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  1. Pedro L. Garrido, Sheldon Goldstein, Jani Lukkarinen & Roderich Tumulka, Paradoxical Reflection in Quantum Mechanics.
    This article concerns a phenomenon of elementary quantum mechanics that is quite counter-intuitive, very non-classical, and apparently not widely known: a quantum particle can get reflected at a potential step downwards. In contrast, classical particles get reflected only at upward steps. As a consequence, a quantum particle can be trapped for a long time (though not forever) in a region surrounded by downward potential steps, that is, on a plateau. Said succinctly, a quantum particle tends not to fall off a (...)
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  2. Sheldon Goldstein & Roderich Tumulka, Arxiv:1003.2129v1 [Quant-Ph] 10 Mar 2010.
    The renewed interest in the foundations of quantum statistical mechanics in recent years has led us to study John von Neumann’s 1929 article on the quantum ergodic theorem. We have found this almost forgotten article, which until now has been available only in German, to be a treasure chest, and to be much misunderstood. In it, von Neumann studied the long-time behavior of macroscopic quantum systems. While one of the two theorems announced in his title, the one he calls the (...)
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  3. Sheldon Goldstein & Roderich Tumulka, Long-Time Behavior of Macroscopic Quantum Systems: Commentary Accompanying the English Translation of John Von Neumann's 1929 Article on the Quantum Ergodic Theorem.
    The renewed interest in the foundations of quantum statistical mechanics in recent years has led us to study John von Neumann’s 1929 article on the quantum ergodic theorem. We have found this almost forgotten article, which until now has been available only in German, to be a treasure chest, and to be much misunderstood. In it, von Neumann studied the long-time behavior of macroscopic quantum systems. While one of the two theorems announced in his title, the one he calls the (...)
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  4. Sheldon Goldstein & Roderich Tumulka, Normal Typicality and Von Neumann's Quantum Ergodic Theorem.
    We discuss the content and significance of John von Neumann’s quantum ergodic theorem (QET) of 1929, a strong result arising from the mere mathematical structure of quantum mechanics. The QET is a precise formulation of what we call normal typicality, i.e., the statement that, for typical large systems, every initial wave function ψ0 from an energy shell is “normal”: it evolves in such a way that |ψt ψt| is, for most t, macroscopically equivalent to the micro-canonical density matrix. The QET (...)
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  5. Sheldon Goldstein & Roderich Tumulka, On the Approach to Thermal Equilibrium of Macroscopic Quantum Systems.
    We consider an isolated, macroscopic quantum system. Let H be a microcanonical “energy shell,” i.e., a subspace of the system’s Hilbert space spanned by the (finitely) many energy eigenstates with energies between E and E + δE. The thermal equilibrium macro-state at energy E corresponds to a subspace Heq of H such that dim Heq/ dim H is close to 1. We say that a system with state vector ψ H is in thermal equilibrium if ψ is “close” to Heq. (...)
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  6. Valia Allori, Sheldon Goldstein, Roderich Tumulka & Nino Zanghi (2013). Predictions and Primitive Ontology in Quantum Foundations: A Study of Examples. British Journal for the Philosophy of Science (2):axs048.
    A major disagreement between different views about the foundations of quantum mechanics concerns whether for a theory to be intelligible as a fundamental physical theory it must involve a ‘primitive ontology’ (PO), i.e. variables describing the distribution of matter in four-dimensional space–time. In this article, we illustrate the value of having a PO. We do so by focussing on the role that the PO plays for extracting predictions from a given theory and discuss valid and invalid derivations of predictions. To (...)
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  7. Roderich Tumulka, Detlef Durr, Sheldon Goldstein & Nino Zanghi, Bohmian Mechanics. Compendium of Quantum Physics.
    Bohmian mechanics is a theory about point particles moving along trajectories. It has the property that in a world governed by Bohmian mechanics, observers see the same statistics for experimental results as predicted by quantum mechanics. Bohmian mechanics thus provides an explanation of quantum mechanics. Moreover, the Bohmian trajectories are defined in a non-conspiratorial way by a few simple laws.
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  8. Valia Allori, Sheldon Goldstein, Roderich Tumulka & and Nino Zanghì (2008). On the Common Structure of Bohmian Mechanics and the Ghirardi–Rimini–Weber Theory: Dedicated to Giancarlo Ghirardi on the Occasion of His 70th Birthday. British Journal for the Philosophy of Science 59 (3):353-389.
