2,414 research outputs found
Consideration of radar target glint from ST during OMV rendezvous
The nature of radar target glint and the factors upon which it depends when using the Hubble Space Telescope as a radar target is discussed. An analysis of the glint problem using a 35 MHz or 94 MHz radar on the orbital maneuvering vehicle is explored. A strategy for overcoming glint is suggested
Topological Test Spaces
A test space is the set of outcome-sets associated with a collection of
experiments. This notion provides a simple mathematical framework for the study
of probabilistic theories -- notably, quantum mechanics -- in which one is
faced with incommensurable random quantities. In the case of quantum mechanics,
the relevant test space, the set of orthonormal bases of a Hilbert space,
carries significant topological structure. This paper inaugurates a general
study of topological test spaces. Among other things, we show that any
topological test space with a compact space of outcomes is of finite rank. We
also generalize results of Meyer and Clifton-Kent by showing that, under very
weak assumptions, any second-countable topological test space contains a dense
semi-classical test space.Comment: 12 pp., LaTeX 2e. To appear in Int. J. Theor. Phy
On Zurek's derivation of the Born rule
Recently, W. H. Zurek presented a novel derivation of the Born rule based on
a mechanism termed environment-assisted invariance, or "envariance" [W. H.
Zurek, Phys. Rev. Lett. 90(2), 120404 (2003)]. We review this approach and
identify fundamental assumptions that have implicitly entered into it,
emphasizing issues that any such derivation is likely to face.Comment: 8 pages; v2: minor clarifications added; v3: reference to Zurek's
quant-ph/0405161 added. To appear in Foundations of Physics (Cushing Volume
Classical Lie algebras and Drinfeld doubles
The Drinfeld double structure underlying the Cartan series An, Bn, Cn, Dn of
simple Lie algebras is discussed.
This structure is determined by two disjoint solvable subalgebras matched by
a pairing. For the two nilpotent positive and negative root subalgebras the
pairing is natural and in the Cartan subalgebra is defined with the help of a
central extension of the algebra.
A new completely determined basis is found from the compatibility conditions
in the double and a different perspective for quantization is presented. Other
related Drinfeld doubles on C are also considered.Comment: 11 pages. submitted for publication to J. Physics
Probabilities from Entanglement, Born's Rule from Envariance
I show how probabilities arise in quantum physics by exploring implications
of {\it environment - assisted invariance} or {\it envariance}, a recently
discovered symmetry exhibited by entangled quantum systems. Envariance of
perfectly entangled ``Bell-like'' states can be used to rigorously justify
complete ignorance of the observer about the outcome of any measurement on
either of the members of the entangled pair. For more general states,
envariance leads to Born's rule, for the outcomes
associated with Schmidt states. Probabilities derived in this manner are an
objective reflection of the underlying state of the system -- they represent
experimentally verifiable symmetries, and not just a subjective ``state of
knowledge'' of the observer. Envariance - based approach is compared with and
found superior to pre-quantum definitions of probability including the {\it
standard definition} based on the `principle of indifference' due to Laplace,
and the {\it relative frequency approach} advocated by von Mises. Implications
of envariance for the interpretation of quantum theory go beyond the derivation
of Born's rule: Envariance is enough to establish dynamical independence of
preferred branches of the evolving state vector of the composite system, and,
thus, to arrive at the {\it environment - induced superselection (einselection)
of pointer states}, that was usually derived by an appeal to decoherence.
Envariant origin of Born's rule for probabilities sheds a new light on the
relation between ignorance (and hence, information) and the nature of quantum
states.Comment: Figure and an appendix (Born's rule for continuous spectra) added.
Presentation improved. (Comments still welcome...
Epistemic and Ontic Quantum Realities
Quantum theory has provoked intense discussions about its interpretation since its pioneer days. One of the few scientists who have been continuously engaged in this development from both physical and philosophical perspectives is Carl Friedrich von Weizsaecker. The questions he posed were and are inspiring for many, including the authors of this contribution. Weizsaecker developed Bohr's view of quantum theory as a theory of knowledge. We show that such an epistemic perspective can be consistently complemented by Einstein's ontically oriented position
Shoot growth of woody trees and shrubs is predicted by maximum plant height and associated traits
1. The rate of elongation and thickening of individual branches (shoots) varies across plant species. This variation is important for the outcome of competition and other plant-plant interactions. Here we compared rates of shoot growth across 44 species from tropical, warm temperate, and cool temperate forests of eastern Australia.2. Shoot growth rate was found to correlate with a suite of traits including the potential height of the species, xylem-specific conductivity, leaf size, leaf area per xylem cross-section, twig diameter (at 40 cm length), wood density and modulus of elasticity.3. Within this suite of traits, maximum plant height was the clearest correlate of growth rates, explaining 50 to 67% of the variation in growth overall (p p 4. Growth rates were not strongly correlated with leaf nitrogen or leaf mass per unit leaf area.5. Correlations between growth and maximum height arose both across latitude (47%, p p p p < 0.0001), reflecting intrinsic differences across species and sites
The open XXZ and associated models at q root of unity
The generalized open XXZ model at root of unity is considered. We review
how associated models, such as the harmonic oscillator, and the lattice
sine-Gordon and Liouville models are obtained. Explicit expressions of the
local Hamiltonian of the spin XXZ spin chain coupled to dynamical
degrees of freedom at the one end of the chain are provided. Furthermore, the
boundary non-local charges are given for the lattice sine Gordon model and the
harmonic oscillator with open boundaries. We then identify the spectrum and
the corresponding Bethe states, of the XXZ and the q harmonic oscillator in the
cyclic representation with special non diagonal boundary conditions. Moreover,
the spectrum and Bethe states of the lattice versions of the sine-Gordon and
Liouville models with open diagonal boundaries is examined. The role of the
conserved quantities (boundary non-local charges) in the derivation of the
spectrum is also discussed.Comment: 31 pages, LATEX, minor typos correcte
Initial elevation bias in subjective reports
Peer reviewedPostprin
The Advanced LIGO Photon Calibrators
The two interferometers of the Laser Interferometry Gravitaional-wave
Observatory (LIGO) recently detected gravitational waves from the mergers of
binary black hole systems. Accurate calibration of the output of these
detectors was crucial for the observation of these events, and the extraction
of parameters of the sources. The principal tools used to calibrate the
responses of the second-generation (Advanced) LIGO detectors to gravitational
waves are systems based on radiation pressure and referred to as Photon
Calibrators. These systems, which were completely redesigned for Advanced LIGO,
include several significant upgrades that enable them to meet the calibration
requirements of second-generation gravitational wave detectors in the new era
of gravitational-wave astronomy. We report on the design, implementation, and
operation of these Advanced LIGO Photon Calibrators that are currently
providing fiducial displacements on the order of
m/ with accuracy and precision of better than 1 %.Comment: 14 pages, 19 figure
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