100 research outputs found
Pseudohermitian invariants and classification of CR mappings in generalized ellipsoids
We discuss the problem of classifying all local CR diffeomorphisms of a
strictly pseudoconvex surface. Our method exploits the Tanaka--Webster
pseudohermitian invariants, their transformation formulae, and the Chern--Moser
invariants. Our main application concerns a class of generalized ellipsoids
where we classify all local CR mappings.Comment: Accepted version, to appear on J. Math. Soc. Japa
Detectability of substellar companions around white dwarfs with Gaia
To date not a single-bona fide planet has been identified orbiting a single
white dwarf. In fact we are ignorant about the final configuration of >95% of
planetary systems. Theoretical models predict a gap in the final distribution
of orbital periods, due to the opposite effects of stellar mass loss (planets
pushed outwards) and tidal interactions (planets pushed inwards) during the RGB
and the AGB stellar expansions. Over its five year primary mission, Gaia is
expected to astrometrically detect the first (few tens of) WD massive
planets/BDs giving first evidence that WD planets exist, at least those in wide
orbits. In this article we present preliminary results of our simulations of
what Gaia should be able to find in this field.Comment: Proceedings of the 19th European Workshop on White Dwarfs (Montr\'eal
11-15 August 2014). To appear on ASP Conference Series; 4 pages, 2 figure
The Gaia Data Release 1 parallaxes and the distance scale of Galactic planetary nebulae
In this paper we gauge the potentiality of Gaia in the distance scale
calibration of planetary nebulae (PNe) by assessing the impact of DR1
parallaxes of central stars of Galactic PNe (CSPNe) against known physical
relations. For selected PNe targets with state-of-the-art data on angular sizes
and fluxes, we derive the distance-dependent parameters of the classical
distance scales, i.e., physical radii and ionized masses, from DR1 parallaxes;
we propagate the uncertainties in the estimated quantities and evaluate their
statistical properties in the presence of large relative parallax errors; we
populate the statistical distance scale diagrams with this sample and discuss
its significance in light of existing data and current calibrations.
We glean from DR1 parallaxes 8 CSPNe with S/N1. We show that this set of
potential calibrators doubles the number of extant trigonometric parallaxes
(from HST and ground-based), and increases by two orders of magnitude the
domain of physical parameters probed previously. We then use the combined
sample of suitable trigonometric parallaxes to fit the
physical-radius-to-surface-brightness relation. This distance scale
calibration, although preliminary, appears solid on statistical grounds, and
suggestive of new PNe physics.
With the tenfold improvement in PNe number statistics and astrometric
accuracy expected from future Gaia releases the new distance scale, already
very intriguing, will be definitively constrained.Comment: New Astronomy, in pres
Isoperimetric inequality in the Grushin plane
We prove a sharp isoperimetric inequality in the Grushin plane and compute the corresponding isoperimetric set
John and uniform domains in generalized Siegel boundaries
Given the pair of vector fields and where , we give a condition on a
bounded domain which ensures that is an
-domain for the Carnot-Carath\'eodory metric. We also
analyze the Ahlfors regularity of the natural surface measure induced at the
boundary by the vector fields.Comment: Minor corrections and updated reference
Levi umbilical surfaces in complex space
We define a complex connection on a real hypersurface of \C^{n+1} which is
naturally inherited from the ambient space. Using a system of Codazzi-type
equations, we classify connected real hypersurfaces in \C^{n+1}, ,
which are Levi umbilical and have non zero constant Levi curvature. It turns
out that such surfaces are contained either in a sphere or in the boundary of a
complex tube domain with spherical section.Comment: 18 page
DAS: a data management system for instrument tests and operations
The Data Access System (DAS) is a metadata and data management software
system, providing a reusable solution for the storage of data acquired both
from telescopes and auxiliary data sources during the instrument development
phases and operations. It is part of the Customizable Instrument WorkStation
system (CIWS-FW), a framework for the storage, processing and quick-look at the
data acquired from scientific instruments. The DAS provides a data access layer
mainly targeted to software applications: quick-look displays, pre-processing
pipelines and scientific workflows. It is logically organized in three main
components: an intuitive and compact Data Definition Language (DAS DDL) in XML
format, aimed for user-defined data types; an Application Programming Interface
(DAS API), automatically adding classes and methods supporting the DDL data
types, and providing an object-oriented query language; a data management
component, which maps the metadata of the DDL data types in a relational Data
Base Management System (DBMS), and stores the data in a shared (network) file
system. With the DAS DDL, developers define the data model for a particular
project, specifying for each data type the metadata attributes, the data format
and layout (if applicable), and named references to related or aggregated data
types. Together with the DDL user-defined data types, the DAS API acts as the
only interface to store, query and retrieve the metadata and data in the DAS
system, providing both an abstract interface and a data model specific one in
C, C++ and Python. The mapping of metadata in the back-end database is
automatic and supports several relational DBMSs, including MySQL, Oracle and
PostgreSQL.Comment: Accepted for pubblication on ADASS Conference Serie
Updates from FOTOSS: Highlights and Statistics from the OATo Photographic Plate Archive
This is a progress report of the on-going work related to the FOTOSS project (Valorizzazione scientifica dellâarchivio di osservazioni FOTOgrafiche del Secolo Scorso di patrimonio dellâOATo). First, we give an up-to-date account of the status of the FOTOSS project, including preliminary informations on the number and characteristics of the digitized plate images; we then present a detailed explanation of the content and usage of the latest realization of the Master Plate Catalog (MPC), along with some general statistics based on the observations recorded in the MPC
NGP Reference Catalogue for the SPICA FGS
This document describes the properties of the NGP Reference Catalogue
used for the WP1400 âInput Star Catalogue for the SPICA missionâ study conducted by the OATo Team for Thales Alenia Space Italia (TASI) within the âFGS Feasibility Consolidation for SPICA Missionâ project commissioned by ESA.This technical note describes the properties of the NGP Reference Catalogue used for the analysis presented by Spagna et al "Input Star Catalogue for SPICA mission" OATO-SPICA-FGS-TNO-001 (07/2020
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