20,488 research outputs found
Evaluation of expected solar flare neutrino events in the IceCube observatory
Since the end of the eighties and in response to a reported increase in the
total neutrino flux in the Homestake experiment in coincidence with a solar
flare, solar neutrino detectors have searched for solar flare signals.
Neutrinos from the decay of mesons, which are themselves produced in collisions
of accelerated protons with the solar atmosphere, would provide a novel window
on the underlying physics of the acceleration process. For our studies we focus
on the IceCube Neutrino Observatory, a cubic kilometer neutrino detector
located at the geographical South Pole. Due to its Supernova data acquisition
system and its DeepCore component, dedicated to low energy neutrinos, IceCube
may be sensitive to solar flare neutrinos and thus permit either a measurement
of the signal or the establishment of more stringent upper limits on the solar
flare neutrino flux. We present an approach for a time profile analysis based
on a stacking method and an evaluation of a possible solar flare signal in
IceCube using the Geant4 toolkit.Comment: Paper submitted to the 34th International Cosmic Ray Conference, The
Hague 201
Spin filling of a quantum dot derived from excited-state spectroscopy
We study the spin filling of a semiconductor quantum dot using excited-state
spectroscopy in a strong magnetic field. The field is oriented in the plane of
the two-dimensional electron gas in which the dot is electrostatically defined.
By combining the observation of Zeeman splitting with our knowledge of the
absolute number of electrons, we are able to determine the ground state spin
configuration for one to five electrons occupying the dot. For four electrons,
we find a ground state spin configuration with total spin S=1, in agreement
with Hund's first rule. The electron g-factor is observed to be independent of
magnetic field and electron number.Comment: 11 pages, 7 figures, submitted to New Journal of Physics, focus issue
on Solid State Quantum Informatio
Nanopositioning of a diamond nanocrystal containing a single NV defect center
Precise control over the position of a single quantum object is important for
many experiments in quantum science and nanotechnology. We report on a
technique for high-accuracy positioning of individual diamond nanocrystals. The
positioning is done with a home-built nanomanipulator under real-time scanning
electron imaging, yielding an accuracy of a few nanometers. This technique is
applied to pick up, move and position a single NV defect center contained in a
diamond nanocrystal. We verify that the unique optical and spin properties of
the NV center are conserved by the positioning process.Comment: 3 pages, 3 figures; high-resolution version available at
http://www.ns.tudelft.nl/q
Excitons in Electrostatic Traps
We consider in-plane electrostatic traps for indirect excitons in coupled
quantum wells, where the traps are formed by a laterally modulated gate
voltage. An intrinsic obstacle for exciton confinement in electrostatic traps
is an in-plane electric field that can lead to exciton dissociation. We propose
a design to suppress the in-plane electric field and, at the same time, to
effectively confine excitons in the electrostatic traps. We present
calculations for various classes of electrostatic traps and experimental proof
of principle for trapping of indirect excitons in electrostatic traps.Comment: 4 pages, 3 figure
Evaluation of the application of ERTS-1 data to the regional land use planning process
The author has identified the following significant results. Employing simple and economical extraction methods, ERTS can provide valuable data to the planners at the state or regional level with a frequency never before possible. Interactive computer methods of working directly with ERTS digital information show much promise for providing land use information at a more specific level, since the data format production rate of ERTS justifies improved methods of analysis
Zero Temperature Phase Transition in Spin-ladders: Phase Diagram and Dynamical studies of Cu(Hp)Cl
In a magnetic field, spin-ladders undergo two zero-temperature phase
transitions at the critical fields Hc1 and Hc2. An experimental review of
static and dynamical properties of spin-ladders close to these critical points
is presented. The scaling functions, universal to all quantum critical points
in one-dimension, are extracted from (a) the thermodynamic quantities
(magnetization) and (b) the dynamical functions (NMR relaxation). A simple
mapping of strongly coupled spin ladders in a magnetic field on the exactly
solvable XXZ model enables to make detailed fits and gives an overall
understanding of a broad class of quantum magnets in their gapless phase
(between Hc1 and Hc2). In this phase, the low temperature divergence of the NMR
relaxation demonstrates its Luttinger liquid nature as well as the novel
quantum critical regime at higher temperature. The general behaviour close
these quantum critical points can be tied to known models of quantum magnetism.Comment: few corrections made, 15 pages, to be published in European Journal
of Physics
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