301 research outputs found
Ground-state properties of unitary bosons: from clusters to matter
Sem informaçãoThe properties of cold Bose gases at unitarity have been extensively investigated in the last few years both theoretically and experimentally. In this Letter we use a family of interactions tuned to two-body unitarity and very weak three-body binding to demonstrate the universal properties of both clusters and matter. We determine the universal properties of finite clusters up to 60 particles and, for the first time, explicitly demonstrate the saturation of energy and density with particle number and compare with bulk properties. At saturation in the bulk we determine the energy, density, two-and three-body contacts, and the condensate fraction. We find that uniform matter is more bound than three-body clusters by nearly 2 orders of magnitude, the two-body contact is very large in absolute terms, and yet the condensate fraction is also very large, greater than 90%. Equilibrium properties of these systems may be experimentally accessible through rapid quenching of weakly interacting boson superfluids.1192215Sem informaçãoSem informaçãoSem informaçãoWe thank Daekyoung Kang for many valuable discussions. The work of J. C. and S. G. was supported by the NUCLEI SciDAC program, and by the U.S. DOE under Contract No. DE-AC52-06NA25396. The work of U. vK. was supported in part by the U. S. Department of Energy, Office of Science, Office of Nuclear Physics, under Award No. DE-FG02-04ER41338, and by the European Union Research and Innovation program Horizon 2020 under Grant Agreement No. 654002. S. V. thanks the hospitality and financial support from LANL and the facilities offered by CENAPAD-SP. Computational resources have been provided by Los Alamos Open Supercomputing. We also used resources provided by NERSC, which is supported by the U. S. DOE under Contract No. DE-AC02-05CH11231
Multi-object spectroscopy of stars in the CoRoT fields I: Early-type stars in the CoRoT-fields IRa01, LRa01, LRa02
Observations of giant stars indicate that the frequency of giant planets is
much higher for intermediate-mass stars than for solar-like stars. Up to now
all known planets of giant stars orbit at relatively far distances from their
host stars. It is not known whether intermediate-mass stars also had many
close-in planets when they were on the main sequence, which were then engulfed
when the star became a giant star. To understand the formation and evolution of
planets it is therefore important to find out whether main-sequence stars of
intermediate-mass have close-in planets or not. A survey for transiting planets
of intermediate-mass stars would be ideal to solve this question, because the
detection of transiting planets is not affected by the rapid rotation of these
stars. As a first step for an efficient survey we need to identify
intermediate-mass stars in the CoRoT-fields, which can then be used as an input
list. To compile the input list we derived the spectral types of essentially
all O, B and A stars down to 14.5 mag in the CoRoT fields IRa01, LRa01, LRa02
taken with the multi-object spectrograph AAOmega. We determined the spectral
types by comparing the spectra with template spectra from a library. In total
we identify 1856 A and B stars that have been observed with CoRoT. Given the
number of planets that have been detected in these fields amongst late-type
stars, we estimate that there are one to four transiting planets of
intermediate-mass stars waiting to be discovered. Our survey not only allows us
to carry out a dedicated planet search programme but is also essential for any
types of studies of the light curves of early-type stars in the CoRoT database.
We also show that it would be possible to extend the survey to all fields that
CoRoT has observed using photometrically determined spectral types.Comment: 57 pages, 12 figures, accepted for publication in Astronomy and
Astrophysic
Sub-stellar companions of intermediate-mass stars with CoRoT: CoRoTâ34b, CoRoTâ35b, and CoRoTâ36b
Theories of planet formation give contradicting results of how frequent close-in giant planets of intermediate mass stars (IMSs; 1.3â€Mââ€3.2Mââ ) are. Some theories predict a high rate of IMSs with close-in gas giants, while others predict a very low rate. Thus, determining the frequency of close-in giant planets of IMSs is an important test for theories of planet formation. We use the CoRoT survey to determine the absolute frequency of IMSs that harbour at least one close-in giant planet and compare it to that of solar-like stars. The CoRoT transit survey is ideal for this purpose, because of its completeness for gas-giant planets with orbital periods of less than 10 d and its large sample of main-sequence IMSs. We present a high precision radial velocity follow-up programme and conclude on 17 promising transit candidates of IMSs, observed with CoRoT. We report the detection of CoRoTâ34b, a brown dwarf close to the hydrogen burning limit, orbiting a 1.1âGyr A-type main-sequence star. We also confirm two inflated giant planets, CoRoTâ35b, part of a possible planetary system around a metal-poor star, and CoRoTâ36b on a misaligned orbit. We find that 0.12±0.10 per cent of IMSs between 1.3â€Mââ€1.6Mâ observed by CoRoT do harbour at least one close-in giant planet. This is significantly lower than the frequency (â 0.70±0.16 per centâ ) for solar-mass stars, as well as the frequency of IMSs harbouring long-period planets (â âŒ8 per centâ )
