849 research outputs found
Quantum incompressibility of a falling Rydberg atom, and a gravitationally-induced charge separation effect in superconducting systems
Freely falling point-like objects converge towards the center of the Earth.
Hence the gravitational field of the Earth is inhomogeneous, and possesses a
tidal component. The free fall of an extended quantum object such as a hydrogen
atom prepared in a high principal-quantum-number stretch state, i.e., a
circular Rydberg atom, is predicted to fall more slowly that a classical
point-like object, when both objects are dropped from the same height from
above the Earth. This indicates that, apart from "quantum jumps," the atom
exhibits a kind of "quantum incompressibility" during free fall in
inhomogeneous, tidal gravitational fields like those of the Earth. A
superconducting ring-like system with a persistent current circulating around
it behaves like the circular Rydberg atom during free fall. Like the electronic
wavefunction of the freely falling atom, the Cooper-pair wavefunction is
"quantum incompressible." The ions of the ionic lattice of the superconductor,
however, are not "quantum incompressible," since they do not possess a globally
coherent quantum phase. The resulting difference during free fall in the
response of the nonlocalizable Cooper pairs of electrons and the localizable
ions to inhomogeneous gravitational fields is predicted to lead to a charge
separation effect, which in turn leads to a large repulsive Coulomb force that
opposes the convergence caused by the tidal, attractive gravitational force on
the superconducting system. A "Cavendish-like" experiment is proposed for
observing the charge separation effect induced by inhomogeneous gravitational
fields in a superconducting circuit. This experiment would demonstrate the
existence of a novel coupling between gravity and electricity via
macroscopically coherent quantum matter.Comment: `2nd Vienna Symposium for the Foundations of Modern Physics'
Festschrift MS for Foundations of Physic
Estimation of the Probability of Error without Ground Truth and Known A Priori Probabilities
The probability of error or, alternatively, the probability of correct classification (PCC) is an important criterion in analyzing the performance of a classifier. Labeled samples (those with ground truth) are usually employed to evaluate the performance of a classifier. Occasionally, the numbers of labeled samples are inadequate, or no labeled samples are available to evaluate a classifier\u27s performance; for example, when crop signatures from one area from which ground truth is available are used to classify another area from which no ground truth is available. This paper reports the results of an experiment to estimate the probability of error using unlabeled test samples (i.e., without the aid of ground truth)
Can a charged ring levitate a neutral, polarizable object? Can Earnshaw's Theorem be extended to such objects?
Stable electrostatic levitation and trapping of a neutral, polarizable object
by a charged ring is shown to be theoretically impossible. Earnshaw's Theorem
precludes the existence of such a stable, neutral particle trap.Comment: 11 pages, 1 figur
Simultaneous Multi-band Radio & X-ray Observations of the Galactic Center Magnetar SGR 17452900
We report on multi-frequency, wideband radio observations of the Galactic
Center magnetar (SGR 17452900) with the Green Bank Telescope for 100
days immediately following its initial X-ray outburst in April 2013. We made
multiple simultaneous observations at 1.5, 2.0, and 8.9 GHz, allowing us to
examine the magnetar's flux evolution, radio spectrum, and interstellar medium
parameters (such as the dispersion measure (DM), the scattering timescale and
its index). During two epochs, we have simultaneous observations from the
Chandra X-ray Observatory, which permitted the absolute alignment of the radio
and X-ray profiles. As with the two other radio magnetars with published
alignments, the radio profile lies within the broad peak of the X-ray profile,
preceding the X-ray profile maximum by 0.2 rotations. We also find that
the radio spectral index is significantly negative between 2 and
9 GHz; during the final 30 days of our observations ,
which is typical of canonical pulsars. The radio flux has not decreased during
this outburst, whereas the long-term trends in the other radio magnetars show
concomitant fading of the radio and X-ray fluxes. Finally, our wideband
measurements of the DMs taken in adjacent frequency bands in tandem are
stochastically inconsistent with one another. Based on recent theoretical
predictions, we consider the possibility that the dispersion measure is
frequency-dependent. Despite having several properties in common with the other
radio magnetars, such as , an
increase in the radio flux during the X-ray flux decay has not been observed
thus far in other systems.Comment: 15 pages, 9 figures, 3 tables; accepted to Ap
Intra-specific Variation, Selection, and Climate Change in the Seas
Marine ecosystems will be impacted by climate change over the next century, where increased temperature and ocean acidification are already changing the physical and chemical nature of the seas. How the marine biota will respond to these impacts is unclear, in particular we lack understanding of organisms' expected evolutionary responses to climate change. Microbes (i.e. bacteria and protists) are particularly important components of marine ecosystems, due to their roles in marine food webs, and their ability to influence climate via biogeochemical cycles.
The majority of research into biological impacts of climate change is performed using short term perturbation experiments, where organisms adapted to present conditions are cultured in conditions predicted to occur up to 90 years in the future. Eco-physiological and/or life-history traits are then used to infer species responses, and in some cases fitness. This thesis suggests why this could be a misleading approach, and places emphasis on the importance of intra-specific variation in adaptation to climate change, using a series of experiments in the heterotrophic dinoflagellate Oxyrrhis marina.
I quantify variation in eco-physiological responses to elevated temperature and pCO2, among geographic isolates of Oxyrrhis, develop a novel molecular method to quantify strain frequencies in mixed populations, and explicitly test the relationship between eco-physiology and competitive fitness. I reveal substantial variation in eco-physiological responses, and show that often this is not indicative of fitness. I then investigate frequency- and density-dependence of selection, and quantify how selection responds to environmental change. I conclude that the importance of intra-specific variation should never be overlooked, and that the best way to quantify selection from this variation is looking for relative changes in selection rates between isolates under experimental climate change conditions
Using Abrupt Changes in Magnetic Susceptibility within Type-II Superconductors to Explore Global Decoherence Phenomena
A phenomenon of a periodic staircase of macroscopic jumps in the admitted
magnetic field has been observed, as the magnitude of an externally applied
magnetic field is smoothly increased or decreased upon a superconducting (SC)
loop of type II niobium-titanium wire which is coated with a
non-superconducting layer of copper. Large temperature spikes were observed to
occur simultaneously with the jumps, suggesting brief transitions to the normal
state, caused by en masse motions of Abrikosov vortices. An experiment that
exploits this phenomenon to explore the global decoherence of a large
superconducting system will be discussed, and preliminary data will be
presented. Though further experimentation is required to determine the actual
decoherence rate across the superconducting system, multiple classical
processes are ruled out, suggesting that jumps in magnetic flux are fully
quantum mechanical processes which may correspond to large group velocities
within the global Cooper pair wavefunction.Comment: 13 pages, 4 figures, part of proceedings for FQMT 2011 conference in
Prague, Czech Republi
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