A good book that explains quantum physics like I'm an idiot?

exchemist said:
Can you cite a reference for any of this stuff? I've never come across it and it sounds woolly to me. Or is your own idea and thus belongs in the Alternative section?
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According to the Cambridge English Dictionary, "wooly" means: "ideas and thinking are confused and not clear". I had to look it up; no one uses it in these parts. If you think what I wrote is "wooly", I can accept "not clear", but I am anything but confused. The model works for me, with or without supporting details.

If I had worked out the details of enough elements on Periodic Table to understand its periodicity and where it derives, would you expect me to claim that I knew all of the details about the properties, atomic spectra, and abundances of all of the others before mentioning that I thought I was onto something? That isn't how science, or anything else works.

Mendeleev ran into all manner of skepticism as well, and his periodicity idea collected a lot of dust on shelves before Pauli came up with a way of predicting new elements based on electron configuration combined with Mendeleev's method of organization. Often, the scope of a problem in science precludes the possibility of any individual providing a complete description of everything at the beginning. Science is an iterative endeavor. Science does not explain everything all at once. Every answer we find brings more questions.

I don't need to cite a reference for E=mc^2. You know exactly where it comes from.

I don't need to cite a reference for "Higgs is the ONLY spin zero boson, and the fundamental particle on which the Standard Model of particle physics rests."

I don't need to cite a reference for "The speed of light (for energy not bound) and rest energy (of matter or energy that is bound) are invariants."

Pick up any physics textbook. If you find these ideas "wooly", you are right in the sense that while we understand E=mc^2 in a general sense, the specifics require a doctoral degree in physics that uses some very, very wooly math to arrive at a non-conclusion about what it means.

I'm just connecting dots here, exchemist. You and alpha brane were discussing Schrödinger's wave equation, and the square box probability potential of atomic structure as a harmonic oscillator for electrons (a very, very old saw used to approximate almost anything periodic in physics). Our quantum physics instructor used a similar treatment to explain quantum tunneling, as I recall. I thought I could add some depth to the discussion.

If instead you prefer "A good book that explains quantum physics like I'm an idiot?", well then, I suppose that isn't "wooly" at all, and also a matter of taste. I prefer a more proactive approach; treat me like I'm an idiot, and I might find several ways return the favor.

I don't feel "wooly" about the things I have written. I'm only suggesting a direction of inquiry. Is this not clear?
 
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danshawen said:
According to the Cambridge English Dictionary, "wooly" means: "ideas and thinking are confused and not clear". I had to look it up; no one uses it in these parts. If you think what I wrote is "wooly", I can accept "not clear", but I am anything but confused. The model works for me, with or without supporting details.

If I had worked out the details of enough elements on Periodic Table to understand its periodicity and where it derives, would you expect me to claim that I knew all of the details about the properties, atomic spectra, and abundances of all of the others before mentioning that I thought I was onto something? That isn't how science, or anything else works.

Mendeleev ran into all manner of skepticism as well, and his periodicity idea collected a lot of dust on shelves before Pauli came up with a way of predicting new elements based on electron configuration combined with Mendeleev's method of organization. Often, the scope of a problem in science precludes the possibility of any individual providing a complete description of everything at the beginning. Science is an iterative endeavor. Science does not explain everything all at once. Every answer we find brings more questions.

I don't need to cite a reference for E=mc^2. You know exactly where it comes from.

I don't need to cite a reference for "Higgs is the ONLY spin zero boson, and the fundamental particle on which the Standard Model of particle physics rests."

I don't need to cite a reference for "The speed of light (for energy not bound) and rest energy (of matter or energy that is bound) are invariants."

Pick up any physics textbook. If you find these ideas "wooly", you are right in the sense that while we understand E=mc^2 in a general sense, the specifics require a doctoral degree in physics that uses some very, very wooly math to arrive at a non-conclusion about what it means.

I'm just connecting dots here, exchemist. You and alpha brane were discussing Schrödinger's wave equation, and the square box probability potential of atomic structure as a harmonic oscillator for electrons (a very, very old saw used to approximate almost anything periodic in physics). Our quantum physics instructor used a similar treatment to explain quantum tunneling, as I recall. I thought I could add some depth to the discussion.

If instead you prefer "A good book that explains quantum physics like I'm an idiot?", well then, I suppose that isn't "wooly" at all, and also a matter of taste. I prefer a more proactive approach; treat me like I'm an idiot, and I might find several ways return the favor.

