2,568 research outputs found
The uniqueness of the invariant polarisation-tensor field for spin-1 particles in storage rings
We argue that the invariant tensor field introduced in [1] is unique under
the condition that the invariant spin field is unique, and thereby complete
that part of the discussion in that paper.Comment: 8 page
Solving String Field Equations: New Uses for Old Tools
It is argued that the (NS-sector) superstring field equations are integrable,
i.e. their solutions are obtainable from linear equations. We adapt the
25-year-old solution-generating "dressing" method and reduce the construction
of nonperturbative superstring configurations to a specific cohomology problem.
The application to vacuum superstring field theory is outlined.Comment: Talk presented by O.L. at the 35th International Symposium Ahrenshoop
on the Theory of Elementary Particles, Berlin, Germany, 26-30 Aug 2002; v2:
minor corrections, textheight adjuste
Management of asthma exacerbations in children
Asthma exacerbations are episodes of worsening asthma symptoms with shortness of breath, cough, wheeze and/or tight chest that require an increase in asthma treatment. A major change in the recommendations for managing mild asthma exacerbations is the move away from using inhaled short-acting beta-2 agonists (SABAs) as the sole reliever, toward a combination of a rapid-onset, long-acting beta-2 agonist, formoterol, in combination with an inhaled corticosteroid (ICS), or a SABA used together with an ICS in separate inhalers, in older children and adolescents. In children <11 years of age who are adherent to daily ICS treatment, the ICS dose should not be increased short term. A written asthma plan should include instructions on how to self-manage asthma exacerbations, and when to present to a medical facility. Oxygen is an essential component of the management of asthma exacerbations at both primary care and emergency department facilities, together with inhaled SABAs via metered-dose inhaler and spacer, and oral corticosteroids
Carrier-envelope phase control over pathway interference in strong-field dissociation of H
The dissociation of an H molecular-ion beam by linearly polarized,
carrier-envelope-phase-tagged 5 fs pulses at 4W/cm with a
central wavelength of 730 nm was studied using a coincidence 3D momentum
imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission
direction of H fragments relative to the laser polarization were observed.
These asymmetries are caused by interference of odd and even photon number
pathways, where net-zero photon and 1-photon interference predominantly
contributes at H+H kinetic energy releases of 0.2 -- 0.45 eV, and
net-2-photon and 1-photon interference contributes at 1.65 -- 1.9 eV. These
measurements of the benchmark H molecule offer the distinct advantage
that they can be quantitatively compared with \textit{ab initio} theory to
confirm our understanding of strong-field coherent control via the
carrier-envelope phase
Continuous image distortion by astrophysical thick lenses
Image distortion due to weak gravitational lensing is examined using a
non-perturbative method of integrating the geodesic deviation and optical
scalar equations along the null geodesics connecting the observer to a distant
source. The method we develop continuously changes the shape of the pencil of
rays from the source to the observer with no reference to lens planes in
astrophysically relevant scenarios. We compare the projected area and the ratio
of semi-major to semi-minor axes of the observed elliptical image shape for
circular sources from the continuous, thick-lens method with the commonly
assumed thin-lens approximation. We find that for truncated singular isothermal
sphere and NFW models of realistic galaxy clusters, the commonly used thin-lens
approximation is accurate to better than 1 part in 10^4 in predicting the image
area and axes ratios. For asymmetric thick lenses consisting of two massive
clusters separated along the line of sight in redshift up to \Delta z = 0.2, we
find that modeling the image distortion as two clusters in a single lens plane
does not produce relative errors in image area or axes ratio more than 0.5%Comment: accepted to GR
Theme Overview: Agriculture and Water Quality in the Cornbelt: Overview of Issues and Approaches
Resource /Energy Economics and Policy, Q25,
On the effective Dirac dynamics of ultracold atoms in bichromatic optical lattices
We study the dynamics of ultracold atoms in tailored bichromatic optical
lattices. By tuning the lattice parameters, one can readily engineer the band
structure and realize a Dirac point, i.e. a true crossing of two Bloch bands.
The dynamics in the vicinity of such a crossing is described by the
one-dimensional Dirac equation, which is rigorously shown beyond the
tight-binding approximation. Within this framework we analyze the effects of an
external potential and demonstrate numerically that it is possible to
demonstrate Klein tunneling with current experimental setups.Comment: 6 pages, 5 figure
Single-shot carrier-envelope-phase measurement in ambient air
The ability to measure and control the carrier envelope phase (CEP) of
few-cycle laser pulses is of paramount importance for both frequency metrology
and attosecond science. Here, we present a phase meter relying on the
CEP-dependent photocurrents induced by circularly polarized few-cycle pulses
focused between electrodes in ambient air. The new device facilitates compact
single-shot, CEP measurements under ambient conditions and promises CEP tagging
at repetition rates orders of magnitude higher than most conventional CEP
detection schemes as well as straightforward implementation at longer
wavelengths
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