12,229 research outputs found
Measurement of Quantum Fluctuations in Geometry
A particular form for the quantum indeterminacy of relative spacetime
position of events is derived from the limits of measurement possible with
Planck wavelength radiation. The indeterminacy predicts fluctuations from a
classically defined geometry in the form of ``holographic noise'' whose spatial
character, absolute normalization, and spectrum are predicted with no
parameters. The noise has a distinctive transverse spatial shear signature, and
a flat power spectral density given by the Planck time. An interferometer
signal displays noise due to the uncertainty of relative positions of
reflection events. The noise corresponds to an accumulation of phase offset
with time that mimics a random walk of those optical elements that change the
orientation of a wavefront. It only appears in measurements that compare
transverse positions, and does not appear at all in purely radial position
measurements. A lower bound on holographic noise follows from a covariant upper
bound on gravitational entropy. The predicted holographic noise spectrum is
estimated to be comparable to measured noise in the currently operating
interferometer GEO600. Because of its transverse character, holographic noise
is reduced relative to gravitational wave effects in other interferometer
designs, such as LIGO, where beam power is much less in the beamsplitter than
in the arms.Comment: 7 pages, 2 figures, LaTeX. Extensive rewrite of original version,
including more detailed analysis. Main result is the same but the estimate of
noise in strain units for GEO600, showing 1/f behavior at low f and flat at
high f, is improved. To appear in Phys. Rev.
Holographic Geometry and Noise in Matrix Theory
Using Matrix Theory as a concrete example of a fundamental holographic
theory, we show that the emergent macroscopic spacetime displays a new
macroscopic quantum structure, holographic geometry, and a new observable
phenomenon, holographic noise, with phenomenology similar to that previously
derived on the basis of a quasi-monochromatic wave theory. Traces of matrix
operators on a light sheet with a compact dimension of size are interpreted
as transverse position operators for macroscopic bodies. An effective quantum
wave equation for spacetime is derived from the Matrix Hamiltonian. Its
solutions display eigenmodes that connect longitudinal separation and
transverse position operators on macroscopic scales. Measurements of transverse
relative positions of macroscopically separated bodies, such as signals in
Michelson interferometers, are shown to display holographic nonlocality,
indeterminacy and noise, whose properties can be predicted with no parameters
except . Similar results are derived using a detailed scattering calculation
of the matrix wavefunction. Current experimental technology will allow a
definitive and precise test or validation of this interpretation of holographic
fundamental theories. In the latter case, they will yield a direct measurement
of independent of the gravitational definition of the Planck length, and a
direct measurement of the total number of degrees of freedom.Comment: 19 pages, 2 figures; v2: factors of Planck mass written explicitly,
typos correcte
Indeterminacy of Holographic Quantum Geometry
An effective theory based on wave optics is used to describe indeterminacy of
position in holographic spacetime with a UV cutoff at the Planck scale.
Wavefunctions describing spacetime positions are modeled as complex
disturbances of quasi-monochromatic radiation. It is shown that the product of
standard deviations of two position wavefunctions in the plane of a holographic
light sheet is equal to the product of their normal separation and the Planck
length. For macroscopically separated positions the transverse uncertainty is
much larger than the Planck length, and is predicted to be observable as a
"holographic noise" in relative position with a distinctive shear spatial
character, and an absolutely normalized frequency spectrum with no parameters
once the fundamental wavelength is fixed from the theory of gravitational
thermodynamics. The spectrum of holographic noise is estimated for the GEO600
interferometric gravitational-wave detector, and is shown to approximately
account for currently unexplained noise between about 300 and 1400Hz. In a
holographic world, this result directly and precisely measures the fundamental
minimum interval of time.Comment: 4 pages, LaTeX. Considerably shortened from earlier version.
