9,742 research outputs found
Application of the Trend Filtering Algorithm on the MACHO Database
Due to the strong effect of systematics/trends in variable star observations,
we employ the Trend Filtering Algorithm (TFA) on a subset of the MACHO database
and search for variable stars. TFA has been applied successfully in planetary
transit searches, where weak, short-lasting periodic dimmings are sought in the
presence of noise and various systematics (due to, e.g., imperfect flat
fielding, crowding, etc). These latter effects introduce colored noise in the
photometric time series that can lead to a complete miss of the signal. By
using a large number of available photometric time series of a given field, TFA
utilizes the fact that the same types of systematics appear in several/many
time series of the same field. As a result, we fit each target time series by a
(least-square-sense) optimum linear combination of templates and
frequency-analyze the residuals. Once a signal is found, we reconstruct the
signal by employing the full model, including the signal, systematics and
noise. We apply TFA on the brightest ~5300 objects from subsets of each of the
MACHO Large Magellanic Cloud fields #1 and #79. We find that the Fourier
frequency analysis performed on the original data detect some 60% of the
objects as trend-dominated. This figure decreases essentially to zero after
using TFA. Altogether, We detect 387 variables in the two fields, 183 of which
would have remained undetected without using TFA. Where possible, we give
preliminary classification of the variables found.Comment: 12 pages, 15 figures, 3 tables with online material; to appear in
Astronomy and Astrophysic
The rich frequency spectrum of the triple-mode variable AC And
Fourier analysis of the light curve of AC And from the HATNet database
reveals the rich frequency structure of this object. Above 30 components are
found down to the amplitude of 3 mmag. Several of these frequencies are not the
linear combinations of the three basic components. We detect period increase in
all three components that may lend support to the Pop I classification of this
variable.Comment: Poster presented at IAU Symposium 301, "Precision Asteroseismology -
Celebration of the Scientific Opus of Wojtek Dziembowski", 19-23 August 2013,
Wroclaw, Polan
Zero temperature properties of mesons in a vector meson extended linear sigma model
A three flavor linear sigma model with vector and axial-vector mesons is
discussed. Preliminary results concerning on the symmetry breaking pattern, the
question of parameterization, as well as the resulting meson masses are
presented.Comment: 4 pages, 0 figures, submitted to the Hot and Cold Baryonic Matter
(HCBM 2010) conference proceeding
Scalar mesons in a linear sigma model with (axial-)vector mesons
The structure of the scalar mesons has been a subject of debate for many
decades. In this work we look for states among the physical
resonances using an extended Linear Sigma Model that contains scalar,
pseudoscalar, vector, and axial-vector mesons both in the non-strange and
strange sectors. We perform global fits of meson masses, decay widths and
amplitudes in order to ascertain whether the scalar states are below
or above 1 GeV. We find the scalar states above 1 GeV to be preferred as
states.Comment: 6 pages, 1 figure, To appear in the proceedings of the XII. Hadron
Physics Conference, Bento Goncalves, Brasil, April, 22 - 27, 201
The status of pentaquark spectroscopy on the lattice
The present work is a summary of the status of lattice pentaquark
calculations. After a pedagogic introduction to the basics of lattice hadron
spectroscopy we give a critical comparison of results presently available in
the literature. Special emphasis is put on presenting some of the possible
pitfalls of these calculations. In particular we discuss at length the choice
of the hadronic operators and the separation of genuine five-quark states from
meson-baryon scattering states.Comment: 13 pages LaTeX, 1 eps figur
Pentaquark hadrons from lattice QCD
We study spin 1/2 isoscalar and isovector candidates in both parity channels
for the recently discovered \Theta^+(1540) pentaquark particle in quenched
lattice QCD. Our analysis takes into account all possible uncertainties, such
as statistical, finite size and quenching errors when performing the chiral and
continuum extrapolations and we have indications that our signal is separated
from scattering states. The lowest mass that we find in the I^P=0^- channel is
in complete agreement with the experimental value of the \Theta^+ mass. On the
other hand, the lowest mass state in the opposite parity I^P=0^+ channel is
much higher. Our findings suggests that the parity of the \Theta^+ is negative.Comment: 13 pages, 5 figures. Final version, appeared in JHE
Effective resource management in digital forensics: an exploratory analysis of triage practices in four English constabularies
This is the author accepted manuscript. The final version is available from Emerald via the DOI in this recordPurpose: Building on the findings of a British Academy-funded project on the development of digital forensics in England and Wales, this article explores how triage, a process that helps prioritise digital devices for in-depth forensic analysis is experienced by digital forensic examiners and police officers in four English police forces. It is argued that while as a strategy triage can address the increasing demand in the examination of digital exhibits, careful consideration needs to be paid to the ways in which its set-up, undertaking and outcomes impact on the ability of law enforcement agencies to solve cases.
Design/methodology/approach: The findings presented are the result of ethnographic observations and semi-structured interviews. They emphasise the challenges in the triage of digital exhibits as they are encountered in everyday practice. The discussion focuses on the tensions between the delivery of timely and accurate investigation results and current gaps in the infrastructural arrangements. It also emphasises the need to provide police officers with a baseline understanding of the role of digital forensics and the importance of clearly defined strategies in the examination of digital devices.
Originality/value:This article aims to bridge policy and practice through an analysis of the ways in which digital forensic practitioners and police officers in four English constabularies reflect on the uses of triage in digital forensics to address backlogs and investigative demands. Highlighting the importance of digital awareness beyond the technical remit of digital forensic units, it offers new insights into the ways in which police forces seek to improve the evidential trail with limited resources.British AcademyEconomic and Social Research Council (ESRC
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