I don't feel "wooly" about the things I have written. I'm only suggesting a direction of inquiry. Is this not clear?
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No. But thanks: enough for me, I think, now.
 
danshawen said:
I don't need to cite a reference for "Higgs is the ONLY spin zero boson, and the fundamental particle on which the Standard Model of particle physics rests."
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For the first part not, the Higgs particle is indeed a spin zero boson. What remains is nonsense, typical for bad popular science journalism, so you would better provide a reference.
 
danshawen said:
According to the Cambridge English Dictionary, "wooly" means: "ideas and thinking are confused and not clear". I had to look it up; no one uses it in these parts. If you think what I wrote is "wooly", I can accept "not clear", but I am anything but confused. The model works for me, with or without supporting details.

If I had worked out the details of enough elements on Periodic Table to understand its periodicity and where it derives, would you expect me to claim that I knew all of the details about the properties, atomic spectra, and abundances of all of the others before mentioning that I thought I was onto something? That isn't how science, or anything else works.

Mendeleev ran into all manner of skepticism as well, and his periodicity idea collected a lot of dust on shelves before Pauli came up with a way of predicting new elements based on electron configuration combined with Mendeleev's method of organization. Often, the scope of a problem in science precludes the possibility of any individual providing a complete description of everything at the beginning. Science is an iterative endeavor. Science does not explain everything all at once. Every answer we find brings more questions.

I don't need to cite a reference for E=mc^2. You know exactly where it comes from.

I don't need to cite a reference for "Higgs is the ONLY spin zero boson, and the fundamental particle on which the Standard Model of particle physics rests."

I don't need to cite a reference for "The speed of light (for energy not bound) and rest energy (of matter or energy that is bound) are invariants."

Pick up any physics textbook. If you find these ideas "wooly", you are right in the sense that while we understand E=mc^2 in a general sense, the specifics require a doctoral degree in physics that uses some very, very wooly math to arrive at a non-conclusion about what it means.

I'm just connecting dots here, exchemist. You and alpha brane were discussing Schrödinger's wave equation, and the square box probability potential of atomic structure as a harmonic oscillator for electrons (a very, very old saw used to approximate almost anything periodic in physics). Our quantum physics instructor used a similar treatment to explain quantum tunneling, as I recall. I thought I could add some depth to the discussion.

If instead you prefer "A good book that explains quantum physics like I'm an idiot?", well then, I suppose that isn't "wooly" at all, and also a matter of taste. I prefer a more proactive approach; treat me like I'm an idiot, and I might find several ways return the favor.

I don't feel "wooly" about the things I have written. I'm only suggesting a direction of inquiry. Is this not clear?
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I'd be shocked you actually learned something that has some relationship to scholarship. Thinking a lack of scholarship can lead to a physics epiphany is pretty comical danshawen.
 
arfa brane said:
It explains (if you can handle calculus equations), why you can't derive quantum mechanics from Newtonian mechanics.
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You certainly cannot (derive QM from classical physics). I agree. I'm not suggesting that you can. What I AM suggesting is that QM stopped extending relativity too soon. The variable for time was eliminated and replaced with probabilities. This is fine up to a point, but it fails THE VERY MOMENT that inertia is reintroduced via Higgs in the Standard Model. Now you must explain the mechanics of inertia, and describe what it is you mean by it. This cannot be accomplished with probabilities, or resorting to descriptions of static Euclidean vector spaces in any number of dimensions.

It CAN be done by extending relativity into the dynamics of quantum spin. This requires intimate knowledge of what time represents on a fundamental level, so that it can be re-introduced in a description of inertia. Relativity as formulated by Einstein falls just a bit short of an augmented description of the nature of time as it relates to energy transfer events.
 
danshawen said:
but it fails THE VERY MOMENT that inertia is reintroduced via Higgs in the Standard Model.
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Unfortunately it isn't.

