580 research outputs found
Density Perturbations in Heavy-Ion Collisions below the Critical Point
Heavy ion collisions at large baryon density may exhibit a first order phase
transition from a chirally symmetric phase to the symmetry broken ground state.
This should then lead to large density inhomogeneities, which affect the
relative hadron multiplicities.Comment: 1 page, 1 figure, contribution to the GSI annual report 200
On the Observation of Phase Transitions in Collisions of Elementary Matter
We investigate the excitation function of directed flow, which can provide a
clear signature of the creation of the QGP and demonstrate that the minimum of
the directed flow does not correspond to the softest point of the EoS for
isentropic expansion. A novel technique measuring the compactness is introduced
to determine the QGP transition in relativistic-heavy ion collisions: The QGP
transition will lead to higher compression and therefore to higher compactness
of the source in coordinate space. This effect can be observed by pion
interferometry. We propose to measure the compactness of the source in the
appropriate principal axis frame of the compactness tensor in coordinate space.Comment: LaTeX, 8 pages, 6 figures, Conference proceedings to CRIS 2000, 3rd
Catania Relativistic Ion Studie
CosmoDM and its application to Pan-STARRS data
The Cosmology Data Management system (CosmoDM) is an automated and flexible
data management system for the processing and calibration of data from optical
photometric surveys. It is designed to run on supercomputers and to minimize
disk I/O to enable scaling to very high throughput during periods of
reprocessing. It serves as an early prototype for one element of the
ground-based processing required by the Euclid mission and will also be
employed in the preparation of ground based data needed in the eROSITA X-ray
all sky survey mission. CosmoDM consists of two main pipelines. The first is
the single-epoch or detrending pipeline, which is used to carry out the
photometric and astrometric calibration of raw exposures. The second is the co-
addition pipeline, which combines the data from individual exposures into
deeper coadd images and science ready catalogs. A novel feature of CosmoDM is
that it uses a modified stack of As- tromatic software which can read and write
tile compressed images. Since 2011, CosmoDM has been used to process data from
the DECam, the CFHT MegaCam and the Pan-STARRS cameras. In this paper we shall
describe how processed Pan-STARRS data from CosmoDM has been used to optically
confirm and measure photometric redshifts of Planck-based Sunyaev-Zeldovich
effect selected cluster candidates.Comment: 11 pages, 4 figures. Proceedings of Precision Astronomy with Fully
Depleted CCDs Workshop (2014). Accepted for publication in JINS
Zipf's law in Nuclear Multifragmentation and Percolation Theory
We investigate the average sizes of the largest fragments in nuclear
multifragmentation events near the critical point of the nuclear matter phase
diagram. We perform analytic calculations employing Poisson statistics as well
as Monte Carlo simulations of the percolation type. We find that previous
claims of manifestations of Zipf's Law in the rank-ordered fragment size
distributions are not born out in our result, neither in finite nor infinite
systems. Instead, we find that Zipf-Mandelbrot distributions are needed to
describe the results, and we show how one can derive them in the infinite size
limit. However, we agree with previous authors that the investigation of
rank-ordered fragment size distributions is an alternative way to look for the
critical point in the nuclear matter diagram.Comment: 8 pages, 11 figures, submitted to PR
Current Status of Quark Gluon Plasma Signals
Compelling evidence for the creation of a new form of matter has been claimed
to be found in Pb+Pb collisions at SPS. We discuss the uniqueness of often
proposed experimental signatures for quark matter formation in relativistic
heavy ion collisions. It is demonstrated that so far none of the proposed
signals like J\psi meson production/suppression, strangeness enhancement,
dileptons, and directed flow unambigiously show that a phase of deconfined
matter has been formed in SPS Pb+Pb collisions. We emphasize the need for
systematic future measurements to search for simultaneous irregularities in the
excitation functions of several observables in order to come close to pinning
the properties of hot, dense QCD matter from data.Comment: 12 pages, 6 figures, Proceedings of the Symposium on Fundamental
Issues in Elementary Matter In Honor and Memory of Michael Danos 241.
WE-Heraeus-Seminar Bad Honnef, Germany, 25--29 September 2000. To appear in
Heavy Ion Phy
Signals of deconfinement? Strangeness and flow in heavy ion collisions
In general, cracks in structural members indicate a level of serviceability of the engineering structures. Usually a hairline crack can be detected by visual inspection, crack gauge, fibre optical sensor, or laser sensor. Recently, an attempt to develop a non-destructive tool for health monitoring of prestressed concrete sleepers in railway tracks using the vibration responses has been established at the University of Wollongong, Australia. However, the fundamental understanding of the dynamic effect due to the cracks in sleepers is insufficient. This paper investigates the dynamic effect of the cracks on the vibration signatures of the railway prestressed concrete sleepers. The modal analysis has been used to evaluate the modal changes in vibration characteristics of the prestressed concrete sleepers in the frequency band between 0 and 1,600 Hz. The sample cracks have been initiated by the impulsive forces attributed to the high capacity drop impact testing machine. Comparison of the modal parameters of the intact and cracked sleepers has been highlighted in terms of natural frequencies and modal damping. This understanding will lead to further development of the economical technology to evaluate the structural integrity of railway track and its components
Standardizing Type Ia Supernova Absolute Magnitudes Using Gaussian Process Data Regression
We present a novel class of models for Type Ia supernova time-evolving
spectral energy distributions (SED) and absolute magnitudes: they are each
modeled as stochastic functions described by Gaussian processes. The values of
the SED and absolute magnitudes are defined through well-defined regression
prescriptions, so that data directly inform the models. As a proof of concept,
we implement a model for synthetic photometry built from the spectrophotometric
time series from the Nearby Supernova Factory. Absolute magnitudes at peak
brightness are calibrated to 0.13 mag in the -band and to as low as 0.09 mag
in the blueshifted -band, where the dispersion includes
contributions from measurement uncertainties and peculiar velocities. The
methodology can be applied to spectrophotometric time series of supernovae that
span a range of redshifts to simultaneously standardize supernovae together
with fitting cosmological parameters.Comment: 47 pages, 15 figures, accepted for publication by Astrophysical
Journa
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