Mastering the Master Space

Supersymmetric gauge theories have an important but perhaps under-appreciated notion of a master space, which controls the full moduli space. For world-volume theories of D-branes probing a Calabi-Yau singularity X the situation is particularly illustrative. In the case of one physical brane, the master space F is the space of F-terms and a particular quotient thereof is X itself. We study various properties of F which encode such physical quantities as Higgsing, BPS spectra, hidden global symmetries, etc. Using the plethystic program we also discuss what happens at higher number N of branes. This letter is a summary and some extensions of the key points of a longer companion paper arXiv:0801.1585.Comment: 10 pages, 1 Figur

Quiver GIT for varieties with tilting bundles

In the setting of a variety X admitting a tilting bundle T we consider the problem of constructing X as a quiver GIT quotient of the algebra A:=EndX(T)opA:=EndX(T)op . We prove that if the tilting equivalence restricts to a bijection between the skyscraper sheaves of X and the closed points of a quiver representation moduli functor for A=EndX(T)opA=EndX(T)op then X is indeed a fine moduli space for this moduli functor, and we prove this result without any assumptions on the singularities of X. As an application we consider varieties which are projective over an affine base such that the fibres are of dimension 1, and the derived pushforward of the structure sheaf on X is the structure sheaf on the base. In this situation there is a particular tilting bundle on X constructed by Van den Bergh, and our result allows us to reconstruct X as a quiver GIT quotient for an easy to describe stability condition and dimension vector. This result applies to flips and flops in the minimal model program, and in the situation of flops shows that both a variety and its flop appear as moduli spaces for algebras produced from different tilting bundles on the variety. We also give an application to rational surface singularities, showing that their minimal resolutions can always be constructed as quiver GIT quotients for specific dimension vectors and stability conditions. This gives a construction of minimal resolutions as moduli spaces for all rational surface singularities, generalising the G-Hilbert scheme moduli space construction which exists only for quotient singularities

On the geometry of C^3/D_27 and del Pezzo surfaces

We clarify some aspects of the geometry of a resolution of the orbifold X = C3/D_27, the noncompact complex manifold underlying the brane quiver standard model recently proposed by Verlinde and Wijnholt. We explicitly realize a map between X and the total space of the canonical bundle over a degree 1 quasi del Pezzo surface, thus defining a desingularization of X. Our analysis relys essentially on the relationship existing between the normalizer group of D_27 and the Hessian group and on the study of the behaviour of the Hesse pencil of plane cubic curves under the quotient.Comment: 23 pages, 5 figures, 2 tables. JHEP style. Added references. Corrected typos. Revised introduction, results unchanged

Face-space: A unifying concept in face recognition research

The concept of a multidimensional psychological space, in which faces can be represented according to their perceived properties, is fundamental to the modern theorist in face processing. Yet the idea was not clearly expressed until 1991. The background that led to the development of face-space is explained, and its continuing influence on theories of face processing is discussed. Research that has explored the properties of the face-space and sought to understand caricature, including facial adaptation paradigms, is reviewed. Face-space as a theoretical framework for understanding the effect of ethnicity and the development of face recognition is evaluated. Finally, two applications of face-space in the forensic setting are discussed. From initially being presented as a model to explain distinctiveness, inversion, and the effect of ethnicity, face-space has become a central pillar in many aspects of face processing. It is currently being developed to help us understand adaptation effects with faces. While being in principle a simple concept, face-space has shaped, and continues to shape, our understanding of face perception

Remarks on quiver gauge theories from open topological string theory

We study effective quiver gauge theories arising from a stack of D3-branes on certain Calabi-Yau singularities. Our point of view is a first principle approach via open topological string theory. This means that we construct the natural A-infinity-structure of open string amplitudes in the associated D-brane category. Then we show that it precisely reproduces the results of the method of brane tilings, without having to resort to any effective field theory computations. In particular, we prove a general and simple formula for effective superpotentials

Refinement in response to validation.

