Hi LP, I haven't read the paper, but I don't disagree with claim. In fact it should not be unexpected.
Even in a macroscopic system a concentration energy can come about as a result of energy being transferred from the measuring system to the system being measured. Of course, such a measuring system would be considered defective because it provides a distorted picture of the energy content of system being measured. However, classical mechanics says a measuring system can be designed in theory to have an arbitrarily small distorting effect, whereas quantum mechanics says this is not possible in theory. Harry On Sat, Aug 18, 2012 at 2:44 PM, <pagnu...@htdconnect.com> wrote: > Hello Harry, > > To be really precise, though, an energy measurement of a particle in a > superposition of energy eigenstates might find it in one of the states > higher than the weighted average energy of its wavefunction. So, you > might say that the measurement increased its energy, but over many such > measurements would just produce the mean energy of the wavefunction. > > While I am not convinced they are correct, the authors of the paper I > referenced end with the conclusion - > > "From a general perspective a phenomenon like the energy concentration in > a composite quantum system can indeed be motivated physically. There exist > processes, where there is a redistribution of energy among different > system degrees of freedom making possible some amounts of system > self-organization. In particular, one could examine the possibility of > concentrating the total energy of the system into a subset of degrees of > freedom producing a decrease of its entropy, which in order to avoid a > violation of the second law of thermodynamics, would compel the release of > energy to the environment, thus keeping the free energy constant. This is > possible only if the system is open..." > > "Concentrating Energy by Measurement" > http://arxiv.org/abs/1012.5868 > > Interesting theory. > > -- LP > > Harry Veeder wrote: >> Actually, I tend agree with Robin that measuring cannot increase the >> energy of the particle. My question reflects my own attempt to >> understand why it is so. Now that I have thought about it, it is >> because one doesn't measure energy per se. Most measurements are >> really the result of calculations based on measurements of length and >> time plugged into a formula. BTW, the same is true of measurements of >> momentum. The modern physicists habit of refering to energy and >> momentum as "observables" is a perscription for phenomenological >> confusion. The resulting measures of length and time are only >> consistent with the supposed law-like properties of energy and >> momemtum on a statiscal level. >> >> Harry >> >> >> >> On Fri, Aug 17, 2012 at 11:31 PM, <pagnu...@htdconnect.com> wrote: >>> Hello Harry, >>> >>> You asked -- >>> "So, the measuring instrument itself will produce energy, if it is used >>> to precisely measure the energy of a particle?" >>> >>> Probably not. >>> But maybe there are subtleties that obey the 2nd Law of Thermodynamics, >>> but allow for some counterintuitive effects. For example, refer to -- >>> >>> "Concentrating Energy by Measurement" >>> http://arxiv.org/abs/1012.5868 >>> >>> -- LP >>> >>> Harry Veeder wrote: >>>> On Fri, Aug 17, 2012 at 8:57 PM, <mix...@bigpond.com> wrote: >>>>> In reply to pagnu...@htdconnect.com's message of Fri, 17 Aug 2012 >>>>> 13:11:31 >>>>> -0400 (EDT): >>>>> Hi, >>>>> [snip] >>>>>>Pardon for this very late postscript, time is hard to find. >>>>>> >>>>>>I believe you assume a wave function totally confined in all >>>>>> 3-dimensions. >>>>>> This is probably not what was intended. It is easy to find papers >>>>>>describing crystal/lattice channel conduction of much higher energy >>>>>>particles (electrons, protons, ...). These are extended states - only >>>>>>confined in one or two dimensions. High energy particles do not >>>>>>necessarily break the lattice structure. >>>>>> >>>>>>-- LP >>>>> >>>>> What I meant to do was calculate the momentum (assuming a kinetic >>>>> energy >>>>> of >>>>> 0.782 MeV for the proton), and divide it into h-bar/2. However it >>>>> appears I got >>>>> something slightly wrong the first time around. The value I get now is >>>>> 2.57 fm >>>>> for a proton, and 0.93 fm for the deuteron. >>>>> >>>>> However I don't really stand behind the entire concept. I don't think >>>>> the energy >>>>> of particles magically increases when they are confined. I do think >>>>> the >>>>> measurement uncertainty increases, but that's not the same thing as >>>>> their actual >>>>> energy. Instead, I see it as a limitation on our ability to measure, >>>>> not >>>>> a >>>>> change in the actual properties of the particle itself. >>>>> IOW the restriction applies to us, not to the particles. >>>>> Regards, >>>>> >>>>> Robin van Spaandonk >>>>> >>>>> http://rvanspaa.freehostia.com/project.html >>>>> >>>> >>>> So, the measuring instrument itself will produce energy, if it is used >>>> to precisely measure the energy of a particle? >>>> >>>> >>>> Harry >>>> >>>> >>>> >>> >>> >> >> >> > >
