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Profile: Hans Halvorson (Princeton University)
  1. David J. Baker & Hans Halvorson, How is Spontaneous Symmetry Breaking Possible?
    We pose and resolve a seeming paradox about spontaneous symmetry breaking in the quantum theory of infinite systems. For a symmetry to be spontaneously broken, it must not be implementable by a unitary operator. But Wigner's theorem guarantees that every symmetry is implemented by a unitary operator that preserves transition probabilities between pure states. We show how it is possible for a unitary operator of this sort to connect the folia of unitarily inequivalent representations. This result undermines interpretations of quantum (...)
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  2. David John Baker, Hans Halvorson & Noel Swanson, The Conventionality of Parastatistics.
    Nature seems to be such that we can describe it accurately with quantum theories of bosons and fermions alone, without resort to parastatistics. This has been seen as a deep mystery: paraparticles make perfect physical sense, so why don't we see them in nature? We consider one potential answer: every paraparticle theory is physically equivalent to some theory of bosons or fermions, making the absence of paraparticles in our theories a matter of convention rather than a mysterious empirical discovery. We (...)
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  3. Hans Halvorson, No Time for Quantum Mechanics.
    I prove that -- given certain physically realistic assumptions -- a quantum-mechanical system cannot have a time observable.
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  4. Noel Swanson & Hans Halvorson, On North's "The Structure of Physics&Quot;.
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  5. Hans Halvorson (forthcoming). Theism and Physical Cosmology. In Charles Taliaferro, Victoria Harrison & Stewart Goetz (eds.), Routledge Companion to Theism.
    Physical cosmology purports to establish precise and testable claims about the origin of the universe. Thus, cosmology bears directly on traditional metaphysical claims -- in particular, claims about whether the universe has a creator (i.e. God). What is the upshot of cosmology for the claims of theism? Does big-bang cosmology support theism? Do recent developments in quantum and string cosmology undermine theism? We discuss the relations between physical cosmology to theism from both historical and systematic points of view.
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  6. David John Baker & Hans Halvorson (2013). How is Spontaneous Symmetry Breaking Possible? Understanding Wigner's Theorem in Light of Unitary Inequivalence. Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 44 (4):464-469.
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  7. Hans Halvorson (2013). Ruetsche on the Pristine and Adulterated in Quantum Field Theory. Metascience 22 (1):69-75.
    Review of Laura Ruetsche's "Interpreting Quantum Theories".
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  8. Hans Halvorson (2013). The Semantic View, If Plausible, Is Syntactic. Philosophy of Science 80 (3):475-478.
  9. Hans Halvorson (2012). What Scientific Theories Could Not Be. Philosophy of Science 79 (2):183-206.
    According to the semantic view of scientific theories, theories are classes of models. I show that this view -- if taken seriously as a formal explication -- leads to absurdities. In particular, this view equates theories that are truly distinct, and it distinguishes theories that are truly equivalent. Furthermore, the semantic view lacks the resources to explicate interesting theoretical relations, such as embeddability of one theory into another. The untenability of the semantic view -- as currently formulated -- threatens to (...)
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  10. Hans Halvorson, Cosmology and Theology. Stanford Encyclopedia of Philosophy.
  11. Hans Halvorson (2011). The Measure of All Things: Quantum Mechanics And. In Mark C. Baker & Stewart Goetz (eds.), The Soul Hypothesis: Investigations Into the Existence of the Soul. Continuum Press. 138.
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  12. David Baker & Hans Halvorson (2010). Antimatter. British Journal for the Philosophy of Science 61 (1):93-121.
    Next SectionThe nature of antimatter is examined in the context of algebraic quantum field theory. It is shown that the notion of antimatter is more general than that of antiparticles. Properly speaking, then, antimatter is not matter made up of antiparticles—rather, antiparticles are particles made up of antimatter. We go on to discuss whether the notion of antimatter is itself completely general in quantum field theory. Does the matter–antimatter distinction apply to all field theoretic systems? The answer depends on which (...)
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  13. Hans Halvorson & Michael Mueger (2006). Algebraic Quantum Field Theory. In J. Butterfield & J. Earman (eds.), Handbook of the philosophy of physics. Kluwer.
    Algebraic quantum field theory provides a general, mathematically precise description of the structure of quantum field theories, and then draws out consequences of this structure by means of various mathematical tools -- the theory of operator algebras, category theory, etc.. Given the rigor and generality of AQFT, it is a particularly apt tool for studying the foundations of QFT. This paper is a survey of AQFT, with an orientation towards foundational topics. In addition to covering the basics of the theory, (...)
