Complex lapse, complex action and path integrals

Imaginary time is often used in quantum tunnelling calculations. This article advocates a conceptually sounder alternative: complex lapse. In the ``3+1'' action for the Einstein gravitational field minimally coupled to a Klein-Gordon field, allowing the lapse function to be complex yields a complex action which generates both the usual Lorentzian theory and its Riemannian analogue, and in particular allows a change of signature between the two. The action and variational equations are manifestly well defined in the Hamiltonian representation, with the momentum fields consequently being complex. The complex action interpolates between the Lorentzian and Riemannian actions as they appear formally in the respective path integrals. Thus the complex-lapse theory provides a unified basis for a path-integral quantum theory of gravity involving both Lorentzian and Riemannian aspects. A major motivation is the quantum-tunnelling scenario for the origin of the universe. Taken as an explanation for the observed quantum tunnelling of particles, the complex-lapse theory determines that the argument of the lapse for the universe now is extremely small but negative.Comment: 12 pages, Te

Toward a Systematic Evidence-Base for Science in Out-of-School Time: The Role of Assessment

Analyzes the tools used in assessments of afterschool and summer science programs, explores the need for comprehensive tools for comparisons across programs, and discusses the most effective structure and format for such a tool. Includes recommendations

Observations on darwiche and Pearl's approach for iterated belief revision

© 2019 International Joint Conferences on Artificial Intelligence. All rights reserved. Notwithstanding the extensive work on iterated belief revision, there is, still, no fully satisfactory solution within the classical AGM paradigm. The seminal work of Darwiche and Pearl (DP approach, for short) remains the most dominant, despite its well-documented shortcomings. In this article, we make further observations on the DP approach. Firstly, we prove that the DP postulates are, in a strong sense, inconsistent with Parikh's relevance-sensitive axiom (P), extending previous initial conflicts. Immediate consequences of this result are that an entire class of intuitive revision operators, which includes Dalal's operator, violates the DP postulates, as well as that the Independence postulate and Spohn's conditionalization are inconsistent with (P). Lastly, we show that the DP postulates allow for more revision polices than the ones that can be captured by identifying belief states with total preorders over possible worlds, a fact implying that a preference ordering (over possible worlds) is an insufficient representation for a belief state

Counteridenticals

A counteridentical is a counterfactual with an identity statement in the antecedent. While counteridenticals generally seem non-trivial, most semantic theories for counterfactuals, when combined with the necessity of identity and distinctness, attribute vacuous truth conditions to such counterfactuals. In light of this, one could try to save the orthodox theories either by appealing to pragmatics or by denying that the antecedents of alleged counteridenticals really contain identity claims. Or one could reject the orthodox theory of counterfactuals in favor of a hyperintensional semantics that accommodates non-trivial counterpossibles. In this paper, I argue that none of these approaches can account for all the peculiar features of counteridenticals. Instead, I propose a modified version of Lewis’s counterpart theory, which rejects the necessity of identity, and show that it can explain all the peculiar features of counteridenticals in a satisfactory way. I conclude by defending the plausibility of contingent identity from objections

Modelling the impact of beliefs and communication on attitude dynamics : a cognitive agent-based approach

In the context of military training for stabilization operation of a crisis zone with civilian population, understanding the formation of attitude and its dynamics is a key issue. This paper presents a multi-agent model for simulating attitude formation and change based on individual's perception of information and its diffusion through communication. We represent the attitude as object-evaluation associations of varying strength proposed by Fazio [1]. Individuals observe military operations. They exchange and revise beliefs about social objects depending on multiple criteria deriving from social psychology theories. They compute their attitude value based on analytic assessment of these beliefs. We illustrate, through several simulation experiments, the role of communication on attitude dynamics

Pauli's Theorem and Quantum Canonical Pairs: The Consistency Of a Bounded, Self-Adjoint Time Operator Canonically Conjugate to a Hamiltonian with Non-empty Point Spectrum

In single Hilbert space, Pauli's well-known theorem implies that the existence of a self-adjoint time operator canonically conjugate to a given Hamiltonian signifies that the time operator and the Hamiltonian possess completely continuous spectra spanning the entire real line. Thus the conclusion that there exists no self-adjoint time operator conjugate to a semibounded or discrete Hamiltonian despite some well-known illustrative counterexamples. In this paper we evaluate Pauli's theorem against the single Hilbert space formulation of quantum mechanics, and consequently show the consistency of assuming a bounded, self-adjoint time operator canonically conjugate to a Hamiltonian with an unbounded, or semibounded, or finite point spectrum. We point out Pauli's implicit assumptions and show that they are not consistent in a single Hilbert space. We demonstrate our analysis by giving two explicit examples. Moreover, we clarify issues sorrounding the different solutions to the canonical commutation relations, and, consequently, expand the class of acceptable canonical pairs beyond the solutions required by Pauli's theorem.Comment: contains corrections to minor typographical errors of the published versio

Surface Pyrolysis of High Energy Materials

The Arrhenius zero-order phenomenological pyrolysis law, commonly used in conjunction with the Vieille ballistic law to study pressure-driven burning of energetic materials, is revisited. Motivated by experimental and theoretical work performed in 1984 in this Laboratory , a relationship among several interplaying parameters is found under steady-state conditions. This relationship corresponds to the Jacobian of the pyrolysis sensitivity parameters used in the Zeldovich-Novozhilov approach. The Arrhenius pyrolysis is still expressed in terms of a global surface activation energy, but consistency with the experimental ballistic law may require an explicit pressure dependence as well. This conclusion is supported by a variety of arguments drawn from different areas. The linear dependence of the pre-exponential factor on surface activation energy (known as kinetic compensation) is proved and extended to the pressure exponent, for any given experimental data set under steady burning. Experimental results are reported for about a dozen solid propellants of different nature. The effects of surface pyrolysis explicit pressure dependence, although modest on steady-state burning, are potentially far-reaching for unsteady regime and/or unstable burning. The paper is mainly focussed on pressure-driven burning and Arrhenius pyrolysis, but the implemented method is believed to apply in general. Thus, enforcing KTSS zero-order phenomenological pyrolysis with the Vieille ballistic law yields similar results and requires an explicit pressure dependence. In case, the Zeldovich ballistic law is enforced instead of the classical Vieille law, no explicit pressure dependence is required. The unifying concept for these different trends is the pyrolysis Jacobian as a consistency requirement between the implemented steady pyrolysis and ballistic laws.

