1,534 research outputs found
A Soldier\u27s Blog: Balancing Service Members\u27 Personal Rights vs. National Security Interests
This Note examines the competing interests between ensuring military personnel\u27s freedom of speech while protecting national security interests. The Author recognizes the necessity of protecting national security interests but emphasizes that military personnel\u27s rights to free speech must be protected as long as such speech poses no threat to military security. In conclusion, clearer protections must be implemented to protect military personnel\u27s right to free speech
The Decay with Highly Improved Staggered Quarks and NRQCD
We report on progress of a lattice QCD calculation of the and
semileptonic form factors. We use a relativistic staggered
action (HISQ) for light and charm quarks, and an improved non-relativistic
(NRQCD) action for bottom, on the second generation MILC ensembles.Comment: Presented at Lattice 2017, the 35th International Symposium on
Lattice Field Theory at Granada, Spain (18-24 June 2017
A Soldier\u27s Blog: Balancing Service Members\u27 Personal Rights vs. National Security Interests
This Note examines the competing interests between ensuring military personnel\u27s freedom of speech while protecting national security interests. The Author recognizes the necessity of protecting national security interests but emphasizes that military personnel\u27s rights to free speech must be protected as long as such speech poses no threat to military security. In conclusion, clearer protections must be implemented to protect military personnel\u27s right to free speech
APPROXIMATIONS IN RECONSTRUCTING DISCONTINUOUS CONDUCTIVITIES IN THE CALDERÓN PROBLEM
In 2014, Astala, Päivärinta, Reyes, and Siltanen conducted numerical experiments reconstructing a piecewise continuous conductivity. The algorithm of the shortcut method is based on the reconstruction algorithm due to Nachman, which assumes a priori that the conductivity is Hölder continuous. In this dissertation, we prove that, in the presence of infinite-precision data, this shortcut procedure accurately recovers the scattering transform of an essentially bounded conductivity, provided it is constant in a neighborhood of the boundary. In this setting, Nachman’s integral equations have a meaning and are still uniquely solvable.
To regularize the reconstruction, Astala et al. employ a high frequency cutoff of the scattering transform. We show that such scattering transforms correspond to Beltrami coefficients that are not compactly supported, but exhibit certain decay at infinity. For this class of Beltrami coefficients, we establish that the complex geometric optics solutions to the Beltrami equation exist and exhibit the same subexponential decay as described in the 2006 work of Astala and Päivärinta. This is a first step toward extending the inverse scattering map of Astala and Päivärinta to non-compactly supported conductivities
Competing risks after coronary bypass surgeryThe influence of death on reintervention
AbstractObjective: For groups of patients at high risk of death, such as older patients, the actual probability of experiencing a nonfatal event, such as reintervention, must be far smaller than the potential probability were there no attrition by death. Competing risks analysis quantifies the difference. Methods: Multivariable analyses were performed for the competing events death before reintervention, reoperation, and percutaneous transluminal coronary angioplasty in 2001 patients after bilateral internal thoracic artery grafting and in 8123 after single internal thoracic artery grafting. Follow-up was 9.7 ± 3.0 years and 10.8 ± 5.2 years in bilateral and single internal thoracic artery groups, respectively. Results: Patients receiving single grafts experienced shorter survival and more reinterventions (P < .0001). However, other risk factors for death included old age (P < .0001), but risk factors for reintervention included young age (P < .0001). This difference confounds interpretation of event-free survival that is clarified by competing risks analysis. Death reduced the potential benefit of bilateral internal thoracic artery grafting on reintervention by angioplasty from a median of 8.5% to 5.5% at 12 years and by reoperation from 9.3% to 6.8%, with progressively greater erosion of benefit from attrition by death as age increased. Competing risks simulation confirmed that young age was a true risk factor for reintervention, excluding the explanation that it reflected simply passive attrition by death as patients age. Conclusions: Even after accounting for attrition by interim deaths, bilateral versus single internal thoracic artery grafting and older age are associated with fewer reinterventions. However, in high-risk patients, its benefit on freedom from reintervention is eroded considerably by death. (J Thorac Cardiovasc Surg 2000;119:1221-32
Charmonium properties from lattice QCD + QED: hyperfine splitting, leptonic width, charm quark mass and
We have performed the first lattice QCD computations of the
properties (masses and decay constants) of ground-state charmonium mesons. Our
calculation uses the HISQ action to generate quark-line connected two-point
correlation functions on MILC gluon field configurations that include
quark masses going down to the physical point, tuning the quark mass from
and including the effect of the quark's electric charge
through quenched QED. We obtain (connected) =
120.3(1.1) MeV and interpret the difference with experiment as the impact on
of its decay to gluons, missing from the lattice calculation. This
allows us to determine =+7.3(1.2) MeV,
giving its value for the first time. Our result of 0.4104(17)
GeV, gives =5.637(49) keV, in agreement
with, but now more accurate than experiment. At the same time we have improved
the determination of the quark mass, including the impact of quenched QED
to give = 0.9841(51) GeV. We have also used
the time-moments of the vector charmonium current-current correlators to
improve the lattice QCD result for the quark HVP contribution to the
anomalous magnetic moment of the muon. We obtain , which is 2.5 higher than the value derived using moments
extracted from some sets of experimental data on . This value for includes our determination of
the effect of QED on this quantity, .Comment: Added extra discussion on QED setup, some new results to study the
effects of strong isospin breaking in the sea (including new Fig. 1) and a
fit stability plot for the hyperfine splitting (new Fig. 7). Version accepted
for publication in PR
The pseudoscalar meson electromagnetic form factor at high Q2 from full lattice QCD
We give an accurate determination of the vector (electromagnetic) form factor, F(Q^2), for a light pseudoscalar meson up to squared momentum transfer Q^2 values of 6 GeV^2 for the first time from full lattice QCD, including u, d, s and c quarks in the sea at multiple values of the lattice spacing. Our results show good control of lattice discretisation and sea quark mass effects. We study a pseudoscalar meson made of valence s quarks but the qualitative picture obtained applies also to the \pi meson, relevant to upcoming experiments at Jefferson Lab. We find that Q^2F(Q^2) becomes flat in the region between Q^2 of 2 GeV^2 and 6 GeV^2, with a value well above that of the asymptotic perturbative QCD expectation, but well below that of the vector-meson dominance pole form appropriate to low Q^2 values. Our calculations show that we can reach higher Q^2 values in future to shed further light on where the perturbative QCD result emerges
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