3,356 research outputs found
Countability properties of some Berkovich spaces
We prove that any compact Berkovich space over the field of Laurent series
over an arbitrary field is angelic. In particular, is it sequentially compact.Comment: 11 page
Foliations invariant by rational maps
We give a classification of pairs (F, f) where F is a holomorphic foliation
on a projective surface and f is a non-invertible dominant rational map
preserving F. We prove that both the map and the foliation are integrable in a
suitable sense.Comment: 17 pages. To appear in Math. Zeitshrift
Degree growth of meromorphic surface maps
We study the degree growth of iterates of meromorphic selfmaps of compact
Kahler surfaces. Using cohomology classes on the Riemann-Zariski space we show
that the degrees grow similarly to those of mappings that are algebraically
stable on some birational model.Comment: 17 pages, final version, to appear in Duke Math Journa
Singular semipositive metrics in non-Archimedean geometry
Let X be a smooth projective Berkovich space over a complete discrete
valuation field K of residue characteristic zero, endowed with an ample line
bundle L. We introduce a general notion of (possibly singular) semipositive (or
plurisubharmonic) metrics on L, and prove the analogue of the following two
basic results in the complex case: the set of semipositive metrics is compact
modulo constants, and each semipositive metric is a decreasing limit of smooth
semipositive ones. In particular, for continuous metrics our definition agrees
with the one by S.-W. Zhang. The proofs use multiplier ideals and the
construction of suitable models of X over the valuation ring of K, using
toroidal techniques.Comment: 49 pages, 1 figure. Accepted in the Journal of Algebraic Geometr
La participation populaire aux grands projets d'infrastructure lancés par les pouvoirs publics
Symetries birationnelles des surfaces feuilletees
We provide a classification of complex projective surfaces with a holomorphic
foliation whose group of birational symetries is infinite.Comment: 42 pages, 2 figure
Measuring elemental abundance ratios in protoplanetary disks at millimeter wavelengths
During the million years of evolution, gas dust and ice in protoplanetary
disks can be chemically reprocessed. There are evidences that the gas-phase
carbon and oxygen abundances are sub-solar in disks belonging to nearby star
forming regions. These findings have a major impact on the composition of the
primary atmosphere of giant planets (but it may also be valid for super-Earths
and sub-Neptunes) as they accrete their gaseous envelopes from the surrounding
material in the disk. In this study, we performed a thermo-chemical modelling
analysis with the aim at testing how reliable and robust are the estimates of
elemental abundance ratios based on (sub-)millimeter observations of molecular
lines. We created a grid of disk models for the following different elemental
abundance ratios: C/O, N/O and S/O, and, we computed the line flux of a set of
carbon-, nitrogen and sulphur-bearing species, namely CN, HCN, NO, CH,
c--CH, HCO, HCN, CHCN, CS, SO, HS and
HCS, that have been detected with present (sub-)millimeter facilities
such as ALMA and NOEMA. We find that the line fluxes, once normalized to the
flux of the CO line, are sensitive to the elemental abundance
ratios. On the other hand, the stellar and disk physical parameters have only a
minor effect of the line flux ratios. Our results demonstrate that a
simultaneous analysis of multiple molecular transitions is a valid approach to
constrain the elemental abundance ratio in protoplanetary disks.Comment: Accepted for publication to A&
Radiation environment along the INTEGRAL orbit measured with the IREM monitor
The INTEGRAL Radiation Environment Monitor (IREM) is a payload supporting
instrument on board the INTEGRAL satellite. The monitor continually measures
electron and proton fluxes along the orbit and provides this information to the
spacecraft on board data handler. The mission alert system broadcasts it to the
payload instruments enabling them to react accordingly to the current radiation
level. Additionally, the IREM conducts its autonomous research mapping the
Earth radiation environment for the space weather program. Its scientific data
are available for further analysis almost without delay.Comment: 5 pages, 7 figures, accepted for publication in A+A letter
HCOOCH3 as a probe of temperature and structure of Orion-KL
We studied the O-bearing molecule HCOOCH3 to characterize the physical
conditions of the different molecular source components in Orion-KL. We
identify 28 methyl formate emission peaks throughout the 50" field of
observations. The two strongest peaks are in the Compact Ridge (MF1) and in the
SouthWest of the Hot Core (MF2). Spectral confusion is still prevailing as half
of the expected transitions are blended over the region. Assuming that the
transitions are thermalized, we derive the temperature at the five main
emission peaks. At the MF1 position we find a temperature of 80K in a 1.8"x0.8"
beam size and 120K on a larger scale (3.6" x2.2"), suggesting an external
source of heating, whereas the temperature is about 130K at the MF2 position on
both scales. Transitions of HCOOCH3 in vt=1 are detected as well and the good
agreement of the positions on the rotational diagrams between the vt=0 and the
vt=1 transitions suggests a similar temperature. The velocity of the gas is
between 7.5 and 8.0km/s depending on the positions and column density peaks
vary from 1.6x10^16 to 1.6x10^17cm^-2. A second velocity component is observed
around 9-10 km/s in a North-South structure stretching from the Compact Ridge
up to the BN object; this component is warmer at the MF1 peak. The two other
C2H4O2 isomers are not detected and the derived upper limit for the column
density is <3x10^14cm^-2 for glycolaldehyde and <2x10^15cm^-2 for acetic acid.
From the 223GHz continuum map, we identify several dust clumps with associated
gas masses in the range 0.8 to 5.8Msun. Assuming that the HCOOCH3 is spatially
distributed as the dust, we find relative abundances of HCOOCH3 in the range
<0.1x10^-8 to 5.2x10^-8. We suggest a relation between the methyl formate
distribution and shocks as traced by 2.12 mum H2 emission.Comment: Accepted for publication in A&
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