Possibility, actuality, and the growth of imagination : the many-worlds approach to quantum physics

Las interpretaciónes de la física cuántica de Everett-DeWitt hablan de una multiplicidad de mundos físicamente coexistenrtes. Éstas imaginativas reacciones a los problemas conceptuales de la mecánica cuántica estándar forman una família de propuestas de "universos múltiples" (PMW en su siglas inglesas) que, sin pleno éxito, han sido tachadas de incoherentes.Everett-DeWitt interpretations of quantum physics speak of a multiplicity of physically coexisting worlds. These imaginative reactions to the conceptual problems of standard quantum mechanics form a family of physicalist "many-worlds" proposals (PMW for short) that have been variously dismissed as "incoherent", so far without full success. A renewed charge by Hilary Putnam now seems to pose deeper trouble for PMW. In a recent paper, he seizes on "Schrödinger's cat" situations to expose how PMW relativization of actuality and basic combinatorics jointly ruin probabilistic talk. Putnam focuses on confirmation and luck. His case against PMW is thought-provoking but also questionable, or so I suggest in this paper. First I argue that, as presented, Putnam's charge doesn't go through. I then consider his argument proper. According to Putnam, experimental DeWittians must count themselves as "lucky" in a seriously incoherent sense. I consider his take on "luck" and deny that defenders of PMW need to so regard themselves. Although extravagant, their position cannot be fruitfully dismissed as incoherent on metascientific grounds. Indeed it attests to the way science rationally helps the imagination to grow

The effect of confinement on the deformation of microfluidic drops

We study the deformation of drops squeezed between the floor and ceiling of a microchannel and subjected to a hyperbolic flow. We observe that the maximum deformation of drops depends on both the drop size and the rate of strain of the external flow and can be described with power laws with exponents 2.59 +/- 0.28 and 0.91 +/- 0.05 respectively. We develop a theoretical model to describe the deformation of squeezed drops based on the Darcy approximation for shallow geometries and the use of complex potentials. The model describes the steady-state deformation of the drops as a function of a non-dimensional parameter Ca d^2, where Ca is the capillary number (proportional to the strain rate and the drop size) and d is a confinement parameter equal to the drop size divided by the channel height. For small deformations, the theoretical model predicts a linear relationship between the deformation of drops and this parameter, in good agreement with the experimental observations.Comment: 6 pages, 7 figure

Realism and the Infinitely Faceted World : Intimations from the 1950s

Breaking away from logical-empiricism, in the early 1950s Stephen Toulmin presented empirical theories as maps, thereby opening a fertile line of reflection about background interests and their impact on abstraction in scientific theorizing. A few years later, pointing to the "qualitative infinity of nature," David Bohm denounced what he regarded as counterproductive constraints on the scientific imagination. In realist circles, these two strands of suggestions would be variously supplemented over the following decades with further recognitions of the epistemic merits of partial approximate descriptions and the role of background knowledge and interests in scientific theorizing.Rompiendo con el empirismo lógico, en la década de 1950 Stephen Toulmin presenta como mapas las teorías empíricas, abriendo así una línea fértil de reflexión sobre los intereses que motivan cada teoría y el impacto de dichos intereses en la abstracción en la teorización teórico/científica. Unos años más tarde David Bohm, señalando el "infinito cualitativo de la naturaleza", denunció lo que él consideraba restricciones contraproducentes en la imaginación científica. En los círculos realistas, estas dos visiones serán complementadas de diversas maneras durante las siguientes décadas con reconocimientos de los méritos epistémicos de las descripciones aproximadas parciales y el papel de los intereses y conocimientos previos en la teorización científica

Eight Myths about Scientific Realism

Selective realist projects have made significant improvements over the last two decades. Judging by the literature, however, antirealist quarters seem little impressed with the results. Section I considers the selectivist case and its perceived shortcomings. One shortcoming is that selectivist offerings are nuanced in ways that deprive them of features that—according to many—cannot be absent from any realism “worth having”. Section II (the main part of the paper) considers eight features widely required of realist positions, none of them honored by selectivist projects. Modulo those requirements, even if selectivists managed to clear other shortcomings of their project selectivism would still not be a position worth considering. Next the historical background and present credentials of the requirements in question are examined. All are found to rest on myths and confusions about science and knowledge. If this is correct, realists and antirealists should reject the requirements

Eight Myths about Scientific Realism

Selective realist projects have made significant improvements over the last two decades. Judging by the literature, however, antirealist quarters seem little impressed with the results. Section I considers the selectivist case and its perceived shortcomings. One shortcoming is that selectivist offerings are nuanced in ways that deprive them of features that—according to many—cannot be absent from any realism “worth having”. Section II (the main part of the paper) considers eight features widely required of realist positions, none of them honored by selectivist projects. Modulo those requirements, even if selectivists managed to clear other shortcomings of their project selectivism would still not be a position worth considering. Next the historical background and present credentials of the requirements in question are examined. All are found to rest on myths and confusions about science and knowledge. If this is correct, realists and antirealists should reject the requirements

Quasiperiodic graphs at the onset of chaos

We examine the connectivity fluctuations across networks obtained when the horizontal visibility (HV) algorithm is used on trajectories generated by nonlinear circle maps at the quasiperiodic transition to chaos. The resultant HV graph is highly anomalous as the degrees fluctuate at all scales with amplitude that increases with the size of the network. We determine families of Pesin-like identities between entropy growth rates and generalized graph-theoretical Lyapunov exponents. An irrational winding number with pure periodic continued fraction characterizes each family. We illustrate our results for the so-called golden, silver and bronze numbers.Comment: arXiv admin note: text overlap with arXiv:1205.190

Experimental analysis of 3D cracking in drying soils using ground-penetrating radar

This paper describes the capabilities of a novel technique to investigate crack formation and propagation in drying soils. The technique is a relatively simple, non-destructive indirect technique using a ground-penetrating-radar (GPR) system to detect cracks that form and propagate inside a soil specimen during desiccation. Although GPR devices have been used for multiple applications, their use in soils for the detection of small desiccation cracks has not been demonstrated yet. The experiment and the methodology used to test the accuracy of a small compact commercial GPR device for crack identification are described. The main objective was to identify what type of signals and what crack width and separation between them can be detected using the GPR device. The results indicate that cracks of 1 or 2mm wide can be detected depending on its position and shape, whereas sub-millimeter cracks are undetectable with the currently existing devices in the market. Regardless of this limitation, the GPR method can be useful to find time-related bounds of when the cracks appear, to point at their location and sometimes at the separation between two of them. Detection of cracks with origin at the bottom or within the specimen was accomplished with this system. Distances of 5 cm or more between cracks can be detected and measured, as well, with accuracy.Peer ReviewedPostprint (author's final draft