384,810 research outputs found
On the hydrostatic approximation of the Navier-Stokes equations in a thin strip
In this paper, we first prove the global well-posedness of a scaled
anisotropic Navier-Stokes system and the hydrostatic Navier-Stokes system in a
2-D striped domain with small analytic data in the tangential variable. Then we
justify the limit from the anisotropic Navier-Stokes system to the hydrostatic
Navier-Stokes system with analytic data
Precision measurement of cosmic magnification from 21 cm emitting galaxies
We show how precision lensing measurements can be obtained through the
lensing magnification effect in high redshift 21cm emission from galaxies.
Normally, cosmic magnification measurements have been seriously complicated by
galaxy clustering. With precise redshifts obtained from 21cm emission line
wavelength, one can correlate galaxies at different source planes, or exclude
close pairs to eliminate such contaminations.
We provide forecasts for future surveys, specifically the SKA and CLAR. SKA
can achieve percent precision on the dark matter power spectrum and the galaxy
dark matter cross correlation power spectrum, while CLAR can measure an
accurate cross correlation power spectrum. The neutral hydrogen fraction was
most likely significantly higher at high redshifts, which improves the number
of observed galaxies significantly, such that also CLAR can measure the dark
matter lensing power spectrum. SKA can also allow precise measurement of
lensing bispectrum.Comment: 11 pages, 8 figures. Accepted to MNRAS. We deleted two figures and
shortened the paper to meet MNRAS's requirement. All main results remain
unchange
Gauge Invariance and QCD Twist-3 Factorization for Single Spin Asymmetries
The collinear factorization at twist-3 for Drell-Yan processes is studied
with the motivation to solve the discrepancy in literature about the single
spin asymmetry in the lepton angular distribution, and to show how QCD gauge
invariance is realized in the hadronic tensor. The obtained result here agrees
with our early result derived with a totally different approach. In addition to
the asymmetry we can construct another two observables to identify the spin
effect. We show that the gauge invariance of different contributions in the
hadronic tensor is made in different ways by summing the effects of gluon
exchanges. More interestingly is that we can show that the virtual correction
to one structure function of the hadronic tensor, hence to some weighted SSA
observables, is completely determined by the quark form factor. This will
simplify the calculation of higher order corrections. The corresponding result
in semi-inclusive DIS is also given for the comparison with Drell-Yan
processes.Comment: Small changes, accepted by JHE
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