Knowledge-based systems (KBSs) are being applied in ever increasing numbers. In parallel with the development of knowledge acquisition tools is the demand for mechanisms to assure their quality, particularly in safety critical applications. Quality assurance is achieved by checking the contents of the KBS at various stages throughout its life cycle. But how does testing for quality assurance aggravate the already well-known knowledge acquisition bottleneck? The partial automation of checking and correcting the knowledge base (KB) is an obvious approach to reducing the bottleneck, but also a more routine treatment of checking will provide improved facilities for quality assurance. In addition to identifying the occurrence offaults, this paper suggests that responding to faults identified by validation is both useful and important. Therefore, refinement should be thought of as a companion to validation

Resolving the role of carbonaceous material in gold precipitation in metasediment-hosted orogenic gold deposits

Carbonaceous material (CM) is commonly associated with gold and sulfides in metasediment-hosted orogenic gold deposits. The role of CM in Au deposition is controversial; CM has been proposed to contribute to gold deposition by reducing Au bisulfide complexes, or by facilitating sulfidation, which destabilizes Au in bisulfide complexes with resultant Au deposition. Integration of petrographic observations, thermodynamic models, and geochemical data from metasediment-hosted orogenic gold deposits in New Zealand, Australia, Canada, and West Africa reveals genetic links between sulfides, CM, and mineralization. The results are consistent with the coexistence of CM and pyrite as a consequence of their codeposition from ore fluids, with a minor proportion of CM originally in situ in the host rocks. Au is deposited when pyrite and CM deposition decreases H2S concentration in ore fluids, destabilizing Au(HS)2-complexes. Most CM in gold deposits is deposited from CO2 and CH4 in ore fluids. These findings are applicable to similar deposits worldwide

Noble gases fingerprint a metasedimentary fluid source in the Macraes orogenic gold deposit, New Zealand

© 2016 Springer-Verlag Berlin Heidelberg The world-class Macraes orogenic gold deposit (∼10 Moz resource) formed during the late metamorphic uplift of a metasedimentary schist belt in southern New Zealand. Mineralising fluids, metals and metalloids were derived from within the metasedimentary host. Helium and argon extracted from fluid inclusions in sulphide mineral grains (three crush extractions from one sample) have crustal signatures, with no evidence for mantle input (R/Ra = 0.03). Xenon extracted from mineralised quartz samples provides evidence for extensive interaction between fluid and maturing organic material within the metasedimentary host rocks, with 132Xe/36Ar ratios up to 200 times greater than air. Similarly, I/Cl ratios for fluids extracted from mineralised quartz are similar to those of brines from marine sediments that have interacted with organic matter and are ten times higher than typical magmatic/mantle fluids. The Macraes mineralising fluids were compositionally variable, reflecting either mixing of two different crustal fluids in the metasedimentary pile or a single fluid type that has had varying degrees of interaction with the host metasediments. Evidence for additional input of meteoric water is equivocal, but minor meteoric incursion cannot be discounted. The Macraes deposit formed in a metasedimentary belt without associated coeval magmatism, and therefore represents a purely crustal metamorphogenic end member in a spectrum of orogenic hydrothermal processes that can include magmatic and/or mantle fluid input elsewhere in the world. There is no evidence for involvement of minor intercalated metabasic rocks in the Macraes mineralising system. Hydrothermal fluids that formed other, smaller, orogenic deposits in the same metamorphic belt have less pronounced noble gas and halogen evidence for crustal fluid-rock interaction than at Macraes, but these deposits also formed from broadly similar metamorphogenic processes

Consultant-2: pre- and post processing of machine learning applications.

The knowledge acquisition bottleneck in the development of large knowledge-based applications has not yet been resolved. One approach which has been advocated is the systematic use of Machine Learning (ML) techniques. However, ML technology poses difficulties to domain experts and knowledge engineers who are not familiar with it. This paper discusses Consultant-2, a system which makes a first step towards providing system support for a pre- and post-processing methodology where a cyclic process of experiments with an ML tool, its data, data description language and parameters attempts to optimize learning performance. Consultant-2 has been developed to support the use of Machine Learning Toolbox (MLT), an integrated architecture of 10 ML tools, and has evolved from a series of earlier systems. Consultant-0 and Consultant-1 had knowledge only about how to choose an ML algorithm based on the nature of the domain data. Consultant-2 is the most sophisticated. It, additionally, has knowledge about how ML experts and domain experts pre-process domain data before a run with the ML algorithm, and how they further manipulate the data and reset parameters after a run of the selected ML algorithm, to achieve a more acceptable result. How these several KBs were acquired and encoded is described. In fact, this knowledge has been acquired by interacting both with the ML algorithm developers and with domain experts who had been using the MLT toolbox on real-world tasks. A major aim of the MLT project was to enable a domain expert to use the toolbox directly; i.e. without necessarily having to involve either a ML specialist or a knowledge engineer. Consultant's principal goal was to provide specific advice to ease this process