Of course, the SM is special relativity, thus, some notion of inertia is part of it. But it is completely unrelated to the Higgs. It is there even without the Higgs. And if one considers the SM on curved background, it is no longer there, with as well as without Higgs.
 
danshawen said:
You certainly cannot (derive QM from classical physics). I agree. I'm not suggesting that you can. What I AM suggesting is that QM stopped extending relativity too soon. The variable for time was eliminated and replaced with probabilities. This is fine up to a point, but it fails THE VERY MOMENT that inertia is reintroduced via Higgs in the Standard Model. Now you must explain the mechanics of inertia, and describe what it is you mean by it. This cannot be accomplished with probabilities, or resorting to descriptions of static Euclidean vector spaces in any number of dimensions.
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a) QM does not get rid of time, nor does QFT.
b) Inertia exists in standard QM and QFT, since both include momentum and the interactions of existing particles/fields lead to changes in momentum.
 
arfa brane said:
From MIT: Schrodinger's equation, with forces. It explains (if you can handle calculus equations), why you can't derive quantum mechanics from Newtonian mechanics. It does however, include this:
"We present a plausibility argument, not a derivation, relating
the classical formulation to the quantum formulation."

http://web.mit.edu/6.763/www/FT03/Lectures/Lecture9.pdf
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Yes the maths is the same I recall from university, so I'm fine with it (though if you go off-piste I may get lost as I have not manipulated these things for many years now:smile:). It seems from this that they do, as I have been saying, use forces to construct the potentials, though it is true that the strictly QM treatment starts from the potentials thereby constructed, rather than utilising the forces per se. Perhaps that is what you meant. Anyway, I think we both know what we mean and it's just a difference of emphasis.
 
You may have noticed I use the coin analogy a lot---sending a beam of photons through a polarizing filter is equivalent to tossing a lot of coins.

I'm not saying quantum particles are like coins, I'm saying the spin of a particle is like the two faces of a coin. Which of two paths a particle takes, that's like two faces of a coin too.
With coins, you got randomness, another 'requirement' in QM.

Schrodinger's equation does not describe spin, but it does describe the probability of a particle tunnelling through a barrier, for instance.
Ok, so why isn't it a problem that spin isn't part of the SE?
 
arfa brane said:
You may have noticed I use the coin analogy a lot---sending a beam of photons through a polarizing filter is equivalent to tossing a lot of coins.

I'm not saying quantum particles are like coins, I'm saying the spin of a particle is like the two faces of a coin. Which of two paths a particle takes, that's like two faces of a coin too.
With coins, you got randomness, another 'requirement' in QM.

Schrodinger's equation does not describe spin, but it does describe the probability of a particle tunnelling through a barrier, for instance.
Ok, so why isn't it a problem that spin isn't part of the SE?
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Not sure I follow you. I've always seen Schroedinger's equation as describing the states that a particle like an electron can be in by virtue of the environment it is in. For example in the atom you get 3 quantum numbers out of it, principal, azimuthal and magnetic, which describe the radial and rotational states of a charged wave-particle, bound by a spherically symmetrical Coulomb potential. Since intrinsic spin is not the result of the environment (i.e. it is intrinsic), why should one expect that Schroedinger's equation would deal with it?
 
exchemist said:
Not sure I follow you. I've always seen Schroedinger's equation as describing the states that a particle like an electron can be in by virtue of the environment it is in. For example in the atom you get 3 quantum numbers out of it, principal, azimuthal and magnetic, which describe the radial and rotational states of a charged wave-particle, bound by a spherically symmetrical Coulomb potential.
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Equally, the electron and proton in a Hydrogen atom exchange virtual photons.

Spin wasn't experimentally observed when Schrodinger derived his equation. It was another surprise.
Nowadays physicists talk about gauge fields with spin degrees of freedom. The photon is spin-1, and is the gauge particle of the electromagnetic field, so the field has three spin degrees of freedom.

And yes, the environment an electron is in determines its possible states, but this environment has to be described in terms of potentials.
 
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arfa brane said:
Equally, the electron and proton in a Hydrogen atom exchange virtual photons.

Spin wasn't experimentally observed when Schrodinger derived his equation. It was another surprise.
Nowadays physicists talk about gauge fields with spin degrees of freedom. The photon is spin-1, and is the gauge particle of the electromagnetic field, so the field has three spin degrees of freedom.

And yes, the environment an electron is in determines its possible states, but this environment has to be described in terms of potentials.
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Not sure how this relates to your question or my attempt at answering it. Sticking to your question (why is it not a problem that the wave equation does not deal with intrinsic spin) , the way I look at it the intrinsic spin,s, of the electron is just like its electric charge, e. It is a given feature of the particle, i.e. it just is. This is in contrast with the properties an electron has by virtue of its environment, such as its energy or the distribution of its wavefunction in space. Schroedinger's equation concerns the latter.

