3,336 research outputs found
Quantitative Storytelling: Science, Narratives, and Uncertainty in Nexus Innovations
Innovations are central instruments of sustainability policies. They project future visions onto technological solutions and enable win-win framings of complex sustainability issues. Yet, they also create new problems by interconnecting different resources such as water, food, and energy, what is known as the â WEF nexus.â In this paper, we apply a new approach called Quantitative Storytelling (QST) to the assessment of four innovations with a strong nexus component in EU policy: biofuels, shale gas, electric vehicles, and alternative water resources. Recognizing irreducible pluralism and uncertainties, QST inspects the relationships between the narratives used to frame sustainability issues and the evidence on those issues. Our experiences outlined two rationales for implementing QST. First, QST can be used to question dominant narratives that promote certain innovations despite evidence against their effectiveness. Second, QST can offer avenues for pluralistic processes of co-creation of alternative narratives and imaginaries. We reflect on the implementation of QST and on the role played by different uncertainties throughout these processes. Our experiences suggest that while the role of nexus assessments using both numbers and narratives may not be instrumental in directly inducing policy change, they are valuable means to open discussions on innovations outside of dominant nexus imaginaries. © The Author(s) 2021.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This research has been funded by the European Union’s H2020 project MAGIC: Moving towards Adaptive Governance in Complexity (MAGIC GA No. 689669); European Union’s FP7 project IANEX: Integrated Assessment of the Nexus: The Case of Hydraulic Fracturing, Marie Curie International Outgoing Fellowship GA No. 623593; and Spanish Ministry of Science’s Juan de la Cierva Fellowship (IJC2019-038847-I/AEI/10.13039/501100011033)
Unveiling a cluster of protostellar disks around the massive protostar GGD 27 MM1
Context. Most stars form in clusters and thus it is important to characterize the protostellar disk population in dense environments to assess whether the environment plays a role in the subsequent evolution. Specifically, it is critical to evaluate whether planet formation is altered with respect to more isolated stars formed in dark clouds. Aims. We seek to investigate the properties of the protostellar disks in the GGD 27 cluster and compare these with those obtained from disks formed in nearby regions. Methods. We used ALMA to observe the star-forming region GGD 27 at 1.14 mm with an unprecedented angular resolution, 40 mas (∼56 au), and sensitivity (∼0.002 M·). Results. We detected a cluster of 25 continuum sources, most of which likely trace disks around Class 0/I protostars. Excluding the two most massive objects, disks masses are in the range 0.003-0.05 M·. The analysis of the cluster properties indicates that GGD 27 displays moderate subclustering. This result, combined with the dynamical timescale of the radio jet (∼104 years), suggests the youthfulness of the cluster. The lack of disk mass segregation signatures may support this as well. We found a clear paucity of disks with Rdisk > 100 au. The median value of the radius is 34 au; this value is smaller than the median of 92 au for Taurus but comparable to the value found in Ophiuchus and in the Orion Nebula Cluster. In GGD 27 there is no evidence of a distance-dependent disk mass distribution (i.e., disk mass depletion due to external photoevaporation), most likely due to the cluster youth. There is a clear deficit of disks for distances 0.04 pc. This suggests that dynamical interactions far from the cluster center are weaker, although the small disks found could be the result of disk truncation. This work demonstrates the potential to characterize disks from low-mass young stellar objects in distant and massive (still deeply embedded) clustered environments.Fil: Busquet, G.. Instituto de Estudios Espaciales de Cataluña; España. Instituto de Ciencias del Espacio (ice); EspañaFil: Girart, J. M.. Instituto de Estudios Espaciales de Cataluña; España. Instituto de Ciencias del Espacio (ice); EspañaFil: Estalella, R.. Universidad de Barcelona; EspañaFil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Galván Madrid, R.. Universidad Nacional Autónoma de México; MéxicoFil: Anglada, G.. Instituto de Astrofísica de Andalucía; EspañaFil: Carrasco González, C.. Universidad Nacional Autónoma de México; MéxicoFil: Añez López, N.. Instituto de Ciencias del Espacio (ice); EspañaFil: Curiel, S.. Universidad Nacional Autónoma de México; MéxicoFil: Osorio, M.. Instituto de Astrofísica de Andalucía; EspañaFil: Rodríguez, L. F.. Universidad Nacional Autónoma de México; MéxicoFil: Torrelles, J. M.. Instituto de Estudios Espaciales de Cataluña; España. Instituto de Ciencias del Espacio (ice); Españ
Evolution of a Kerr-Newman black hole in a dark energy universe
This paper deals with the study of the accretion of dark energy with equation
of state onto Kerr-Newman black holes. We have obtained that when
the mass and specific angular momentum increase, and that whereas the
specific angular momentum increases up to a given plateau, the mass grows up
unboundedly. On the regime where the dominant energy condition is violated our
model predicts a steady decreasing of mass and angular momentum of black holes
as phantom energy is being accreted. Masses and and angular momenta of all
black holes tend to zero when one approaches the big rip. The results that
cosmic censorship is violated and that the black hole size increases beyond the
universe size itself are discussed in terms of considering the used models as
approximations to a more general descriptions where the metric is
time-dependent.Comment: 11 figures added. Some explanations extended. E-mails updated.
