27,206 research outputs found

    Anvil or Onion? Determinism as a Layered Concept

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    Stephen Kellert (1993) has argued that Laplacean determinism in classical physics is actually a layered concept, where various properties or layers composing this form of determinism can be peeled away. Here, I argue that a layered conception of determinism is inappropriate and that we should think in terms of different deterministic models applicable to different kinds of systems. The upshot of this analysis is that the notion of state is more closely tied to the kind of system being investigated than is usually considered in discussions of determinism. So when investigating determinism corresponding changes to the appropriate notion of state–and, perhaps, the state space itself–also need to be considered

    The Hidden Premise in the Causal Argument for Physicalism

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    The causal argument for physicalism is anayzed and it's key premise--the causal closure of physics--is found wanting. Therefore, a hidden premise must be added to the argument to gain its conclusion, but the hidden premise is indistinguishable from the conclusion of the causal argument. Therefore, it begs the question on physicalism

    Quantum Time Arrows, Semigroups and Time-Reversal in Scattering

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    Two approaches toward the arrow of time for scattering processes have been proposed in rigged Hilbert space quantum mechanics. One, due to Arno Bohm, involves preparations and registrations in laboratory operations and results in two semigroups oriented in the forward direction of time. The other, employed by the Brussels-Austin group, is more general, involving excitations and de-excitations of systems, and apparently results in two semigroups oriented in opposite directions of time. It turns out that these two time arrows can be related to each other via Wigner's extensions of the spacetime symmetry group. Furthermore, their are subtle differences in causality as well as the possibilities for the existence and creation of time-reversed states depending on which time arrow is chose

    Brussels-Austin Nonequilibrium Statistical Mechanics in the Early Years: Similarity Transformations between Deterministic and Probabilistic Descriptions

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    The fundamental problem on which Ilya Prigogine and the Brussels-Austin Group have focused can be stated briefly as follows. Our observations indicate that there is an arrow of time in our experience of the world (e.g., decay of unstable radioactive atoms like Uranium, or the mixing of cream in coffee). Most of the fundamental equations of physics are time reversible, however, presenting an apparent conflict between our theoretical descriptions and experimental observations. Many have thought that the observed arrow of time was either an artifact of our observations or due to very special initial conditions. An alternative approach, followed by the Brussels-Austin Group, is to consider the observed direction of time to be a basics physical phenomenon and to develop a mathematical formalism that can describe this direction as being due to the dynamics of physical systems. In part I of this essay, I review and assess an attempt to carry out an approach that received much of their attention from the early 1970s to the mid 1980s. In part II, I will discuss their more recent approach using rigged Hilbert spaces.Comment: 22 pages, Part I of two parts; updated institutional affiliatio

    Humidity resistant solar cell contacts

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    Gold-platinum solar cell contact is developed which does not exhibit chemical reactivity of titanium or porosity of silver. This contact offers excellent ohmic characteristics and stability in humid air

    The Value-of-Information in Matching with Queues

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    We consider the problem of \emph{optimal matching with queues} in dynamic systems and investigate the value-of-information. In such systems, the operators match tasks and resources stored in queues, with the objective of maximizing the system utility of the matching reward profile, minus the average matching cost. This problem appears in many practical systems and the main challenges are the no-underflow constraints, and the lack of matching-reward information and system dynamics statistics. We develop two online matching algorithms: Learning-aided Reward optimAl Matching (LRAM\mathtt{LRAM}) and Dual-LRAM\mathtt{LRAM} (DRAM\mathtt{DRAM}) to effectively resolve both challenges. Both algorithms are equipped with a learning module for estimating the matching-reward information, while DRAM\mathtt{DRAM} incorporates an additional module for learning the system dynamics. We show that both algorithms achieve an O(Ï”+ÎŽr)O(\epsilon+\delta_r) close-to-optimal utility performance for any Ï”>0\epsilon>0, while DRAM\mathtt{DRAM} achieves a faster convergence speed and a better delay compared to LRAM\mathtt{LRAM}, i.e., O(ÎŽz/Ï”+log⁥(1/Ï”)2))O(\delta_{z}/\epsilon + \log(1/\epsilon)^2)) delay and O(ÎŽz/Ï”)O(\delta_z/\epsilon) convergence under DRAM\mathtt{DRAM} compared to O(1/Ï”)O(1/\epsilon) delay and convergence under LRAM\mathtt{LRAM} (ÎŽr\delta_r and ÎŽz\delta_z are maximum estimation errors for reward and system dynamics). Our results reveal that information of different system components can play very different roles in algorithm performance and provide a systematic way for designing joint learning-control algorithms for dynamic systems

    The Economic Effects in 2002 of Chronic Wasting Disease (CWD) in Wisconsin

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    Wisconsin's 600,000 deer hunters will bear the brunt of the economic losses from chronic wasting disease (CWD) in the Wisconsin deer herd. Though studies have not been done to pinpoint a precise value, preliminary estimates place the losses to deer hunters at between 70millionand70 million and 100 million this fall. CWD will also cause deer hunters to spend less on their sport this year than they have in the past. However, the impacts of reduced hunter spending on the Wisconsin economy should not be too large. Losses to the deer hunting economy will be counterbalanced as resident hunters spend their money elsewhere in the economy. Some spending by nonresident hunters will be lost, but deer hunting is a very small part of the tourist economy. Nevertheless, some people in rural areas will suffer economically as fewer urban deer hunters spend money on the services they provide. If additional bad news about CWD is forthcoming before fall, the losses could be much larger.