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# Topic: Consistent histories

###### In the News (Sun 19 May 13)

 Super Copenhagen Interpretation (Consistent Histories) Consistent histories is standard quantum mechanics presented in a coherent fashion with the ambiguities and lack of clarity found in the usual textbook presentations replaced with a clear set of logical rules and principles for reasoning about a quantum system. Histories can be used to describe how a particle interacts with a measuring apparatus, and how the outcome of a measurement (e.g., the position of a pointer) is related to some property of the particle before the measurement took place. Consistent histories can be used to analyze various quantum paradoxes, such as the interference produced by a particle passing through a double slit, or the correlated pair of particles considered by Einstein, Podolksy, and Rosen. www.lns.cornell.edu /spr/2006-04/msg0073817.html   (860 words)

 Consistent histories - Wikipedia, the free encyclopedia The interpretation based on consistent histories is used in combination with the insights about quantum decoherence. In some views the interpretation based on consistent histories does not change anything about the paradigm of the Copenhagen interpretation that only the probabilities calculated from quantum mechanics and the wave function have a physical meaning. The consistent histories approach can be interpreted as a way of understanding which sets of classical questions can be consistently asked of a single quantum system, and which sets of questions are fundamentally inconsistent, and thus meaningless when asked together. en.wikipedia.org /wiki/Consistent_histories   (707 words)

 Decoherent Histories Inconsistent In the consistent histories formulation of quantum theory, the probabilistic predictions and retrodictions made from observed data depend on the choice of a consistent set. W e begin with a brief description of the simplest version of the consistent histories formulation of non-relativistic quantum mechanics, in which sets of histories correspond to sets of projective decompositions. While consistent histories can be defined abstractly on any Hilbert space H, it is generally assumed that operators corresponding to the Hamiltonian H and other physically interesting observables, such as position, momentum and spin, are given. www.qedcorp.com /pcr/pcr/mgmwrong.html   (2517 words)

 Consistent Histories Home Page   (Site not responding. Last check: 2007-10-12) The approach found in many textbooks, in which a wave function is used to calculate the probability that a measurement carried out on some quantum system will yield a particular outcome, is not very satisfactory, for two reasons. For example, by using consistent histories it is possible to assign a probability for the time at which an unstable particle, such as a radioactive atom, will decay, even if it is out in interstellar space far from any measuring device. The consistent histories approach has also been employed to analyze problems in quantum computation and quantum cryptography. quantum.phys.cmu.edu /CHS/histories.html   (444 words)

 An Exchange of Letters in PHYSICS TODAY on Quantum Theory Without Observers (A family,'' as discussed by Goldstein, consists of a realm and all its coarse grainings.) It is essential to restrict statements relating the probabilities of occurrence of histories to a given family containing them. Unfortunately, his discussion of consistent histories is, in certain respects, misleading; at the very least, it is out of date. There is one aspect of consistent histories that was perfectly clear in the very first paper on the topic and in all our subsequent work: a quantum history consists of a sequence of events at successive times, and these events correspond to subspaces of the quantum Hilbert space. www.math.rutgers.edu /~oldstein/papers/qtwoe/qtwoe.html   (5069 words)

 Decoherent Histories The histories with which DH is concerned are histories of observables, for example of positions of particles. DH is primarily concerned with histories of observables, not of wave functions, which play only a secondary role, as a theoretical ingredient in the formulation of laws governing the evolution of quantum observables via the probabilities assigned to histories. Too many histories have been assigned probabilities: to be well defined, DH must restrict, by some further condition or other, the class of decoherent families whose elements are to be assigned probabilities. www.math.rutgers.edu /~oldstein/papers/qts/node2.html   (1516 words)

 smolinsix   (Site not responding. Last check: 2007-10-12) Decoherence takes place when the states become orthogonal, the wavefunction collapses, and macroscopic interference effects are thereby eliminated.] The consistent histories approach extends this idea into a set of temporal evolutions in which a consistent set of such reductions (in the sense that their probabilities add to 1) take place. The consistent histories approach has problems similar to the many worlds interpretation, viz., it permits consistent nonclassical descriptions of reality. The latter claim is argued to be consistent with our experience because we have evolved to view the world in classical categories since they are the only ones that could ensure our survival (this is the line taken by Murray Gell-Mann and James Hartle, for instance). www3.baylor.edu /~Bruce_Gordon/smolinsix.htm   (1681 words)

