22,777 research outputs found
On correlation functions of integrable models associated to the six-vertex R-matrix
We derive an analog of the master equation obtained recently for correlation
functions of the XXZ chain for a wide class of quantum integrable systems
described by the R-matrix of the six-vertex model, including in particular
continuum models. This generalized master equation allows us to obtain multiple
integral representations for the correlation functions of these models. We
apply this method to derive the density-density correlation functions of the
quantum non-linear Schrodinger model.Comment: 21 page
Kinematics of Current Region Fragmentation in Semi-Inclusive Deeply Inelastic Scattering
Different kinematical regimes of semi-inclusive deeply inelastic scattering
(SIDIS) processes correspond to different underlying partonic pictures, and it
is important to understand the transition between them. This is particularly
the case when there is sensitivity to intrinsic transverse momentum, in which
case kinematical details can become especially important. We address the
question of how to identify the current fragmentation region --- the
kinematical regime where a factorization picture with fragmentation functions
is appropriate. We distinguish this from soft and target fragmentation regimes.
Our criteria are based on the kinematic regions used in derivations of
factorization theorems. We argue that, when hard scales are of order a few
GeVs, there is likely significant overlap between different rapidity regions
that are normally understood to be distinct. We thus comment on the need to
take this into account with more unified descriptions of SIDIS, which should
span all rapidities for the produced hadron. Finally, we propose general
criteria for estimating the proximity to the current region at large Q.Comment: 9 Pages, 5 figures; minor clarifications and corrections, version
appearing in Physics Letters
A Search for H-alpha Absorption in the Exosphere of the Transiting Extrasolar Planet HD 209458b
There is evidence that the transiting planet HD 209458b has a large exosphere
of neutral hydrogen, based on a 15% decrement in Lyman-alpha flux that was
observed by Vidal-Madjar et al. during transits. Here we report upper limits on
H-alpha absorption by the exosphere. The results are based on optical spectra
of the parent star obtained with the Subaru High Dispersion Spectrograph.
Comparison of the spectra taken inside and outside of transit reveals no
exospheric H-alpha signal greater than 0.1% within a 5.1A band (chosen to have
the same Delta_lambda/lambda as the 15% Ly-alpha absorption). The corresponding
limit on the column density of n=2 neutral hydrogen is N_2 <~ 10^9 cm^{-2}.
This limit constrains proposed models involving a hot (~10^4 K) and
hydrodynamically escaping exosphere.Comment: To appear in PASJ [9 pages, 5 figures]. Minor corrections to match
published versio
A human colonic crypt culture system to study regulation of stem cell-driven tissue renewal and physiological function
The intestinal epithelium is one of the most rapidly renewing tissues in the human body and fulfils vital physiological roles such as barrier function and transport of nutrients and fluid. Investigation of gut epithelial physiology in health and disease has been hampered by the lack of ex vivo models of the native human intestinal epithelium. Recently, remarkable progress has been made in defining intestinal stem cells and in generating intestinal organoid cultures. In parallel, we have developed a 3D culture system of the native human colonic epithelium that recapitulates the topological hierarchy of stem cell-driven tissue renewal and permits the physiological study of native polarized epithelial cells. Here we describe methods to establish 3D cultures of intact human colonic crypts and conduct real-time imaging of intestinal tissue renewal, cellular signalling, and physiological function, in conjunction with manipulation of gene expression by lentiviral or adenoviral transduction. Visualization of mRNA- and protein-expression patterns in cultured human colonic crypts, and cross-validation with crypts derived from fixed mucosal biopsies, is also described. Alongside studies using intestinal organoids, the near-native human colonic crypt culture model will help to bridge the gap that exists between investigation of colon cancer cell lines and/or animal (tissue) studies, and progression to clinical trials. To this end, the near native human colonic crypt model provides a platform to aid the development of novel strategies for the prevention of inflammatory bowel disease and cancer
Laughlin states on the Poincare half-plane and its quantum group symmetry
We find the Laughlin states of the electrons on the Poincare half-plane in
different representations. In each case we show that there exist a quantum
group symmetry such that the Laughlin states are a representation of
it. We calculate the corresponding filling factor by using the plasma analogy
of the FQHE.Comment: 9 pages,Late
Mapping the Kinematical Regimes of Semi-Inclusive Deep Inelastic Scattering
We construct a language for identifying kinematical regions of transversely
differential semi-inclusive deep inelastic scattering cross sections with
particular underlying partonic pictures, especially in regions of moderate to
low where sensitivity to kinematical effects outside the usual very high
energy limit becomes non-trivial. The partonic pictures map to power law
expansions whose leading contributions ultimately lead to well-known QCD
factorization theorems. We propose methods for estimating the consistency of
any particular region of overall hadronic kinematics with the kinematics of a
given underlying partonic picture. The basic setup of kinematics of
semi-inclusive deep inelastic scattering is also reviewed in some detail.Comment: 37 pages, 11 Figure
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