2,401 research outputs found
A proof of the Gutzwiller Semiclassical Trace Formula using Coherent States Decomposition
The Gutzwiller semiclassical trace formula links the eigenvalues of the
Scrodinger operator ^H with the closed orbits of the corresponding classical
mechanical system, associated with the Hamiltonian H, when the Planck constant
is small ("semiclassical regime"). Gutzwiller gave a heuristic proof, using the
Feynman integral representation for the propagator of ^H. Later on
mathematicians gave rigorous proofs of this trace formula, under different
settings, using the theory of Fourier Integral Operators and Lagrangian
manifolds. Here we want to show how the use of coherent states (or gaussian
beams) allows us to give a simple and direct proof.Comment: 17 pages, LaTeX, available on http://qcd.th.u-psud.f
Analysis Tools for Discovering Strong Parity Violation at Hadron Colliders
Several arguments suggest parity violation may be observable in high energy
strong interactions. We introduce new analysis tools for describing the
azimuthal dependence of multi-particle distributions, or "azimuthal flow."
Analysis uses the representations of the orthogonal group O(2) and dihedral
groups necessary to define parity correctly in two dimensions.
Classification finds that collective angles used in event-by-event statistics
represent inequivalent tensor observables that cannot generally be represented
by a single "reaction plane". Many new parity-violating observables exist that
have never been measured, while many new parity-conserving observables formerly
lumped together are now distinguished. We use the concept of "event shape
sorting" to suggest separating right- and left-handed events, and we discuss
the effects of transverse and longitudinal spin. The analysis tools are
statistically robust, and can be applied equally to low or high multiplicity
events at the Tevatron, or , and the .Comment: 18 pages, 2 figures. Final version, accepted for publication in PRD.
Updated references. Modified presentation and discussion of previous wor
Efficient numerical diagonalization of hermitian 3x3 matrices
A very common problem in science is the numerical diagonalization of
symmetric or hermitian 3x3 matrices. Since standard "black box" packages may be
too inefficient if the number of matrices is large, we study several
alternatives. We consider optimized implementations of the Jacobi, QL, and
Cuppen algorithms and compare them with an analytical method relying on
Cardano's formula for the eigenvalues and on vector cross products for the
eigenvectors. Jacobi is the most accurate, but also the slowest method, while
QL and Cuppen are good general purpose algorithms. The analytical algorithm
outperforms the others by more than a factor of 2, but becomes inaccurate or
may even fail completely if the matrix entries differ greatly in magnitude.
This can mostly be circumvented by using a hybrid method, which falls back to
QL if conditions are such that the analytical calculation might become too
inaccurate. For all algorithms, we give an overview of the underlying
mathematical ideas, and present detailed benchmark results. C and Fortran
implementations of our code are available for download from
http://www.mpi-hd.mpg.de/~globes/3x3/ .Comment: 13 pages, no figures, new hybrid algorithm added, matches published
version, typo in Eq. (39) corrected; software library available at
http://www.mpi-hd.mpg.de/~globes/3x3
Indication of Anisotropy in Electromagnetic Propagation over Cosmological Distances
We report a systematic rotation of the plane of polarization of
electromagnetic radiation propagating over cosmological distances. The effect
is extracted independently from Faraday rotation, and found to be correlated
with the angular positions and distances to the sources. Monte Carlo analysis
yields probabilistic P-values of order 10^(-3) for this to occur as a
fluctuation. A fit yields a birefringence scale of order 10^(25) meters.
