16,007 research outputs found
Quantum Counterfactuals and Locality
Stapp's counterfactual argument for quantum nonlocality based upon a Hardy
entangled state is shown to be flawed. While he has correctly analyzed a
particular framework using the method of consistent histories, there are
alternative frameworks which do not support his argument. The framework
dependence of quantum counterfactual arguments, with analogs in classical
counterfactuals, vitiates the claim that nonlocal (superluminal) influences
exist in the quantum world. Instead it shows that counterfactual arguments are
of limited use for analyzing these questions.Comment: 8 pages, 1 PSTricks figur
Reproductive biology of carpenter seabream (Argyrozona argyrozona) (Pisces: Sparidae) in a marine protected area
The carpenter seabream (Argyrozona argyrozona) is an
endemic South African sparid that comprises an important part of the handline fishery. A three-year study (1998â2000) into its reproductive biology within the Tsitsikamma National Park revealed that these fishes are
serial spawning late gonochorists. The size at 50% maturity (L50) was estimated at 292 and 297 mm FL for both females and males, respectively. A likelihood ratio test revealed that there was no significant difference between male and female L50 (P>0.5). Both monthly gonadosomatic indices
and macroscopically determined ovarian stages strongly indicate that A. argyrozona within the Tsitsikamma
National Park spawn in the astral summer between November and April. The presence of postovulatory follicles (POFs) confirmed a six-month spawning season, and monthly proportions of early (0â6 hour old) POFs showed that spawning frequency was highest (once every 1â2 days) from December to March. Although spawning season was more highly correlated to photoperiod (r = 0.859) than temperature
(r = â0.161), the daily proportion of spawning fish was strongly correlated (r= 0.93) to ambient temperature over
the range 9â22oC. These results indicate that short-term upwelling events, a strong feature in the Tsitsikamma
National Park during summer, may negatively affect carpenter fecundity. Both spawning frequency and duration
(i.e., length of spawning season) increased with fish length. As a result of the allometric relationship between
annual fecundity and fish mass a 3-kg fish was calculated to produce fivefold more eggs per kilogram of body weight
than a fish of 1 kg. In addition to producing more eggs per unit of weight each year, larger fish also produce
significantly larger eggs
A role for the developing lexicon in phonetic category acquisition
Infants segment words from fluent speech during the same period when they are learning phonetic categories, yet accounts of phonetic category acquisition typically ignore information about the words in which sounds appear. We use a Bayesian model to illustrate how feedback from segmented words might constrain phonetic category learning by providing information about which sounds occur together in words. Simulations demonstrate that word-level information can successfully disambiguate overlapping English vowel categories. Learning patterns in the model are shown to parallel human behavior from artificial language learning tasks. These findings point to a central role for the developing lexicon in phonetic category acquisition and provide a framework for incorporating top-down constraints into models of category learning
Consistent Quantum Counterfactuals
An analysis using classical stochastic processes is used to construct a
consistent system of quantum counterfactual reasoning. When applied to a
counterfactual version of Hardy's paradox, it shows that the probabilistic
character of quantum reasoning together with the ``one framework'' rule
prevents a logical contradiction, and there is no evidence for any mysterious
nonlocal influences. Counterfactual reasoning can support a realistic
interpretation of standard quantum theory (measurements reveal what is actually
there) under appropriate circumstances.Comment: Minor modifications to make it agree with published version. Latex 8
pages, 2 figure
On Vector Bundles of Finite Order
We study growth of holomorphic vector bundles E over smooth affine manifolds.
We define Finsler metrics of finite order on E by estimates on the holomorphic
bisectional curvature. These estimates are very similar to the ones used by
Griffiths and Cornalba to define Hermitian metrics of finite order. We then
generalize the Vanishing Theorem of Griffiths and Cornalba to the Finsler
context. We develop a value distribution theory for holomorphic maps from the
projectivization of E to projective space. We show that the projectivization of
E can be immersed into a projective space of sufficiently large dimension via a
map of finite order.Comment: version 2 has some typos corrected; to appear in Manuscripta
Mathematic
Topological quantum gate entangler for a multi-qubit state
We establish a relation between topological and quantum entanglement for a
multi-qubit state by considering the unitary representations of the Artin braid
group. We construct topological operators that can entangle multi-qubit state.
In particular we construct operators that create quantum entanglement for
multi-qubit states based on the Segre ideal of complex multi-projective space.
We also in detail discuss and construct these operators for two-qubit and
three-qubit states.Comment: 6 page
Degeneracy measures for the algebraic classification of numerical spacetimes
We study the issue of algebraic classification of the Weyl curvature tensor,
with a particular focus on numerical relativity simulations. The spacetimes of
interest in this context, binary black hole mergers, and the ringdowns that
follow them, present subtleties in that they are generically, strictly
speaking, Type I, but in many regions approximately, in some sense, Type D. To
provide meaning to any claims of "approximate" Petrov class, one must define a
measure of degeneracy on the space of null rays at a point. We will investigate
such a measure, used recently to argue that certain binary black hole merger
simulations ring down to the Kerr geometry, after hanging up for some time in
Petrov Type II. In particular, we argue that this hangup in Petrov Type II is
an artefact of the particular measure being used, and that a geometrically
better-motivated measure shows a black hole merger produced by our group
settling directly to Petrov Type D.Comment: 14 pages, 7 figures. Version 2 adds two references
Universal Self Force from an Extended-Object Approach
We present a consistent extended-object approach for determining the self
force acting on an accelerating charged particle. In this approach one
considers an extended charged object of finite size , and calculates
the overall contribution of the mutual electromagnetic forces. Previous
implementations of this approach yielded divergent terms
that could not be cured by mass-renormalization. Here we explain the origin of
this problem and fix it. We obtain a consistent, universal, expression for the
extended-object self force, which conforms with Dirac's well known formula.Comment: Latex, one postscript figure, 4 page
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