27,702 research outputs found
Bell's Theorem and Locally-Mediated Reformulations of Quantum Mechanics
Bell's Theorem rules out many potential reformulations of quantum mechanics,
but within a generalized framework, it does not exclude all "locally-mediated"
models. Such models describe the correlations between entangled particles as
mediated by intermediate parameters which track the particle world-lines and
respect Lorentz covariance. These locally-mediated models require the
relaxation of an arrow-of-time assumption which is typically taken for granted.
Specifically, some of the mediating parameters in these models must
functionally depend on measurement settings in their future, i.e., on input
parameters associated with later times. This option (often called
"retrocausal") has been repeatedly pointed out in the literature, but the
exploration of explicit locally-mediated toy-models capable of describing
specific entanglement phenomena has begun only in the past decade. A brief
survey of such models is included here. These models provide a continuous and
consistent description of events associated with spacetime locations, with
aspects that are solved "all-at-once" rather than unfolding from the past to
the future. The tension between quantum mechanics and relativity which is
usually associated with Bell's Theorem does not occur here. Unlike conventional
quantum models, the number of parameters needed to specify the state of a
system does not grow exponentially with the number of entangled particles. The
promise of generalizing such models to account for all quantum phenomena is
identified as a grand challenge.Comment: 61 pages, 2 figures; accepted for publication by Rev. Mod. Phy
Threshold analyses and Lorentz violation
In the context of threshold investigations of Lorentz violation, we discuss
the fundamental principle of coordinate invariance, the role of an effective
dynamical framework, and the conditions of positivity and causality. Our
analysis excludes a variety of previously considered Lorentz-breaking
parameters and opens an avenue for viable dispersion-relation investigations of
Lorentz violation.Comment: 9 page
Analyticity of the Scattering Amplitude, Causality and High-Energy Bounds in Quantum Field Theory on Noncommutative Space-Time
In the framework of quantum field theory (QFT) on noncommutative (NC)
space-time with the symmetry group , we prove that the
Jost-Lehmann-Dyson representation, based on the causality condition taken in
connection with this symmetry, leads to the mere impossibility of drawing any
conclusion on the analyticity of the -scattering amplitude in
, being the scattering angle. Discussions on the possible
ways of obtaining high-energy bounds analogous to the Froissart-Martin bound on
the total cross-section are also presented.Comment: 25 page
Quantum states and space-time causality
Space-time symmetries and internal quantum symmetries can be placed on equal
footing in a hyperspin geometry. Four-dimensional classical space-time emerges
as a result of a decoherence that disentangles the quantum and the space-time
degrees of freedom. A map from the quantum space-time to classical space-time
that preserves the causality relations of space-time events is necessarily a
density matrix.Comment: 9 pages, to appear in the Proceedings of the 2nd International
Symposium on Information Geometry and its Application
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