Once in a blue moon ⊠rare adnexal tumor: From the clinical and videodermoscopical aspects to the mohs surgery and the histological diagnosis
The adnexal tumours are a very heterogeneous group of lesions, more and more studied in the literature. The squamoid eccrine ductal carcinoma (SEDC) is a rare malignant variant that combines ductal structures with squamous differentiation. We report a case of dermoscopic and histological diagnosis of SEDC, treated with Mohs Surgery and with no recurrence of a tumour after 12 months of follow up
CiĂȘncias da natureza e interdisciplinaridade: a percepção dos estudantes sobre questĂ”es de avaliaçÔes de larga escala
Buscando fornecer subsĂdios para o entendimento a respeito da construção e utilização do conhecimento quĂmico e reflexĂ”es sobre a forma como ele Ă© ensinado, este trabalho investiga um grupo de dez doutorandos em quĂmica de uma Universidade pĂșblica do Brasil. A investigação se baseou em dois grupos de entrevistas, analisadas de forma qualitativa, criando-se categorias para codificação das concepçÔes dos quĂmicos em diversos temas. Neste trabalho, sĂŁo expostos e discutidos os conteĂșdos das falas deste grupo de pĂłs-graduandos a respeito de suas concepçÔes realistas. A partir desses dados, e dialogando com referenciais da filosofia e do ensino de quĂmica, apresentamos apontamentos sobre aspectos peculiares ao fazer e ensinar quĂmica
The Percolation Signature of the Spin Glass Transition
Magnetic ordering at low temperature for Ising ferromagnets manifests itself
within the associated Fortuin-Kasteleyn (FK) random cluster representation as
the occurrence of a single positive density percolating network. In this paper
we investigate the percolation signature for Ising spin glass ordering -- both
in short-range (EA) and infinite-range (SK) models -- within a two-replica FK
representation and also within the different Chayes-Machta-Redner two-replica
graphical representation. Based on numerical studies of the EA model in
three dimensions and on rigorous results for the SK model, we conclude that the
spin glass transition corresponds to the appearance of {\it two} percolating
clusters of {\it unequal} densities.Comment: 13 pages, 6 figure
The GAPS programme with HARPS-N@TNG IV: A planetary system around XO-2S
We performed an intensive radial velocity monitoring of XO-2S, the wide
companion of the transiting planet-host XO-2N, using HARPS-N at TNG in the
framework of the GAPS programme. The radial velocity measurements indicate the
presence of a new planetary system formed by a planet that is slightly more
massive than Jupiter at 0.48 au and a Saturn-mass planet at 0.13 au. Both
planetary orbits are moderately eccentric and were found to be dynamically
stable. There are also indications of a long-term trend in the radial
velocities. This is the first confirmed case of a wide binary whose components
both host planets, one of which is transiting, which makes the XO-2 system a
unique laboratory for understanding the diversity of planetary systems.Comment: 7 pages, 3 figures, accepted on A&A Lette
The GAPS Programme with HARPS-N@TNG IX. The multi-planet system KELT-6: detection of the planet KELT-6 c and measurement of the Rossiter-McLaughlin effect for KELT-6 b
Aims. For more than 1.5 years we monitored spectroscopically the star KELT-6
(BD+312447), known to host the transiting hot Saturn KELT-6b, because a
previously observed long-term trend in radial velocity time series suggested
the existence of an outer companion. Methods. We collected a total of 93 new
spectra with the HARPS-N and TRES spectrographs. A spectroscopic transit of
KELT-6b was observed with HARPS-N, and simultaneous photometry was obtained
with the IAC-80 telescope. Results. We proved the existence of an outer planet
with a mininum mass Msini=3.710.21 M and a
moderately eccentric orbit () of period P3.5
years. We improved the orbital solution of KELT-6b and obtained the first
measurement of the Rossiter-McLaughlin effect, showing that the planet has a
likely circular, prograde, and slightly misaligned orbit, with a projected
spin-orbit angle =3611 degrees. We improved the KELT-6b
transit ephemeris from photometry, and we provided new measurements of the
stellar parameters. KELT-6 appears as an interesting case to study the
formation and evolution of multi-planet systems.Comment: Letter, 4 figures, accepted for publication in A&A. Some language
editing and numbering of the paper series changed (from X to IX
- âŠ