What sort of an experiment can refute QM or QFTs?

[bob012345]

If you're not going to give an example, then don't give it. Hints like this are a good way to get a warning. Please take heed.

I was just trying to avoid a potential controversy. My example then is if experiments proved the existence of the so-called Hydrino state, the hypothetical state below the ground state of Hydrogen, that might be considered a refutation of QM as currently understood.

 

[Nullstein]

I was just trying to avoid a potential controversy. My example then is if experiments proved the existence of the so-called Hydrino state, the hypothetical state below the ground state of Hydrogen, that might be considered a refutation of QM as currently understood.

It woudn't. One would just modify the Hamiltonian so it predicts the modified energy spectrum. However, this theory seems to be pseudo-science anyway.

 

[PeterDonis]

I was just trying to avoid a potential controversy.

The way to do that is to not mention the potentially controversial thing at all. Hinting at it and then saying you can't give more detail because it might get you banned is not avoiding controversy, it's inviting a warning for yourself. Again, please take heed.

 

[PeterDonis]

One would just modify the Hamiltonian so it predicts the modified energy spectrum.

That might still be problematic because you can't just arbitrarily modify the Hamiltonian. The standard Hamiltonian for the electron in the hydrogen atom is not just taken from thin air; it is derived from the standard non-relativistic kinetic energy and the Coulomb potential of the nucleus. (There are additional fine and hyperfine structure terms as well, but those don't matter for this discussion.)

 

[Nullstein]

That might still be problematic because you can't just arbitrarily modify the Hamiltonian. The standard Hamiltonian for the electron in the hydrogen atom is not just taken from thin air; it is derived from the standard non-relativistic kinetic energy and the Coulomb potential of the nucleus. (There are additional fine and hyperfine structure terms as well, but those don't matter for this discussion.)

That's right, but if this didn't produce the correct results, it would just show that the Coulomb potential wasn't the full story. As you noted, there is also e.g. fine structure, but we didn't take its discovery as an argument to reject quantum theory. We just added some higher order terms to account for the discrepancy.

 

[PeterDonis]

if this didn't produce the correct results, it would just show that the Coulomb potential wasn't the full story.

But then you would have to show where the additional potential was coming from, and explain why it wasn't showing up in any other experiments. Unless in this hypothetical we are also saying that lots of other experiments would also have to have come out differently.

As you noted, there is also e.g. fine structure, but we didn't take its discovery as an argument to reject quantum theory. We just added some higher order terms to account for the discrepancy.

Exactly: these additional terms were due to interactions we already knew were there, just of smaller magnitude so the initial model didn't include them. We added them as measurements became more accurate and we began to see the effects of the higher order terms.

That's very different from having to add a whole new interaction to the model. That might be possible, but it would be very difficult.

 

[bob012345]

The way to do that is to not mention the potentially controversial thing at all. Hinting at it and then saying you can't give more detail because it might get you banned is not avoiding controversy, it's inviting a warning for yourself. Again, please take heed.

I am sorry. I used poor judgement saying that and I apologize.

 

[bob012345]

But then you would have to show where the additional potential was coming from, and explain why it wasn't showing up in any other experiments. Unless in this hypothetical we are also saying that lots of other experiments would also have to have come out differently.

I agree completely with the first sentence but I'm not sure I understand what you mean in the second sentence?

 

[PeterDonis]

I'm not sure I understand what you mean in the second sentence?

Just that if, hypothetically, we imagine that the results of many experiments we have already done were different, then those results might support a different theory. But that sort of hypothetical might not be what the OP intended.

 

[Paul Colby]

The standard Hamiltonian for the electron in the hydrogen atom is not just taken from thin air; it is derived from the standard non-relativistic kinetic energy and the Coulomb potential of the nucleus.

It’s even a little better than that. Equation 14.1.1 in Weinberg vol I is a relativistic Lagrangian bit taken straight from the standard model. The coulomb central potential is the usual one, of course, but the Dirac equation is used for the electron. Adding the em field back in for the Lamb shift is straight forward. Always been impressed by how cleanly this works out.

 

[vanhees71]

Sure, there's not the slightest hint for any violation of the standard-model prediction for the hydrogen atom, although it's among the most accurately measured and theoretically calculated phenomena ever. The reason for this effort is that one always looks for violations of the predictions of the Standard Model and physics beyond it, because (a) one still looks for possible new particles that could make up the "dark matter" in the cosmological standard model needed to explain the velocity curves of stars in most galaxies and also the structure formation in the evolution of the universe in the big-bang model and (b) to overcome the fine-tuning problem.

