59,051 research outputs found
Comparative Analysis of Five XML Query Languages
XML is becoming the most relevant new standard for data representation and
exchange on the WWW. Novel languages for extracting and restructuring the XML
content have been proposed, some in the tradition of database query languages
(i.e. SQL, OQL), others more closely inspired by XML. No standard for XML query
language has yet been decided, but the discussion is ongoing within the World
Wide Web Consortium and within many academic institutions and Internet-related
major companies. We present a comparison of five, representative query
languages for XML, highlighting their common features and differences.Comment: TeX v3.1415, 17 pages, 6 figures, to be published in ACM Sigmod
Record, March 200
Bose-Einstein Correlations in a Space-Time Approach to e+ e- Annihilation into Hadrons
A new treatment of Bose-Einstein correlations is incorporated in a space-time
parton-shower model for e+ e- annihilation into hadrons. Two alternative
afterburners are discussed, and we use a simple calculable model to demonstrate
that they reproduce successfully the size of the hadron emission region. One of
the afterburners is used to calculate two-pion correlations in e+ e- -> Z^0 ->
hadrons and e+ e- -> W+ W- -> hadrons. Results are shown with and without
resonance decays, for correlations along and transverse to the thrust jet axis
in these two classes of events.Comment: 30 pages, Latex, 8 figure
First atom lifetime and scattering length measurements
The results of a search for hydrogen-like atoms consisting of
mesons are presented. Evidence for atom production
by 24 GeV/c protons from CERN PS interacting with a nickel target has been seen
in terms of characteristic pairs from their breakup in the same target
() and from Coulomb final state interaction (). Using
these results the analysis yields a first value for the atom lifetime
of fs and a first model-independent measurement of
the S-wave isospin-odd scattering length
( for isospin ).Comment: 14 pages, 8 figure
Model wavefunctions for interfaces between lattice Laughlin states
We study the interfaces between lattice Laughlin states at different
fillings. We propose a class of model wavefunctions for such systems
constructed using conformal field theory. We find a nontrivial form of charge
conservation at the interface, similar to the one encountered in the field
theory works from the literature. Using Monte Carlo methods, we evaluate the
correlation function and entanglement entropy at the border. Furthermore, we
construct the wavefunction for quasihole excitations and evaluate their mutual
statistics with respect to quasiholes originating at the same or the other side
of the interface. We show that some of these excitations lose their anyonic
statistics when crossing the interface, which can be interpreted as
impermeability of the interface to these anyons. Contrary to most of the
previous works on interfaces between topological orders, our approach is
microscopic, allowing for a direct simulation of e.g. an anyon crossing the
interface. Even though we determine the properties of the wavefunction
numerically, the closed-form expressions allow us to study systems too large to
be simulated by exact diagonalization.Comment: A number of changes were made in response to referees' comments:
large parts of the text were rewritten, new results were added, some of the
old results were reinterpreted, the discussion of connection to earlier works
was expande
Collective Bulk and Edge Modes through the Quantum Phase Transition in Graphene at
Undoped graphene in a strong, tilted magnetic field exhibits a radical change
in conduction upon changing the tilt-angle, which can be attributed to a
quantum phase transition from a canted antiferromagnetic (CAF) to a
ferromagnetic (FM) bulk state at filling factor . This behavior
signifies a change in the nature of the collective ground state and excitations
across the transition. Using the time-dependent Hartree-Fock approximation, we
study the collective neutral (particle-hole) excitations in the two phases,
both in the bulk and on the edge of the system. The CAF has gapless neutral
modes in the bulk, whereas the FM state supports only gapped modes in its bulk.
At the edge, however, only the FM state supports gapless charge-carrying
states. Linear response functions are computed to elucidate their sensitivity
to the various modes. The response functions demonstrate that the two phases
can be distinguished by the evolution of a local charge pulse at the edge.Comment: 15 pages, 23 figure
Sensor Simulation and position calibration for the CMS pixel detector
In this paper a detailed simulation of irradiated pixel sensors was used to
investigate the effects of radiation damage on charge sharing and position
determination. The simulation implements a model of radiation damage by
including two defect levels with opposite charge states and trapping of charge
carriers. We show that charge sharing functions extracted from the simulation
can be parameterized as a function of the inter-pixel position and used to
improve the position determination. For sensors irradiated to Phi=5.9x10^14
n/cm^2 a position resolution below 15 um can be achieved after calibration.Comment: Presented at the 14th Int. Workshop on Vertex Detectors (Vertex
2005), November 7-11 2005, Chuzenji Lake, Nikko, Japan. 4 pages, 1 figur
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