Counterintuitive Features Research Articles

COSMIC RAY DIFFUSION FRONTS IN THE VIRGO CLUSTER

The pair of large radio lobes in the Virgo cluster, each about 23 kpc in radius, have curiously sharp outer edges where the radio-synchrotron continuum flux declines abruptly. However, just adjacent to this sharp transition, the radio flux increases. This radio limb-brightening is observed over at least half of the perimeter of both lobes. We describe slowly propagating steady state diffusion fronts that explain these counterintuitive features. Because of the natural buoyancy of radio lobes, the magnetic field is largely tangent to the lobe boundary, an alignment that polarizes the radio emission and dramatically reduces the diffusion coefficient of relativistic electrons. As cosmic ray electrons diffuse slowly into the cluster gas, the local magnetic field and gas density are reduced as gas flows back toward the radio lobe. Radio emission peaks can occur because the synchrotron emissivity increases with magnetic field and then decreases with the density of non-thermal electrons. A detailed comparison of steady diffusion fronts with quantitative radio observations may reveal information about the spatial variation of magnetic fields and the diffusion coefficient of relativistic electrons. On larger scales, some reduction of the gas density inside the Virgo lobes due to cosmic ray pressure must occur and may be measurable. Such X-ray observations could reveal important information about the presence of otherwise unobservable non-thermal components such as relativistic electrons of low energy or proton cosmic rays.

Complexes of Be and Mg with unsaturated hydrocarbon molecules: Inter- and intramolecular cooperativity of binding

Ab initio calculations are employed to investigate attachment of Group II light metal atoms to hydrocarbon molecules with pairs of double carbon–carbon bonds. Comparison of the atom attachment to one and between two such bonds reveals cooperative binding for some cases, with some counter-intuitive features. Dependence of its manifestation on the system composition and geometry is investigated for a series of metal–hydrocarbon complexes. Attachment-induced catalytic isomerisation of the system is considered at molecular level as well. The complexes are characterized and compared in terms of geometry, stability and various electronic properties.

Rotations of 4nπ and the Kinematic Design of Parallel Manipulators

For parallel manipulator systems a fundamental distinction is drawn between displacement and motion. The former is a spatial relation adequately modelled by standard vector and matrix algebra. The latter is a spatial trajectory whose 'history' also requires modelling. Quaternion, spinor and Clifford algebra representations are utilised for this purpose - specifically for rigid body finite rotation in 3D space. Each involves rotation half-angles and hence exhibits apparently counter-intuitive features, notably that rotations of 0 and 2π are not equivalent, whereas rotations of 0 and 4π are equivalent. In general, rotations of 4nπ are not equivalent to rotations of (4n+2)π, where n is any integer. These representations have real physical manifestations, demonstrated here for parallel manipulator designs, adapted from a mechanical model devised by Dirac.

The Adaptive Dynamics of Turnout

We present a dynamic model of turnout in which voters’ behavior in one election depends only on whether they voted in the last election and whether their party won. This assumption may be justified by assuming citizens satisfice or by assuming they adjust subjective beliefs about being pivotal in ways that depend on whether they voted and on the outcome of the election. Regardless of the individual-level mechanism, the assumption that prior voter turnout and prior electoral outcome affect current turnout has empirical support, and we show that it implies turnout dynamics that are in accord with observed dynamics in several countries. Thus, this assumption or something very much like it is a necessary feature of any model of turnout. The ensuing model meets a basic requirement of any turnout model, substantial steady-state turnout, and correctly predicts some counterintuitive dynamical features of aggregate turnout—including declining turnout despite close elections and nonmonotonic changes—following significant political events such as the (re)establishment of democracy or major wars.

