Heterotic T-Duality and the Renormalization Group

We consider target space duality transformations for heterotic sigma models and strings away from renormalization group fixed points. By imposing certain consistency requirements between the T-duality symmetry and renormalization group flows, the one loop gauge beta function is uniquely determined, without any diagram calculations. Classical T-duality symmetry is a valid quantum symmetry of the heterotic sigma model, severely constraining its renormalization flows at this one loop order. The issue of heterotic anomalies and their cancelation is addressed from this duality constraining viewpoint.Comment: 17 pages, Late

Two-Loop Beta Functions Without Feynman Diagrams

Starting from a consistency requirement between T-duality symmetry and renormalization group flows, the two-loop metric beta function is found for a d=2 bosonic sigma model on a generic, torsionless background. The result is obtained without Feynman diagram calculations, and represents further evidence that duality symmetry severely constrains renormalization flows.Comment: 4 pp., REVTeX. Added discussion on scheme (in)dependence; final version to appear in Phys. Rev. Let

An apodizing phase plate coronagraph for VLT/NACO

We describe a coronagraphic optic for use with CONICA at the VLT that provides suppression of diffraction from 1.8 to 7 lambda/D at 4.05 microns, an optimal wavelength for direct imaging of cool extrasolar planets. The optic is designed to provide 10 magnitudes of contrast at 0.2 arcseconds, over a D-shaped region in the image plane, without the need for any focal plane occulting mask.Comment: 9 pages, 5 figures, to appear in Proc. SPIE Vol. 773

Extended Gravity Theories and the Einstein-Hilbert Action

I discuss the relation between arbitrarily high-order theories of gravity and scalar-tensor gravity at the level of the field equations and the action. I show that $(2n+4)$-order gravity is dynamically equivalent to Brans-Dicke gravity with an interaction potential for the Brans-Dicke field and $n$ further scalar fields. This scalar-tensor action is then conformally equivalent to the Einstein-Hilbert action with $n+1$ scalar fields. This clarifies the nature and extent of the conformal equivalence between extended gravity theories and general relativity with many scalar fields.Comment: 12 pages, Plain Latex, SUSSEX-AST-93/7-

Confirmation and characterization of the protoplanet HD100546 b - Direct evidence for gas giant planet formation at 50 au

We present the first multi-wavelength, high-contrast imaging study confirming the protoplanet embedded in the disk around the Herbig Ae/Be star HD100546. The object is detected at $L'$ ($\sim 3.8\,\mu m$) and $M'$ ($\sim 4.8\,\mu m$), but not at $K_s$ ($\sim 2.1\,\mu m$), and the emission consists of a point source component surrounded by spatially resolved emission. For the point source component we derive apparent magnitudes of $L'=13.92\pm0.10$ mag, $M'=13.33\pm0.16$ mag, and $K_s>15.43\pm0.11$ mag (3$\sigma$ limit), and a separation and position angle of $(0.457\pm0.014)"$ and $(8.4\pm1.4)^\circ$, and $(0.472\pm0.014)"$ and $(9.2\pm1.4)^\circ$ in $L'$ and $M'$, respectively. We demonstrate that the object is co-moving with HD100546 and can reject any (sub-)stellar fore-/background object. Fitting a single temperature blackbody to the observed fluxes of the point source component yields an effective temperature of $T_{eff}=932^{+193}_{-202}$ K and a radius for the emitting area of $R=6.9^{+2.7}_{-2.9}$ R$_{\rm Jupiter}$. The best-fit luminosity is $L=(2.3^{+0.6}_{-0.4})\cdot 10^{-4}\,L_{\rm Sun}$. We quantitatively compare our findings with predictions from evolutionary and atmospheric models for young, gas giant planets, discuss the possible existence of a warm, circumplanetary disk, and note that the de-projected physical separation from the host star of $(53\pm2)$ au poses a challenge standard planet formation theories. Considering the suspected existence of an additional planet orbiting at $\sim$13--14 au, HD100546 appears to be an unprecedented laboratory to study the formation of multiple gas giant planets empirically.Comment: Accepted for publication in ApJ; 13 pages incl. 9 figures, 2 tables and references in ApJ-styl

Classical and Quantum Solutions and the Problem of Time in R2R^2 Cosmology

We have studied various classical solutions in $R^2$ cosmology. Especially we have obtained general classical solutions in pure $R^2$\ cosmology. Even in the quantum theory, we can solve the Wheeler-DeWitt equation in pure $R^2$\ cosmology exactly. Comparing these classical and quantum solutions in $R^2$\ cosmology, we have studied the problem of time in general relativity.Comment: 17 pages, latex, no figure, one reference is correcte

Status and new operation modes of the versatile VLT/NACO

This paper aims at giving an update on the most versatile adaptive optics fed instrument to date, the well known and successful NACO . Although NACO is only scheduled for about two more years at the Very Large Telescope (VLT), it keeps on evolving with additional operation modes bringing original astronomical results. The high contrast imaging community uses it creatively as a test-bench for SPHERE and other second generation planet imagers. A new visible wavefront sensor (WFS) optimized for Laser Guide Star (LGS) operations has been installed and tested, the cube mode is more and more requested for frame selection on bright sources, a seeing enhancer mode (no tip/tilt correction) is now offered to provide full sky coverage and welcome all kind of extragalactic applications, etc. The Instrument Operations Team (IOT) and Paranal engineers are currently working hard at maintaining the instrument overall performances but also at improving them and offering new capabilities, providing the community with a well tuned and original instrument for the remaining time it is being used. The present contribution delivers a non-exhaustive overview of the new modes and experiments that have been carried out in the past months.Comment: 10 pages, 7 figures, SPIE 2010 Astronomical Instrumentation Proceedin