17520420
Gauge invariant regularization in the AdS/CFT correspondence and ghost D-branes
A field theoretic understanding of how the radial direction in the AdS/CFT correspondence plays the role of a gauge invariant measure of energy scale has long been missing. In SU(N) Yang–Mills, a realization of a gauge invariant cutoff has been achieved by embedding the theory in spontaneously broken SU(N|N) gauge theory. With the recent discovery of ghost D-branes an AdS/CFT correspondence version of this scheme is now possible. We show that a very simple construction precisely ties the two pictures together providing a concrete understanding of the radial RG flow on the field theory side.
13411572
New Developments in the Continuous Renormalization Group
Over the last several years, there has been a resurgence of interest in using non-perturbative approximation methods based on Wilson's continuous renormalization group. In this lecture, I review progress particularly in the past year, concentrating on theoretical issues in the structure of the exact renormalization group and its approximations.
14167872
Exact scheme independence at one loop
The requirement that the quantum partition function be invariant under a renormalization group transformation results in a wide class of exact renormalization group equations, differing in the form of the kernel. Physical quantities should not be sensitive to the particular choice of the kernel. We demonstrate this scheme independence in four dimensional scalar field theory by showing that, even with a general kernel, the one-loop beta function may be expressed only in terms of the effective action vertices, and thus, under very general conditions, the universal result is recovered.
120318744
General covariance and open string interactions
Abstract It has been suggested that Witten's open string cubic interaction is independent of the background geometry. We investigate this suggestion in detail with a view to understanding the role of closed strings in Witten's open string field theory. The standard oscillator formulation of the vertex requires the use of a metric, if it is to be generally covariant, indicating that closed string interactions are required. However by changing to variables better suited to treating the midpoint, we show explicitly that it is possible to transform away all reference to the background metric. This supports the assertion that the cubic action (of Horowitz, Lykken, Rohm and Strominger) can also describe closed strings.
15153074
An exact RG formulation of quantum gauge theory
A gauge invariant Wilsonian effective action is constructed for pure SU(N) Yang-Mills theory by formulating the corresponding flow equation. Manifestly gauge invariant calculations can be performed i.e. without gauge fixing or ghosts. Regularisation is implemented in a novel way which realises a spontaneously broken SU(N|N) supergauge theory. As an example we sketch the computation of the one-loop ? function, performed for the first time without any gauge fixing.
15360602
Two phases for compact U(1) pure gauge theory in three dimensions.
We show that if actions more general than the usual simple plaquette action ({approximately}{ital F}{sup 2}{sub {mu}{nu}}) are considered, then compact U(1) {ital pure} gauge theory in three Euclidean dimensions can have two phases. Both phases are confining phases; however, in one phase the monopole condensate spontaneously {open_quote}{open_quote}magnetizes.{close_quote}{close_quote} For a certain range of parameters the phase transition is continuous, allowing the definition of a strong coupling continuum limit. We note that these observations have relevance to the {open_quote}{open_quote}fictitious{close_quote}{close_quote} gauge field theories of strongly correlated electron systems, such as those describing high-{ital T}{sub {ital c}} superconductors. {copyright} {ital 1996 The American Physical Society.}
55583676
EAGLE multi-object AO concept study for the E-ELT
EAGLE is the multi-object spatially-resolved near-IR spectrograph instrument concept for the E- ELT, relying on a distributed Adaptive Optics, so-called Multi Object Adaptive Optics. This paper presents the results of a phase A study. Using 84x84 actuator deformable mirrors, the performed analysis demonstrates that 6 laser guide stars and up to 5 natural guide stars of magnitude R < 17, picked-up in a 7.3 � diameter patrol field of view, allow us to obtain an overall performance in terms of Ensquared Energy of 35% in a 75x75mas 2 spaxel at H band whatever the target direction in the centred 5 � science field for median seeing conditions. The computed sky coverage at galactic latitudes |b |∼ 60 is close to 90%.
17891976
A Shack¿Hartmann wavefront sensor projected on to the sky with reduced focal anisoplanatism
A method for producing a laser guide star wavefront sensor for adaptive optics with reduced focal anisoplanatism is presented. A theoretical analysis and numerical simulations have been carried out and the results are presented. The technique, named Sky-Projected Laser Array Shack-Hartmann (SPLASH), is shown to suffer considerably less from focal anisoplanatism than a conventional laser guide star system. The method is potentially suitable for large telescope apertures (∼8 m), and possibly for extremely large telescopes.
2587128
Shack-Hartmann sensor improvement using optical binning.
We present a design improvement for a recently proposed type of Shack-Hartmann wavefront sensor that uses a cylindrical (lenticular) lenslet array. The improved sensor design uses optical binning and requires significantly fewer detector pixels than the corresponding conventional or cylindrical Shack-Hartmann sensor, and so detector readout noise causes less signal degradation. Additionally, detector readout time is significantly reduced, which reduces the latency for closed loop systems and data processing requirements. We provide simple analytical noise considerations and Monte Carlo simulations, we show that the optically binned Shack-Hartmann sensor can offer better performance than the conventional counterpart in most practical situations, and our design is particularly suited for use with astronomical adaptive optics systems.