11,143 research outputs found
Using the BFKL resummation to fit DIS data: collinear and running coupling effects
The proton structure function F2 is studied in the low x regime using BFKL
evolution. The next to leading logarithmic (NLL) analysis requires the
inclusion of running coupling effects which lead to off-diagonal terms in the
evolution kernel. An all-orders resummation is used to improve the collinear
behavior of the NLL BFKL result. We emphasize the theoretical uncertainties
that appear throughout the analysis and give a comparison to the combined HERA
data.Comment: 4 pages, 5 figures, proceedings of the XX Workshop on Deep-Inelastic
Scattering and Related Subjects, 26-30 March, University of Bonn (2012
Stellar Motions in the Polar Ring Galaxy NGC 4650A
We present the first measurement of the stellar kinematics in the polar ring
of NGC 4650A. There is well defined rotation, with the stars and gas rotating
in the same direction, and with similar amplitude. The gaseous and stellar
kinematics suggest an approximately flat rotation curve, providing further
support for the hypothesis that the polar material resides in a disk rather
than in a ring. The kinematics of the emission line gas at and near the center
of the S0 suggests that the polar disk lacks a central hole. We have not
detected evidence for two, equal mass, counterrotating stellar polar streams,
as is predicted in the resonance levitation model proposed by Tremaine & Yu. A
merger seems the most likely explanation for the structure and kinematics of
NGC 4650A.Comment: 4 pages, accepted for publication in ApJ Letter
Exclusive central production of heavy quarks at the LHC
We study the exclusive production of heavy flavors at central rapidities in
hadron-hadron collisions within the kT factorisation formalism. Since this
involves regions of small Bjorken x in the unintegrated gluon densities, we
include the next-to-leading order BFKL contributions working directly in
transverse momentum representation. Our results are presented in a form
suitable for Monte Carlo implementation.Comment: 10 pages, 1 figur
Gluon Saturation and Black Hole Criticality
We discuss the recent proposal in hep-th/0611312 where it was shown that the
critical anomalous dimension associated to the onset of non-linear effects in
the high energy limit of QCD coincides with the critical exponent governing the
radius of the black hole formed in the spherically symmetric collapse of a
massless scalar field. We argue that a new essential ingredient in this mapping
between gauge theory and gravity is continuous self-similarity, not present in
the scalar field case but in the spherical collapse of a perfect fluid with
barotropic equation of state. We identify this property with geometric scaling,
present in DIS data at small values of Bjorken x. We also show that the
Choptuik exponent in dimension five tends to the QCD critical value in the
traceless limit of the energy momentum tensor.Comment: Talk given at 12th International Conference on Elastic and
Diffractive Scattering: Forward Physics and QCD, Hamburg, DESY, Germany,
21-25 May 200
Are Transition Economy Workers Underpaid?
We examine the extent to which workers in transition and developed market economies are able to obtain wages that fully reflect their skills and labor force characteristics. We find that workers in two transition economies, the Czech Republic and Poland, are able to better attain the maximum wage available than are workers in a sample of developed market economies. This greater wage-setting efficiency in the transition economies appears to be more the result of social and demographic characteristics of the labor force than of the mechanisms for setting wages or of labor market policies.labor markets, wage inefficiency, job search, stochastic frontier, economic transition
First order perturbations of the Einstein-Straus and Oppenheimer-Snyder models
We derive the linearly perturbed matching conditions between a Schwarzschild
spacetime region with stationary and axially symmetric perturbations and a FLRW
spacetime with arbitrary perturbations. The matching hypersurface is also
perturbed arbitrarily and, in all cases, the perturbations are decomposed into
scalars using the Hodge operator on the sphere. This allows us to write down
the matching conditions in a compact way. In particular, we find that the
existence of a perturbed (rotating, stationary and vacuum) Schwarzschild cavity
in a perturbed FLRW universe forces the cosmological perturbations to satisfy
constraints that link rotational and gravitational wave perturbations. We also
prove that if the perturbation on the FLRW side vanishes identically, then the
vacuole must be perturbatively static and hence Schwarzschild. By the dual
nature of the problem, the first result translates into links between
rotational and gravitational wave perturbations on a perturbed
Oppenheimer-Snyder model, where the perturbed FLRW dust collapses in a
perturbed Schwarzschild environment which rotates in equilibrium. The second
result implies in particular that no region described by FLRW can be a source
of the Kerr metric.Comment: LaTeX; 29 page
The Stellar and Gas Kinematics of Several Irregular Galaxies
We present long-slit spectra of three irregular galaxies from which we
determinethe stellar kinematics in two of the galaxies (NGC 1156 and NGC 4449)
and ionized-gas kinematics in all three (including NGC 2366). We compare this
to the optical morphology and to the HI kinematics of the galaxies. In the
ionized gas, we see a linear velocity gradient in all three galaxies. In NGC
1156 we also detect a weak linear velocity gradient in the stars of (5+/-1/sin
i) km/s/kpc to a radius of 1.6 kpc. The stars and gas are rotating about the
same axis, but this is different from the major axis of the stellar bar which
dominates the optical light of the galaxy. In NGC 4449 we do not detect
organized rotation of the stars and place an upper limit of (3/sin i) km/s/kpc
to a radius of 1.2 kpc. For NGC 4449, which has signs of a past interaction
with another galaxy, we develop a model to fit the observed kinematics of the
stars and gas. In this model the stellar component is in a rotating disk seen
nearly face-on while the gas is in a tilted disk with orbits whose planes
precess in the gravitational potential. This model reproduces the apparent
counter-rotation of the inner gas of the galaxy. The peculiar orbits of the gas
are presumed due to acquisition of gas in the past interaction.Comment: To be published in ApJ, November 20, 200
Low-Grade Appendiceal Mucinous Neoplasm Involving the Endometrium and Presenting with Mucinous Vaginal Discharge.
Primary appendiceal mucinous lesions are uncommon and represent a spectrum from nonneoplastic mucous retention cysts to invasive adenocarcinoma. Low-grade appendiceal mucinous neoplasms (LAMNs) represent an intermediate category on this spectrum and can be classified according to whether or not they are confined to the appendix. Although LAMNs are frequently confined to the appendix, they can also spread to the peritoneum and clinically progress as pseudomyxoma peritonei (i.e., mucinous ascites). Thus, the appropriate classification of appendiceal primary neoplasia is essential for prognosis and influences clinical management. In addition, the precise classification, management, and clinical outcome of patients with disseminated peritoneal disease remain controversial. Here, we report an unusual case of LAMN with pseudomyxoma peritonei that initially presented with mucinous and bloody vaginal discharge. Pathological evaluation revealed low-grade appendiceal mucinous neoplasm with secondary involvement of the peritoneum, ovaries, and endometrial surface. Therefore, LAMN should be considered in the differential diagnosis of mucinous vaginal discharge
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