66 results found
Ahmed SN, Dowker F, Surya S, Scalar Field Green Functions on Causal Sets
We examine the validity and scope of Johnston's models for scalar fieldretarded Green functions on causal sets in 2 and 4 dimensions. As in thecontinuum, the massive Green function can be obtained from the massless one,and hence the key task in causal set theory is to first identify the masslessGreen function. We propose that the 2-d model provides a Green function for themassive scalar field on causal sets approximated by any topologically trivial 2dimensional spacetime. We explicitly demonstrate that this is indeed the casein a Riemann normal neighbourhood. In 4-d the model can again be used toprovide a Green function for the massive scalar field in a Riemann normalneighbourhood which we compare to Bunch and Parker's continuum Green function.We find that the same prescription can also be used for deSitter spacetime andthe conformally flat patch of anti deSitter spacetime. Our analysis then allowsus to suggest a generalisation of Johnston's model for the Green function for acausal set approximated by 3 dimensional flat spacetime.
Buck M, Dowker F, Jubb I, et al., 2017, The Sorkin–Johnston state in a patch of the trousers spacetime, Classical and Quantum Gravity, Vol: 34, Pages: 055002-055002, ISSN: 0264-9381
Dowker F, Zalel S, 2017, Evolution of universes in causal set cosmology, Comptes Rendus Physique, ISSN: 1631-0705
Belenchia A, Benincasa DMT, Dowker F, 2016, The continuum limit of a 4-dimensional causal set scalar d'Alembertian, CLASSICAL AND QUANTUM GRAVITY, Vol: 33, ISSN: 0264-9381
Benincasa DMT, Borsten L, Buck M, et al., 2014, Quantum information processing and relativistic quantum fields, CLASSICAL AND QUANTUM GRAVITY, Vol: 31, ISSN: 0264-9381
Dowker F, 2014, The birth of spacetime atoms as the passage of time, FLOW OF TIME, Vol: 1326, Pages: 18-25, ISSN: 0077-8923
Dowker F, Henson J, Wallden P, 2014, A histories perspective on characterizing quantum non-locality, NEW JOURNAL OF PHYSICS, Vol: 16, ISSN: 1367-2630
Dowker F, 2013, Introduction to causal sets and their phenomenology, GENERAL RELATIVITY AND GRAVITATION, Vol: 45, Pages: 1651-1667, ISSN: 0001-7701
Dowker F, 2013, Physics meets the big C, PHYSICS WORLD, Vol: 26, Pages: 20-20, ISSN: 0953-8585
Dowker F, Glaser L, 2013, Causal set d'Alembertians for various dimensions, CLASSICAL AND QUANTUM GRAVITY, Vol: 30, ISSN: 0264-9381
Afshordi N, Buck M, Dowker F, et al., 2012, A ground state for the causal diamond in 2 dimensions, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Clements K, Dowker F, Wallden P, 2012, Physical Logic
In R.D. Sorkin's framework for logic in physics a clear separation is madebetween the collection of unasserted propositions about the physical world andthe affirmation or denial of these propositions by the physical world. Theunasserted propositions form a Boolean algebra because they correspond tosubsets of an underlying set of spacetime histories. Physical rules ofinference, apply not to the propositions in themselves but to the affirmationand denial of these propositions by the actual world. This physical logic mayor may not respect the propositions' underlying Boolean structure. We provethat this logic is Boolean if and only if the following three axioms hold: (i)The world is affirmed, (ii) Modus Ponens and (iii) If a proposition is deniedthen its negation, or complement, is affirmed. When a physical system isgoverned by a dynamical law in the form of a quantum measure with the rule thatevents of zero measure are denied, the axioms (i) - (iii) prove to be too rigidand need to be modified. One promising scheme for quantum mechanics as quantummeasure theory corresponds to replacing axiom (iii) with axiom (iv) Nature isas fine grained as the dynamics allows.
Dowker F, Elizalde E, Kirsten K, 2012, Applications of zeta functions and other spectral functions in mathematics and physics: a special issue in honour of Stuart Dowker's 75th birthday PREFACE, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 45, ISSN: 1751-8113
Benincasa DMT, Dowker F, Schmitzer B, 2011, The random discrete action for two-dimensional spacetime, CLASSICAL AND QUANTUM GRAVITY, Vol: 28, ISSN: 0264-9381
Dowker F, 2011, Spacetime discreteness, Lorentz invariance and locality, 5th International Workshop on Decoherence, Information, Complexity and Entropy (DICE) - Space-Time-Matter - Current Issues in Quantum Mechanics and Beyond, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Dowker F, 2011, Useless Qubits in "Relativistic Quantum Information"
I draw attention to previous work that shows that the observablescorresponding to relativistic quantum field modes commonly employed in paperson "relativistic quantum information" cannot be measured by ideal measurements.
Benincasa DMT, Dowker F, 2010, Scalar Curvature of a Causal Set, PHYSICAL REVIEW LETTERS, Vol: 104, ISSN: 0031-9007
Contaldi CR, Dowker F, Philpott L, 2010, Polarization diffusion from spacetime uncertainty, Classical and Quantum Gravity, Vol: 27, Pages: 172001-172001, ISSN: 0264-9381
Dowker F, Henson J, Sorkin RD, 2010, Discreteness and the transmission of light from distant sources, PHYSICAL REVIEW D, Vol: 82, ISSN: 2470-0010
Dowker F, Johnston S, Sorkin RD, 2010, Hilbert spaces from path integrals, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 43, ISSN: 1751-8113
Dowker F, Johnston S, Surya S, 2010, On extending the quantum measure, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 43, ISSN: 1751-8113
Philpott L, Dowker F, Sorkin R, 2009, Massless particle diffusion in causal set theory, 4th International Workshop on Decoherence, Information, Complexity and Entropy (DICE) - From Quantum Mechanics through Complexity to Spacetime - The Role of Emergent Dynamical Structures, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Philpott L, Dowker F, Sorkin RD, 2009, Energy-momentum diffusion from spacetime discreteness, PHYSICAL REVIEW D, Vol: 79, ISSN: 2470-0010
Dowker F, Ghazi-Tabatabai Y, 2008, Dynamical wavefunction collapse models in quantum measure theory, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 41, ISSN: 1751-8113
Dowker F, Ghazi-Tabatabai Y, 2008, The Kochen-Specker theorem revisited in quantum measure theory, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 41, ISSN: 1751-8113
Barnett M, Dowker F, Rideout D, 2007, Popescu-Rohrlich boxes in quantum measure theory, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 40, Pages: 7255-7264, ISSN: 1751-8113
Craig D, Dowker F, Henson J, et al., 2007, A Bell inequality analog in quantum measure theory, Journal of Physics A: Mathematical and Theoretical, Vol: 40, Pages: 501-523, ISSN: 1751-8113
Craig D, Dowker F, Henson J, et al., 2007, A Bell inequality analog in quantum measure theory, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 40, Pages: 501-523, ISSN: 1751-8113
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