International School for Advanced Studies

About: International School for Advanced Studies is a education organization based out in Trieste, Friuli-Venezia Giulia, Italy. It is known for research contribution in the topics: Galaxy & Dark matter. The organization has 3751 authors who have published 13433 publications receiving 588454 citations. The organization is also known as: SISSA & Scuola Internazionale Superiore di Studi Avanzati.

Fundamental Algebraic Geometry

Abstract: Grothendieck topologies, fibered categories and descent theory: Introduction Preliminary notions Contravariant functors Fibered categories Stacks Construction of Hilbert and Quot schemes: Construction of Hilbert and Quot schemes Local properties and Hilbert schemes of points: Introduction Elementary deformation theory Hilbert schemes of points Grothendieck's existence theorem in formal geometry with a letter of Jean-Pierre Serre: Grothendieck's existence theorem in formal geometry The Picard scheme: The Picard scheme Bibliography Index

Theory of the electric polarization in crystals

Abstract: Contrary to common textbook statements, the macroscopic electric polarization of a crystal cannot be unambiguously defined as the dipole of a unit cell. The only measurable quantities are either derivatives of the polarization (dielectric susceptibility, Born effective charges, piezoelectricity, pyroelectricity) or finite differences (ferroelectricity). The differential concept is a basic one in theoretical work too. I sketch here the basic theory and the state of the art in its implementation to real materials, both for induced and spontaneous polarization; for the latter case, I also propose a novel approach.

Planck intermediate results: XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds

Abstract: Within ten nearby (d < 450 pc) Gould belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the gas column density structures, quantified by the gradient of the column density, NH. The selected regions, covering several degrees in size, are analysed at an effective angular resolution of 10′ FWHM, thus sampling physical scales from 0.4 to 40 pc in the nearest cloud. The column densities in the selected regions range from NH≈ 1021 to1023 cm-2, and hence they correspond to the bulk of the molecular clouds. The relative orientation is evaluated pixel by pixel and analysed in bins of column density using the novel statistical tool called “histogram of relative orientations”. Throughout this study, we assume that the polarized emission observed by Planck at 353 GHz is representative of the projected morphology of the magnetic field in each region, i.e., we assume a constant dust grain alignment efficiency, independent of the local environment. Within most clouds we find that the relative orientation changes progressively with increasing NH, from mostly parallel or having no preferred orientation to mostly perpendicular. In simulations of magnetohydrodynamic turbulence in molecular clouds this trend in relative orientation is a signature of Alfvenic or sub-Alfvenic turbulence, implying that the magnetic field is significant for the gas dynamics at the scales probed by Planck. We compare the deduced magnetic field strength with estimates we obtain from other methods and discuss the implications of the Planck observations for the general picture of molecular cloud formation and evolution.

Supermassive black hole demography: the match between the local and accreted mass functions

Abstract: We have performed a detailed analysis of the local supermassive black hole (SMBH) mass function based on both kinematic and photometric data and we have derived an accurate analytical fit in the range 10 6 M BH/M� 5 × 10 9 .W efind a total SMBH mass density of (4.2 ± 1.1) × 10 5 MMpc −3 , about 25 per cent of which is contributed by SMBHs residing in bulges of late-type galaxies. Exploiting up-to-date luminosity functions of hard X-ray and optically selected active galactic nuclei (AGNs), we have studied the accretion history of the SMBH population. If most of the accretion occurs at constant ˙ MBH/MBH ,a s in the case of Eddington-limited accretion and consistent with recent observational estimates, the local SMBH mass function is fully accounted for by mass accreted by X-ray selected AGNs, with bolometric corrections indicated by current observations and a standard mass-to-light conversion efficiency � � 10 per cent. The analysis of the accretion history highlights that the most massive BHs (associated with bright optical quasi-stellar objects) accreted their mass faster and at higher redshifts (typically at z > 1.5), while the lower-mass BHs responsible for most of the hard X-ray background have mostly grown at z < 1.5. The accreted mass function matches the local SMBH mass function if, during the main accretion phases, � � 0.09 (+0.04, −0.03) and the Eddington ratio λ = L/L Edd � 0.3 (+0.3, −0.1) (68 per cent confidence errors). The visibility time, during which AGNs are luminous enough to be detected by the currently available X-ray surveys, ranges from �0.1 Gyr for present-day BH masses M 0 � 10 6 Mto �0.3 Gyr for M 0 10 9 M� . The mass accreted during luminous phases is 25-30 per cent even if we assume extreme values of � (� � 0.3-0.4). An unlikely fine tuning of the parameters would be required to account for the local SMBH mass function accommodating a dominant contribution from 'dark' BH growth (due, for example, to BH coalescence). Ke yw ords: black hole physics - galaxies: active - galaxies: evolution - galaxies: nuclei - cosmology: miscellaneous.