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  14. Mark Sainsbury, Cory Juhl, Nicholas Asher, Hans Halvorson, Lawrence Sklar & Jim Hankinson (2006). Tracy Lupher. In Borchert (ed.), Philosophy of Science. Macmillan. 164-202.
     
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  15. Hans Halvorson (2004). A Note on Information Theoretic Characterizations of Physical Theories. Studies in History and Philosophy of Modern Physics 35 (2):277-293.
    Clifton, Bub, and Halvorson (CBH) have recently argued that quantum theory is characterized by its satisfaction of three fundamental information-theoretic constraints. However, it is not difficult to construct apparent counterexamples to the CBH characterization theorem. In this paper, we discuss the limits of the characterization theorem, and we provide some technical tools for checking whether a theory (specified in terms of the convex structure of its state space) falls within these limits.
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  16. Hans Halvorson (2004). Complementarity of Representations in Quantum Mechanics. Studies in History and Philosophy of Science Part B 35 (1):45-56.
    We show that Bohr's principle of complementarity between position and momentum descriptions can be formulated rigorously as a claim about the existence of representations of the CCRs. In particular, in any representation where the position operator has eigenstates, there is no momentum operator, and vice versa. Equivalently, if there are nonzero projections corresponding to sharp position values, all spectral projections of the momentum operator map onto the zero element.
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  17. Hans Halvorson (2004). On Information-Theoretic Characterizations of Physical Theories. Studies in History and Philosophy of Science Part B 35 (2):277-293.
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  18. J. Butterfield & H. Halvorson (2003). Robert K. Clifton 1964–2002. Studies in History and Philosophy of Science Part B 34 (1):1-3.
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  19. Rob Clifton, Jeffrey Bub & Hans Halvorson (2003). Characterizing Quantum Theory in Terms of Information-Theoretic Constraints. Foundations of Physics 33 (11):1561-1591.
    We show that three fundamental information-theoretic constraints -- the impossibility of superluminal information transfer between two physical systems by performing measurements on one of them, the impossibility of broadcasting the information contained in an unknown physical state, and the impossibility of unconditionally secure bit commitment -- suffice to entail that the observables and state space of a physical theory are quantum-mechanical. We demonstrate the converse derivation in part, and consider the implications of alternative answers to a remaining open question about (...)
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  20. Hans Halvorson (2002). On Quanta, Mind, and Matter: Hans Primas in Context - H. Atmanspacher, A. Amann, U. Muller-Herold (Eds), Kluwer, Boston, 1999, Pp. 398 + VIII, US$192.00£133.56 (Hardback), ISBN 0-7923-5696-. [REVIEW] Studies in History and Philosophy of Science Part B 33 (4):744-747.
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  21. Hans Halvorson & Rob Clifton (2002). No Place for Particles in Relativistic Quantum Theories? Philosophy of Science 69 (1):1-28.
    David Malament (1996) has recently argued that there can be no relativistic quantum theory of (localizable) particles. We consider and rebut several objections that have been made against the soundness of Malament’s argument. We then consider some further objections that might be made against the generality of Malament’s conclusion, and we supply three no‐go theorems to counter these objections. Finally, we dispel potential worries about the counterintuitive nature of these results by showing that relativistic quantum field theory itself explains the (...)
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  22. Hans Halvorson & Rob Clifton (2002). Reconsidering Bohr's Reply to EPR. In T. Placek & J. Butterfield (eds.), Non-locality and Modality. Kluwer. 3--18.
    Although Bohr's reply to the EPR argument is supposed to be a watershed moment in the development of his philosophy of quantum theory, it is difficult to find a clear statement of the reply's philosophical point. Moreover, some have claimed that the point is simply that Bohr is a radical positivist. In this paper, we show that such claims are unfounded. In particular, we give a mathematically rigorous reconstruction of Bohr's reply to the _original_ EPR argument that clarifies its logical (...)
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  23. J. C. Beall, T. Bigaj, T. Fernando, B. Fitelson, N. Foo, W. Goldfarb, D. Gregory, T. Hailperin, H. Halvorson & K. Harris (2001). Arló-Costa, H., 479 Armour-Garb, B., 593 Azzouni, J., 329 Batens, D., 267. Journal of Philosophical Logic 30 (619).
