pathogenicity IAV where extensive viral replication throughout the lungs, coupled with cytokine amplification mediated by plasmacytoid dendritic cells, leads to fulminant pneumonia, lung inflammation and high mortality. IAV was controlled within epithelial barriers where non-canonical autophagy reduced IAV fusion with endosomes and activation of interferon signalling. Conditional mouse models and ex vivo analysis showed that protection against IAV infection of lung was independent of phagocytes and other leucocytes. This establishes non-canonical autophagy in airway epithelial cells as a novel innate defence that restricts IAV infection and lethal inflammation at respiratory surfaces