32,373 research outputs found
On the Relation Between Quantum Mechanical and Classical Parallel Transport
We explain how the kind of ``parallel transport'' of a wavefunction used in
discussing the Berry or Geometrical phase induces the conventional parallel
transport of certain real vectors. These real vectors are associated with
operators whose commutators yield diagonal operators; or in Lie algebras those
operators whose commutators are in the (diagonal) Cartan subalgebra.Comment: 3 pages, no figure
Observing the Galaxy's massive black hole with gravitational wave bursts
An extreme-mass-ratio burst (EMRB) is a gravitational wave signal emitted
when a compact object passes through periapsis on a highly eccentric orbit
about a much more massive object, in our case a stellar mass object about a
10^6 M_sol black hole. EMRBs are a relatively unexplored means of probing the
spacetime of massive black holes (MBHs). We conduct an investigation of the
properties of EMRBs and how they could allow us to constrain the parameters,
such as spin, of the Galaxy's MBH. We find that if an EMRB event occurs in the
Galaxy, it should be detectable for periapse distances r_p < 65 r_g for a \mu =
10 M_sol orbiting object, where r_g = GM/c^2 is the gravitational radius. The
signal-to-noise ratio scales as \rho ~ -2.7 log(r_p/r_g) + log(\mu/M_sol) +
4.9. For periapses r_p < 10 r_g, EMRBs can be informative, and provide good
constraints on both the MBH's mass and spin. Closer orbits provide better
constraints, with the best giving accuracies of better than one part in 10^4
for both the mass and spin parameter.Comment: 25 pages, 17 figures, 1 appendix. One more typo fixe
Expectations for extreme-mass-ratio bursts from the Galactic Centre
When a compact object on a highly eccentric orbit about a much more massive
body passes through periapsis it emits a short gravitational wave signal known
as an extreme-mass-ratio burst (EMRB). We consider stellar mass objects
orbiting the massive black hole (MBH) found in the Galactic Centre. EMRBs
provide a novel means of extracting information about the MBH; an EMRB from the
Galactic MBH could be highly informative regarding the MBH's mass and spin if
the orbital periapsis is small enough. However, to be a useful astronomical
tool EMRBs must be both informative and sufficiently common to be detectable
with a space-based interferometer. We construct a simple model to predict the
event rate for Galactic EMRBs. We estimate there could be on average ~2 bursts
in a two year mission lifetime for LISA. Stellar mass black holes dominate the
event rate. Creating a sample of 100 mission realisations, we calculate what we
could learn about the MBH. On average, we expect to be able to determine the
MBH mass to ~1% and the spin to ~0.1 using EMRBs.Comment: 22 pages, 5 figures, 2 appendices. Minor changes to reflect published
versio
Analysis and test for space shuttle propellant dynamics
This report presents the results of a study to develop an analytical model capable of predicting the dynamic interaction forces on the Shuttle External Tank, due to large amplitude propellant slosh during RTLS separation. The report details low-g drop tower and KC-135 test programs that were conducted to investigate propellant reorientation during RTLS. In addition, the development of a nonlinear finite element slosh model (LAMPS2, two dimensional, and one LAMPS3, three dimensional) is presented. Correlation between the model and test data is presented as a verification of the modeling approach
Analysis and test for space shuttle propellant dynamics (1/10th scale model test results). Volume 1: Technical discussion
Space shuttle propellant dynamics during ET/Orbiter separation in the RTLS (return to launch site) mission abort sequence were investigated in a test program conducted in the NASA KC-135 "Zero G" aircraft using a 1/10th-scale model of the ET LOX Tank. Low-g parabolas were flown from which thirty tests were selected for evaluation. Data on the nature of low-g propellant reorientation in the ET LOX tank, and measurements of the forces exerted on the tank by the moving propellent will provide a basis for correlation with an analytical model of the slosh phenomenon
Emotional and behavioral reaction to intrusive thoughts.
A self-report measure of the emotional and behavioral reactions to intrusive thoughts was developed. The article presents data that confirm the stability, reliability, and validity of the new seven-item measure. Emotional and behavioral reactions to intrusions emerged as separate factors on the Emotional and Behavioral Reactions to Intrusions Questionnaire (EBRIQ), a finding confirmed by an independent stress study. Test-retest reliability over 30 to 70 days was good. Expected relationships with other constructs were significant. Stronger negative responses to intrusions were associated with lower mindfulness scores and higher ratings of experiential avoidance, thought suppression, and intensity and frequency of craving. The EBRIQ will help explore differences in reactions to intrusive thoughts in clinical and nonclinical populations, and across different emotional and behavioral states. It will also be useful in assessing the effects of therapeutic approaches such as mindfulness
Correlation of AH-1G airframe test data with a NASTRAN mathematical model
Test data was provided for evaluating a mathematical vibration model of the Bell AH-1G helicopter airframe. The math model was developed and analyzed using the NASTRAN structural analysis computer program. Data from static and dynamic tests were used for comparison with the math model. Static tests of the fuselage and tailboom were conducted to verify the stiffness representation of the NASTRAN model. Dynamic test data were obtained from shake tests of the airframe and were used to evaluate the NASTRAN model for representing the low frequency (below 30 Hz) vibration response of the airframe
Analysis and test for space shuttle propellant dynamics: 1/60th scale model test results
During the abort sequence, the ET and orbiter separate under aerodynamic loading, with propellant remaining in the ET. The separation event included a seven second decelerating coast period during which the residual propellant accelerates relative to the ET/orbiter. At separation, ET clearance was primarily provided by aerodynamics acting on the ET to move it away. The motion of the propellant, primarily LOX, significantly influenced the resulting ET motion and could cause the ET to recontact the orbiter. A test program was conducted involving thirty-two drops with 1/60th scale models of the ET LOX tank. The objective was to acquire data on the nature of low g propellant reorientation, in the ET LOX tank, and to measure the forces exerted on the tank by the moving propellant
The Pioneer anomaly: the measure of a topological phase defect of light in cosmology
It is shown that a wave vector representing a light pulse in an adiabatically
evolving expanding space should develop, after a round trip (back and forth to
the emitter) a geometric phase for helicity states at a given fixed position
coordinate of this expanding space.In a section of the Hopf fibration of the
Poincare sphere that identifies a projection to the physically allowed states,
the evolution defines a parallel transported state that can be joined
continuously with the initial state by means of the associated
Berry-Pancharatnam connection. The connection allows to compute an anomaly in
the frequency for the vector modes in terms of the scale factor of the
space-time background being identical to the reported Pioneer Anomaly.Comment: 10 pages, some minor notation changes have been made. Some additional
remarks were writte
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