Dependence on redshift z rules out a local effect. Barring hidden systematic
bias in the data, the correlation indicates a new cosmological effect.Comment: 5 pages, 1 figure, ReVTeX. For more information, see
http://www.cc.rochester.edu/college/rtc/Borge/aniso.htm
Sudden natural death in a suicide attempt
In this article, we report an unusual case of sudden death arising from a ruptured basilar artery aneurysm during a suicide attempt. A 72-year-old male was found dead in his home after sustaining superficial flesh gunshot wounds (entrance and exit) involving the forehead. The victim had been depressed for several months and had frank suicide intention. The pertinent autopsy findings revealed a superficial nonpenetrating bullet path of the scalp with no skull fractures or brain injuries. However, brain examination identified subarachnoid hemorrhage and subdural clot about the brainstem and within the posterior fossa linked to a basilar artery aneurysm rupture. The cause and manner of death and contributing factors of the "non-lethal" gunshot wounds are discussed
Signatures of Pseudoscalar Photon Mixing in CMB Radiation
We model the effect of photon and ultra-light pseudoscalar mixing on the
propagation of electromagnetic radiation through the extragalactic medium. The
medium is modelled as a large number of magnetic domains, uncorrelated with one
another. We obtain an analytic expression for the different Stokes parameters
in the limit of small mixing angle. The different Stokes parameters are found
to increase linearly with the number of domains. We also verify this result by
direct numerical simulations. We use this formalism to estimate the effect of
pseudoscalar-photon mixing on the Cosmic Microwave Background (CMB)
polarization. We impose limits on the model parameters by the CMB observations.
We find that the currently allowed parameter range admits a CMB circular
polarization up to order .Comment: 17 pages, 5 figure
Connection between the elastic GEp/GMp and P to Delta form factors
It is suggested that the falloff in Qsq of the P to Delta magnetic form
factor GM* is related to the recently observed falloff of the elastic electric
form factor GEp/GMp. Calculation is carried out in the framework of a GPD
mechanism
Photon Generalized Parton Distributions
We present a calculation of the generalized parton distributions of the
photon using overlaps of photon light-front wave functions.Comment: Talk given at LightCone 2011, 4 pages, 3 figure
Risk of severe COVID-19 in patients with inflammatory rheumatic diseases treated with immunosuppressive therapy in Scotland
Objective: To investigate the association of severe coronavirus disease 2019 (COVID-19) in patients with inflammatory
rheumatic diseases (IRDs) treated with immunosuppressive drugs.
Method: A list of 4633 patients on targeted – biological or targeted synthetic – DMARDs in March 2020 was linked to a case–
control study that includes all cases of COVID-19 in Scotland.
Results: By 22 November 2021, 433 of the 4633 patients treated with targeted DMARDS had been diagnosed with COVID-19,
of whom 58 had been hospitalized. With all those in the population not on DMARDs as the reference category, the rate ratio for
hospitalized COVID-19 associated with DMARD treatment was 2.14 [95% confidence interval (CI) 2.02–2.26] in those on
conventional synthetic (cs) DMARDs, 2.01 (95% CI 1.38–2.91) in those on tumour necrosis factor (TNF) inhibitors as the only
targeted agent, and 3.83 (95% CI 2.65–5.56) in those on other targeted DMARDs. Among those on csDMARDs, rate ratios for
hospitalized COVID-19 were lowest at 1.66 (95% CI 1.51–1.82) in those on methotrexate and highest at 5.4 (95% CI 4.4–6.7) in
those on glucocorticoids at an average dose > 10 mg/day prednisolone equivalent.
Conclusion: The risk of hospitalized COVID-19 is elevated in IRD patients treated with immunosuppressive drugs compared
with the general population. Of these drugs, methotrexate, hydroxychloroquine, and TNF inhibitors carry the lowest risk. The
highest risk is associated with prednisolone. A larger study is needed to estimate reliably the risks associated with each class of
targeted DMAR
Moments of Nucleon Generalized Parton Distributions in Lattice QCD
Calculation of moments of generalized parton distributions in lattice QCD
requires more powerful techniques than those previously used to calculate
moments of structure functions. Hence, we present a novel approach that
exploits the full information content from a given lattice configuration by
measuring an overdetermined set of lattice observables to provide maximal
statistical constraints on the generalized form factors at a given virtuality,
t. In an exploratory investigation using unquenched QCD configurations at
intermediate sea quark masses, we demonstrate that our new technique is
superior to conventional methods and leads to reliable numerical signals for
the n=2 flavor singlet generalized form factors up to 3 GeV^2. The contribution
from connected diagrams in the flavor singlet sector to the total quark angular
momentum is measured to an accuracy of the order of one percent.Comment: 16 pages, 8 figures, LaTeX, minor elaboration of formalism and
singular value decomposition for non-specialists and addition of several
reference
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