Conclusions are unchanged. Submitted to PR
Interferometers as Probes of Planckian Quantum Geometry
A theory of position of massive bodies is proposed that results in an
observable quantum behavior of geometry at the Planck scale, . Departures
from classical world lines in flat spacetime are described by Planckian
noncommuting operators for position in different directions, as defined by
interactions with null waves. The resulting evolution of position wavefunctions
in two dimensions displays a new kind of directionally-coherent quantum noise
of transverse position. The amplitude of the effect in physical units is
predicted with no parameters, by equating the number of degrees of freedom of
position wavefunctions on a 2D spacelike surface with the entropy density of a
black hole event horizon of the same area. In a region of size , the effect
resembles spatially and directionally coherent random transverse shear
deformations on timescale with typical amplitude . This quantum-geometrical "holographic noise" in position is not
describable as fluctuations of a quantized metric, or as any kind of
fluctuation, dispersion or propagation effect in quantum fields. In a Michelson
interferometer the effect appears as noise that resembles a random Planckian
walk of the beamsplitter for durations up to the light crossing time. Signal
spectra and correlation functions in interferometers are derived, and predicted
to be comparable with the sensitivities of current and planned experiments. It
is proposed that nearly co-located Michelson interferometers of laboratory
scale, cross-correlated at high frequency, can test the Planckian noise
prediction with current technology.Comment: 23 pages, 6 figures, Latex. To appear in Physical Review
Light-like Signals in General relativity and Cosmology
The modelling of light-like signals in General Relativity taking the form of
impulsive gravitational waves and light-like shells of matter is examined.
Systematic deductions from the Bianchi identities are made. These are based
upon Penrose's hierarchical classification of the geometry induced on the null
hypersurface history of the surface by its imbedding in the space-times to the
future and to the past of it. The signals are not confined to propagate in a
vacuum and thus their interaction with matter (a burst of radiation propagating
through a cosmic fluid, for example) is also studied. Results are accompanied
by illustrative examples using cosmological models, vacuum space-times, the de
sitter univers and Minkowskian space-time.Comment: 21 pages, latex, no figure
Persian Gulf response to a wintertime shamal wind event
The results from a~1 km resolution Hybrid Coordinate Ocean Model (HYCOM),forced by 1/2° Navy Operational Global Atmospheric Prediction System (NOGAPS) atmospheric data, were used in order to study the dynamic response of the Persian Gulf to winter time shamal forcing. Shamal winds are strong northwesterly winds that occur in the Persian Gulf area behind southeast moving cold fronts. The period from 20 November to 5 December 2004 included a well-defined shamal event that lasted 4–5 days. In addition to strong winds (16ms_1) the winter shamal also brought cold dry air(Ta=20 °C, qa=10 gkg-1) which led to a net heat loss in excess of 1000 W m-2 by increasing the latent heat flux. This resulted in SST cooling of up to 10°C most notably in the northern and shallower shelf regions. A sensitivity experiment with a constant specific humidity of qa= 15 gkg-1 confirmed that about 38% of net heat loss was due to the air– sea humidity differences. The time integral of SST cooling closely followed the air–sea heat loss, indicating an approximate one-dimensional vertical heat balance. It was found that the shamal induced convective vertical mixing provided a direct mechanism for the erosion of stratification and deepening of the mixed layer by 30m. The strong wind not only strengthened the circulation in the entire Persian Gulf but also established a northwestward flowing Iranian Coastal Current (ICC,25–30cms-1) from the Strait of Hormuz to about 52°E, where it veered off shore. The strongest negative sea level of 25–40cm was generated in the northern most portion of the Gulf while the wind set up against the coast of the United Arab Emirates established a positive sea level of 15–30 cm. The transport through the Strait of Hormuz at 56.2°E indicated an enhanced out flow of 0.25Sv (Sv=106 m3 s-1) during 24 November followed by an equivalent in flow on the next day
Enhancement of pigmeat quality by altering pre-slaughter management
End of project reportThe studies presented in this report were conducted to investigate the effect of breed, slaughter weight, castration of male pigs and strategic feeding strategies on the performance of pigs to slaughter and on
their carcass quality.
The effect of breed, gender and feeding regimen on the performance of pigs and their carcass quality was examined in the first study (Section 3). From weaning to slaughter Landrace-sired pigs grew at a similar rate but had a better feed conversion efficiency compared with Duroc-sired pigs.
