13,555 research outputs found
A 4-neutrino model with a Higgs triplet
We take as a starting point the Gelmini -- Roncadelli model enlarged by a
term with explicit lepton number violation in the Higgs potential and add a
neutrino singlet field coupled via a scalar doublet to the usual leptons. This
scenario allows us to take into account all three present indications in favour
of neutrino oscillations provided by the solar, atmospheric and LSND neutrino
oscillation experiments. Furthermore, it suggests a model which reproduces
naturally one of the two 4-neutrino mass spectra favoured by the data. In this
model the solar neutrino problem is solved by large mixing MSW \nu_e\to\nu_\tau
transitions and the atmospheric neutrino problem by transitions of \nu_\mu into
a sterile neutrino.Comment: Latex, 14 pages, no figure
Evidence for A Two-dimensional Quantum Wigner Solid in Zero Magnetic Field
We report the first experimental observation of a characteristic nonlinear
threshold behavior from dc dynamical response as an evidence for a Wigner
crystallization in high-purity GaAs 2D hole systems in zero magnetic field. The
system under increasing current drive exhibits voltage oscillations with
negative differential resistance. They confirm the coexistence of a moving
crystal along with striped edge states as observed for electrons on helium
surfaces. However, the threshold is well below the typical classical levels due
to a different pinning and depinning mechanism that is possibly related to a
quantum process
Numerical Relativity Injection Infrastructure
This document describes the new Numerical Relativity (NR) injection
infrastructure in the LIGO Algorithms Library (LAL), which henceforth allows
for the usage of NR waveforms as a discrete waveform approximant in LAL. With
this new interface, NR waveforms provided in the described format can directly
be used as simulated GW signals ("injections") for data analyses, which include
parameter estimation, searches, hardware injections etc. As opposed to the
previous infrastructure, this new interface natively handles sub-dominant modes
and waveforms from numerical simulations of precessing binary black holes,
making them directly accessible to LIGO analyses. To correctly handle
precessing simulations, the new NR injection infrastructure internally
transforms the NR data into the coordinate frame convention used in LAL.Comment: 20 pages, 2 figures, technical repor
Field-induced resonant tunneling between parallel two-dimensional electron systems
Resonant tunneling between two high-mobility two-dimensional (2D) electron systems in a double quantum well structure has been induced by the action of an external Schottky gate field. Using one 2D electron gas as source and the other as drain, the tunnel conductance between them shows a strong resonance when the gate field aligns the ground subband edges of the two quantum wells
Independently contacted two-dimensional electron systems in double quantum wells
A new technique for creating independent ohmic contacts to closely spaced two-dimensional electron systems in double quantum well (DQW) structures is described. Without use of shallow diffusion or precisely controlled etching methods, the present technique results in low-resistance contacts which can be electrostatically switched between the two-conducting layers. The method is demonstrated with a DQW consisting of two 200 Ã… GaAs quantum wells separated by a 175 Ã… AlGaAs barrier. A wide variety of experiments on Coulomb and tunnel-coupled 2D electron systems is now accessible
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