    Bohmian mechanics and the Ghirardi–Rimini–Weber theory provide opposite resolutions of the quantum measurement problem: the former postulates additional variables (the particle positions) besides the wave function, whereas the latter implements spontaneous collapses of the wave function by a nonlinear and stochastic modification of Schrödinger's equation. Still, both theories, when understood appropriately, share the following structure: They are ultimately not about wave functions but about ‘matter’ moving in space, represented by either particle trajectories, fields on space-time, or a discrete set of (...)
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  9. Valia Allori, Sheldon Goldstein, Roderich Tumulka & Nino Zanghi (2008). On the Common Structure of Bohmian Mechanics and the Ghirardi-Rimini-Weber Theory. British Journal for the Philosophy of Science 59 (3):353 - 389.
    Bohmian mechanics and the Ghirardi-Rimini-Weber theory provide opposite resolutions of the quantum measurement problem: the former postulates additional variables (the particle positions) besides the wave function, whereas the latter implements spontaneous collapses of the wave function by a nonlinear and stochastic modification of Schrödinger's equation. Still, both theories, when understood appropriately, share the following structure: They are ultimately not about wave functions but about 'matter' moving in space, represented by either particle trajectories, fields on space-time, or a discrete set of (...)
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  10. Valia Allori, Sheldon Goldstein, Roderich Tumulka & Nino Zanghì (2008). On the Common Structure of Bohmian Mechanics and the Ghirardi–Rimini–Weber Theory Dedicated to GianCarlo Ghirardi on the Occasion of His 70th Birthday. British Journal for the Philosophy of Science 59 (3):353-389.
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  11. Roderich Tumulka (2007). Comment on “The Free Will Theorem”. Foundations of Physics 37 (2):186-197.
    In a recent paper Conway and Kochen, Found. Phys. 36, 2006, claim to have established that theories of the Ghirardi-Rimini-Weber (RW) type, i.e., of spontaneous wave function collapse, cannot be made relativistic. On the other hand, relativistic GRW-type theories have already been presented, in my recent paper, J. Stat. Phys. 125, 2006, and by Dowker and Henson, J. Stat. Phys. 115, 2004. Here, I elucidate why these are not excluded by the arguments of Conway and Kochen.
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  12. Roderich Tumulka (2007). Determinate Values for Quantum Observables. British Journal for the Philosophy of Science 58 (2):355 - 360.
    This is a comment on J. A. Barrett's article 'The Preferred-Basis Problem and the Quantum Mechanics of Everything' ([2005]), which concerns theories postulating that certain quantum observables have determinate values, corresponding to additional (often called 'hidden') variables. I point out that it is far from clear, for most observables, what such a postulate is supposed to mean, unless the postulated additional variable is related to a clear ontology in space-time, such as particle world lines, string world sheets, or fields.
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  13. Martin Daumer, Detlef Duerr, Sheldon Goldstein, Tim Maudlin, Roderich Tumulka & Nino Zanghi, The Message of the Quantum?
    We criticize speculations to the effect that quantum mechanics is fundamentally about information. We do this by pointing out how unfounded such speculations in fact are. Our analysis focuses on the dubious claims of this kind recently made by Anton Zeilinger.
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  14. Roderich Tumulka (2006). A Relativistic Version of the Ghirardi–Rimini–Weber Model. Journal of Statistical Physics 125:821-840.
     
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  15. Detlef Dürr, Sheldon Goldstein, Roderich Tumulka & Nino Zanghí (2005). On the Role of Density Matrices in Bohmian Mechanics. Foundations of Physics 35 (3):449-467.
  16. Sheldon Goldstein, James Taylor, Roderich Tumulka & Nino Zanghi (2005). Are All Particles Real? Studies in History and Philosophy of Science Part B 36 (1):103-112.
    In Bohmian mechanics elementary particles exist objectively, as point particles moving according to a law determined by a wavefunction. In this context, questions as to whether the particles of a certain species are real---questions such as, Do photons exist? Electrons? Or just the quarks?---have a clear meaning. We explain that, whatever the answer, there is a corresponding Bohm-type theory, and no experiment can ever decide between these theories. Another question that has a clear meaning is whether particles are intrinsically distinguishable, (...)
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