2,459,782 research outputs found
Zero cycles with modulus and zero cycles on singular varieties
Given a smooth variety and an effective Cartier divisor , we
show that the cohomological Chow group of 0-cycles on the double of along
has a canonical decomposition in terms of the Chow group of 0-cycles and the Chow group of 0-cycles with modulus on .
When is projective, we construct an Albanese variety with modulus and show
that this is the universal regular quotient of .
As a consequence of the above decomposition, we prove the Roitman torsion
theorem for the 0-cycles with modulus. We show that is
torsion-free and there is an injective cycle class map if is affine. For a smooth affine surface ,
this is strengthened to show that is an extension of by .Comment: 62 pages. Final version to appear in Compositio Mat
A Search for Interstellar CHD
We report on a search for Interstellar CH2D+. Four transitions occur in
easily accessible portions of the spectrum; we report on emission at the
frequencies of these transitions toward high column density star-forming
regions. While the observations can be interpreted as being consistent with a
detection of the molecule, further observations will be needed to secure that
identification. The CH2D+ rotational spectrum has not been measured to high
accuracy. Lines are weak, as the dipole moment induced by the inclusion of
deuterium in the molecule is small. Astronomical detection is favored by
observations toward strongly deuterium-fractionated sources. However, enhanced
deuteration is expected to be most significant at low temperatures. The
sparseness of the available spectrum and the low excitation in regions of high
fractionation make secure identification of CH2D+ difficult. Nonetheless, owing
to the importance of CH3+ to interstellar chemistry, and the lack of rotational
transitions of that molecule owing to its planar symmetric structure, a measure
of its abundance would provide key data to astrochemical models.Comment: 2 pages, 1 figure, submitted to IAU Symposium 251, Organic Matte
Measurement of CHD on Titan at Submillimeter Wavelengths
We present the first radio/submillimeter detection of monodeuterated methane
(CHD) in Titan's atmosphere, using archival data from of the Atacama Large
Millimeter/submillimeter Array (ALMA). The and
transitions at 465.235 and 465.250 GHz ( mm) were measured at
significance levels of and , respectively. These two
lines were modeled using the Non-linear optimal Estimator for MultivariatE
spectral analySIS (NEMESIS) radiative transfer code to determine the
disk-averaged CHD volume mixing ratio = in Titan's
stratosphere (at altitudes km). By comparison with the CH vertical
abundance profile measured by Cassini-Huygens mass spectrometry, the resulting
value for D/H in CH is . This is consistent
with previous ground-based and in-situ measurements from the Cassini-Huygens
mission, though slightly lower than the average of the previous values.
Additional CHD observations at higher spatial resolution will be required
to determine a value truly comparable with the Cassini-Huygens CH
measurements, by measuring CHD with ALMA close to Titan's equator. In the
post-Cassini era, spatially resolved observations of CHD with ALMA will
enable the latitudinal distribution of methane to be determined, making this an
important molecule for further studies.Comment: 9 pages, 4 figure
Measurement of the production of charm jets tagged with D mesons in pp collisions at = 7 TeV
The production of charm jets in proton-proton collisions at a center-of-mass
energy of TeV was measured with the ALICE detector at the CERN
Large Hadron Collider. The measurement is based on a data sample corresponding
to a total integrated luminosity of , collected using a
minimum-bias trigger. Charm jets are identified by the presence of a D
meson among their constituents. The D mesons are reconstructed from their
hadronic decay DK. The D-meson tagged jets are
reconstructed using tracks of charged particles (track-based jets) with the
anti- algorithm in the jet transverse momentum range
and pseudorapidity
. The fraction of charged jets containing a D-meson
increases with from to . The distribution of D-meson tagged jets as a
function of the jet momentum fraction carried by the D meson in the
direction of the jet axis () is reported for two ranges
of jet transverse momenta, and
in the intervals
and , respectively. The
data are compared with results from Monte Carlo event generators (PYTHIA 6,
PYTHIA 8 and Herwig 7) and with a Next-to-Leading-Order perturbative Quantum
Chromodynamics calculation, obtained with the POWHEG method and interfaced with
PYTHIA 6 for the generation of the parton shower, fragmentation, hadronisation
and underlying event.Comment: 29 pages, 8 captioned figures, 3 tables, authors from page 24,
published version, figures at http://alice-publications.web.cern.ch/node/525
Tentative Detection of Deuterated Methane toward the Low-Mass Protostar IRAS 04368+2557 in L1527
The millimeter-wave rotational transition line () of
deuterated methane CHD has tentatively been detected toward the low-mass
Class 0 protostar IRAS 04368+2557 in L1527 with the Heinrich Hertz
Submillimeter Telescope. This is the first detection of CHD in interstellar
clouds, if confirmed. The column density and fractional abundance of CHD
are determined to be cm and , respectively, where we assume the rotational temperature of 25
K. The column density and fractional abundance of the gaseous CH are
estimated to be cm and , respectively, by adopting the molecular D/H ratios of 2--7% reported
for various molecules in L1527. The fractional abundance of CH is higher
than or comparable to that found in high-mass star-forming cores by infrared
observations. It is sufficiently high for triggering the efficient production
of various carbon-chain molecules in a lukewarm region near the protostar,
which supports the picture of the warm carbon-chain chemistry.Comment: 13 page
Algebraic cycles on Severi-Brauer schemes of prime degree over a curve
Let be a perfect field and let be a prime number different from the
characteristic of . Let be a smooth, projective and geometrically
integral -curve and let be a Severi-Brauer -scheme of relative
dimension . In this paper we show that contains
a subgroup isomorphic to for every in the range . We deduce that, if is a number field, then is finitely
generated for every in the indicated range.Comment: 6 page
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