2,741 research outputs found
Consequences of simultaneous chiral symmetry breaking and deconfinement for the isospin symmetric phase diagram
The thermodynamic bag model (tdBag) has been applied widely to model quark
matter properties in both heavy-ion and astrophysics communities. Several
fundamental physics aspects are missing in tdBag, e.g., dynamical chiral
symmetry breaking (DSB) and repulsions due to the vector interaction are
both included explicitly in the novel vBag quark matter model of Kl\"ahn and
Fischer (2015) (Astrophys. J. 810, 134 (2015)). An important feature of vBag is
the simultaneous DSB and deconfinement, where the latter links vBag to a
given hadronic model for the construction of the phase transition. In this
article we discuss the extension to finite temperatures and the resulting phase
diagram for the isospin symmetric medium.Comment: 6 pages, 2 figures, Contribution to the Topical Issue Exploring
strongly interacting matter at high densities - NICA White Paper edited by
David Blaschke et a
Increasing the Traceability Through Targeted Data Acquisition for Given Product Process Combinations
AbstractToday's manufacturing companies are faced with the challenge to achieve a high adherence to delivery dates under volatile market demands and to achieve a high efficiency of the order to delivery process. This challenging situation can only be handled with the help of an optimal alignment of the production, the production planning as well as the production controlling processes. Sufficient and high quality information from the production are the major basis for successfully mastering the tasks of production planning and control. With the help of the approach proposed in this paper, companies can start setting up a targeted data acquisition concept for their product process combination. It helps them, amongst other things, preventing production problems and responding rapidly to fluctuating customer needs
VLT Spectroscopy of Globular Cluster Systems, I. The Photometric and Spectroscopic Dataset
We present Lick line-index measurements of extragalactic globular clusters in
seven early-type galaxies (NGC 1380, 2434, 3115, 3379, 3585, 5846, and 7192)
with different morphological types (E-S0) located in field and group/cluster
environments. High-quality spectra were taken with the FORS2 instrument at
ESO's Very Large Telescope. About 50% of our data allow an age resolution dt/t
~ 0.3 and a metallicity resolution ~0.25-0.4 dex, depending on the absolute
metallicity. Globular cluster candidates are selected from deep B, V, R, I, K
FORS2/ISAAC photometry with 80-100% success rate inside one effective radius.
Using combined optical/near-infrared colour-colour diagrams we present a method
to efficiently reduce fore-/background contamination down to <10%. We find
clear signs for bi-modality in the globular cluster colour distributions of NGC
1380, 3115, and 3585. The colour distributions of globular clusters in NGC
2434, 3379, 5846, and 7192 are consistent with a broad single-peak
distribution. For the analysed globular cluster systems the slopes of projected
radial surface density profiles, of the form Sigma(R) ~ R^-Gamma, vary between
~0.8 and 2.6. Using globular clusters as a tracer population we determine total
dynamical masses of host galaxies out to large radii (~1.6 - 4.8 Reff). For the
sample we find masses in the range ~8.8*10^10 Msolar up to ~1.2*10^12 Msolar.
The line index data presented here will be used in accompanying papers of this
series to derive ages, metallicities and abundance ratios. A compilation of
currently available high-quality Lick index measurements for globular clusters
in elliptical, lenticular, and late-type galaxies is provided and will serve to
augment the current data set. [abridged]Comment: A&A accepted, 42 page
Equations of state for supernovae and compact stars
A review is given of various theoretical approaches for the equation of state (EoS) of dense matter, relevant for the description of core-collapse supernovae, compact stars, and compact star mergers. The emphasis is put on models that are applicable to all of these scenarios. Such EoS models have to cover large ranges in baryon number density, temperature, and isospin asymmetry. The characteristics of matter change dramatically within these ranges, from a mixture of nucleons, nuclei, and electrons to uniform, strongly interacting matter containing nucleons, and possibly other particles such as hyperons or quarks. As the development of an EoS requires joint efforts from many directions, different theoretical approaches are considered and relevant experimental and observational constraints which provide insights for future research are discussed. Finally, results from applications of the discussed EoS models are summarized
How Well Do We Know The Supernova Equation of State?