The theoretical foundation for alternative theories (like SUSY extensions of the Standard Model) is, however, still standard QFT (including SUSY extensions of course). There are very few generic features that are valid for any local relativistic QFT. One is the relation between spin and statistics (half-integer-spin fields have to be quantized as fermions those of integer spin as bosons) and the invariance under the CPT transformation. Both predictions are tested thoroughly as well with no contradictions found (while all the symmetries, P, T, C, CP, etc. are observed to be violated by the weak interaction).

 

[Nullstein]

But then you would have to show where the additional potential was coming from, and explain why it wasn't showing up in any other experiments. Unless in this hypothetical we are also saying that lots of other experiments would also have to have come out differently.

Sure, I don't deny that. As I said, this "hydrino" is pseudo-science anyway. But we can still discuss what the reaction of the physics community to such an unlikely discovery would have been.

Exactly: these additional terms were due to interactions we already knew were there, just of smaller magnitude so the initial model didn't include them. We added them as measurements became more accurate and we began to see the effects of the higher order terms.

That's very different from having to add a whole new interaction to the model. That might be possible, but it would be very difficult.

Of course it would be hard, I don't deny that either. Luckily, no such thing as a hydrino was ever discovered. But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort.

 

[MathematicalPhysicist]

Sure, I don't deny that. As I said, this "hydrino" is pseudo-science anyway. But we can still discuss what the reaction of the physics community to such an unlikely discovery would have been.

Of course it would be hard, I don't deny that either. Luckily, no such thing as a hydrino was ever discovered. But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort.

So do you say the rather disturbing thing:"you cannot falsify Quantum Theory"?

 

[Nullstein]

So do you say the rather disturbing thing:"you cannot falsify Quantum Theory"?

Where did you get that from? I said the opposite in post #26.

 

[bob012345]

Sure, I don't deny that. As I said, this "hydrino" is pseudo-science anyway. But we can still discuss what the reaction of the physics community to such an unlikely discovery would have been.

Of course it would be hard, I don't deny that either. Luckily, no such thing as a hydrino was ever discovered. But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort.

Why would you say Luckily, no such thing as a hydrino was ever discovered? If such a thing existed it might be a boon to science and technology. Why would you not want it to be true?

 

[MathematicalPhysicist]

Where did you get that from? I said the opposite in post #26.

From what you wrote here:" But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort."

I guess you cannot falsify a dogma which states that the world is not classic.
Either it's classic or it's not, but if it's not classical, then is this reality depends on a specific observer?
Who is he?

 

[Nullstein]

Why would you say Luckily, no such thing as a hydrino was ever discovered? If such a thing existed it might be a boon to science and technology. Why would you not want it to be true?

Luckily, because our best theories remain valid and we don't have to deal with these pseudo-science models. I don't see how it would benefit science and technology. Most likely, matter, as we know it, would have very different properties then and human life would be impossible.

From what you wrote here:" But in the unlikely event that it is discovered, the reaction of the physics community would likely not be the rejection of quantum theory. Instead, we would take this as an indication of beyond standard model physics and try to add new terms to the Lagrangian. There would probably immediately be lots of papers on the arXiv in this direction. Rejection of QT would likely be the very last resort."

I guess you cannot falsify a dogma which states that the world is not classic.
Either it's classic or it's not, but if it's not classical, then is this reality depends on a specific observer?
Who is he?

If you drop a ball and it goes upwards, you have falsified gravity, but not quantum theory. Similarly, you cannot just pick any arbitrary experiment to falsify quantum theory. You must design the experiment in a way so it tests an actual prediction of quantum theory. Quantum theory doesn't predict that balls have to fall down. Gravity does. These "hydrinos" are just not in direct contradictions with quantum theory, so their discovery would not falsify quantum theory. I told you in post #26 what kind of experiments are needed to falsify quantum theory. It's possible to conduct such experiments, so I don't see the problem. QT is not a dogma.

 

[Vanadium 50]

dogma

Puh-lese.

Any successor to quantum theory needs to explain everything QM does. Which means it needs to make very, very similar predictions over the range its been tested.

 

[bob012345]

Luckily, because our best theories remain valid and we don't have to deal with these pseudo-science models. I don't see how it would benefit science and technology. Most likely, matter, as we know it, would have very different properties then and human life would be impossible.

