Is wave propagation computable or can wave computers beat the turing machine?

According to the Church-Turing Thesis a number function is computableby the mathematically defined Turing machine if and only ifit is computable by a physical machine. In 1983 Pour-El andRichards defined a three-dimensional wave u(t,x) such that theamplitude u(0,x) at time 0 is computable and the amplitude u(1,x)at time 1 is continuous but not computable. Therefore, theremight be some kind of wave computer beating the Turing machine.By applying the framework of Type 2 Theory of Effectivity (TTE),in this paper we analyze computability of wave propagation.In particular, we prove that the wave propagator is computableon continuously differentiable waves, where one derivative islost, and on waves from Sobolev spaces. Finally, we explainwhy the Pour-El-Richards result probably does not help to designa wave computer which beats the Turing machine. 2000 Mathematical Subject Classification: 03D80, 03F60, 35L05,68Q05.     

Re-use? Is this re-use?

An initiative such as the Intergeo project has the clear mission to allow many teachers to gain easy access to resources that can support their teaching practice when using them. Re-use then appears when the sole usage is insufficient and needs adaptations to the specific context. This paper investigates the common practices of re-use in computer science literature, describes how it was implemented in the i2geo platform, and how the actual usage of the platform shows that the definition we first envisioned and that is widespread is short sighted. Following the observations of the practices, generalizations of the notion of re-use are proposed.     

What Is Entitlement?

In his seminal paper, “Content Preservation,” Tyler Burge defends an original account of testimonial knowledge. The originality of the account is due, in part, to the fact that it is cast within a novel epistemic framework. The central feature of that framework is the introduction of the concept of entitlement, which is alleged to be a distinctive type of positive epistemic support or warrant. Entitlement and justification, according to Burge, are sub-species of warrant. Justification is the internalist form of warrant, but entitlement is epistemically externalist. My focus in this paper is Burge’s conception of entitlement, and there are three primary issues that I wish to address. What is the relationship between entitlement and the more traditional concept of justification? In what sense is entitlement epistemically externalist? Has Burge introduced a new epistemic concept or merely coined a new term for a familiar epistemic concept?     

Dismantle or remanufacture?

In this paper we study a firm’s disposition decision for returned end-of-use products, which can either be remanufactured and sold, or dismantled into parts that can be reused. We formulate this problem as a multi-period stochastic dynamic program, and find the structure of the optimal policy, which consists of monotonic switching curves. Specifically, if it is optimal to remanufacture in a given period and for given inventory levels, then it is also optimal to remanufacture when the inventory of part(s) is higher or the inventory of remanufactured product is lower.     

Is nature quantum non-local,complex holistic,or what?: II — Applications

In Part I of this paper [A. Sengupta, Is nature quantum non-local, complex holistic, or what? I–Theory & analysis. Nonlinear Anal.: RWA (2009) (in press)] to be referenced “I-”, we examined the linear–nonlinear divide of the natural world in an attempt to seek a rationale for the question “Is nature interactively nonlinear and holistic, or is it additively linear and reductionist?”: Is Nature governed by entanglements of linear superposition or does it represent the nonlinear holism of emergence, self-organization, and complexity? This second part carries the debate forward to propose that Quantum Mechanics is an effective linear representation of a fully chaotic, maximally illposed, multifunctional negworld that obviously is not just a mirror image of the functional real world we inhabit: in fact we argue that nonlinear complex holism represents a stronger form of entanglement than linear quantum non-locality. The bi-directionality of a self-organized, emergent, engine-pump system is analyzed with reference to the role of gravity as the compressive agent responsible for generation and maintenance of structures and life in Nature; we also explore the applicability of chanoxity to the metaphorical resolution of some of the long-standing paradoxes and puzzles in quantum measurement and non-locality, in Prigoginian intrinsic irreversibility, and in some core issues in cosmology and gravitational black holes.Holism is to be seen as complementing mainstream reductionism–linear science has after all stood the test of the last 400 years as quantum mechanics is acknowledgedly one of the most successful yet possibly one of the most mysterious of scientific theories: the success lies in its capacity to classify and predict the physical world, the mystery in what this physical world must be like to behave quantum mechanically–providing a unified picture of the dialectics of the evolutionary dynamics of Nature.     

