723 research outputs found
Energy dependence of transverse quark flow in heavy ion collisions
Energy dependence of quark transverse flow carries information about
dynamical properties (equation of state, initial conditions) of deconfined
matter produced in heavy ion collisions. We assume quark-antiquark matter
formation in Pb+Pb collisions at CERN SPS and Au+Au collisions at RHIC energies
and determine quark transverse flow at the critical temperature of the
quark-hadron phase transition. Coalescence of massive quarks is calculated in
the MICOR hadronization model and hadronic final state effects are considered
using the GROMIT cascade program. Comparing theoretical results to data,
transverse flow values are determined and energy dependence is discussed.Comment: Presented at the International Workshop on Hot and Dense Matter in
Ultrarelativistic Heavy Ion Collisions (BP2004). Submitted to APH Heavy Ion
Physics. 10 pages, 6 figure
The production of charm mesons from quark matter at CERN SPS and RHIC
We study the production of charm mesons and other charm baryons from quark
matter at CERN SPS and RHIC energies. Using quark coalescence models as
hadronization mechanism, we predict particle ratios, absolute yields and
transverse momentum spectra.Comment: 4 pages in Latex, 2 PS figure, to be published in the proceedings of
the SQM'2000 Conference, Berkeley, CA, July 20-25, 2000. Submitted to J.
Phys.
New analytic solutions of the non-relativistic hydrodynamical equations
New solutions are found for the non-relativistic hydrodynamical equations.
These solutions describe expanding matter with a Gaussian density profile. In
the simplest case, thermal equilibrium is maintained without any interaction,
the energy is conserved, and the process is isentropic. More general solutions
are also obtained that describe explosions driven by heat production, or
contraction of the matter caused by energy loss.Comment: 6 pages, LaTeX. Submitted to Physics Letters B. Shortened from 9
pages, errors corrected in the "More general solutions" sectio
Limits to the presence of transiting circumbinary planets in CoRoT data
The CoRoT mission during its flight-phase 2007-2012 delivered the
light-curves for over 2000 eclipsing binaries. Data from the Kepler mission
have proven the existence of several transiting circumbinary planets. Albeit
light-curves from CoRoT have typically lower precision and shorter coverage,
CoRoT's number of targets is similar to Kepler, and some of the known
circumbinary planets could potentially be detected in CoRoT data as well. The
aim of this work has been a revision of the entire CoRoT data-set for the
presence of circumbinary planets, and the derivation of limits to the
abundances of such planets. We developed a code which removes the light curve
of the eclipsing binaries and searches for quasi-periodic transit-like features
in a light curve after removal of binary eclipses and instrumental features.
The code needs little information on the sample systems and can be used for
other space missions as well, like Kepler, K2, TESS and PLATO. The code is
broad in the requirements leading to detections, but was tuned to deliver an
amount of detections that is manageable in a subsequent, mainly visual,
revision about their nature. In the CoRoT sample we identified three planet
candidates whose transits would have arisen from a single pass across the
central binary. No candidates remained however with transit events from
multiple planetary orbits. We calculated the upper limits for the number of
Jupiter, Saturn and Neptune sized planets in co-planar orbits for different
orbital period ranges. We found that there are much less giant planets in
short-periodic orbits around close binary systems than around single stars.Comment: Accepted for publication in A&A, 11 pages, 4 figures and 4 tables.
Updated to fix error in acknowledgemen
Long-term evolution of FU Orionis objects at infrared wavelengths
We investigate the brightness evolution of 7 FU Orionis systems in the 1-100
micrometer wavelength range using data from the Infrared Space Observatory
(ISO). The ISO measurements were supplemented with 2MASS and MSX observations
performed in the same years as the ISO mission (1995-98). The spectral energy
distributions (SEDs) based on these data points were compared with earlier ones
derived from the IRAS photometry as well as from ground-based observations
carried out around the epoch 1983. In 3 cases (Z CMa, Parsamian 21, V1331 Cyg)
no difference between the two epochs was seen within the measurement
uncertainties. V1057 Cyg, V1515 Cyg and V1735 Cyg have become fainter at
near-infrared wavelengths while V346 Nor has become slightly brighter. V1057
Cyg exhibits a similar flux change also in the mid-infrared. At lambda >= 60
micrometer most of the sources remained constant; only V346 Nor seems to fade.
Our data on the long-term evolution of V1057 Cyg agree with the model
predictions of Kenyon & Hartmann (1991) and Turner et al. (1997) at near- and
mid-infrared wavelengths, but disagree at lambda > 25 micrometer. We discuss if
this observational result at far-infrared wavelengths could be understood in
the framework of the existing models.Comment: 9 pages, 3 figures, to be published in Astronomy & Astrophysic
Simple predictions from ALCOR_c for rehadronisation of charmed quark matter
We study the production of charmed hadrons with the help of ALCOR_c, the
algebraic coalescence model for rehadronisation of charmed quark matter.
Mesonic ratios are introduced as factors connecting various antibaryon to
baryon ratios. The resulting simple relations could serve as tests of quark
matter formation and coalescence type rehadronization in heavy ion collisions.Comment: 7 pages in Latex, 1 PS figur
Experiment-based Comparison of Prediction Methods for Pump Head Degradation with Viscous and Power-law Fluids
Although several methods are known to calculate pump performance with highly viscous and non-Newtonian fluids, research has not yet determined all the key parameters of these predictions. It is unclear how these parameters depend on the pump geometry and the delivered fluid rheology, which can vary widely in the chemical industry. In our study, the performance curves of a radial centrifugal pump with a viscous Newtonian glycerol solution and a non-Newtonian power-law fluid were experimentally compared. The head degradation of the pump was also presumed with the ANSI/HI and the Ofuchi methods, which are evident and commonly used for viscous Newtonian fluids, but not for non-Newtonians. The required constants were estimated based on experimental data
for both models, and the Ofuchi method was adapted to power-law fluid. Based on our results, the Ofuchi method proved to apply for head degradation prediction with the examined power-law fluid.
This work is licensed under a Creative Commons Attribution 4.0 International License
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