 The Reference Frame: He believes it's true but he can't prove it   (Site not responding. Last check: 2007-10-12) While quantum mechanics describes all these other permutations and histories and their respective amplitudes according to precise rules, it is not so surprising, in general, that they exist: that is, if we also make the natural assumption that all mathematical structures exist (and you agree with this right?). Second, the whole point of a the Consistent Histories interpretation of quantum mechanics is to predict the (probabilities of different outcomes in the) future. You won't be able to find non-classical histories that decohere, and you certainly have not found an example - the history with the googolplex is completely classical and of course that it is an OK history to include into a set of consistent histories. motls.blogspot.com /2005/01/he-believes-its-true-but-he-cant-prove.html   (13100 words)

 CHAPTER EIGHT   (Site not responding. Last check: 2007-10-12) As long as we are able to observe only what we know in history and our own present experience, we only know what is received and can in any reasonable level understand neither the offer wave nor the process of transaction in any given historic event. In the Consistent Histories Interpretation we have a similar situation because there the observed event again is a fundamental input in the sense that it determines the set of possible histories consistent with the observation made. There is no attempt to try to explain why a specific event happened except for the fact that it be consistent with the observed fact. www.acns.com /~mm9n/quan/QT8.htm   (1454 words)

 [No title] However, Griffiths' framework for consistent counterfactual reasoning within quantum theory can be applied directly to the first part of my nonlocality argument, and it then validates straightforwardly, within that framework, this first part of my argument. Consistent Histories} \vspace{.2in} The basic question pertaining to the use of counterfactual reasoning to deduce a conflict between nonlocality and the predictions of quantum theory is whether the counterfactual reasoning used in those proofs is itself compatible with the precepts of quantum theory. If one is to allow any sort of counterfactual reasoning at all, even in the classical limit that emerges from quantum theory in the limit where Planck's constant is set to zero, one needs spell out what the general conditions are for valid counterfactual reasoning in a quantum context. www-physics.lbl.gov /~stapp/ncch1.txt   (6697 words)

 [No title] According to this viewpoint, you could not go back in time unless history showed that you had already arrived in the past and, while there, had not killed your great great grandfather or committed any other acts that would conflict with your situation in the present. The alternative histories hypothesis sounds rather like Richard Feynman's way of expressing quantum theory as a sum over histories, which was described in Chapters 4 and 8. But the rocket would remain in the same space-time and therefore the same history, which would have to be consistent. suif.stanford.edu /~jeffop/WWW/hawking.txt   (2095 words)

 PowerPedia:Quantum mechanics - PESWiki   (Site not responding. Last check: 2007-10-12) The idea that each photon had to consist of energy in terms of quanta was a remarkable achievement as it effectively removed the possibility of fl body radiation attaining infinite energy if it were to be explained in terms of wave forms only. The consistent histories generalizes the conventional Copenhagen interpretation and attempts to provide a natural interpretation of quantum cosmology. The theory is based on a consistency criterion that then allows the history of a system to be described so that the probabilities for each history obey the additive rules of classical probability while being consistent with the Schrödinger equation. peswiki.com /index.php/PowerPedia:Quantum_mechanics   (6984 words)

 Robert Griffiths Supplying the missing link(s) and working out a fully consistent form of quantum theory is the goal of a research program which I initiated in 1984, and which, with major contributions by Roland Omnes, Murray Gell-Mann, and James Hartle, has resulted in what is now called the consistent (or decoherent) history approach to quantum theory. At present my research program is focused on applying consistent history methods and ideas to quantum information theory and quantum computation. We are also looking for (special) relativistic counterparts of some aspects of the consistent history interpretation which at present are best understood for nonrelativistic systems. info.phys.cmu.edu /people/faculty/griffiths_bob   (357 words)

