201 research outputs found
Spectral isolation of naturally reductive metrics on simple Lie groups
We show that within the class of left-invariant naturally reductive metrics
on a compact simple Lie group , every
metric is spectrally isolated. We also observe that any collection of
isospectral compact symmetric spaces is finite; this follows from a somewhat
stronger statement involving only a finite part of the spectrum.Comment: 19 pages, new title and abstract, revised introduction, new result
demonstrating that any collection of isospectral compact symmetric spaces
must be finite, to appear Math Z. (published online Dec. 2009
Inclusive Hadron Production in Photon-Photon Collisions at Next-to-Leading Order
We study inclusive charged-hadron production in collisions of quasireal
photons at NLO in perturbative QCD, using fragmentation functions recently
extracted from PEP and LEP1 data. We superimpose the direct (DD),
single-resolved (DR), and double-resolved (RR) gamma-gamma channels. First, we
confront existing data taken by TASSO at PETRA and by MARK II at PEP with our
NLO calculations. We also make comparisons with the neutral-kaon to
charged-hadron ratio measured by MARK II. Then, we present NLO predictions for
LEP2, a next-generation e+e- linear collider (NLC) in the TESLA design, and a
Compton collider obtained by converting a NLC. We analyze transverse-momentum
and rapidity spectra with regard to the scale dependence, the interplay of the
DD, DR, and RR components, the sensitivity to the gluon density in the resolved
photon, and the influence of gluon fragmentation. It turns out that the
inclusive measurement of small-p_T hadrons at a Compton collider would greatly
constrain the gluon density of the photon and the gluon fragmentation function.Comment: 16 pages, 12 Postscript figure
'Making Friends or Making Things?': Interfirm Transactions in the Sheffield Metal-working Cluster
The paper comprises an examination of the material inputs of a sample of 70 small firms in the Sheffield metal-working cluster and an assessment of the extent to which purchases are accompanied by face-to-face (embodied) transactions. It is shown that there are no significant differences between the level of embodied transactions accompanying local (intra-cluster) material links and those associated with non-local flows. It seems that, on this measure at least and within this cluster, the Sheffield metal-working cluster lacks the dense network of embodied transactions with local suppliers suggested in the wider literature. The lower-than-expected measures of embodied transactions suggest that one of the mechanisms for the transfer of knowledge between buyers and suppliers within an industrial cluster is poorly developed in this particular case.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Chronic COVID-19 Syndrome and Chronic Fatigue Syndrome (ME/CFS) following the first pandemic wave in Germany - a first analysis of a prospective observational study
OBJECTIVE: Characterization of the clinical features of patients with persistent symptoms after mild to moderate COVID-19 infection and exploration of factors associated with the development of Chronic COVID-19 Syndrome (CCS). METHODS: Setting: Charité Fatigue Center with clinical immunologists and rheumatologist, neurologists and cardiologists at Charité University hospital. Participants: 42 patients who presented with persistent moderate to severe fatigue six months following a mostly mild SARS-CoV-2 infection at the Charité Fatigue Center from July to November 2020. Main outcome measures: The primary outcomes were clinical and paraclinical data and meeting diagnostic criteria for Chronic Fatigue Syndrome (ME/CFS). Relevant neurological and cardiopulmonary morbidity was excluded. RESULTS: The median age was 36.5, range 22–62, 29 patients were female and 13 male. At six months post acute COVID-19 all patients had fatigue (Chalder Fatigue Score median 25 of 33, range 14–32), the most frequent other symptoms were post exertional malaise (n=41), cognitive symptoms (n=40), headache (n=38), and muscle pain (n=35). Most patients were moderately to severely impaired in daily live with a median Bell disability score of 50 (range 15–90) of 100 (healthy) and Short Form 36 (SF-36) physical function score of 63 (range 15-80) of 100. 19 of 42 patients fulfilled the 2003 Canadian Consensus Criteria for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). These patients reported more fatigue in the Chalder Fatigue Score (p=0.006), more stress intolerance (p=0.042) and more frequent and longer post exertional malaise (PEM) (p=0.003), and hypersensitivity to noise (p=0.029), light (p=0.0143) and temperature (p=0.024) compared to patients not meeting ME/CFS criteria. Handgrip force was diminished in most patients compared to healthy control values, and lower in CCS/CFS compared to non-CFS CCS (Fmax1 p=0.085, Fmax2, p=0.050, Fmean1 p=0.043, Fmean2 p=0.034, mean of 10 repeat handgrips, 29 female patients). Mannose-binding lectin (MBL) deficiency was observed frequently (22% of all patients) and elevated IL-8 levels were found in 43% of patients. CONCLUSIONS: Chronic COVID-19 Syndrome at months 6 is a multisymptomatic frequently debilitating disease fulfilling diagnostic criteria of ME/CFS in about half of the patients in our study. Research in mechanisms and clinical trials are urgently needed
Measurement of the Isolated Photon Cross Section in p-pbar Collisions at sqrt{s}=1.96 TeV
The cross section for the inclusive production of isolated photons has been
measured in p anti-p collisions at sqrt{s}=1.96 TeV with the D0 detector at the
Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV
and have pseudorapidity |eta|<0.9. The cross section is compared with the
results from two next-to-leading order perturbative QCD calculations. The
theoretical predictions agree with the measurement within uncertainties.Comment: 7 pages, 5 figures, submitted to Phys.Lett.
Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV
We report the results of a study of color coherence effects in ppbar
collisions based on data collected by the D0 detector during the 1994-1995 run
of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8
TeV. Initial-to-final state color interference effects are studied by examining
particle distribution patterns in events with a W boson and at least one jet.
The data are compared to Monte Carlo simulations with different color coherence
implementations and to an analytic modified-leading-logarithm perturbative
calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
Search for electroweak production of single top quarks in collisions.
We present a search for electroweak production of single top quarks in the electron+jets and muon+jets decay channels. The measurements use ~90 pb^-1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DZero detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process ppbar->tb+X of 39 pb. The upper limit for the t-channel process ppbar->tqb+X is 58 pb. (arXiv
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