30,812 research outputs found
Dynamical Supersymmetry Breaking and Low Energy Gauge Mediation
Dynamical breaking of supersymmetry was long thought to be an exceptional
phenomenon, but recent developments have altered this view. A question of great
interest in the current framework is the value of the underlying scale of
supersymmetry breaking. The "little hierarchy" problem suggests that
supersymmetry should be broken at low energies. Within one class of models, low
energy breaking be achieved as a consequence of symmetries, without requiring
odd coincidences. The low energy theories are distinguished by the presence or
absence of symmetries; in either case, and especially the latter one often
finds modifications of the minimal gauge-mediated spectrum which can further
ameliorate problems of fine tuning. Various natural mechanisms exist to solve
the problem in this framework.Comment: 20 pages (minor change in referencing
Contracting for Impure Public Goods: Carbon Offsets and Additionality
Governments contracting with private agents for the provision of an impure public good must contend with agents who would potentially supply the good absent any payments. This additionality problem is centrally important in the use of carbon offsets as part of climate change mitigation. Analyzing optimal contracts for forest carbon sequestration, an important offset category, we conduct a national-scale simulation using results from an econometric model of land-use change. The results indicate that for an increase in forest area of 50 million acres, annual government expenditures with optimal contracts are about $4 billion lower compared than under a uniform subsidy.Carbon Sequestration, Incentive Contracting, Offsets, Additionality
Aeropropulsive characteristics of twin single-expansion-ramp vectoring nozzles installed with forward-swept wings and canards
The Langley 16 foot transonic tunnel was used to determine the aeropropulsive characteristics of twin single-expansion-ramp vectoring nozzles installed in a wing-body configuration with forward-swept wings. The configuration was tested with and without fixed canards. The test conditions included free-stream Mach numbers of 0.60, 0.90, and 1.20. The model angle of attack ranged from -2 deg to 14 deg; the nozzle pressure ratio ranged from 1.0 (jet off) to 9.0. The Reynolds number based on the wing mean aerodynamic chord varied from 3.0 x 10 to the 6th power to 4.8 x 10 to the 6th power, depending on Mach number. Aerodynamic characteristics were analyzed to determine the effects of thrust vectoring and the canard effects on the wing-afterbody-nozzle and the wing-afterbody portions of the model. Thrust vectoring had no effect on the angle of attack for the onset of flow separation on the wing but resulted in reduced drag at angle-of-attack values above that required for wing flow separation. The canard was found to have little effect on the thrust-induced lift resulting from vectoring, since canard effects occurred primarily on the wing
Interference effects of thrust reversing on horizontal tail effectiveness of twin-engine fighter aircraft at Mach numbers from 0.15 to 0.90
An investigation was conducted in the Langley 16 foot Transonic Tunnel to determine the interference effects of thrust reversing on horizontal tail effectiveness of a twin engine, general research fighter model at approach and in-flight speeds. Twin vertical tails at three longitudinal locations were tested at a cant angle of 0 deg. One configuration was also tested at a cant angle of 20 deg. Two nonaxisymmetric nozzle reverser concepts were studied. Test data were obtained at Mach numbers of 0.15, 0.60, and 0.90 and at angles of attack from -3 to 9 deg. Nozzle pressure ratios varied from jet off to 7.0, depending upon Mach number. At landing approach speed (Mach number 0.15), thrust reverser operation usually resulted in large variations (up to 70% increase) in horizontal tail effectiveness as nozzle pressure ratio was varied at zero angle of attack or as angle of attack was varied at constant nozzle pressure ratio. There was always a decrease in effectiveness at Mach numbers of 0.60 and 0.90 as a result of reverser operation
Quantum Flux and Reverse Engineering of Quantum Wavefunctions
An interpretation of the probability flux is given, based on a derivation of
its eigenstates and relating them to coherent state projections on a quantum
wavefunction. An extended definition of the flux operator is obtained using
coherent states. We present a "processed Husimi" representation, which makes
decisions using many Husimi projections at each location. The processed Husimi
representation reverse engineers or deconstructs the wavefunction, yielding the
underlying classical ray structure. Our approach makes possible interpreting
the dynamics of systems where the probability flux is uniformly zero or
strongly misleading. The new technique is demonstrated by the calculation of
particle flow maps of the classical dynamics underlying a quantum wavefunction.Comment: Accepted to EP
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