635 research outputs found
The orbit structure of Dynkin curves
Let G be a simple algebraic group over an algebraically closed field k;
assume that Char k is zero or good for G. Let \cB be the variety of Borel
subgroups of G and let e in Lie G be nilpotent. There is a natural action of
the centralizer C_G(e) of e in G on the Springer fibre \cB_e = {B' in \cB | e
in Lie B'} associated to e. In this paper we consider the case, where e lies in
the subregular nilpotent orbit; in this case \cB_e is a Dynkin curve. We give a
complete description of the C_G(e)-orbits in \cB_e. In particular, we classify
the irreducible components of \cB_e on which C_G(e) acts with finitely many
orbits. In an application we obtain a classification of all subregular orbital
varieties admitting a finite number of B-orbits for B a fixed Borel subgroup of
G.Comment: 12 pages, to appear in Math
Neutrino masses and mixing from neutrino oscillation data
We discuss what information about the neutrino mass spectrum and the elements
of the neutrino mixing matrix can be inferred from the results of neutrino
oscillation experiments. The cases of three and four massive neutrinos are
considered. It is shown that the general characteristics of the neutrino mixing
matrix are quite different from those of the quark mixing matrix.Comment: 4 pages, including 2 figures. Talk presented by S.M. Bilenky at the
XVI International Workshop on Weak Interactions and Neutrinos, Capri, Italy,
June 22-28 199
Inflammatory breast cancer: dynamic contrast-enhanced MR in patients receiving bevacizumab. Initial experience
To retrospectively compare three dynamic contrast material-enhanced
magnetic resonance (MR) imaging (dynamic MR imaging) analytic methods to
determine the parameter or combination of parameters most strongly associated
with changes in tumor microvasculature during treatment with bevacizumab alone
and bevacizumab plus chemotherapy in patients with inflammatory or locally
advanced breast cancer. MATERIALS AND METHODS: This study was conducted in
accordance with the institutional review board of the National Cancer Institute
and was compliant with the Privacy Act of 1974. Informed consent was obtained
from all patients. Patients with inflammatory or locally advanced breast cancer
were treated with one cycle of bevacizumab alone (cycle 1) followed by six cycles
of combination bevacizumab and chemotherapy (cycles 2-7). Serial dynamic MR
images were obtained, and the kinetic parameters measured by using three dynamic
analytic MR methods (heuristic, Brix, and general kinetic models) and two
region-of-interest strategies were compared by using two-sided statistical tests.
A P value of .01 was required for significance. RESULTS: In 19 patients, with use
of a whole-tumor region of interest, the authors observed a significant decrease
in the median values of three parameters measured from baseline to cycle 1:
forward transfer rate constant (Ktrans) (-34% relative change, P=.003), backflow
compartmental rate constant extravascular and extracellular to plasma (Kep) (-15%
relative change, P<.001), and integrated area under the gadolinium concentration
curve (IAUGC) at 180 seconds (-23% relative change, P=.009). A trend toward
differences in the heuristic slope of the washout curve between responders and
nonresponders to therapy was observed after cycle 1 (bevacizumab alone, P=.02).
The median relative change in slope of the wash-in curve from baseline to cycle 4
was significantly different between responders and nonresponders (P=.009).
CONCLUSION: The dynamic contrast-enhanced MR parameters Ktrans, Kep, and IAUGC at
180 seconds appear to have the strongest association with early physiologic
response to bevacizumab. Clinical trial registration no. NCT0001654
On the equivalence of the Langevin and auxiliary field quantization methods for absorbing dielectrics
Recently two methods have been developed for the quantization of the
electromagnetic field in general dispersing and absorbing linear dielectrics.
The first is based upon the introduction of a quantum Langevin current in
Maxwell's equations [T. Gruner and D.-G. Welsch, Phys. Rev. A 53, 1818 (1996);
Ho Trung Dung, L. Kn\"{o}ll, and D.-G. Welsch, Phys. Rev. A 57, 3931 (1998); S.
Scheel, L. Kn\"{o}ll, and D.-G. Welsch, Phys. Rev. A 58, 700 (1998)], whereas
the second makes use of a set of auxiliary fields, followed by a canonical
quantization procedure [A. Tip, Phys. Rev. A 57, 4818 (1998)]. We show that
both approaches are equivalent.Comment: 7 pages, RevTeX, no figure
Energy Flow in the Hadronic Final State of Diffractive and Non-Diffractive Deep-Inelastic Scattering at HERA
An investigation of the hadronic final state in diffractive and
non--diffractive deep--inelastic electron--proton scattering at HERA is
presented, where diffractive data are selected experimentally by demanding a
large gap in pseudo --rapidity around the proton remnant direction. The
transverse energy flow in the hadronic final state is evaluated using a set of
estimators which quantify topological properties. Using available Monte Carlo
QCD calculations, it is demonstrated that the final state in diffractive DIS
exhibits the features expected if the interaction is interpreted as the
scattering of an electron off a current quark with associated effects of
perturbative QCD. A model in which deep--inelastic diffraction is taken to be
the exchange of a pomeron with partonic structure is found to reproduce the
measurements well. Models for deep--inelastic scattering, in which a
sizeable diffractive contribution is present because of non--perturbative
effects in the production of the hadronic final state, reproduce the general
tendencies of the data but in all give a worse description.Comment: 22 pages, latex, 6 Figures appended as uuencoded fil
A Search for Selectrons and Squarks at HERA
Data from electron-proton collisions at a center-of-mass energy of 300 GeV
are used for a search for selectrons and squarks within the framework of the
minimal supersymmetric model. The decays of selectrons and squarks into the
lightest supersymmetric particle lead to final states with an electron and
hadrons accompanied by large missing energy and transverse momentum. No signal
is found and new bounds on the existence of these particles are derived. At 95%
confidence level the excluded region extends to 65 GeV for selectron and squark
masses, and to 40 GeV for the mass of the lightest supersymmetric particle.Comment: 13 pages, latex, 6 Figure
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC
Measurements of inclusive jet suppression in heavy ion collisions at the LHC
provide direct sensitivity to the physics of jet quenching. In a sample of
lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated
luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with
a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the
transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the
anti-kt algorithm with values for the distance parameter that determines the
nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of
the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp.
Jet production is found to be suppressed by approximately a factor of two in
the 10% most central collisions relative to peripheral collisions. Rcp varies
smoothly with centrality as characterized by the number of participating
nucleons. The observed suppression is only weakly dependent on jet radius and
transverse momentum. These results provide the first direct measurement of
inclusive jet suppression in heavy ion collisions and complement previous
measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables,
submitted to Physics Letters B. All figures including auxiliary figures are
available at
http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02
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