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Peter Morgan

Publications and source records attributed to Peter Morgan.

31 records · Page 2Linked to original sources
arXiv2008

Violation of Bell inequalities through the coincidence-time loophole

The coincidence-time loophole was identified by Larsson & Gill (Europhys. Lett. 67, 707 (2004)); a concrete model that exploits this loophole has recently been described by De Raedt et al. (Found. Phys., to appear). It is emphasized here that De Raedt et al.'s model is experimentally testable. De Raedt et al.'s model also introduces contextuality in a novel and classically more natural way than the use of contextual particle properties, by introducing a probabilistic model of a limited set of degrees of freedom of the measurement apparatus, so that it can also be seen as a random field model. Even though De Raedt et al.'s model may well contradict detailed Physics, it nonetheless provides a way to simulate the logical operation of elements of a quantum computer, and may provide a way forward for more detailed random field models.

quant-ph↗
arXiv2007

Lie fields revisited

A class of interacting classical random fields is constructed using deformed *-algebras of creation and annihilation operators. The fields constructed are classical random field versions of "Lie fields". A vacuum vector is used to construct linear forms over the algebras, which are conjectured to be states over the algebras. Assuming this conjecture is true, the fields constructed are "quantum random fields" in the sense that they have Poincare invariant vacua with a fluctuation scale determined by Planck's constant. A nonlocal particle interpretation of the formalism is shown to be the same as a particle interpretation of a quantum field theory.

quant-ph↗
arXiv2006

Weakened linearity for quantum fields

There are still no interacting models of the Wightman axioms, suggesting that the axioms are too tightly drawn. Here a weakening of linearity for quantum fields is proposed, with the algebra still linear but with the quantum fields no longer required to be tempered distributions, allowing explicit interacting quantum field models. Interacting quantum fields should be understood to be nonlinear quantum fields in this sense, because a set of effective field theories encodes a dependence on the energy scale of measurement -- which is a nontrivial property of the test functions -- so that correlation functions are implicitly nonlinear functions of test functions in the conventional formalism. In Local Quantum Physics terms, the algebraic models constructed here do not satisfy the additivity property. Finite nonlinear deformations of quantized electromagnetism are constructed as examples.

quant-ph↗
arXiv2006

Displacement deformed quantum fields

A displacement operator d_ζis introduced, verifying commutation relations [d_ζ, a_f^\dagger]=[d_ζ, a_f]=ζ(f)d_ζwith field creation and annihilation operators that verify [a_f,a_g]=0, [a_f,a_g^\dagger]=(g,f), as usual. f and g are test functions, ζis a Poincare invariant real-valued function on the test function space, and (g,f) is a Poincare invariant Hermitian inner product. The *-algebra generated by all these operators, and a state defined on it, nontrivially extends the *-algebra of creation and annihilation operators and its Fock space representation. If the usual requirement for linearity is weakened, as suggested in quant-ph/0512190, we obtain a deformation of the free quantum field.

quant-ph↗
arXiv2006

Models of measurement for quantum fields and for classical continuous random fields

A quantum field model for an experiment describes thermal fluctuations explicitly and quantum fluctuations implicitly, whereas a comparable continuous random field model would describe both thermal and quantum fluctuations explicitly. An ideal classical measurement does not affect the results of later measurements, in contrast to ideal quantum measurements, but we can describe the consequences of the thermal and quantum fluctuations of classically non-ideal measurement apparatuses explicitly. Some details of continuous random fields and of Bell inequalities for random fields will be discussed.

quant-ph↗
arXiv2006

Bell inequalities for random fields

The assumptions required for the derivation of Bell inequalities are not usually satisfied for random fields in which there are any thermal or quantum fluctuations, in contrast to the general satisfaction of the assumptions for classical two point particle models. Classical random field models that explicitly include the effects of quantum fluctuations on measurement are possible for experiments that violate Bell inequalities.

cond-mat.other↗
arXiv2005

A succinct presentation of the quantized Klein-Gordon field, and a similar quantum presentation of the classical Klein-Gordon random field

A succinct presentation of the algebraic structure of the quantized Klein-Gordon field can be given in terms of a Lorentz invariant inner product. A presentation of a classical Klein-Gordon \emph{random} field at non-zero temperature can be given in the same noncommutative algebraic style, allowing a detailed comparison of the quantized Klein-Gordon field with a classical Klein-Gordon random field.

quant-ph↗
arXiv2003

A relativistic variant of the Wigner function

The conventional Wigner function is inappropriate in a quantum field theory setting because, as a quasiprobability density over phase space, it is not manifestly Lorentz covariant. A manifestly relativistic variant is constructed as a quasiprobability density over trajectories instead of over phase space.

quant-ph↗
arXiv2003

The derivation of Bell inequalities for beables

The derivation of Bell inequalities for beables is well-known to require a "no-conspiracy" assumption. This assumption is widely accepted, the alternative being correlations between instrument settings and hidden beables. Two further assumptions are identified here: (1) a "no-contextuality" assumption, similar to the prohibition of contextuality that is required to derive the Kochen-Specker theorem, which is closely related to the "no-conspiracy" assumption; (2) a "no-correlation" assumption, which prohibits correlations between hidden beables. The three assumptions together are less acceptable than the "no-conspiracy" assumption alone.

quant-ph↗
arXiv2003

Bell inequalities and incompatible measurements

Bell inequalities are a consequence of measurement incompatibility (not, as generally thought, of nonlocality). In classical terms, this is equivalent to contextuality -- measurement devices do have a significant effect. Contextual models are reasonable in classical physics, which always took the view that we ignore measurement devices whenever possible, but if that isn't good enough then we do have to model measurement devices. It is also argued that quantum theory should only be taken with counterfactual seriousness, because measurement incompatibility is a counterfactual concept.

quant-ph↗
arXiv2003

A geometry for the electroweak field

The structure of the electroweak theory is suggested by classical geometrical ideas. A nonlinear map is constructed, from a 12-dimensional linear space of three Weyl spinors onto the 12-dimensional tangent bundle of the Stiefel manifold of orthonormal tetrads associated with the Lorentz group -- except, inevitably, for a set of measure zero. In the approach of this paper, the electroweak field is more natural than the Dirac field. This may be just a curiosity since it may not survive quantization, but it suggests a path to bosonization of the electroweak field in (3+1) dimensions.

hep-th↗
arXiv2001

A classical perspective on nonlocality in quantum field theory

A classical statistical field theory hidden variable model for the quantized Klein-Gordon model is constructed that preserves relativistic signal locality and is relativistically covariant, but is at the same time relativistically nonlocal, paralleling the Hegerfeldt nonlocality of quantum theory. It is argued that the relativistic nonlocality of this model is acceptable to classical physics, but in any case the approach taken here characterizes the nonlocality of the quantized Klein-Gordon model in terms of concepts from classical statistical field theory.

quant-ph↗