102 research outputs found
A Conformally Invariant Holographic Two-Point Function on the Berger Sphere
We apply our previous work on Green's functions for the four-dimensional
quaternionic Taub-NUT manifold to obtain a scalar two-point function on the
homogeneously squashed three-sphere (otherwise known as the Berger sphere),
which lies at its conformal infinity. Using basic notions from conformal
geometry and the theory of boundary value problems, in particular the
Dirichlet-to-Robin operator, we establish that our two-point correlation
function is conformally invariant and corresponds to a boundary operator of
conformal dimension one. It is plausible that the methods we use could have
more general applications in an AdS/CFT context.Comment: 1+49 pages, no figures. v2: Several typos correcte
Search for Single Top Production at LEP
Single top production in e+e- annihilations is searched for in data collected
by the L3 detector at centre-of-mass energies from 189 to 209 GeV,
corresponding to a total integrated luminosity of 634 pb-1. Investigating
hadronic and semileptonic top decays, no evidence of single top production at
LEP is obtained and upper limits on the single top cross section as a function
of the centre-of-mass energy are derived. Limits on possible anomalous
couplings, as well as on the scale of contact interactions responsible for
single top production are determined
Flavour Independent Search for Neutral Higgs Bosons at LEP
A flavour independent search for the CP-even and CP-odd neutral Higgs bosons
h and A is performed in 624/pb of data collected with the L3 detector at LEP at
centre-of-mass energies between 189 and 209GeV. Higgs boson production through
the e^+e^- -> Z h and the e^+e^- ->h A processes is considered and decays of
the Higgs bosons into hadrons are studied. No significant signal is observed
and 95% confidence level limits on the hZZ and hAZ couplings are derived as a
function of the Higgs boson masses. Assuming the Standard Model cross section
for the Higgs-strahlung process and a 100% branching fraction into hadrons, a
95% confidence level lower limit on the mass of the Higgs boson is set at
110.3GeV
Measurement of the Probability of Gluon Splitting into Charmed Quarks in Hadronic Z Decays
We have measured the probability, n(g->cc~), of a gluon splitting into a
charm-quark pair using 1.7 million hadronic Z decays collected by the L3
detector. Two independent methods have been applied to events with a three-jet
topology. One method relies on tagging charmed hadrons by identifying a lepton
in the lowest energy jet. The other method uses a neural network based on
global event shape parameters. Combining both methods, we measure n(g->cc~)=
[2.45 +/- 0.29 +/- 0.53]%
Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at root(s)=192-202GeV
A search for the lightest neutral CP-even and the neutral CP-odd Higgs bosons
of the Minimal Supersymmetric Standard Model is performed using 233.2 pb-1 of
integrated luminosity collected with the L3 detector at LEP at centre-of-mass
energies 192-202 GeV. No signal is observed and lower mass limits are given as
a function of tan(beta) for two scalar top mixing hypotheses. For tan(beta)
greater than 0.8, they are mh > 83.4 GeV and mA > 83.8 GeV at 95 % confidence
level
Direct radiative forcing and atmospheric absorption by boundary layer aerosols in the southeastern US: model estimates on the basis of new observations
In an effort to reduce uncertainties in the quantification of aerosol direct radiative forcing (ADRF) in the southeastern United States (US), a field column experiment was conducted to measure aerosol radiative properties and effects at Mt. Mitchell, North Carolina, and at an adjacent valley site. The experimental period was from June 1995 to mid-December 1995. The aerosol optical properties (single scattering albedo and asymmetry factor) needed to compute ADRF were obtained on the basis of a procedure involving a Mie code and a radiative transfer code in conjunction with the retrieved aerosol size distribution, aerosol optical depth, and diffuse-to-direct solar irradiance ratio. The regional values of ADRF at the surface and top of atmosphere (TOA), and atmospheric aerosol absorption are derived using the obtained aerosol optical properties as inputs to the column radiation model (CRM) of the community climate model (CCM3). The cloud-free instantaneous TOA ADRFs for highly polluted (HP), marine (M) and continental (C) air masses range from 20.3 to â24.8, 1.3 to â10.4, and 1.9 to â13.4 W mâ2, respectively. The mean cloud-free 24-h ADRFs at the TOA (at the surface) for HP, M, and C air masses are estimated to be â8±4 (â33±16), â7±4 (â13±8), and â0.14±0.05 (â8±3) W mâ2, respectively. On the assumption that the fractional coverage of clouds is 0.61, the annual mean ADRFs at the TOA and the surface are â2±1, and â7±2 W mâ2, respectively. This also implies that aerosols currently heat the atmosphere over the southeastern US by 5±3 W mâ2 on annual timescales due to the aerosol absorption in the troposphere
The Earth: Plasma Sources, Losses, and Transport Processes
This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, 1999) are addressed
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