121,874 research outputs found
On the spatial interaction of visual working memory and attention: Evidence for a global effect from memory-guided saccades
No full textHerwig A, Beisert M, Schneider WX. On the spatial interaction of visual working memory and attention: Evidence for a global effect from memory-guided saccades. Journal of Vision. 2010;10(5):1-10.Recent work indicates that covert visual attention and eye movements on the one hand, and covert visual attention and visual working memory on the other hand are closely interrelated. Two experiments address the question whether all three processes draw on the same spatial representations. Participants had to memorize a target location for a subsequent memory-guided saccade. During the memory interval, task-irrelevant distractors were briefly flashed on some trials either near or remote to the memory target. Results showed that the previously flashed distractors attract the saccade's landing position. However, attraction was only found, if the distractor was presented within a sector of +/- 20 degrees around the target axis, but not if the distractor was presented outside this sector. This effect strongly resembles the global effect in which saccades are directed to intermediate locations between a target and a simultaneously presented neighboring distractor stimulus. It is argued that covert visual attention, eye movements, and visual working memory recruit the same spatial mechanisms that can probably be ascribed to attentional priority maps
On Yangian Symmetries in Planar N=4 SYM
No full textPlanar N=4 supersymmetric Yang-Mills theory appears to be perturbatively integrable. This work reviews integrability in terms of a Yangian algebra and compares the application to the problems of anomalous dimensions and scattering amplitudes
The Complete One-Loop Dilatation Operator of N=4 Super Yang-Mills Theory
No full textWe continue the analysis of hep-th/0303060 in the one-loop sector and present the complete psu(2,2|4) dilatation operator of N=4 Super Yang-Mills theory. This operator generates the matrix of one-loop anomalous dimensions for all local operators in the theory. Using an oscillator representation we show how to apply the dilatation generator to a generic state. By way of example, we determine the planar anomalous dimensions of all operators up to and including dimension 5.5, where we also find some evidence for integrability. Finally, we investigate a number of subsectors of N=4 SYM in which the dilatation operator simplifies. Among these we find the previously considered so(6) and su(2) subsectors, a su(2|4) subsector isomorphic to the BMN matrix model at one-loop, a su(2|3) supersymmetric subsector of nearly eighth-BPS states and, last but not least, a non-compact sl(2) subsector whose dilatation operator lifts uniquely to the full theory
Higher-Loop Integrability in N=4 Gauge Theory
No full textThe dilatation operator measures scaling dimensions of local operator in a conformal field theory. Algebraic methods of constructing the dilatation operator in four-dimensional N=4 gauge theory are reviewed. These led to the discovery of novel integrable spin chain models in the planar limit. Making use of Bethe ansaetze, a superficial discrepancy in the AdS/CFT correspondence was found, we discuss this issue and give a possible resolution
Review of AdS/CFT Integrability: An Overview
No full textThis is the introductory chapter of a review collection on integrability in the context of the AdS/CFT correspondence. In the collection, we present an overview of the achievements and the status of this subject as of the year 2010. © 2011 Springer
Review of AdS/CFT Integrability, Chapter VI.1: Superconformal Symmetry
No full textAspects of the D=4, N=4 superconformal symmetry relevant to the AdS/CFT duality and integrability are reviewed. These include the Lie superalgebra psu(2,2|4), its representations, conformal transformations and correlation functions in N=4 super Yang-Mills theory as well as an illustration of the AdS5xS5 superspace on which the dual string theory is formulated
Spin Chain for Quantum Strings
No full textWe review and compare the integrable structures in N=4 gauge theory and string theory on AdS5xS5. Recently, Bethe ansaetze for gauge theory/weak coupling and string theory/strong coupling were proposed to describe scaling dimensions in the su(2) subsector. Here we investigate the Bethe equations for quantum string theory, naively extrapolated to weak coupling. Excitingly, we find a spin chain Hamiltonian similar, but not equal, to the gauge theory dilatation operator
The su(2|3) Dynamic Spin Chain
No full textThe complete one-loop, planar dilatation operator of the N=4 superconformal gauge theory was recently derived and shown to be integrable. Here, we present further compelling evidence for a generalisation of this integrable structure to higher orders of the coupling constant. For that we consider the su(2|3) subsector and investigate the restrictions imposed on the spin chain Hamiltonian by the symmetry algebra. This allows us to uniquely fix the energy shifts up to the three-loop level and thus prove the correctness of a conjecture in hep-th/0303060. A novel aspect of this spin chain model is that the higher-loop Hamiltonian, as for N=4 SYM in general, does not preserve the number of spin sites. Yet this dynamic spin chain appears to be integrable
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