tag:blogger.com,1999:blog-8148573551417578681.post3139618801454246047..comments2021-01-15T10:36:20.149-08:00Comments on Dark Buzz: Flaws in Bohmian mechanicsRogerhttp://www.blogger.com/profile/03474078324293158376noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-8148573551417578681.post-44373034687804066352016-12-29T18:12:16.248-08:002016-12-29T18:12:16.248-08:00You wrote: "Quantum mechanics, is local and c...You wrote: "Quantum mechanics, is local and causal."<br /><br />Compare this with Niels Bohr's view: "The apparent contradiction (referring to the paper of Einstein, Podolsky, and Rosen) in fact discloses only an essential inadequacy of the customary viewpoint of natural philosophy for a rational account of physical phenomena. Indeed the finite interaction between object and measuring agencies conditioned by the very existence of the quantum of action entails the necessity of the final renunciation of the classical ideal of causality and a radical revision of our attitude towards the problem of physical reality."Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-53550239521108335942016-12-29T00:38:05.869-08:002016-12-29T00:38:05.869-08:00I think that what you say would hold if and only i...I think that what you say would hold if and only if the observed quantities (causes or effects) were being _continuously_ measured. But in such a case, QM no longer shows its peculiar features anyway; it has already been reduced to the classical mechanics!<br /><br />In the realm where QM does stay operative showing its peculiar QMcal features, there always _is_ IAD to its phenomena (whether there is entanglement or not)---at least in the mainstream QM, that is. <br /><br />Consider the (possibly) simplest example. Suppose there are only two atoms in the entire universe; one in the ground state, another in an excited state. This is the initially given condition.(That is, this state has been _measured_, somehow, to exist as the initial condition.) The excited atom then takes ``down'' a quantum jump. The resulting radiation (i.e. the ``photon'') is absorbed by the other atom existing at a distance, after a _finite_ lapse of time. Since the time interval is finite, you are justified in saying that there is no IAD. <br /><br />But that is really speaking missing the real nature of QM. After all, the moment you say ``measurements'', you are referring to the classical variables (at least in some, implicit, way).<br /><br />To focus on the quantum-ness, we have to look not at the _results_ of two consecutive _measurements_, but what happens _in between_ them.<br /><br />In this case, observe that the entire evolution has happened with that single wavefunction (of this simple universe) which involves all the electrons of the two atoms. Since _every_ evolution of the wavefunction does involve IAD, there _was_ IAD even here---i.e., even if the radiation and absorption events (you may regard them as ``measurements'') were separated in time.<br /><br />I think that's the crux of the issue. It's the measurements that introduce the classicality, including the finite durations. However, the Schrodinger evolution by itself always is instantaneously effective everywhere---it is necessarily nonlocal.<br /><br />Best,<br /><br />--Ajit<br />[E&OE]<br />Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-54018875050744369872016-12-28T22:46:50.004-08:002016-12-28T22:46:50.004-08:00Yes, the Fourier theory implies that the wave func...Yes, the Fourier theory implies that the wave function can have an instantaneous action at a distance, but there is no such effect on observables. Any observable cause and effect can be explain by a propagation of fields (or particles) from the cause to the effect.Rogerhttps://www.blogger.com/profile/03474078324293158376noreply@blogger.comtag:blogger.com,1999:blog-8148573551417578681.post-91900185110321439372016-12-28T20:16:11.390-08:002016-12-28T20:16:11.390-08:00Roger,
QM involves the Fourier theory at its core...Roger,<br /><br />QM involves the Fourier theory at its core, and the latter necessarily brings in the premise of instantaneous action at a distance (IAD) i.e. nonlocality. If so, how do you say that QM is local? What are your reasons for saying so?<br /><br />--Ajit<br />[E&OE]<br />Ajit R. Jadhavhttp://ajitjadhav.wordpress.comnoreply@blogger.com