A non-local hidden-variable model that violates Leggett-type inequalities

Recent experiments of Gröblacher et al proved the violation of a Leggett-type inequality that was claimed to be valid for a broad class of non-local hidden-variable theories. The impossibility of constructing a non-local and realistic theory, unless it entails highly counterintuitive features, seems thus to have been experimentally proved. This would bring us close to a definite refutation of realism. Indeed, realism was proved to be also incompatible with locality, according to a series of experiments testing Bell inequalities. The present paper addresses the said experiments of Gröblacher et al and presents an explicit, contextual and realistic, model that reproduces the predictions of quantum mechanics. It thus violates the Leggett-type inequality that was established with the aim of ruling out a supposedly broad class of non-local models. We can thus conclude that plausible contextual, realistic, models are still tenable. This restates the possibility of a future completion of quantum mechanics by a realistic and contextual theory which is not in a class containing only highly counterintuitive models. The class that was ruled out by the experiments of Gröblacher et al is thus proved to be a limited one, arbitrarily separating models that physically belong in the same class.

Towards gold shells shaped by carbon cores: From a gold cage to a core–shell aurocarbon

A new aurocarbon species, C 10Au 18, is investigated in terms of its geometry, stability, charge distribution and properties involving changes of the electronic and charge state. The system consists of a carbon-radical core inside a gold shell. The property variations upon adding the carbon molecular ‘dopant’ to the gold cage cluster of equivalent geometry are analyzed via isolating the effects of the shell shape change and core influence. The charge distribution in the system exhibits interesting, sometimes counterintuitive features. An approximate splitting of the total binding energy into the in-shell and core–shell components is attempted, indicating comparable values for both.

A classification of hidden-variable properties

Hidden variables are extra components added to try to banish counterintuitive features of quantum mechanics. We start with a quantum-mechanical model and describe various properties that can be asked of a hidden-variable model. We present six such properties and a Venn diagram of how they are related. With two existence theorems and three no-go theorems (EPR, Bell and Kochen–Specker), we show which properties of empirically equivalent hidden-variable models are possible and which are not. Formally, our treatment relies only on classical probability models, and physical phenomena are used only to motivate which models to choose.

Snippets of physics

The statistical mechanics of a system of particles interacting through gravity leads to several counter-intuitive features. We explore one of them, called Antonov instability, in this installment.

Evaluating and generalizing constraint diagrams

The constraint diagram language was designed to be used in conjunction with the unified modelling language (UML), primarily for placing formal constraints on software models. In particular, constraint diagrams play a similar role to the textual object constraint language (OCL) in that they can be used for specifying system invariants and operation contracts in the context of a UML model. Unlike the OCL, however, constraint diagrams can be used independently of the UML. In this paper, we illustrate a range of intuitive and counter-intuitive features of constraint diagrams and highlight some (potential) expressiveness limitations. The counter-intuitive features are related to how the individual pieces of syntax interact. A generalized version of the constraint diagram language that overcomes the illustrated counter-intuitive features and limitations is proposed. In order to discourage specification readers and writers from overlooking certain semantic information, the generalized notation allows this information to be expressed more explicitly than in the non-generalized case. The design of the generalized notation takes into account five language design principles which are discussed in the paper. We provide a formalization of the syntax and semantics for generalized constraint diagrams. Moreover, we establish a lower bound on the expressiveness of the generalized notation and show that they are at least as expressive as constraint diagrams.

From Insect Sense Organs to Biomimetic Walking Robots [Exploratory DSP

In this article, we have pointed out several features of the sensory systems of insects that help these animals control their extraordinarily adaptable and agile locomotion on land. These impressive but often counterintuitive features allow the effects of sensory input to be adjusted continually according to the activity in which the insect is actively engaged, in contrast with hardwired reflexes that must be overcome as the animal switches from one activity to another. The pertinent question is how engineers can incorporate these and other features of biological systems into walking robots.

Turning physicists into quantum mechanics

Quantum computing, quantum encryption and quantum teleportation: today's physics journals sound morelike Star Trek than ever. Based on the weird and counterintuitive features of quantum mechanics, these concepts have been brought to fruition in recent years by theorists and experimentalists alike. Indeed, these ideas are now leaving physics laboratories and being used by industry to make real products. Who knows what revolutions await in computation and communications from these budding breakthroughs?