What Is Variable Bandwidth?

We propose a new notion of variable bandwidth that is based on the spectral subspaces of an elliptic operator where p > 0 is a strictly positive function. Denote by the orthogonal projection of A_p corresponding to the spectrum of A_p in ; the range of this projection is the space of functions of variable bandwidth with spectral set in Λ. We will develop the basic theory of these function spaces. First, we derive (nonuniform) sampling theorems; second, we prove necessary density conditions in the style of Landau. Roughly, for a spectrum the main results say that, in a neighborhood of , a function of variable bandwidth behaves like a band‐limited function with local bandwidth . Although the formulation of the results is deceptively similar to the corresponding results for classical band‐limited functions, the methods of proof are much more involved. On the one hand, we use the oscillation method from sampling theory and frame‐theoretic methods; on the other hand, we need the precise spectral theory of Sturm‐Liouville operators and the scattering theory of one‐dimensional Schrödinger operators. © 2017 Wiley Periodicals, Inc.     

Is Personal Identity Analysable?

Trenton Merricks has argued that given endurantism personal identity is unanalysable in terms of psychological continuity, while Anthony Brueckner has argued against this claim. This article shows that neither philosopher has made a compelling case and also shows what it would take to settle the issue either way. It is then argued that whether personal identity is analysable or not may not be of crucial importance to those wanting to defend a psychological continuity approach to personal identity.     

Discriminator or dual discriminator?

Varieties are considered with p(x, y, z), a single ternary operation, which acts as a local discriminator or dual discriminator on the subdirectly irreducible elements. If p(x, y, z) is "global", then all subvarieties are finitely based. In the general case a continuum of non-finitely based subvarieties are presented. A graph theoretical picture leads to a variety of groupoids connecting the left-zero and the right-zero semigroups. For this variety some open problems are presented. Received October 7, 1998; accepted in final form October 4, 1999.     

Correct or incorrect application of CAPM? Correct or incorrect decisions with CAPM?

This paper focuses on inconsistencies arising from the use of NPV and CAPM for capital budgeting. It shows that: (i) CAPM capital budgeting decision-making based on disequilibrium NPV is deductively inferred by the capital asset pricing model, (ii) the use of the disequilibrium NPV is widespread in finance both as a decision rule and as a valuation tool, (iii) the disequilibrium NPV does not guarantee additivity nor consistency with arbitrage pricing, so that it is unreliable for valuation, (iv) Magni’s [Magni, C.A., 2002. Investment decisions in the theory of finance: Some antinomies and inconsistencies. European Journal of Operational Research 137, 206–217; Magni, C.A., 2007a. Project valuation and investment decisions: CAPM versus arbitrage. Applied Financial Economics Letters 3 (2), 137–140] criticism of the NPV criterion refers to the disequilibrium NPV, and De Reyck’s [De Reyck, B., 2005. On investment decisions in the theory of finance: Some antinomies and inconsistencies. European of Operational Research 161, 499–504] project valuation method, on the basis of which Magni’s criticism to NPV is objected, leaves decision makers open to arbitrage losses and incorrect decisions.     

Are plastic yielding and work hardening sensitive to the boundary conditions?

The plane strain shear of a single crystal strip with one active slip system placed in a mixed device with one clamped and one free boundary is considered. Since dislocations pile up against only the clamped boundary, the plastic yielding and work hardening differ essentially from those of a hard device, showing clearly their sensitivity to the boundary conditions. An analytical solution to this problem within continuum dislocation theory is found explicitly which exhibits the energetic and dissipative thresholds for dislocation nucleation, the Bauschinger translational work hardening, and the size effects. (© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

How Fast Is the Bandit?

Abstract

In this article we investigate the rate of convergence of the so-called two-armed bandit algorithm. The behavior of the algorithm turns out to be highly non standard: no central limit theorem, possible occurrence of two different rates of convergence with positive probability.