The phenomenon of broken spacetime symmetry in the quantum theory of infinite systems seems to point toward an unorthodox ontology. The standard conception of the physical meaning of these symmetries, as changes in coordinates, conflicts with the apparent physical inequivalence of symmetry-related states. I argue that this apparent conflict is an artifact of a subtle error in the extant account of physical equivalence due to Halvorson and Clifton.
The phenomenon of broken spacetime symmetry in the quantum theory of infinite systems seems to point toward an unorthodox ontology. The standard conception of the physical meaning of these symmetries, as changes in coordinates, conflicts with the apparent physical inequivalence of symmetry-related states. I argue that this apparent conflict is an artifact of a subtle error in the extant account of physical equivalence due to Halvorson and Clifton.
This essay expounds the algebraic framework describing general physical the-ories, within which the phenomenon of spontaneous symmetry breaking (SSB) makes its appearance in infinite quantum systems. This is in contrast with the fact that a large class of theories- both classical and quantum, finite and infinite- are termed, in the conventional account of classical and quantum mechanics, as exhibiting SSB. This discrepancy will be understood in the light of an interpretation that finds the symmetry breaking to be in some respects stronger in the algebraic account than is generally the case in the conventional picture. The case of SSB in the standard account of quantum field theory (QFT) will then be discussed, and it will be argued that, although one would expect a connection with the algebraic account to be possible, this turns out to be problematic. Finally the role of the idealisation of infinite systems, crucial to algebraic SSB, will be dis-cussed.
“For me then this is the real problem with quantum theory: the apparently essential conflict between any sharp formulation and fundamental relativity. That is to say, we have an apparent incompatibility, at the deepest level, between the two fundamental pillars of contemporary theory...” J. S. Bell (2004, p. 171) The inability to delineate a unified physical ontology that accounts simultaneously for the laws of special relativity and the results of quantum experiments has been a defining problem in physics for more than 100 years. Although various primitive ontologies (including Bohmian pilot wave, spontaneous collapse, and objective collapse theories) along with wave function realism ontologies, many-worlds interpretations, and multi-field theories address the tension between special relativity and quantum mechanics, none has successfully resolved it. This analysis addresses the problem by positing an ontic, mixed ontology composed of a “discrete” 4D spacetime and a physical, ultra-high dimensional (3 x N) “Planck Space.” Together, Planck Space and the three spatial dimensions of 4D spacetime form a tightly integrated ((3 x N) + 3) hyperspace (the “Dual Ontology”). 4D spacetime’s three spatial dimensions and the N dimensions of Planck Space are composed of two substructures: discrete, three-dimensional, quantized units of space ("Planck Spheres") and an ontic State of Absolute Nothingness (the "SOAN") whose sole physical characteristic is onticness. Critically, the Dual Ontology’s structure replaces 1) the continuous, differentiable manifold of 4D spacetime with a discrete 4D spacetime and 2) mathematical 3N configuration spaces with a physical (3 x N) Planck Space. Moreover, structurally and dynamically, the Dual Ontology is predicated on the one-to-one mapping and identity between the Planck Spheres that simultaneously form 4D spacetime and Planck Space. The one-to-one mapping and identity physically and theoretically support an integrated quantum dynamics based upon the dynamic evolution of single and N-body quantum states in 4D spacetime in full compliance with the laws of special relativity and the instantaneous collapse of all quantum states in an ontic Planck Space, where special and general relativity and more generally, 4D spacetime’s laws of physics, do not apply.
We consider symmetry as a foundational concept in quantum mechanics and rewrite quantum mechanics and measurement axioms in this description. We argue that issues related to measurements and physical reality of states can be better understood in this view. In particular, the abstract concept of symmetry provides a basis-independent definition for observables. Moreover, we show that the apparent projection/collapse of the state as the final step of measurement or decoherence is the result of breaking of symmetries. This phenomenon is comparable with a phase transition by spontaneous symmetry breaking, and makes the process of decoherence and classicality a natural fate of complex systems consisting of many interacting subsystems. Additionally, we demonstrate that the property of state space as a vector space representing symmetries is more fundamental than being an abstract Hilbert space, and its L2 integrability can be obtained from the imposed condition of being a representation of a symmetry group and general properties of probability distributions.
Approaches to Ontology: Candidate General Ontologies for Situating Quantum Field (P Simons) 'Quanta', Tropes, or Processes: Ontologies for QFT Beyond the Myth of Substance (J Seibt) Analytical Ontologists in Action: A Comment on Seibt and Simons (M Kuhlmann) How Do Field Theories Refer to Entities in a Field? (S Y Auyang) Field Ontologies for QFT: A Naive View of the Quantum Field (A Wayne) Comments on Paul Teller's Book, An Interpretive Introduction to Quantum Field Theory (G Fleming) So What Is the Quantum Field? (P Teller) Relativity, Measurement and Renormalization: On the Nature of Measurement Records in Relativistic Quantum Field (J A Barrett) No Place for Particles in Relativistic Quantum Theories? (H Halvorson & R Clifton) Events and Covariance in the Interpretation of Quantum Field (D Dieks) Measurement and Ontology: What Kind of Evidence Can We Have for Quantum Fields? (B Falkenburg) Renormalization and the Disunity of Science (N Huggett) Gauge Symmetries and the Vacuum: The Interpretation of Gauge Symmetry (M Redhead) Comment on Redhead: The Interpretation of Gauge Symmetry (M Drieschner et al.) Is the Zero-Point Energy Real? (S Saunders) Two Comments on the Vacuum in Algebraic Quantum Field (M Redei).
Recent investigations concerning foundations of quantum theory require new approaches to the problem of observation of physical events. V. Belavkin showed that standard quantum mechanics describes only the closed microworld in which there is no place for some macroscopically visible events. Though any quantum phenomenon is observable from the macroworld. That situation means non‐equivalence of Heisenberg’s representation to Schrodinger’s one in quantum mechanics. It would seem quantum theory is more general than classical mechanics. It is expressed, in particular, by well‐known Bohr’s principle of correspondence. I think the above‐mentioned Belavkin’s result puts under doubt the opinion concerning universal character of quantum theory. What ontological meaning has the concept of existence of physical event? Is distinction between observable event and non‐observable one anthropological, or not? In that context I discuss the new aspects of the observation problem in the physical theory. In my report I discuss philosophical arguments for the thesis that distinction between observable event and non‐observable one is ontological. In this connection I consider a number of objective ontological criteria of observability / non‐observability such as distinguishableness / indistinguishableness of physical states, symmetricalness and asymmetricalness of observation relations. The ontological sense of observation is analyzed in the context of relations between objects which are into spaces with different dimensions.
Quantum measurement predictions are consistent with relativity for macroscopic observations, but there is no consensus on how to explain this consistency in fundamental terms. The prevailing assumption is that the relativistic structure of spacetime should provide the framework for any microphysical account. This bias is due, in large part, to our intuitions about local causality, the idea that all physical processes propagate through space in a continuous manner. I argue that relativity is not a guarantor of local causality, and is not about ontological features of spacetime. It is, rather, an expression of the observational equivalence of spacetime descriptions of physical processes. This observational equivalence is due to the essentially probabilistic nature of quantum theory.