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    Ettin in the Playground
     
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    Default Why is it possible to build analogs of quantum effects using conventional mechanics?

    There's a couple of experiments I've read about where people model quantum phenomena using materials that follow classical mechanics. The [url=https://en.wikipedia.org/wiki/Sonic_black_hole]sonic black hole[/i] is one, or specifically the claim that it gives off a sonic analog of hawking radiation.

    The thing that always bugged me about these experiments is that they're modeling things that are supposedly non-deterministic using deterministic systems. Doesn't that imply that the normal versions of these things can be explained without invoking non-determinism?
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    Ettin in the Playground
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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Stochastic and deterministic systems have a lot in common. A deterministic system that is partially observed or which has chaotic dynamics is effectively stochastic. Also, randomness only enters QM when you're explaining the outcome of measurements - the wave equation itself is deterministic.

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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    @NichG is right, a deterministic system can seem as effectively stochastic, think for example a dice. When you throw a dice in fact it's deterministic, If you know all the angles and force, the elasticity etc. you could predict the value of any give throw, but at the same time you can model the throw as stochastic. In fact any very complex deterministic model can be better understood by using probabilities then exact modeling, which is foundation of Chaos theory.

    As for QM in fact you are right, there are deterministic interpretation of quantum mechanics, for example Pilot wave theory. Additionally multiverse theory assume that every outcome happens, just you can observe one instance of that, which also for me makes it quite deterministic.
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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    I dont understand why people cling to determinism. Isnt it like killed three times over on the quantum scale?

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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by Rydiro View Post
    I dont understand why people cling to determinism. Isnt it like killed three times over on the quantum scale?
    In general, for any stochastic system if you write the update equations in terms of distributions, those update equations themselves become deterministic. For example, going from a stochastic ODE such as the Langevin equation to the equivalent Fokker-Planck formulation. This is generally accompanied by going from a finite number of degrees of freedom (position, velocity, etc variables) to an infinite number of degrees of freedom (parameters of joint distributions over all positions, velocities, etc).

    In some sense, classical stochastic systems are even more non-deterministic than quantum ones in that for classical systems there is an actual set of values at any point in time and the distributions are just a description of inferred probabilities, whereas in quantum mechanical systems the probability amplitudes are the actual fundamental degrees of freedom of the theory and there is not really such a thing as 'the particle's actual position' or 'the particle's actual velocity' that those amplitudes are just approximating. Also, the QM equation of motion is a time-reversible wave equation in which entropy does not increase, whereas the classical Fokker-Planck equations that are equivalent are descriptions with an arrow of time and monotonically increasing entropy.

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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by NichG View Post
    In some sense, classical stochastic systems are even more non-deterministic than quantum ones
    I knew that to be the case, but the argument for it is pretty complicated. And i dont know enough about the physics there. Throwing the Quantum buzzword in seemed easier and more understandable.

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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by Rydiro View Post
    I dont understand why people cling to determinism. Isnt it like killed three times over on the quantum scale?
    Only if you accept the Copenhagen interpretation. Collapsing a wave function being random is an assumption and slightly unfalsifiable, so not really scientific.
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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by Mastikator View Post
    Only if you accept the Copenhagen interpretation. Collapsing a wave function being random is an assumption and slightly unfalsifiable, so not really scientific.
    Its what the measurements spit out. The opposite claim, that there are underlying mechanics we just cant measure is at least more unscientific because it postulates something exists which cant be measured.
    As you said, whether its 'real' randomness or not is atm a philosophical debate.
    That you cannot predict the outcome of your measurements in-universe as a single determined state is the current scientific knowledge. So your actual predictions will be probability distributions and thus not deterministic.