Explanation of the Gibbs paradox within the framework of quantum thermodynamics

The issue of the Gibbs paradox is that when considering mixing of two gases within classical thermodynamics, the entropy of mixing appears to be a discontinuous function of the difference between the gases: it is finite for whatever small difference, but vanishes for identical gases. The resolution offered in the literature, with help of quantum mixing entropy, was later shown to be unsatisfactory precisely where it sought to resolve the paradox. Macroscopic thermodynamics, classical or quantum, is unsuitable for explaining the paradox, since it does not deal explicitly with the difference between the gases. The proper approach employs quantum thermodynamics, which deals with finite quantum systems coupled to a large bath and a macroscopic work source. Within quantum thermodynamics, entropy generally loses its dominant place and the target of the paradox is naturally shifted to a decrease of the maximally available work before and after mixing (mixing ergotropy). In contrast to entropy this is an unambiguous quantity. For almost identical gases the mixing ergotropy continuously goes to zero, thus resolving the paradox. In this approach the concept of "difference between the gases" gets a clear operational meaning related to the possibilities of controlling the involved quantum states. Difficulties which prevent resolutions of the paradox in its entropic formulation do not arise here. The mixing ergotropy has several counterintuitive features. It can increase when less precise operations are allowed. In the quantum situation (in contrast to the classical one) the mixing ergotropy can also increase when decreasing the degree of mixing between the gases or when decreasing their distinguishability. These points go against a direct association of physical irreversibility with lack of information.

Current flow patterns in a Faraday disc

A simple model is developed in order to calculate the flow of current in a Faraday discwhen it is delivering power to an external circuit. Several counter-intuitive features emergewhich are not revealed by a qualitative discussion. The argument is non-relativistic, and itis conducted in the laboratory frame of reference.

Relativity and Religion: The Abuse of Einstein's Theory

AbstractEinstein's special theory of relativity has had a wide influence on fields far removed from physics. It has given the impression that physics has shown that there are now no absolute truths, that all beliefs are relative to the observer, and that traditional stable landmarks have been washed away. We each have our own frame of reference that is as good as any other frame, so that there are no absolute standards by which our actions may be judged. The predictions of relativity theory, such as the elimination of simultaneity, the variation of mass with velocity, and the equivalence of mass and energy, are all highly counterintuitive and yet are precisely confirmed by detailed measurements. The clear rocklike mechanical physics of Newton seems to have dissolved into a swirling mist of unintelligible concepts, and familiar certainties seem to have disappeared.A detailed analysis of relativity theory shows, however, a completely different picture. Properly understood, it is a logical extension of Newtonian physics that expresses the relations of space and time in a more exact and elegant way and in the process shows forth more clearly the invariant features of the world. The apparently counterintuitive features appear as natural consequences that extend and refine our classical concepts. The traditional landmarks remain, but God's world is more subtle than we had previously imagined.

The CBA Learning Module Series, instructional design, and future directions.