 Super Copenhagen Interpretation (Consistent Histories) Consistent histories is standard quantum mechanics presented in a Consistent histories can be used to analyze various quantum Consistent histories have inspired a new formulation of QM, which seems www.physicsforums.com /showthread.php?p=970473   (3191 words)

 Divine Action Topic: Clarke, Chris. “The Histories Interpretation of Quantum Theory and the Problem of ... A “consistent” histories approach tries to rule out superpositions of macroscopically distinguishable states by considering only those histories whose probabilities obey classical logic. This leads Clarke to propose a specific definition of consistency in terms of logical exclusivity and the rules of quantum mechanics, the physical significance of which arises through decoherence. As it turns out, although all classically acceptable histories are consistent, not all consistent histories are acceptable; additional structure is needed to single out acceptable histories. www.counterbalance.net /ctns-vo/clark-body.html   (842 words)

 Quantum Reality For consistency, all devices should be treated as quantum devices, however we know when we "look" at the outcome of an experiment we always see an outcome, i.e. The goal of the axiomization of probability theory however is to ensure mathematical consistency, not to reflect philosophical considerations. Consistent Histories is a modern variant of Copenhagen that concentrates on applying standard logic and probability theory to a specific choice of sample space ("framework"). www.quantum.bowmain.com /Quantum_Reality.htm   (12990 words)

 Decoherence Thus at the root of our unease with quantum mechanics is the clash between the principle of superposition-the consequence of the linearity of equation 1-and the everyday classical reality in which this principle appears to be violated. The many-histories interpretation builds on the foundation of Everett's many-worlds interpretation, but with the addition of three crucial ingredients: the notion of sets of alternative coarsegrained histories of a quantum system, the decoherence of the histories in a set, and their approximate determinism near the effectively classical limit. The definition of consistent histories for a closed quantum system was first proposed by Robert Griffiths. dhushara.tripod.com /book/quantcos/decoh/decoh.htm   (2996 words)

 Many Worlds Theory FAQ They call their approach the "many-histories" approach, where each "coarse-grained or classical history" is associated with a unique time-ordered sequence of sets of irreversible events, including measurements, records, observations and the like. Climbing up the tree from child to parent moves to progressively coarser grained consistent histories until eventually the top is reached where the history has *no* defining events (and thus consistent with everything!). The classical histories each have a probability assigned to them and probabilities are additive in the sense that the sum of the probabilities associated a set classical histories is equal to the probability associated with the unique parent history defined by the set. kuoi.asui.uidaho.edu /~kamikaze/doc/many-worlds-faq.html   (15875 words)

 Quantum Metaphysics In the consistent histories view, as in Copenhagen and many worlds, the wave function allows you to calculate the probabilities that the universe will take various paths. Theoretical work has provided for a logically consistent histories theory that agrees with all known data without the introduction of holistic, nonlocal, or mystical elements. In this theory, the only consistent paths (or histories) are those for which probabilities add as they do classically. www.meta-religion.com /Physics/Spirituality/quantum_metaphysics.htm   (3348 words)

 Professor Stephen Hawking It says that one has to find a consistent solution of the equations of physics, even if space-time is so warped, that it is possible to travel into the past. In some histories space-time will be so warped, that objects like rockets will be able to travel into their pasts. But each history is complete and self contained, describing not only the curved space-time, but also the objects in it. www.hawking.org.uk /lectures/warps3.html   (1603 words)

