88 research outputs found
Parity realization in Vector-like theories from Fermion Bilinears
We reconsider in this paper the old aim of trying to understand if the
observed realization of discrete symmetries as Parity or CP in the QCD vacuum
can be satisfied from first principles. We show how under the appropriate
assumptions implicitely done by Vafa and Witten in their old paper on parity
realization in vector-like theories, all parity and CP odd operators
constructed from fermion bilinears of the form should
take a vanishing vacuum expectation value in a vector-like theory with N
degenerate flavours (N>1). In our analysis the Vafa-Witten theorem on the
impossibility to break spontaneously the flavour symmetry in a vector-like
theory plays a fundamental role.Comment: 12 pages, no figures To be published in JHE
Next-to-leading order QCD corrections to W+W- production via vector-boson fusion
Vector-boson fusion processes constitute an important class of reactions at
hadron colliders, both for signals and backgrounds of new physics in the
electroweak interactions.
We consider what is commonly referred to as W+W- production via vector-boson
fusion (with subsequent leptonic decay of the Ws), or, more precisely, e+ nu_e
mu- nubar_mu + 2 jets production in proton-proton scattering, with all resonant
and non-resonant Feynman diagrams and spin correlations of the final-state
leptons included, in the phase-space regions which are dominated by t-channel
electroweak-boson exchange.
We compute the next-to-leading order QCD corrections to this process, at
order alpha^6 alpha_s.
The QCD corrections are modest, changing total cross sections by less than
10%. Remaining scale uncertainties are below 2%. A fully-flexible
next-to-leading order partonic Monte Carlo program allows to demonstrate these
features for cross sections within typical vector-boson-fusion acceptance cuts.
Modest corrections are also found for distributions.Comment: 29 pages, 14 figure
Geometric Algorithm for Abelian-Gauge Models
Motivated by the sign problem in several systems, we have developed a
geometric simulation algorithm based on the strong coupling expansion which can
be applied to abelian pure gauge models. We have studied the algorithm in the
U(1) model in 3 and 4 dimensions, and seen that it is practical and is
similarly efficient to the standard heat-bath algorithm, but without the
ergodicity problems which comes from the presence of vortices. We have also
applied the algorithm to the Ising gauge model at the critical point, and we
find hints of a better asymptotic behaviour of the autocorrelation time, which
therefore suggests the possibility of a smaller dynamical critical exponent
with respect to the standard heat-bath algorithm.Comment: 16 pages, 11 figure
Genomic analyses of hair from Ludwig van Beethoven
Ludwig van Beethoven (1770–1827) remains among the most influential and popular classical music composers. Health problems significantly impacted his career as a composer and pianist, including progressive hearing loss, recurring gastrointestinal complaints, and liver disease. In 1802, Beethoven requested that following his death, his disease be described and made public. Medical biographers have since proposed numerous hypotheses, including many substantially heritable conditions. Here we attempt a genomic analysis of Beethoven in order to elucidate potential underlying genetic and infectious causes of his illnesses. We incorporated improvements in ancient DNA methods into existing protocols for ancient hair samples, enabling the sequencing of high-coverage genomes from small quantities of historical hair. We analyzed eight independently sourced locks of hair attributed to Beethoven, five of which originated from a single European male. We deemed these matching samples to be almost certainly authentic and sequenced Beethoven\u27s genome to 24-fold genomic coverage. Although we could not identify a genetic explanation for Beethoven\u27s hearing disorder or gastrointestinal problems, we found that Beethoven had a genetic predisposition for liver disease. Metagenomic analyses revealed furthermore that Beethoven had a hepatitis B infection during at least the months prior to his death. Together with the genetic predisposition and his broadly accepted alcohol consumption, these present plausible explanations for Beethoven\u27s severe liver disease, which culminated in his death. Unexpectedly, an analysis of Y chromosomes sequenced from five living members of the Van Beethoven patrilineage revealed the occurrence of an extra-pair paternity event in Ludwig van Beethoven\u27s patrilineal ancestry
Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world
Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic.
Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality.
Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States.
Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis.
Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection
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