Skinner (1958) described some of the early teaching machines and the behavioral technology underlying their operation. However, it wasn't until the late 1990s that the teaching machine finally came of age with the aid of modern computers and software. In this article, I discuss one model of computer-based training that has been used to teach behavior analysis. Features of the model relevant to a behavior analytic approach to instructional design are highlighted. I talk about how the model addresses fluency, reinforcement, and strategies for teaching conditional discriminations and concepts. Other applications of the model (e.g., exam preparation for certification in other disciplines, skills needed by factory workers, elementary and high school curricula, paraprofessional skills) are entertained and research questions are posed. ********** In the past few years, the fluency-based computer program CBA Learning Module Series (Eversole, 1998) has been used by approximately 600 people to prepare for the certification exam in behavior analysis. The purpose of this discussion is to describe the basic instructional design model used for the CBA Learning Module Series, other instructional applications of the model, and future research directions. First, let's discuss the CBA Learning Module Series. The CBA Learning Module Series The model used in the CBA Learning Model Series is based on one taught by Guy Bruce and John Eshleman in a workshop on instructional design I attended at the Association for Behavior Analysis conference (Bruce & Eshleman, 1996a). In that workshop (and the more recent book Instructional Design Made Easy [Bruce, 1999]), the focus is on an efficient leaming program that provides instructions, practice, and consequences that reduce the leaming time required to achieve competent performance. In particular, design features included development of goals and valid performance objectives, presentation of instructions during practice and only when needed, strategies to ensure appropriate stimulus control, consequences that reduce leaming time (e.g., immediate praise or corrective feedback), evaluation of leaming efficiency, and revision of content as needed. Behavior analysts are well versed on the advantages of most of these elements. Therefore, I will provide a basic description and focus only on a few features that may be counter-intuitive and as they have been applied to the development of the CBA Learning Module Series. In the Series, aside from a few screens explaining how to use the program, the user is first presented with a question or stem, and four options. If the user is not sure of the answer, s/he may click on a hint button. The hint directly or indirectly provides the correct answer. Also, a text book reference is provided for individuals desiring additional material. A second button click causes the hint to disappear. If a correct option is then clicked, a brief praise statement is provided. If an incorrect selection is made, a corrective feedback statement is given. Each 5-minute timed module includes approximately 20 such frames. After 5 minutes, the user cannot answer any more questions and the number and percent correct is presented. Users are advised to practice the modules until they get 100% correct within the time allotted, and then to do occasional review sessions. I do not know of anyone who has completed any of the modules with 100% correct on the first practice. To achieve this criterion, and thus foster maintenance (Binder, 1993), learners have to be fluent responders to most questions--they have to answer quickly and accurately. There are some counter-intuitive features of the CBA Learning Module Series. Note that the Series begins with a question or stem, thus by-passing instructional material that may not be needed by the learner. This is done so that the learner doesn't have to spend time on material s/he already knows--s/be simply answers the question and then moves on to the next question. …

Plasmon-assisted transmission of entangled photons.

The state of a two-particle system is said to be entangled when its quantum-mechanical wavefunction cannot be factorized into two single-particle wavefunctions. This leads to one of the strongest counter-intuitive features of quantum mechanics, namely non-locality. Experimental realization of quantum entanglement is relatively easy for photons; a starting photon can spontaneously split into a pair of entangled photons inside a nonlinear crystal. Here we investigate the effects of nanostructured metal optical elements on the properties of entangled photons. To this end, we place optically thick metal films perforated with a periodic array of subwavelength holes in the paths of the two entangled photons. Such arrays convert photons into surface-plasmon waves--optically excited compressive charge density waves--which tunnel through the holes before reradiating as photons at the far side. We address the question of whether the entanglement survives such a conversion process. Our coincidence counting measurements show that it does, so demonstrating that the surface plasmons have a true quantum nature. Focusing one of the photon beams on its array reduces the quality of the entanglement. The propagation of the surface plasmons makes the array effectively act as a 'which way' detector.

Effect of Doppler broadening on the transparency and dispersion of the generalized double dark resonance

Spectroscopy of the Doppler broadened Rb atomic vapour coherently driven by two coupling fields is presented. Double dark resonances have been observed in different geometries of the coupling fields. A simple four-level model explains the basic counter-intuitive features of experimental spectra. The eigenvalues of the atom-field system distinguishing between the various geometries clarify the physics.