 Jonstraveladventures: All Things Unrelated Griffiths was one of the originators (along with Roland Omnes, Murray Gell-Mann, and James Hartle) of what is known as the consistent histories approach to quantum mechanics, which acts rather like a completion of the Copenhagen interpretation. In the consistent histories approach the idea of decoherence is bought onto more solid foundations by an absence theorem which is related to the flow of information from a quantum system into its quantum (though possibly macroscopic) environment. Anyway, the consistent histories approach is something that I'd like to learn more about and from the sounds of the talk there are things which you can say in this interpretation which would be completely taboo in normal textbooks. jonstraveladventures.blogspot.com /2006/08/all-things-unrelated.html   (1457 words)

 Genetic reconstruction of individual colorectal tumor histories -- Tsao et al. 97 (3): 1236 -- Proceedings of the ... The history of this founder cell can be traced back along a single lineage because of the bottleneck nature of progression. The tumor histories derived from their MS mutations are illustrated in Fig. The data are consistent with genetic progression in the absence of visible progression, suggesting progenitor clone sizes are often below the threshold of clinical detection after loss of MMR. www.pnas.org /cgi/content/full/97/3/1236   (5007 words)

 april 2002 synthetic zero When Fay Dowker began her presentation on the consistent histories formulation, that approach was generally regarded as the best hope for resolving the problems of quantum cosmology.... While the 'classical' world we observe, in which particles have definite positions, may be one of the consistent worlds described by a solution to the theory, Dowker and Kent's results showed that there had to be an infinite number of other worlds too. ....[the consistent histories approach imposes] on reality a radical context dependence: one cannot talk meaningfully about the existence of any object or the truth of any statement without first completely specifying the questions that are to be asked. www.syntheticzero.com /apr2002.php   (4699 words)

 Time An example of time travel in the original Star Trek series is an episode where Dr. McCoy falls through a time portal in a city "on the edge of forever," and changes the past in a way that erases the Enterprise and her crew, with the exception of Captain Kirk and Mr. The most prominent is the "grandfather paradox," in which you travel back in time and kill your grandfather before you were born, which means you could not have been born to then travel back in time to kill your grandfather. The Consistent Histories approach to the grandparent paradox is the most simplistic and probably hardest to defend. zebu.uoregon.edu /1998/js/lectures/lec18.html   (3540 words)

 Amazon.com: Consistent Quantum Theory: Books: Robert B. Griffiths   (Site not responding. Last check: 2007-10-12) The conceptual framework of the consistent histories approach is sharply delinerated, there is an abundance of examples, open questions are honestly identified, and there are references to more detailed studies. This is a very interesting, clearly written introduction to the consistent histories (CH) interpretation of quantum mechanics that addresses many of the short-comings of the traditional Copenhagen interpretation. The key concept Griffiths introduces is the "consistent quantum framework" or "consistent quantum family." The idea is that there are multiple such frameworks, but accurate statements can be made only by choosing one of them and staying with it. amazon.com /Consistent-Quantum-Theory-Robert-Griffiths/dp/0521539293   (2147 words)

 Phase-space decoherence: A comparison between consistent histories and environment induced superselection We evaluate the Decoherence Functional of Consistent Histories for coarse grained phase space two-time projected histories. Using the measures proposed by Dowker and Halliwell we find that the consistency of the histories improves with increasing bath temperature, time and final grain size and decreases with initial grain size. The results agree in general with expectations while the anomalous dependence of the consistency on the initial grain size is discussed. www.physics.adelaide.edu.au /mathphysics/abstracts/ADP-93-208-M19.html   (203 words)

 Quantum Theory The consistent histories approach to quantum theory was initiated at Carnegie Mellon in 1984, and was subsequently developed both here and at several other institutions. At the present time it provides the only fully consistent procedure for integrating probability theory into standard quantum mechanics without appealing to measurements or hidden variables. Current research at Carnegie Mellon includes the application of consistent histories ideas to resolve some of the long-standing paradoxes of quantum theory, such as two-slit interference and Einstein-Podolsky-Rosen correlated states, without having to invoke mysterious long-range influences or other ghostly effects. info.phys.cmu.edu /research/groups/quantumtheory.asp   (267 words)

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