References updated. Conclusions unchanged. Accepted in Gravitation &
Cosmolog
Modeling the Accretion Disk around the High-mass Protostar GGD 27-MM1
Recent high angular resolution (≃40 mas) ALMA observations at 1.14 mm resolve a compact (R ≃ 200 au), flattened dust structure perpendicular to the HH 80─81 jet emanating from the GGD 27-MM1 high-mass protostar, making it a robust candidate for a true accretion disk. The jet─disk system (HH 80─81/GGD 27-MM1) resembles those found in association with low- and intermediate-mass protostars. We present radiative transfer models that fit the 1.14 mm ALMA dust image of this disk, which allow us to obtain its physical parameters and predict its density and temperature structure. Our results indicate that this accretion disk is compact (R disk ≃ 170 au) and massive (≃5 M ☉), at about 20% of the stellar mass of ≃20 M ☉. We estimate the total dynamical mass of the star─disk system from the molecular line emission, finding a range between 21 and 30 M ☉, which is consistent with our model. We fit the density and temperature structures found by our model with power-law functions. These results suggest that accretion disks around massive stars are more massive and hotter than their low-mass siblings, but they still are quite stable. We also compare the temperature distribution in the GGD 27─MM1 disk with that found in low- and intermediate-mass stars and discuss possible implications for the water snow line. We have also carried out a study of the distance based on Gaia DR2 data and the population of young stellar objects in this region and from the extinction maps. We conclude that the source distance is within 1.2 and 1.4 kpc, closer than what was derived in previous studies (1.7 kpc).Fil: Añez López, N.. Instituto de Ciencias del Espacio; EspañaFil: Osorio, M.. Instituto de Astrofísica de Andalucía; EspañaFil: Busquet, G.. Instituto de Ciencias del Espacio; EspañaFil: Girart, J. M.. Instituto de Ciencias del Espacio; EspañaFil: Macías, E.. European Southern Observatory; ChileFil: Carrasco González, C.. Instituto de Radioastronomía y Astrofísica; MéxicoFil: Curiel, S.. Universidad Nacional Autonoma de Mexico. Instituto de Astronomia; MéxicoFil: Estalella, R.. Universidad de Barcelona. Facultad de Física; EspañaFil: Fernandez Lopez, Manuel. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Galván Madrid, R.. Instituto de Radioastronomía y Astrofísica; MéxicoFil: Kwon, J.. University of tokyo; JapónFil: Torrelles, J. M.. Institut de Ciencies de l’Espai; Españ
Diffusion in Stationary Flow from Mesoscopic Non-equilibrium Thermodynamics
We analyze the diffusion of a Brownian particle in a fluid under stationary
flow. By using the scheme of non-equilibrium thermodynamics in phase space, we
obtain the Fokker-Planck equation which is compared with others derived from
kinetic theory and projector operator techniques. That equation exhibits
violation of the fluctuation dissipation-theorem. By implementing the
hydrodynamic regime described by the first moments of the non-equilibrium
distribution, we find relaxation equations for the diffusion current and
pressure tensor, allowing us to arrive at a complete description of the system
in the inertial and diffusion regimes. The simplicity and generality of the
method we propose, makes it applicable to more complex situations, often
encountered in problems of soft condensed matter, in which not only one but
more degrees of freedom are coupled to a non-equilibrium bath.Comment: 10 pages, accepted in Phys. Rev.
Diffusion in Stationary Flow from Mesoscopic Non-equilibrium Thermodynamics
We analyze the diffusion of a Brownian particle in a fluid under stationary
flow. By using the scheme of non-equilibrium thermodynamics in phase space, we
obtain the Fokker-Planck equation which is compared with others derived from
kinetic theory and projector operator techniques. That equation exhibits
violation of the fluctuation dissipation-theorem. By implementing the
hydrodynamic regime described by the first moments of the non-equilibrium
distribution, we find relaxation equations for the diffusion current and
pressure tensor, allowing us to arrive at a complete description of the system
in the inertial and diffusion regimes. The simplicity and generality of the
method we propose, makes it applicable to more complex situations, often
encountered in problems of soft condensed matter, in which not only one but
more degrees of freedom are coupled to a non-equilibrium bath.Comment: 10 pages, accepted in Phys. Rev.
An Overview of the 2014 ALMA Long Baseline Campaign
A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to
make accurate images with resolutions of tens of milliarcseconds, which at
submillimeter (submm) wavelengths requires baselines up to ~15 km. To develop
and test this capability, a Long Baseline Campaign (LBC) was carried out from
September to late November 2014, culminating in end-to-end observations,
calibrations, and imaging of selected Science Verification (SV) targets. This
paper presents an overview of the campaign and its main results, including an
investigation of the short-term coherence properties and systematic phase
errors over the long baselines at the ALMA site, a summary of the SV targets
and observations, and recommendations for science observing strategies at long
baselines. Deep ALMA images of the quasar 3C138 at 97 and 241 GHz are also
compared to VLA 43 GHz results, demonstrating an agreement at a level of a few
percent. As a result of the extensive program of LBC testing, the highly
successful SV imaging at long baselines achieved angular resolutions as fine as
19 mas at ~350 GHz. Observing with ALMA on baselines of up to 15 km is now
possible, and opens up new parameter space for submm astronomy.Comment: 11 pages, 7 figures, 2 tables; accepted for publication in the
Astrophysical Journal Letters; this version with small changes to
affiliation
Two Loop Scalar Self-Mass during Inflation
We work in the locally de Sitter background of an inflating universe and
consider a massless, minimally coupled scalar with a quartic self-interaction.
We use dimensional regularization to compute the fully renormalized scalar
self-mass-squared at one and two loop order for a state which is released in
Bunch-Davies vacuum at t=0. Although the field strength and coupling constant
renormalizations are identical to those of lfat space, the geometry induces a
non-zero mass renormalization. The finite part also shows a sort of growing
mass that competes with the classical force in eventually turning off this
system's super-acceleration.Comment: 31 pages, 5 figures, revtex4, revised for publication with extended
list of reference
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