81,052 research outputs found
Renormalization of twist-four operators in light-cone gauge
We compute one-loop renormalization group equations for non-singlet
twist-four operators in QCD. The calculation heavily relies on the light-cone
gauge formalism in the momentum fraction space that essentially rephrases the
analysis of all two-to two and two-to-three transition kernels to purely
algebraic manipulations both for non- and quasipartonic operators. This is the
first brute force calculation of this sector available in the literature.
Fourier transforming our findings to the coordinate space, we checked them
against available results obtained within a conformal symmetry-based formalism
that bypasses explicit diagrammatic calculations and confirmed agreement with
the latter.Comment: 58 pages, 16 figures; dedicated to the memory of Eduard A. Kurae
Enhancement of charged macromolecule capture by nanopores in a salt gradient
Nanopores spanning synthetic membranes have been used as key components in
proof-of-principle nanofluidic applications, particularly those involving
manipulation of biomolecules or sequencing of DNA. The only practical way of
manipulating charged macromolecules near nanopores is through a voltage
difference applied across the nanopore-spanning membrane. However, recent
experiments have shown that salt concentration gradients applied across
nanopores can also dramatically enhance charged particle capture from a low
concentration reservoir of charged molecules at one end of the nanopore. This
puzzling effect has hitherto eluded a physically consistent theoretical
explanation. Here, we propose an electrokinetic mechanism of this enhanced
capture that relies on the electrostatic potential near the pore mouth. For
long pores with diameter much greater than the local screening length, we
obtain accurate analytic expressions showing how salt gradients control the
local conductivity which can lead to increased local electrostatic potentials
and charged analyte capture rates. We also find that the attractive
electrostatic potential may be balanced by an outward, repulsive electroosmotic
flow (EOF) that can in certain cases conspire with the salt gradient to further
enhance the analyte capture rate.Comment: 10 pages, 6 Figure
On the formation of density filaments in the turbulent interstellar medium
This study is motivated by recent observations on ubiquitous interstellar
density filaments and guided by modern theories of compressible
magnetohydrodynamic (MHD) turbulence. The interstellar turbulence shapes the
observed density structures. As the fundamental dynamics of compressible MHD
turbulence, perpendicular turbulent mixing of density fluctuations entails
elongated density structures aligned with the local magnetic field, accounting
for low-density parallel filaments seen in diffuse atomic and molecular gas.
The elongation of low-density parallel filaments depends on the turbulence
anisotropy. When taking into account the partial ionization, we find that the
minimum width of parallel filaments in the cold neutral medium and molecular
clouds is determined by the neutral-ion decoupling scale perpendicular to
magnetic field. In highly supersonic MHD turbulence in molecular clouds, both
low-density parallel filaments due to anisotropic turbulent mixing and
high-density filaments due to shock compression exist.Comment: 13 pages, 6 figures, accepted for publication in ApJ. arXiv admin
note: text overlap with arXiv:1802.0098
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