Browsing by Subject "resonances"
Now showing 1 - 4 of 4
- Results Per Page
- Sort Options
Item Astrometry, Radial Velocity, And Photometry: The Hd 128311 System Remixed With Data From Hst, Het, And Apt(2014-11) McArthur, Barbara E.; Benedict, G. Fritz; Henry, Gregory W.; Hatzes, Artie; Cochran, William D.; Harrison, Thomas E.; Johns-Krull, Chris; Nelan, Ed; McArthur, Barbara E.; Benedict, G. Fritz; Cochran, William D.We have used high-cadence radial velocity measurements from the Hobby-Eberly Telescope with published velocities from the Lick 3 m Shane Telescope, combined with astrometric data from the Hubble Space Telescope (HST) Fine Guidance Sensors to refine the orbital parameters of the HD 128311 system, and determine an inclination of 55.degrees 95 +/- 14.degrees 55 and true mass of 3.789(+0.924)(-0.432) M-JUP for HD 128311 c. The combined radial velocity data also reveal a short period signal which could indicate a third planet in the system with an M sin i of 0.133 +/- 0.005 M-JUP or stellar phenomena. Photometry from the T12 0.8 m automatic photometric telescope at the Fairborn Observatory and HST are used to determine a photometric period close to, but not within the errors of the radial velocity signal. We performed a cross-correlation bisector analysis of the radial velocity data to look for correlations with the photometric period and found none. Dynamical integrations of the proposed system show long-term stability with the new orbital parameters of over 10 million years. Our new orbital elements do not support the claims of HD 128311 b and c being in mean motion resonance.Item Giant Enhancement of Stimulated Brillouin Scattering in the Subwavelength Limit(2012-01) Rakich, Peter T.; Reinke, Charles; Camacho, Ryan; Davids, Paul; Wang, Zheng; Wang, ZhengStimulated Brillouin scattering (SBS) is traditionally viewed as a process whose strength is dictated by intrinsic material nonlinearities with little dependence on waveguide geometry. We show that this paradigm breaks down at the nanoscale, as tremendous radiation pressures produce new forms of SBS nonlinearities. A coherent combination of radiation pressure and electrostrictive forces is seen to enhance both forward and backward SBS processes by orders of magnitude, creating new geometric degrees of freedom through which photon-phonon coupling becomes highly tailorable. At nanoscales, the backward-SBS gain is seen to be 10(4) times greater than in conventional silica fibers with 100 times greater values than predicted by conventional SBS treatments. Furthermore, radically enhanced forward-SBS processes are 10(5) times larger than any known waveguide system. In addition, when nanoscale silicon waveguides are cooled to low temperatures, a further 10-100 times increase in SBS gain is seen as phonon losses are reduced. As a result, a 100-mu m segment of the waveguide has equivalent nonlinearity to a kilometer of fiber. Couplings of this magnitude would enable efficient chip-scale stimulated Brillouin scattering in silicon waveguides for the first time. More generally, we develop a new full-vectorial theoretical formulation of stimulated Brillouin scattering that accurately incorporates the effects of boundary-induced nonlinearities and radiation pressure, both of which are seen to have tremendous impact on photon-phonon coupling at subwavelength scales. This formalism, which treats both intermode and intramode coupling within periodic and translationally invariant waveguide systems, reveals a rich landscape of new stimulated Brillouin processes when applied to nanoscale systems.Item Quantal Time Asymmetry: Mathematical Foundation And Physical Interpretation(2010-07) Bohm, A.; Bohm, A.Time in standard quantum mechanics extends from -infinity < t < + infinity; this is the result of a mathematical theorem (Stone-von Neumann) for the solutions of the Schrodinger equation for states or of the Heisenberg equation for observables. In reality t does not extend to t -> -infinity since according to causality, a quantum state phi(+) must be prepared first at a particular time t = t(0), before the probability vertical bar(psi(-)(t),phi+(t(0))vertical bar(2) for an observable psi(-) can be measured in it at t > t(0) (Feynman (1948)). In experiments on single Ba(+) ions, Dehmelt and others observed this finite preparation time as the ensemble of onset-times t(0)(1),t(0)(2), ..., t(0)(n) of dark periods. How the semigroup time evolution, t(0) equivalent to 0 < t < infinity with a beginning of time t(0), can suggest the parametrization of the resonance pole position of the Z-boson at S= s(R) as s(R) = (M(R) - i Gamma(R)/2)(2) in terms of a mass M(R) and a width Gamma(R) given by a lifetime tau = (h) over bar/Gamma(R), is the subject of this contribution dedicated to Augusto Garcia.Item Slow Light Through Tightly-Coupled Light Waves And Acoustic Waves In Nanoscale Waveguides(2013-03) Wang, Z.; Qiu, W. J.; Rakich, P.; Shin, H.; Dong, H.; Wang, Zheng; Dong, HuiWe develop a general framework of evaluating slow-light performance using Stimulated Brillouin Scattering (SBS) in optical waveguides via the overlap integral between optical and elastic eigen-modes. We show that spatial symmetry of the optical force dictates the selection rules of the excitable elastic modes. By applying this method to a rectangular silicon waveguide, we demonstrate the spatial distributions of optical force and elastic eigen-modes jointly determine the magnitude and scaling of SBS gain coefficient in both forward and backward SBS processes. We further apply this method to inter-modal SBS process, and demonstrate that the coupling between distinct optical modes is necessary to excite elastic modes with all possible symmetries.