225 research outputs found
Generating a checking sequence with a minimum number of reset transitions
Given a finite state machine M, a checking sequence is an input sequence that is guaranteed to lead to a failure if the implementation under test is faulty and has no more states than M. There has been much interest in the automated generation of a short checking sequence from a finite state machine. However, such sequences can contain reset transitions whose use can adversely affect both the cost of applying the checking sequence and the effectiveness of the checking sequence. Thus, we sometimes want a checking sequence with a minimum number of reset transitions rather than a shortest checking sequence. This paper describes a new algorithm for generating a checking sequence, based on a distinguishing sequence, that minimises the number of reset transitions used.This work was supported in part by Leverhulme Trust grant number F/00275/D, Testing State Based Systems, Natural Sciences and Engineering Research Council (NSERC) of Canada grant number RGPIN 976, and Engineering and Physical Sciences Research Council grant number GR/R43150, Formal Methods and Testing (FORTEST)
X-ray photoemission study of NiS_{2-x}Se_x (x = 0.0 - 1.2)
Electronic structure of NiS_{2-x}Se_x system has been investigated for
various compositions (x) using x-ray photoemission spectroscopy. An analysis of
the core level as well as the valence band spectra of NiS_2 in conjunction with
many-body cluster calculations provides a quantitative description of the
electronic structure of this compound. With increasing Se content, the on-site
Coulomb correlation strength (U) does not change, while the band width W of the
system increases, driving the system from a covalent insulating state to a
pd-metallic state.Comment: 19 pages, 6 figures, To appear in Phys. Rev. B, 200
Following Gluonic World Lines to Find the QCD Coupling in the Infrared
Using a parametrization of the Wilson loop with the minimal-area law, we
calculate the polarization operator of a valence gluon, which propagates in the
confining background. This enables us to obtain the infrared freezing (i.e.
finiteness) of the running strong coupling in the confinement phase, as well as
in the deconfinement phase up to the temperature of dimensional reduction. The
momentum scale defining the onset of freezing is found both analytically and
numerically. The nonperturbative contribution to the thrust variable,
originating from the freezing, makes the value of this variable closer to the
experimental one.Comment: 25 pages, 5 figure
W=0 Pairing in Carbon Nanotubes away from Half Filling
We use the Hubbard Hamiltonian on the honeycomb lattice to represent the
valence bands of carbon single-wall nanotubes. A detailed symmetry
analysis shows that the model allows W=0 pairs which we define as two-body
singlet eigenstates of with vanishing on-site repulsion. By means of a
non-perturbative canonical transformation we calculate the effective
interaction between the electrons of a W=0 pair added to the interacting ground
state. We show that the dressed W=0 pair is a bound state for resonable
parameter values away from half filling. Exact diagonalization results for the
(1,1) nanotube confirm the expectations. For nanotubes of length ,
the binding energy of the pair depends strongly on the filling and decreases
towards a small but nonzero value as . We observe the existence
of an optimal doping when the number of electrons per C atom is in the range
1.21.3, and the binding energy is of the order of 0.1 1 meV.Comment: 16 pages, 6 figure
Radiative decays with light scalar mesons and singlet-octet mixing in ChPT
We study different types of radiative decays involving f0(980) and a0(980)
mesons within a unified ChPT-based approach at one-loop level. Light scalar
resonances which are seen in pi pi, pi eta, K K-bar channels of phi(1020)
radiative decays and in J/psi decays are responsible for key questions of
low-energy dynamics in the strong interaction sector, and decays phi(1020) ->
gamma a0(980), phi(1020) -> gamma f0(980), a0(980) -> gamma gamma, f0(980) ->
gamma gamma are of interest for current experimental programs in Juelich,
Frascati and Novosibirsk. From theoretical point of view it is important to
verify whether light scalar mesons are members of some flavor octet or nonet.
We find a value of mixing angle dictated by consistency with experiment and
coupling structures of ChPT Lagrangian. Decay widths f0(980)/a0(980) -> gamma
rho(770)/omega(782), which are not studied experimentally yet, are predicted.
We also obtain several relations between widths, which hold independently of
coupling constants and represent a fingerprint of the model.Comment: 18 pages, 8 figures; misprints in text and tables corrected,
discussion extended, references added; version accepted for publication in
Eur.Phys.J.
A population of hypercompact HII regions identified from young HII regions
CONTEXT: The derived physical parameters for young H regions are normally determined assuming the emission region to be optically-thin. However, this is unlikely to hold for young H regions such as Hyper-compact H (HC H) and Ultra-compact H (UC H) regions and leads to the underestimation of their properties. This can be overcome by fitting the SEDs over a wide range of radio frequencies. AIMS: Two primary goals are (1) determining physical properties from radio SEDs and finding potential HC H regions; (2) using these physical properties to investigate their evolution. METHODS: We used Karl G. Jansky Very Large Array (VLA) to make observations of X-band and K-band with angular-resolutions of ~ 1:7âČâČ and ~ 0:7âČâČ, respectively, toward 114 H regions with rising-spectra . We complement our observations with VLA archival data and construct SEDs between 1-26 GHz and model them assuming an ionisation-bounded H region with uniform density. RESULTS: The sample has a mean electron density of n = 1.6 x 10 cm, diameter diam = 0.14 pc, and emission measure EM = 1.9 x 10 pc cm. We identify 16 HC H region candidates and 8 intermediate objects between the classes of HC H and UC H regions. The n, diam, and EM change as expected, however, the Lyman continuum flux is relatively constant over time. We find that about 67% of Lyman continuum photons are absorbed by dust within these H regions and the dust absorption fraction tends to be more significant for more compact and younger H regions. CONCLUSIONS: Young H regions are commonly located in dusty clumps; HC H regions and intermediate objects are often associated with various masers, outflows, broad radio recombination lines, and extended green objects, and the accretion at the two stages tends to be quickly reduced or halted
Accuracy of Auxiliary Field Approach for Baryons
We provide a check of the accuracy of the auxiliary field formalism used to
derive the Effective Hamiltonian for baryons in the Field Correlator Method. To
this end we compare the solutions for the Effective Hamiltonian with those
obtained from the solution of the Salpeter equation. Comparing these results
gives a first estimate of the systematic uncertainty due to the use of the
auxiliary field formalism for baryons.Comment: 6 pages, 2 tables; published versio
Bulk micromegas detectors for large TPC applications
A large volume TPC will be used in the near future in a variety of experiments including T2K. The bulk Micromegas detector for this TPC is built using a novel production technique particularly suited for compact and robust low mass detectors. The capability to pave a large surface with a simple mounting solution and small dead space between modules is of particular interest for these applications. We have built several large bulk Micromegas detectors (27 x 26 cm2) and we have tested them in the former HARP field cage setup with a magnetic field. Cosmic ray data have been acquired in a variety of experimental conditions. Good detector performances and space point resolution have been achieved
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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