I'm not a physicist so I don't know whether there are equations that explain intrinsic spin or intrinsic electric charge. I rather thought there were not and they are still, even today, just an experimentally validated given. But looked at this way it is clear both are quite outside the scope of Schroedinger's equation.
 
danshawen said:
You certainly cannot (derive QM from classical physics). I agree. I'm not suggesting that you can. What I AM suggesting is that QM stopped extending relativity too soon. The variable for time was eliminated and replaced with probabilities. This is fine up to a point, but it fails THE VERY MOMENT that inertia is reintroduced via Higgs in the Standard Model. Now you must explain the mechanics of inertia, and describe what it is you mean by it. This cannot be accomplished with probabilities, or resorting to descriptions of static Euclidean vector spaces in any number of dimensions.

It CAN be done by extending relativity into the dynamics of quantum spin. This requires intimate knowledge of what time represents on a fundamental level, so that it can be re-introduced in a description of inertia. Relativity as formulated by Einstein falls just a bit short of an augmented description of the nature of time as it relates to energy transfer events.
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Arfa, your insistence has got me looking a few things up and I found this: https://en.wikipedia.org/wiki/De_Broglie–Bohm_theory

This view certainly does seem to abolish forces, or at least treats them as classical expressions of a potential, which it seems to regard as the more fundamental entity. So I can see now, I think, where your view of all this may come from.

And actually I suppose, having now thought about it, there is no a priori reason why force should be more fundamental than potential, except in the sense that force is what one must measure in order to characterise a potential. Is that how you see it?
 
The Pauli equation is non-relativistic, but it does predict spin. As such, it can be thought of as occupying the middle ground between:

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--https://en.wikipedia.org/wiki/Pauli_equation.

I have an article by Gerard t'Hooft about gauge theories. In it he says that a force is what restores a broken symmetry, and I can't say I fully understand this yet. But it does hint that symmetry is more fundamental than forces, and that understanding the symmetry (of a field) is important to see why that's true.
 
arfa brane said:
--https://en.wikipedia.org/wiki/Pauli_equation.

I have an article by Gerard t'Hooft about gauge theories. In it he says that a force is what restores a broken symmetry, and I can't say I fully understand this yet. But it does hint that symmetry is more fundamental than forces, and that understanding the symmetry (of a field) is important to see why that's true.
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But surely, what the all Pauli equation does is account for the space quantisation (i.e. in the presence of an external field) of a particle with charge and spin, isn't it? As in the Stern-Gerlach experiment, for instance. It says nothing about intrinsic spin itself, does it?

So it seems to me it does not "predict spin" (s) , it just predicts the quantisation of spin states m (s) due to an external environment acting on a particle that has intrinsic charge and spin. Or have I misunderstood?

I'd be interested in what you have to say further about force when you have digested the article. For me it is a new way to think about things to make force a (classical) consequence of potential, rather than vice versa.
 
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Ok. I've read that quantum mechanics is really about phases and phase changes.

When an electron absorbs or emits a photon there is a change in the phase of the electron matter field. Photons can be any frequency so the change in phase is arbitrary, and this is the global symmetry of the electron field. IOW if you have a double slit experiment with electrons, changing the global phase of the field between the slits and the screen won't change the interference pattern, but changing the phase of half the field (i.e. with say a magnet between the slits, or an electron half or quarter wave plate) will change the pattern.

This global symmetry is a choice of gauge, and the photon (any photon) is the gauge particle, or "force-carrier". The magnet acts like it is exchanging electromagnetic photons with the electron field, or equivalently there is a magnetic force and a vector potential.

I'll let Gerardus sum it up:
" The connection between the two fields lies in the interaction between the charge of the electron with the electromagnetic field. Because of this interaction, the propagation of an electron matter wave in an electric field can be described properly only if the electric potential is specified.

Similarly, to describe an electron in a magnetic field the magnetic vector potential must be specified. Once these two potentials are assigned definite values, the phase of the electron wave is fixed everywhere. The local symmetry of electromagnetism, however, allows the electric potential to be given any arbitrary value which can be chosen independently at every point [in spacetime]. For this reason the phase of the electron field can also take on any value at any point. "

I still need to see why using a half wave electron plate on one slit is the same as using a shielded magnet on both slits. Either setup constitutes a measurement or a preparation, experimentally.
 