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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by Rydiro View Post
    Its what the measurements spit out. The opposite claim, that there are underlying mechanics we just cant measure is at least more unscientific because it postulates something exists which cant be measured.
    As you said, whether its 'real' randomness or not is atm a philosophical debate.
    That you cannot predict the outcome of your measurements in-universe as a single determined state is the current scientific knowledge. So your actual predictions will be probability distributions and thus not deterministic.
    Yes, but this thread is pretty much philosophical : ) like what it means to be random ? is our fate determined ? is there Laplace demon who knows how everything starts and ends ? or is every second just some random noise in quantum field ? Settling on "it's easiest to calculate outcome with probability distribution so it's stochasting" is quite boring answer I would say : )
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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by Rydiro View Post
    Its what the measurements spit out. The opposite claim, that there are underlying mechanics we just cant measure is at least more unscientific because it postulates something exists which cant be measured.
    As you said, whether its 'real' randomness or not is atm a philosophical debate.
    That you cannot predict the outcome of your measurements in-universe as a single determined state is the current scientific knowledge. So your actual predictions will be probability distributions and thus not deterministic.
    In the many worlds interpretation it would be fully deterministic. In the pilot light interpretation it would be fully deterministic. If you pick the Copenhagen interpretation then the universe follows a neigh-deterministic timeline that breaks down at the subatomic level. You can prefer one interpretation over the other but [the dude] like, that's just your opinion man [/the dude]. I have equal standing in saying that the many worlds interpretation is correct, the measurements only look like they spit out unpredictable outcomes, they spit out all the outcomes in different worlds.. Then the underlying mechanics are truly deterministic, and all probabilities are real.
    Last edited by Mastikator; 2021-03-16 at 09:57 AM.
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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by Rydiro View Post
    Its what the measurements spit out. The opposite claim, that there are underlying mechanics we just cant measure is at least more unscientific because it postulates something exists which cant be measured.
    As you said, whether its 'real' randomness or not is atm a philosophical debate.
    The fact that we can build equivalent systems without randomness implies that randomness is not a necessary part

    Quote Originally Posted by Rydiro View Post
    Its what the measurements spit out. The opposite claim, that there are underlying mechanics we just cant measure is at least more unscientific because it postulates something exists which cant be measured.
    The existence of quarks is accepted even though it's also accepted that we can never seperate them out and observe them directly like we do with electrons and such
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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Also, black holes are not quantum phenomenons. Gravity is famously the one phenomenon that we can't explain with quantum mechanics. Getting that figured out may be the biggest open question in physics.
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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by Yora View Post
    Also, black holes are not quantum phenomenons. Gravity is famously the one phenomenon that we can't explain with quantum mechanics. Getting that figured out may be the biggest open question in physics.
    There are quite a few possible candidates for quantum gravity. One of the main problems is that so far we cannot test them with experiments the same way the advanced elementary particle theories are not verifiable with currently available technology. Besides, the main problem IIRC with quantum gravity is less about not being able to explain gravity and more about technical problems with building a viable mathematical machinery that will grasp the key ideas.

    That being said, there are already some interesting cosmological results using those possible quantum gravity theories. One of the most renown was the last publication by Hawking, where it was proven that black holes actually do not destroy information - they just scramble it beyond recognition. I did not follow the newer advances, so there might be much more right now.
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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by Yora View Post
    Also, black holes are not quantum phenomenons. Gravity is famously the one phenomenon that we can't explain with quantum mechanics. Getting that figured out may be the biggest open question in physics.
    The OP referred to Hawking radiation, which is a quantum phenomenon in the study of black holes. It involves quantum field theory modeled on the curved spacetime of a black hole solution to general relativity.
    Quote Originally Posted by Harnel View Post
    where is the atropal? and does it have a listed LA?

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    Default Re: Why is it possible to build analogs of quantum effects using conventional mechani

    Quote Originally Posted by gomipile View Post
    The OP referred to Hawking radiation, which is a quantum phenomenon in the study of black holes. It involves quantum field theory modeled on the curved spacetime of a black hole solution to general relativity.
    Hawking radiation is a result of considering quantum electrodynamics in a classic curved spacetime. Quantum gravity is about quantizing the spacetime itself. The same difference as between including classic electromagnetic fields in quantum mechanics and quantizing the electromagnetic field itself.
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