2001, a transplant odyssey: Epilogue

In 1960, the mathematician Ernst Specker described a simple example of nonclassical correlations, the counter-intuitive features of which he dramatized using a parable about a seer, who sets an impossible prediction task to his daughter’s suitors. We revisit this example here, using it as an entrée to three central concepts in quantum foundations: contextuality, Bell-nonlocality, and complementarity. Specifically, we show that Specker’s parable offers a narrative thread that weaves together a large number of results, including the following: the impossibility of measurement-noncontextual and outcome-deterministic ontological models of quantum theory (the 1967 Kochen–Specker theorem), in particular, the recent state-specific pentagram proof of Klyachko; the impossibility of Bell-local models of quantum theory (Bell’s theorem), especially the proofs by Mermin and Hardy and extensions thereof; the impossibility of a preparation-noncontextual ontological model of quantum theory; the existence of triples of positive operator valued measures (POVMs) that can be measured jointly pairwise but not triplewise. Along the way, several novel results are presented: a generalization of a theorem by Fine connecting the existence of a joint distribution over outcomes of counterfactual measurements to the existence of a measurement-noncontextual and outcome-deterministic ontological model; a generalization of Klyachko’s proof of the Kochen–Specker theorem from pentagrams to a family of star polygons; a proof of the Kochen–Specker theorem in the style of Hardy’s proof of Bell’s theorem (i.e., one that makes use of the failure of the transitivity of implication for counterfactual statements); a categorization of contextual and Bell-nonlocal correlations in terms of frustrated networks; a derivation of a new inequality testing preparation noncontextuality; some novel results on the joint measurability of POVMs and the question of whether these can be modeled noncontextually. Finally, we emphasize that Specker’s parable of the overprotective seer provides a novel type of foil to quantum theory, challenging us to explain why the particular sort of contextuality and complementarity embodied therein does not arise in a quantum world.

A theoretical investigation of the remarkable nuclear spin-spin coupling pattern in [(NC)(5)Pt-Tl(CN)](-).

We address the problem of the interpretation of heavy nucleus spin-spin couplings for systems being studied in solution. Solvation can create counterintuitive features concerning the spin-spin couplings, which are enhanced by relativistic effects due to the presence of heavy nuclei. This should therefore be taken into consideration for the discussion of spectra obtained from solution. Evidence for such solvent effects is provided by a relativistic density functional study of [(NC)(5)Pt-Tl(CN)](-) (I). It is demonstrated that the remarkable experimentally observed spin-spin coupling pattern, e.g., (2)J(Tl-C) >> (1)J(Tl-C) and J(Pt-Tl) approximately 57 kHz, is semiquantitatively reproduced by our calculations if both relativistic effects and solvation are taken into account. Solvent effects are very substantial and shift the Pt-Tl coupling by more than 100%, e.g. Relativistic increase of s-orbital density at the heavy nuclei, charge donation by the solvent, and the specific features of the multicenter C-Pt-Tl-C bond are responsible for the observed coupling pattern.

Topic neutrality and the parity thesis: a surrejoinder to Williams

In an important paper, Clifford Williams advanced a Lockean-style argument to justify the parity thesis, viz., that there is no intellectual advantage to Christian physicalism or Christian dualism. In an article in Religious Studies I offered a critique of Williams's parity thesis and he has published a rejoinder to me in the same journal centring on my rejection of topic neutrality as an appropriate way to set up the mind–body debate. In this surrejoinder to Williams, I present his three main arguments and respond to each: (1) The dualist rejection of topic neutrality is flawed because it expresses a conceptual approach to the mind–body problem instead of the preferable empirical approach. The latter favours physicalism and, in any case, clearly supports topic neutrality. (2) If the dualist rejects the first argument, then a second parity thesis can be advanced in which an essentialist view of soul and the brain are presented in which each is essentially a thinking and feeling entity. Thus, an essentialist parity thesis is preserved. (3) If the dualist rejects the second argument, a new topic neutrality emerges in the dialectic, so topic neutrality is unavoidable. Against the first argument, I claim that Williams makes two central confusions that undermine his case and that he fails to show how the mind–body debate can be settled empirically. Against the second argument, I claim that it leaves Williams vulnerable to a topic-neutral approach to God and it merely proffers a verbal shift with a new dualism between normal and ‘special’ matter. Against the third argument, I point out that it misrepresents the dualist viewpoint and leads to two counterintuitive features that follow from topic neutrality.