Scientific change and the meanings of terms : an examination of P.K. Feyerabend's incommensurability theses

Feyerabend's incommensurability thesis concerning scientific change engenders a number of logical problems. While it is possible to examine Feyerabend's theory in relation to his historical arguments, the defects implicit in his arguments for the theory render more appropriate an analytical approach. These defects arise from the conjunction of presuppositions and theses that form the background to Feyerabend's claims for an incommensurability thesis. This background contains Feyerabend's criticisms of the traditional empiricism of the twentieth century and its reductionist account of scientific development, his objections to any attempt to rationalize science, his claim that there are fundamental conceptual and ontological changes in science, and his adoption of a meaning variance thesis which envisages wholesale changes in the meanings of all descriptive terms when one theory is replaced by another. While the criticism against traditional empiricism can be upheld, it does not necessitate the conclusion that alternative theories are incommensurable. Feyerabend's attack on Lakatos' rational Reconstructionism is not conclusive: he overlooks the possibility that there do exist standards of criticism, which can be termed "rational", operating within the sciences. The suggestion, supported by Hanson and Kuhn, that there are fundamental conceptual changes in science is open to criticism. The case against radical meaning variance is more complex as it requires the support of a theory of meaning. It is not clear that Feyerabend can, using Wharf's controversial ideas about language, provide a suitable theory of meaning to support his claims. A more satisfactory theory of meaning, based on views of Frege and Wittgenstein, while not denying some changes in the meanings of scientific terms, does not entail the consequence that there are necessarily radical changes in meaning from theory to theory. Although the objections to traditional empiricism are sound and a moderate thesis of meaning variance is acceptable, these do not give rise to the view that competing theories are incommensurable. Historical evidence shows the need to take into consideration the gradual, rather than revolutionary, nature of scientific development. This is compatible both with a moderate thesis of meaning variance and with a modification of the network model developed by Duhem, Quine and Hesse

AI-Rehab: a framework for AI driven neurorehabilitation training - the profiling challenge

One of the health clinic challenges is rehabilitation therapy cognitive impairment that can happen after brain injury, dementia and in normal cognitive decline due to aging. Current cognitive rehabilitation therapy has been shown to be the most effective way to address this problem. However, a) it is not adaptive for every patient, b) it has a high cost, and c) it is usually implemented in clinical environments. The Task Generator (TG) is a free tool for the generation of cognitive training tasks. However, TG is not designed to adapt and monitor the cognitive progress of the patient. Hence, we propose in the BRaNT project an enhancement of TG with belief revision and machine learning techniques, gamification and remote monitoring capabilities to enable health professionals to provide a long-term personalized cognitive rehabilitation therapy at home. The BRaNT is an interdisciplinary effort that addresses scientific limitations of current practices as well as provides solutions towards the sustainability of health systems and contributes towards the improvement of quality of life of patients. This paper proposes the AI-Rehab framework for the BRaNT, explains profiling challenge in the situation of insufficient data and presents an alternate AI solutions which might be applicable once enough data is available.info:eu-repo/semantics/publishedVersio

Remapping Critical Thinking Theory: A Critique of Richard Paul\u27s Model of Critical Thinking

This project is a critical examination of Richard Paul\u27s theoretical conceptualization of critical thinking. In his relentless criticism of the didactic approach characterizing current academic instruction, Paul develops a model of critical thinking that he refers to as critical thinking in the strong sense. The model posits dialogue as the methodological strategy that helps overcome egocentric and socio-centric thinking and thereby facilitates the achievement of ethically rational development. By egocentric and socio-centric thinking, Paul means the thinking that is bound, respectively by one point of view and social context. The model in question is intended not only to displace didactic instruction but also to transcend the overemphasis on logic that characterizes current critical thinking theorizing. While Paul\u27s work points to a promising theoretical horizon, it betrays the very educational ideal that it sets out to pursue. Not only is it the exemplification of the didactic approach that it is intended to displace, but it is also carried out in a conceptual framework that reinforces the modernist view of effective thinking as the rigorous application of rational standards in the determination of the truthfulness of issues. By giving preeminence to logic and rational standards in the thinking process, Paul\u27s view legitimizes a style of inquiry that is conducive to definitive closure. It is fundamentally reductionist: it tends to privilege exclusion over integration, object over relationship. This paper presents an alternative view of critical thinking the theoretical underpinning of which includes a conception of knowledge as immanent. Its primary concern is the achievement of understanding or the production of meaning through persistent explorations of relational structures as opposed to discrete objects. It therefore dismisses any quest for a secure foundation of knowing as illusory. This work is presenting as its starting point the conventional model of educational practice. It provides a brief description of the didactic approach against which Paul levels his criticism. Then, it moves to offer Paul\u27s actual criticism, his view of critical thinking and a critique of his model. Finally, the paper presents a reconfiguration of the theoretical landscape of critical thinking. It formulates and justifies a non-objectivist conception of critical thinking