209,297 research outputs found
Shuttle system ascent aerodynamic and plume heating
The shuttle program provided a challenge to the aerothermodynamicist due to the complexity of the flow field around the vehicle during ascent, since the configuration causes multiple shock interactions between the elements. Wind tunnel tests provided data for the prediction of the ascent design heating environment which involves both plume and aerodynamic heating phenomena. The approach for the heating methodology based on ground test firings and the use of the wind tunnel data to formulate the math models is discussed
Second-order superposition operations via Hong-Ou-Mandel interference
We propose an experimental scheme to implement a second-order nonlocal
superposition operation and its variants by way of Hong-Ou-Mandel interference.
The second-order coherent operations enable us to generate a NOON state with
high particle number in a heralded fashion and also can be used to enhance the
entanglement properties of continuous variable states. We discuss the
feasibility of our proposed scheme considering realistic experimental
conditions such as on-off photodetectors with nonideal efficiency and imperfect
single-photon sources.Comment: published version, 6 pages, 6 figure
Proving the correctness of the flight director program EADIFD, volume 1
EADIFD is written in symbolic assembly language for execution on the C4000 airborne computer. It is a subprogram of an aircraft navigation and guidance program and is used to generate pitch and roll command signals for use in terminal airspace. The proof of EADIFD was carried out by an inductive assertion method consisting of two parts, a verification condition generator and a source language independent proof checker. With the specifications provided by NASA, EADIFD was proved correct. The termination of the program is guaranteed and the program contains no instructions that can modify it under any conditions
Evaluation of atmospheric density models and preliminary functional specifications for the Langley Atmospheric Information Retrieval System (LAIRS)
This document presents the results of an extensive survey and comparative evaluation of current atmosphere and wind models for inclusion in the Langley Atmospheric Information Retrieval System (LAIRS). It includes recommended models for use in LAIRS, estimated accuracies for the recommended models, and functional specifications for the development of LAIRS
Neutron Electric Dipole Moment at Fixed Topology
We describe the finite volume effects of CP-odd quantities, such as the
neutron electric dipole moment and the anapole moment in the -vacuum,
under different topological sectors. We evaluate the three-point Green's
functions for the electromagnetic current in a fixed non-trivial topological
sector in order to extract these CP-odd observables. We discuss the role of
zero modes in the CP-odd Green's function and show that, in the quenched
approximation, there is a power divergence in the quark mass for CP-odd
quantities at finite volume.Comment: 12 pages, revised manuscript to be publishe
Dark matter and dark gauge fields
Following the unexpected theoretical discovery of a mass dimension one
fermionic quantum field of spin one half, we now present first results on two
_local_ versions. The Dirac and Majorana fields of the standard model of
particle physics are supplemented by their natural counterparts in the dark
matter sector. The possibility that a mass dimension transmuting symmetry may
underlie a new standard model of particle physics is briefly suggested.Comment: This manuscript combines a plenary talk (by DVA) and an invited talk
(by DS) at "Dark 2007 - Sixth International Heidelberg Conference on Dark
Matter in Astro and Particle Physics (Sydney, Australia, 24th-28th September
2007)." 11 pages. v2: minor typos correcte
Dynamics of thermalisation in small Hubbard-model systems
We study numerically the thermalisation and temporal evolution of the reduced
density matrix for a two-site subsystem of a fermionic Hubbard model prepared
far from equilibrium at a definite energy. Even for very small systems near
quantum degeneracy, the subsystem can reach a steady state resembling
equilibrium. This occurs for a non-perturbative coupling between the subsystem
and the rest of the lattice where relaxation to equilibrium is Gaussian in
time, in sharp contrast to perturbative results. We find similar results for
random couplings, suggesting such behaviour is generic for small systems.Comment: 4 pages, 5 figure
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