A sub-product construction of Poincare-Einstein metrics

Given any two Einstein (pseudo-)metrics, with scalar curvatures suitably related, we give an explicit construction of a Poincar\'e-Einstein (pseudo-)metric with conformal infinity the conformal class of the product of the initial metrics. We show that these metrics are equivalent to ambient metrics for the given conformal structure. The ambient metrics have holonomy that agrees with the conformal holonomy. In the generic case the ambient metric arises directly as a product of the metric cones over the original Einstein spaces. In general the conformal infinity of the Poincare metrics we construct is not Einstein, and so this describes a class of non-conformally Einstein metrics for which the (Fefferman-Graham) obstruction tensor vanishes.Comment: 23 pages Minor correction to section 5. References update

Exact beta function from the holographic loop equation of large-N QCD_4

We construct and study a previously defined quantum holographic effective action whose critical equation implies the holographic loop equation of large-N QCD_4 for planar self-avoiding loops in a certain regularization scheme. We extract from the effective action the exact beta function in the given scheme. For the Wilsonean coupling constant the beta function is exacly one loop and the first coefficient agrees with its value in perturbation theory. For the canonical coupling constant the exact beta function has a NSVZ form and the first two coefficients agree with their value in perturbation theory.Comment: 42 pages, latex. The exponent of the Vandermonde determinant in the quantum effective action has been changed, because it has been employed a holomorphic rather than a hermitean resolution of identity in the functional integral. Beta function unchanged. New explanations and references added, typos correcte

General Argyres-Douglas Theory

We construct a large class of Argyres-Douglas type theories by compactifying six dimensional (2,0) A_N theory on a Riemann surface with irregular singularities. We give a complete classification for the choices of Riemann surface and the singularities. The Seiberg-Witten curve and scaling dimensions of the operator spectrum are worked out. Three dimensional mirror theory and the central charges a and c are also calculated for some subsets, etc. Our results greatly enlarge the landscape of N=2 superconformal field theory and in fact also include previous theories constructed using regular singularity on the sphere.Comment: 55 pages, 20 figures, minor revision and typos correcte

Twisted local systems solve the (holographic) loop equation of large-N QCD_4

We construct a holographic map from the loop equation of large-N QCD in d=2 and d=4, for planar self-avoiding loops, to the critical equation of an equivalent effective action. The holographic map is based on two ingredients: an already proposed holographic form of the loop equation, such that the quantum contribution is reduced to a regularized residue; a new conformal map from the region encircled by the based loop to a cuspidal fundamental domain in the upper half-plane, such that the regularized residue vanishes at the cusp. As a check, we study the first coefficient of the beta function and that part of the second coefficient which arises from the rescaling anomaly, in passing from the Wilsonian to the canonically normalised (holographic) effective action.Comment: 42 pages, latex; abstract shortened and a reference added as suggested by the referee; typos in Eq.(72,76,77,82,83,84) correcte

Status report of the accelerator for multiply charged ions in Grenoble

International audienceThe status report of the Multiply Charged Ion Accelerator of the CEA-Grenoble is presented. This facility is devoted to the production of multiply charged ions (up to Xe31+) in the low energy domain (1–20 q keV). A new 14.5 GHz high magnetic field electron cyclotron resonance ion source of the Caprice type has been installed, the transmission of the beam line increased, resulting in a large enhancement of the available beam intensity. Ion selection and deceleration are simplified. Emittances as low as before are achieved. Performances for various beams are presented, together with updated beam emittance measurements. The intensity enhancement is especially large for highly charged ion beams like Ar17+ (100 times more intensity), and enables routine delivery to experiments of more than 10 μA of Xe25+ at 20 q keV in 20 π mm mrad. The range of available charge states was extended to Xe31+ (with a reasonable intensity of 180 nA). Future prospects include the extension of the energy range down to a few q eV

Submicronic Laue diffraction to determine in-depth strain in very closely matched complex HgCdTe/CdZnTe heterostructures with a 10 −5 resolution

International audienc

Quaternionic Heisenberg groups as naturally reductive homogeneous spaces

In this paper, we describe the geometry of the quaternionic Heisenberg groups from a Riemannian viewpoint. We show, in all dimensions, that they carry an almost 3- contact metric structure which allows us to define the metric connection that equips these groups with the structure of a naturally reductive homogeneous space. It turns out that this connection, which we shall call the canonical connection because of its analogy to the 3-Sasaki case, preserves the horizontal and vertical distributions and even the quaternionic contact (qc) structure of the quaternionic Heisenberg groups. We focus on the 7-dimensional case and prove that the canonical connection can also be obtained by means of a cocalibrated G2 structure. We then study the spinorial properties of this group and present the noteworthy fact that it is the only known example of a manifold which carries generalized Killing spinors with three different eigenvalues.DFG (Alemanha

A new white beam x-ray microdiffraction setup on the BM32 beamline at the European Synchrotron Radiation Facility

International audienceA white beam microdiffraction setup has been developed on the bending magnet source BM32 at the European Synchrotron Radiation Facility. The instrument allows routine submicrometer beam diffraction to perform orientation and strain mapping of polycrystalline samples. The setup features large source to optics distances allowing large demagnification ratios and small beam sizes. The optics of the beamline is used for beam conditioning upstream a secondary source, suppressing any possible interference of beam conditioning on beam size and position. The setup has been designed for an easy and efficient operation with position control tools embedded on the sample stage, a high magnification large aperture optical microscope, and fast readout detectors. Switching from the white beam mode to the monochromatic mode is made easy by an automatic procedure and allows the determination of both the deviatoric and hydrostatic strain tensors