26,365 research outputs found
S-Duality Constraints On Effective Potentials For Gaugino Condensation
We clarify the role of approximate S-duality in effective supergravity
theories that are the low energy limits of string theories, and show how this
partial symmetry may be used to constrain effective lagrangians for gaugino
condensation.Comment: 22 page
Reduced order system identification for UAVs
Reduced order models representing the dynamic behaviour of symmetric aircraft are well known and can be easily derived from the standard equations of motion. In flight testing, accurate measurements of the dependent variables which describe the linearised reduced order models for a particular flight condition are vital for successful system identification. However, not all the desired measurements such as the rate of change in vertical velocity (W. ) can be accurately measured in practice. In order to determine such variables two possible solutions exist: reconstruction or differentiation. This paper addresses the effect of both methods on the reliability of the parameter estimates. The methods are used in the estimation of the aerodynamic derivatives for the Aerosonde UAV from a recreated flight test scenario in Simulink. Subsequently, the methods are then applied and compared using real data obtained from flight tests of the Cranfield University Jetstream 31 (G-NFLA) research aircraft
The Y^2 Stellar Evolutionary Tracks
We present a database of the latest stellar models of the (Yonsei-Yale)
collaboration. This database contains the stellar evolutionary tracks from the
pre-main-sequence birthline to the helium core flash that were used to
construct the isochrones. We also provide a simple interpolation routine
that generates stellar tracks for given sets of parameters (metallicity, mass,
and -enhancement).Comment: 7 pages, TeX, 1 eps figure. ApJS, 2003, vol.144 (Feb), in pres
Airline Alliances, Carve-Outs and Collusion
In this paper, we ask how antitrust immunity subject to a carve-out affects collusion incentives in international airline alliances. We show that the gains from economies of density due to higher interline traffic under the alliance strengthen the incentive to collude on the interhub segment, while the accompanying revenue gain heightens the incentive to defect from collusive behavior. These two effects exactly cancel in the case of linear demands and linear economies of density. Under this approximation, the incentives for interhub collusion are no different before and after the emergence of an airline alliance subject to a carve-out.collusion, carve-out
Laser phase noise effects on the dynamics of optomechanical resonators
We investigate theoretically the influence of laser phase noise on the
cooling and heating of a generic cavity optomechanical system. We derive the
back-action damping and heating rates and the mechanical frequency shift of the
radiation pressure-driven oscillating mirror, and derive the minimum phonon
occupation number for small laser linewidths. We find that in practice laser
phase noise does not pose serious limitations to ground state cooling. We then
consider the effects of laser phase noise in a parametric cavity driving scheme
that minimizes the back-action heating of one of the quadratures of the
mechanical oscillator motion. Laser linewidths narrow compared to the decay
rate of the cavity field will not pose any problems in an experimental setting,
but broader linewidths limit the practicality of this back-action evasion
method.Comment: 9 pages, 7 figure
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