Generalized geometry of two-dimensional vacua

We derive the conditions for unbroken supersymmetry for a Mink_2, (2,0) vacuum, arising from Type II supergravity on a compact eight-dimensional manifold M_8. When specialized to internal manifolds enjoying SU(4)xSU(4) structure the resulting system is elegantly rewritten in terms of generalized complex geometry. This particular class of vacua violates the correspondence between supersymmetry conditions and calibrations conditions of D branes (supersymmetry-calibrations correspondence). Our analysis includes and extends previous results about the failure of the supersymmetry-calibrations correspondence, and confirms the existence of a precise relation between such a failure and a subset of the supersymmetry conditions.Comment: 31 pages, 1 figure. v2: minor corrections, references adde

Pure spinor equations to lift gauged supergravity

We rewrite the equations for ten-dimensional supersymmetry in a way formally identical to a necessary and sufficient G-structure system in N=2 gauged supergravity, where all four-dimensional quantities are replaced by combinations of pure spinors and fluxes in the internal space. This provides a way to look for lifts of BPS solutions without having to reduce or even rewrite the ten-dimensional action. In particular this avoids the problem of consistent truncation, and the introduction of unphysical gravitino multiplets.Comment: 61 page

All AdS_7 solutions of type II supergravity

In M-theory, the only AdS_7 supersymmetric solutions are AdS_7 x S^4 and its orbifolds. In this paper, we find and classify new supersymmetric solutions of the type AdS_7 x M_3 in type II supergravity. While in IIB none exist, in IIA with Romans mass (which does not lift to M-theory) there are many new ones. We use a pure spinor approach reminiscent of generalized complex geometry. Without the need for any Ansatz, the system determines uniquely the form of the metric and fluxes, up to solving a system of ODEs. Namely, the metric on M_3 is that of an S^2 fibered over an interval; this is consistent with the Sp(1) R-symmetry of the holographically dual (1,0) theory. By including D8 brane sources, one can numerically obtain regular solutions, where topologically M_3 = S^3.Comment: 45 pages, 4 figures. v2: solution with single D8 added; references added; minor correction

Contrasting SYK-like Models

We contrast some aspects of various SYK-like models with large-$N$ melonic behavior. First, we note that ungauged tensor models can exhibit symmetry breaking, even though these are 0+1 dimensional theories. Related to this, we show that when gauged, some of them admit no singlets, and are anomalous. The uncolored Majorana tensor model with even $N$ is a simple case where gauge singlets can exist in the spectrum. We outline a strategy for solving for the singlet spectrum, taking advantage of the results in arXiv:1706.05364, and reproduce the singlet states expected in $N=2$. In the second part of the paper, we contrast the random matrix aspects of some ungauged tensor models, the original SYK model, and a model due to Gross and Rosenhaus. The latter, even though disorder averaged, shows parallels with the Gurau-Witten model. In particular, the two models fall into identical Andreev ensembles as a function of $N$. In an appendix, we contrast the (expected) spectra of AdS$_2$ quantum gravity, SYK and SYK-like tensor models, and the zeros of the Riemann Zeta function.Comment: 45 pages, 17 figures; v2: minor improvements and rearrangements, refs adde

New Supersymmetric Localizations from Topological Gravity

Supersymmetric field theories can be studied exactly on suitable off-shell supergravity backgrounds. We show that in two dimensions such backgrounds are identifiable with BRST invariant backgrounds of topological gravity coupled to an abelian topological gauge multiplet. This latter background is required for the consistent coupling of the topological `matter' YM theory to topological gravity. We make use of this topological point of view to obtain, in a simple and straightforward way, a complete classification of localizing supersymmetric backgrounds in two dimensions. The BRST invariant topological backgrounds are parametrized by both Killing vectors and $S^1$-equivariant cohomology of the 2-dimensional world-sheet. We reconstruct completely the supergravity backgrounds from the topological data: some of the supergravity fields are twisted versions of the topological backgrounds, but others are "composite", i.e. they are non-linear functionals of them. We recover all the known localizing 2-dimensional backgrounds and (infinitely) many more that have not been explored so far. We show that the supersymmetric $\Omega$-deformation is nothing but the background value of the ghost-for-ghost of topological gravity, a result which holds for other dimensions too. The new localizing backgrounds are characterized by non-trivial fluxes for both the graviphotons of the supergravity multiplet.Comment: 45 pages, 2 figures, revised introduction, version published on JHE

Frustrated Modernity: Kerewo Histories and Historical Consciousness, Gulf Province, Papua New Guinea

This thesis takes Kerewo historical consciousness as the frame for an analysis of the ways in which reflections on the past are fundamentally informed by orientations towards the future. In particular, I draw on various representations of the historical event of the killing of missionary James Chalmers in 1901, and its consequences, to explore local conceptions of modernity as a moral state withheld from Kerewo in the absence of a reconciliation with their past. This particular historical episode occupies a central place in contemporary Kerewo understandings of their perceived marginality within the post-Independence state of Papua New Guinea, and more widely in the world system. This marginality is manifest in Kerewo daily experience as a lack of services and infrastructure, despite the presence in the area of a multi-billion dollar resource extraction enterprise. The roots of this perceived lack of ‘modernity’ are sought in the colonial past, and articulated in moral terms through historical narratives. The colonial era emerges from these narratives as the period in which Kerewo were exposed to modernity in its ideological and material forms. Yet, the promises and expectation of an amelioration of life conditions engendered by several colonial discourses never materialised, leaving contemporary Kerewo people with a sense of frustrated modernity. It is the conflation of the colonial era with the idea of modernity that informs Kerewo historical consciousness, and thus it is by ritually addressing the colonial past that Kerewo people seek to transform the ‘frustrated modernity’ of the present into a better future. What emerges from the analysis of the historical and ethnographic material that constitutes the core of this dissertation is that historical consciousness consists fundamentally of a social process – which emerges from the social labour of history- making – to apprehend present conditions through reflection on the past informed by competing orientations toward the future

AdS_6 solutions of type II supergravity

Very few AdS_6 x M_4 supersymmetric solutions are known: one in massive IIA, and two IIB solutions dual to it. The IIA solution is known to be unique; in this paper, we use the pure spinor approach to give a classification for IIB supergravity. We reduce the problem to two PDEs on a two-dimensional space Sigma. M_4 is then a fibration of S^2 over Sigma; the metric and fluxes are completely determined in terms of the solution to the PDEs. The results seem likely to accommodate near-horizon limits of (p,q)-fivebrane webs studied in the literature as a source of CFT_5's. We also show that there are no AdS_6 solutions in eleven-dimensional supergravity.Comment: 37 pages; v2: references and equations (5.1) added, version published in Journal of High Energy Physics; v3: equation (5.1b) correcte

Expectation values from any quantum measurement

We present a method to estimate the mean value of any observable and its higher moments by measuring any other observable. This method is general and can be applied to any quantum system. In the case of estimating the mean energy of an isolated system, the estimate can be further improved by measuring the other observable at different times. Intuitively, this method uses interplay and correlations between the measured and the estimated observable, and the state of the system. We provide two bounds: one that is looser but analytically computable, and one that is tighter but requires solving a non-convex optimization problem. The method can be used to estimate expectation values and related quantities such as temperature and work in setups in which performing measurements in a highly entangled basis is difficult, finding use in state-of-the-art quantum simulators. As a demonstration, we show that in Heisenberg and Ising models of ten sites in the localized phase, performing two-qubit measurements excludes 97.5\% and 96.7\% of the possible range of energies, respectively, when estimating the ground state energy.Comment: 5+9 pages, 5 figures, 5 tables. Questions and comments are welcom