We give an overview about equations of state (EOS) which are currently available for simulations of core-collapse supernovae and neutron star mergers. A few selected important aspects of the EOS, such as the symmetry energy, the maximum mass of neutron stars, and cluster formation, are confronted with constraints from experiments and astrophysical observations. There are just very few models which are compatible even with this very restricted set of constraints. These remaining models illustrate the uncertainty of the uniform nuclear matter EOS at high densities. In addition, at finite temperatures the medium modifications of nuclear clusters represent a conceptual challenge. In conclusion, there has been significant development in the recent years, but there is still need for further improved general purpose EOS tables
The Chemistry of Extragalactic Globular Clusters
We present preliminary results of VLT/FORS spectroscopy of globular clusters
in nearby early-type galaxies. Our project aims at studying the chemistry and
determine the ages of globular cluster (sub-)populations. First results
indicate that the different galaxies host from little to significant
intermediate-age populations, and that the latter have alpha-element over iron
ratios closer to solar than the old population that show an alpha-element
enhancement similar to the diffuse stellar light.Comment: 4 pages (incl 2 figures) to appear in the proceedings of
"Extragalactic Globular Cluster Systems", ed.M.Kissler-Patig, Springer; see
also related contributions by T.H.Puzia and M.Hempel et a
How the Selection of Training Data and Modeling Approach Affects the Estimation of Ammonia Emissions from a Naturally Ventilated Dairy Barn-Classical Statistics versus Machine Learning
Environmental protection efforts can only be effective in the long term with a reliable quantification of pollutant gas emissions as a first step to mitigation. Measurement and analysis strategies must permit the accurate extrapolation of emission values. We systematically analyzed the added value of applying modern machine learning methods in the process of monitoring emissions from naturally ventilated livestock buildings to the atmosphere. We considered almost 40 weeks of hourly emission values from a naturally ventilated dairy cattle barn in Northern Germany. We compared model predictions using 27 different scenarios of temporal sampling, multiple measures of model accuracy, and eight different regression approaches. The error of the predicted emission values with the tested measurement protocols was, on average, well below 20%. The sensitivity of the prediction to the selected training dataset was worse for the ordinary multilinear regression. Gradient boosting and random forests provided the most accurate and robust emission value predictions, accompanied by the second-smallest model errors. Most of the highly ranked scenarios involved six measurement periods, while the scenario with the best overall performance was: One measurement period in summer and three in the transition periods, each lasting for 14 days
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Particulate Matter Dispersion Modeling in Agricultural Applications: Investigation of a Transient Open Source Solver
Agriculture is a major emitter of particulate matter (PM), which causes health problems and can act as a carrier of the pathogen material that spreads diseases. The aim of this study was to investigate an open-source solver that simulates the transport and dispersion of PM for typical agricultural applications. We investigated a coupled Eulerian–Lagrangian solver within the open source software package OpenFOAM. The continuous phase was solved using transient large eddy simulations, where four different subgrid-scale turbulence models and an inflow turbulence generator were tested. The discrete phase was simulated using two different Lagrangian solvers. For the validation case of a turbulent flow of a street canyon, the flowfield could be recaptured very well, with errors of around 5% for the non-equilibrium turbulence models (WALE and dynamicKeq) in the main regions. The inflow turbulence generator could create a stable and accurate boundary layer for the mean vertical velocity and vertical profile of the turbulent Reynolds stresses R11. The validation of the Lagrangian solver showed mixed results, with partly good agreements (simulation results within the measurement uncertainty), and partly high deviations of up to 80% for the concentration of particles. The higher deviations were attributed to an insufficient turbulence regime of the used validation case, which was an experimental chamber. For the simulation case of PM dispersion from manure application on a field, the solver could capture the influence of features such as size and density on the dispersion. The investigated solver is especially useful for further investigations into time-dependent processes in the near-source area of PM sources
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