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arfa brane said:
Ok. I've read that quantum mechanics is really about phases and phase changes.

When an electron absorbs or emits a photon there is a change in the phase of the electron matter field. Photons can be any frequency so the change in phase is arbitrary, and this is the global symmetry of the electron field. IOW if you have a double slit experiment with electrons, changing the global phase of the field between the slits and the screen won't change the interference pattern, but changing the phase of half the field (i.e. with say a magnet between the slits, or an electron half or quarter wave plate) will change the pattern.

This global symmetry is a choice of gauge, and the photon (any photon) is the gauge particle, or "force-carrier". The magnet acts like it is exchanging electromagnetic photons with the electron field, or equivalently there is a magnetic force and a vector potential.

I'll let Gerardus sum it up:
" The connection between the two fields lies in the interaction between the charge of the electron with the electromagnetic field. Because of this interaction, the propagation of an electron matter wave in an electric field can be described properly only if the electric potential is specified.

Similarly, to describe an electron in a magnetic field the magnetic vector potential must be specified. Once these two potentials are assigned definite values, the phase of the electron wave is fixed everywhere. The local symmetry of electromagnetism, however, allows the electric potential to be given any arbitrary value which can be chosen independently at every point [in spacetime]. For this reason the phase of the electron field can also take on any value at any point. "

I still need to see why using a half wave electron plate on one slit is the same as using a shielded magnet on both slits. Either setup constitutes a measurement or a preparation, experimentally.
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Certainly when an electron changes state through absorption or emission of a photon, the symmetry of its wavefunction is inverted. This is because the photon itself is intrinsically antisymmetric. So (symmetric e) emits/absorbs (antisymmetric γ) -> (antisymmetric e), while (antisymmetric e) emits/absorbs (antisymmetric γ) -> symmetric e. This is observed in the selection rules for atomic and molecular spectra: the strongly occurring transitions are those in which the symmetry of the electron's wavefunction changes. For example an electron in an s orbital (symmetric) cannot be excited to another s orbital but can be excited to a p orbital (antisymmetric).

If you introduce a magnetic field, you make the environment of the electron no longer spherically symmetrical and it can then then orientate its intrinsic spin either with or against the field. These are now 2 alternative states, with different energy (orientating with the field has the higher energy). This phenomenon is called "space quantisation".

Evidently you are reading a QFT explanation of what happens, written in terms of this thing called the "electron matter field". You can do quite a lot of quantum mechanics without resorting to QFT. (We did not cover QFT at all at university, since one can have a satisfactory QM account of the behaviour of atoms and molecules without using it at all.) So QM =/= QFT. But I'm sure the phase idea is very important in both, as it comes out of the wave nature of matter which is fundamental to QM.

I suppose that, one of these days, I really ought to try to get my head round QFT. I do not pretend that I understand it at the moment.
 
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I have to say that the article is quite long, and I find there are key concepts I've had to winkle out.

It comes with diagrams, but these are obviously just conveniences, an electron matter field is represented like waves you would see in a wave tank (if you've used one of those to investigate wave mechanics), the slits have classical wave patterns emerging. There are four of these diagrams, the first one is just the classical wave interference detected on a screen (or with incidence counters).

The next is a representation of a global change in the phase of this electron "matter field". A wave plate is inserted in front of the slits, which shifts the phase (globally) by 180° and this has no effect on the interference pattern--a global change in phase can't be detected.

The next diagram has a half wave plate in front of one slit, the matter field is then altered "locally", and the interference pattern changes (it isn't destroyed because no path information is being detected). The last diagram has a shielded magnet in front of, and between, both slits, and the pattern looks the same as a local change in phase. How does a shielded magnet interact with a beam of electrons?
Unfortunately, t'Hooft doesn't explain why, just that it's what happens.

Another clue from the article: "It can easily be demonstrated that a theory of electron fields alone, with no other forms of matter or radiation, [an electron universe], is not invariant with respect to a local gauge transformation." (viz, the diagrams).
Then he says: "Suppose one wanted to make the theory [of electron fields] consistent with a local gauge symmetry. ...
perhaps another field could be added that would compensate for the changes in electron phase. ...
It turns out that the required field is a vector one, corresponding to a field quantum with spin 1." Which is of course, the electromagnetic field.

In field theories an electron is a field, a photon is also "the" electromagnetic field.
 
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