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  24. Rob Clifton & Hans Halvorson (2001). Are Rindler Quanta Real? Inequivalent Particle Concepts in Quantum Field Theory. British Journal for the Philosophy of Science 52 (3):417-470.
    Philosophical reflection on quantum field theory has tended to focus on how it revises our conception of what a particle is. However, there has been relatively little discussion of the threat to the ‘reality’ of particles posed by the possibility of inequivalent quantizations of a classical field theory, i.e. inequivalent representations of the algebra of observables of the field in terms of operators on a Hilbert space. The threat is that each representation embodies its own distinctive conception of what a (...)
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  25. Rob Clifton & Hans Halvorson (2001). Entanglement and Open Systems in Algebraic Quantum Field Theory. Studies in History and Philosophy of Science Part B 32 (1):1-31.
    Entanglement has long been the subject of discussion by philosophers of quantum theory, and has recently come to play an essential role for physicists in their development of quantum information theory. In this paper we show how the formalism of algebraic quantum field theory (AQFT) provides a rigorous framework within which to analyse entanglement in the context of a fully relativistic formulation of quantum theory. What emerges from the analysis are new practical and theoretical limitations on an experimenter's ability to (...)
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  26. Hans Halvorson (2001). A Philosopher's Understanding of Quantum Mechanics: Possibilities and Impossibilities of a Modal Interpretation Pieter Vermaas. British Journal for the Philosophy of Science 52 (2):387-391.
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  27. Hans Halvorson (2001). Locality, Localization, and the Particle Concept: Topics in the Foundations of Quantum Field Theory. Dissertation, University of Pittsburgh
    This dissertation reconsiders some traditional issues in the foundations of quantum mechanics in the context of relativistic quantum field theory (RQFT); and it considers some novel foundational issues that arise first in the context of RQFT. The first part of the dissertation considers quantum nonlocality in RQFT. Here I show that the generic state of RQFT displays Bell correlations relative to measurements performed in any pair of spacelike separated regions, no matter how distant. I also show that local systems in (...)
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  28. Hans Halvorson (2001). On the Nature of Continuous Physical Quantities in Classical and Quantum Mechanics. Journal of Philosophical Logic 30 (1):27-50.
    Within the traditional Hilbert space formalism of quantum mechanics, it is not possible to describe a particle as possessing, simultaneously, a sharp position value and a sharp momentum value. Is it possible, though, to describe a particle as possessing just a sharp position value (or just a sharp momentum value)? Some, such as Teller, have thought that the answer to this question is No - that the status of individual continuous quantities is very different in quantum mechanics than in classical (...)
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  29. Hans Halvorson (2001). Reeh-Schlieder Defeats Newton-Wigner: On Alternative Localization Schemes in Relativistic Quantum Field Theory. Philosophy of Science 68 (1):111-133.
    Many of the "counterintuitive" features of relativistic quantum field theory have their formal root in the Reeh-Schlieder theorem, which in particular entails that local operations applied to the vacuum state can produce any state of the entire field. It is of great interest then that I.E. Segal and, more recently, G. Fleming (in a paper entitled "Reeh-Schlieder meets Newton-Wigner") have proposed an alternative "Newton-Wigner" localization scheme that avoids the Reeh-Schlieder theorem. In this paper, I reconstruct the Newton-Wigner localization scheme and (...)
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  30. Pieter Vermaas & Hans Halvorson (2001). Reviews-A Philosopher's Understanding of Quantum Mechanics: Possibilities and Impossibilities of a Modal Interpretation. British Journal for the Philosophy of Science 52 (2):387-392.
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  31. Hans Halvorson & Rob Clifton (1999). Maximal Beable Subalgebras of Quantum-Mechanical Observables. International Journal of Theoretical Physics 38:2441-2484.
    The centerpiece of Jeffrey Bub's book Interpreting the Quantum World is a theorem (Bub and Clifton 1996) which correlates each member of a large class of no-collapse interpretations with some 'privileged observable'. In particular, the Bub-Clifton theorem determines the unique maximal sublattice L(R,e) of propositions such that (a) elements of L(R,e) can be simultaneously determinate in state e, (b) L(R,e) contains the spectral projections of the privileged observable R, and (c) L(R,e) is picked out by R and e alone. In (...)
     
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  32. Hans Halvorson, Plantinga on Providence and Physics.
    Discussion of Alvin Plantinga's book, "Where the Conflict Really Lies".
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