Landrace-sired pigs also had a higher carcass lean and greater muscle depth than Duroc-sired pigs.
Entire male pigs grew more efficiently, had lower lean content in their carcasses and had a reduced kill out yield when compared with gilts. The eye muscle depth was greater for gilts than entire males.
Diluting the diet with grass-meal (GM) reduced growth rate, caused a deterioration in feed conversion efficiency, reduced back fat thickness, reduced eye muscle thickness and reduced kill out yield compared to the control feeding regimen of a cereal based diet. Compensatory growth was observed
during a re-alimentation period following a period of diet dilution with grass-meal. However,
where it did occur, in most cases it was only partial. Adding 5% rapeseed oil instead of lard to the finisher diet increased nitrogen utilization efficiency and phosphorous utilization efficiency.
The effect of gender (boar, castrate, gilt) and slaughter weight (80 to 120kg) on pig performance, carcass quality, meat quality, and nitrogen excretion was investigated in the second study (Section 4).
Boars grew faster than gilts and more efficiently than castrates or gilts. Castrates had a higher kill out
yield than boars. Nitrogen excretion from castrates was similar to gilts which were both higher than that from boars. The processing value of carcasses from castrates may be higher than that of boars and
gilts. In particular castrates had heavier loins and bellies than either boars or gilts. Carcasses from castrates and gilts had a higher temperature (recorded 24 hours post slaughter) than boars. However,
pH24 was not affected by gender. The intramuscular fat content of the l. dorsi in castrates was higher than that of boars or gilts, however at 1.65% this was well below the level (2.0%) above which any
noticeable sensory attributes might be detected.
Feed intake increased with increasing slaughter weight and feed conversion efficiency deteriorated. N
excretion also increased with each increment in weight. Carcass lean content increased up to 90kg live EOP 4939.doc 4 25/10/2005
weight then reached a plateau and declined after 110kg live weight. Heavier carcasses yielded more product for approximately the same slaughtering cost and the associated larger muscles could make it
easier to use seam butchery techniques that result in lean, well-trimmed, attractive cuts and joints. The pH45 and pH24 were reduced with increasing slaughter weight and drip loss increased. Heavier pigs
may be more prone to the development of PSE than lighter pigs as their carcass temperature remains higher for longer than that of lighter pigs
Upper-Ocean Response to Hurricane Ivan in a 1/25 Degrees Nested Gulf of Mexico HYCOM
[ 1] A 20-layer, 1/25 degrees nested Gulf of Mexico (GoM) Hybrid Coordinate Ocean Model (HYCOM) has been employed to examine the evolving three-dimensional ocean response to Hurricane Ivan during 14 - 16 September 2004. Results from several combinations of numerical experiments with and without assimilation of satellite-altimetry sea-surface height (SSH) are being analyzed and compared for the September 2004 hurricane period. A comparison of simulated zonal and meridional velocities using data assimilation shows improved agreement with profiler observations. The amplitude of the cold wake ( similar to 6 degrees C) produced by these simulations compared reasonably well with the observed changes in SST before and after the storm; however, the region of extreme cooling varied depending on the simulated location of the warm core eddy (WCE) that had detached from the Loop Current ( LC). While the simulated location of the WCE and LC in the assimilation runs agree better with satellite altimetry, the storm-induced SST cooling was 40% - 50% greater than the observed cooling. Overall, similar to 64% of the cooling was due to vertical mixing caused by turbulence generated from strong shear-stress across the base of the mixed layer. Vertical advection (upwelling) caused a significant portion of cooling (23.4%) in those runs that included data assimilation; a three fold increase from the nonassimilative runs (7%). This enhanced upper- ocean cooling was caused primarily by the prestorm thermal stratification; a shallower thermocline ( similar to 40 m) and a stronger upper- thermocline temperature gradient compared with the nonassimilative runs. In all the experiments the air-sea exchange was a small component of the mixed-layer heat budget which overall accounted for similar to 4
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