Reduction in Science
Structure, Examples, Philosophical Problems
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21 Result(s)
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Heinz-Jürgen Schmidt
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Article
Open AccessThermodynamics of the Spin Square
Small spin systems at the interface between analytical studies and experimental application have been intensively studied in recent decades. The spin ring consisting of four spins with uniform antiferromagneti...
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Open AccessEinstein’s photon box revisited
We present a reformulation of Bohr’s analysis of Einstein’s thought experiment with the photon box, which hopefully settles some unclear issues. The box is weighed by two position measurements, the first immed...
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Open AccessCorrection to: Conditional Action and Quantum Versions of Maxwell’s Demon
The article “Conditional Action and Quantum Versions of Maxwell’s Demon”, written by Heinz‑Jurgen Schmidt, was originally published electronically on the publisher’s internet portal on 30 September 2020 withou...
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Open AccessSupersymmetric spin–phonon coupling prevents odd integer spins from quantum tunneling
Quantum tunneling of the magnetization is a phenomenon that impedes the use of small anisotropic spin systems for storage purposes even at the lowest temperatures. Phonons, usually considered for temperature d...
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Open AccessConditional Action and Quantum Versions of Maxwell’s Demon
We propose a new way of looking at the quantum Maxwell’s demon problem in terms of conditional action. A “conditional action” on a system is a unitary time evolution, selected according to the result of a prev...
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Article
Reduction and Extremality of Finite Observables
We investigate the theory of finite observables, i.e., resolutions of the finite-dimensional identity by means of positive operators, that have a physical interpretation in terms of measurement schemes. We foc...
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Coexistence of qubit effects
Two quantum events, represented by positive operators (effects), are coexistent if they can occur as possible outcomes in a single measurement scheme. Equivalently, the corresponding effects are coexistent if and...
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Heisenberg-Integrable Spin Systems
We investigate certain classes of integrable classical or quantum spin systems. The first class is characterized by the recursively defined property P saying that the spin system consists of a single spin or can ...
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Chapter
Lectures on Quantum Theory (1922–23 and 1926–27)
Hilbert’s lectures on radiation theory (Hilbert 1912* , this Volume, Chapter 5) contain a discussion of Planck’s radiation formula and also comment on the underlying quantum hypothesis. But it is in two lecture c...
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Photon Stars
We discuss numerical solutions of Einstein's field equation describing static, spherically symmetric conglomerations of a photon gas. These equations imply a back reaction of the metric on the energy density o...
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Reflections on spacetime — foundations, philosophy and history
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A minimal interpretation of general relativistic spacetime geometry
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A Minimal Interpretation of General Relativistic Spacetime Geometry
A mathematical theory usually admits of various equivalent formulations. It is not only possible to choose different sets of axioms but also the decision of what is considered as a basic concept and what as a ...
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Book
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Chapter
Introduction
The theme of reduction bears broadly on the logic, the methodology and the epistemology of scientific change, on the rationality and continuity of scientific progress,and on the unity and growth of scientific ...
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Chapter
Tangent Embedding — A Special Kind of Approximate Reduction
This paper presents a definition of an intertheoretic relation which is based on G. Ludwig’s concept of “approximate embedding”.
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On the foundations of the physical probability concept
An exact formulation of the frequency interpretation of probability is proposed on the basis of G. Ludwig's concept of physical theories. Starting from a short outline of this concept, a formal definition of w...
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Kinematics as a Theory of Coincidences
In this article, “kinematics” will be considered as a pre-theory of mechanics dealing with macroscopic bodies in the laboratory. An axiomatic account of such a pre-theory should meet the following requirements:
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The structure of Stern-Gerlach experiments and Ludwig's approach to quantum theory
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Book