That makes little sense to me. If something turned out to be experimentally true that was currently considered pseudo-science, do you not think it could and would then become the domain of legitimate science? Are physicists incapable with dealing with a surprise discovery outside the current widely accepted mainstream?

As far as utility goes, hypothetical transitions to lower energy levels of Hydrogen should be an energy source that could benefit humanity if it were true.

 

[bob012345]

Puh-lese.

Any successor to quantum theory needs to explain everything QM does. Which means it needs to make very, very similar predictions over the range its been tested.

Yes but candidate theories might take decades or even centuries to get to that point. For example SED theory or Stephen Wolfram's ideas as depicted in A New Kind of Science.

 

[Nullstein]

That makes little sense to me. If something turned out to be experimentally true that was currently considered pseudo-science, do you not think it could and would then become the domain of legitimate science? Are physicists incapable with dealing with a surprise discovery outside the current widely accepted mainstream?

As far as utility goes, hypothetical transitions to lower energy levels of Hydrogen should be an energy source that could benefit humanity if it were true.

I really don't want to discuss this specific "theory." I just wanted to point out that it would not be the kind of discovery that would pose a serious threat to quantum theory, because it's not in direct contradiction with it. You'd have to come up with something more drastic.

 

[PeterDonis]

Why would you say Luckily, no such thing as a hydrino was ever discovered? If such a thing existed it might be a boon to science and technology. Why would you not want it to be true?

I don't see how it would benefit science and technology. Most likely, matter, as we know it, would have very different properties then and human life would be impossible.

If something turned out to be experimentally true that was currently considered pseudo-science, do you not think it could and would then become the domain of legitimate science?

This is getting off topic. The thread is not about the general philosophy of science but about the specific question in the OP.

 

[PeterDonis]

Yes but candidate theories might take decades or even centuries to get to that point. For example SED theory or Stephen Wolfram's ideas as depicted in A New Kind of Science.

This thread is not about candidate theories to replace QM/QFT but about experiments that could refute QM/QFT. Please stay on topic.

 

[bob012345]

I really don't want to discuss this specific "theory." I just wanted to point out that it would not be the kind of discovery that would pose a serious threat to quantum theory, because it's not in direct contradiction with it. You'd have to come up with something more drastic.

Sticking to experiments, suppose some clever future experiment showed it was possible to simultaneously measure an electron's position and momentum to a greater precision than the HUP? Would not such a result stab at the heart of the core of all QT, the wave nature of matter?

 

[Paul Colby]

Would not such a result stab at the heart of the core of all QT, the wave nature of matter?

Scientific consensus has quite a bit of inertia behind it. Just one experiment and one paper is unlikely to shift it too greatly. First one would have to be convinced the paper's claims are accurate. This alone would take forming a scientific consensus.

 

[bob012345]

Scientific consensus has quite a bit of inertia behind it. Just one experiment and one paper is unlikely to shift it too greatly. First one would have to be convinced the paper's claims are accurate. This alone would take forming a scientific consensus.

Surely but if broadly accepted, would it meet the OP criteria of refuting QT? Of course even if such a thing happened it would not stop the usefulness of the legion of calculational techniques developed in the last 100 years.

 

[Paul Colby]

Surely but if broadly accepted, would it meet the OP criteria of refuting QT?

Well, I’m thinking not but couldn’t say because I don’t know how QM would be changed by this new finding. Somewhere somehow all the things we know today need to be included in any new formulation. This new formulation might well be called QM when the dust clears.

 

[ohwilleke]

What would a falsification of QM look like, if you could do it?

Realistically, you'd be looking at something like superdeterminism in which the universe acts in a manner that is deterministic but observed to be random because it is chaotic in the mathematical sense, with extreme sensitivity of behavior to initial conditions in a way that current experiments are too imprecise to observe but one might imagine some future experiment being capable of observing.

It would be so similar to QM, however, that it would be terribly difficult to find a way to distinguish the two experimentally and there would be little or not applied science benefit to using one over the other. It would suggest strategies to address "the measurement problem", but it isn't at all obvious that equivalent approaches couldn't be developed in the context of orthodox QM.

 

[CoolMint]

How would you falsify a tested quantum computer? What sort of scientific twist would it take?

https://edition.cnn.com/2019/10/23/tech/google-quantum-supremacy-scn/index.html

https://www.nature.com/articles/s41586-019-1666-5

 

[CoolMint]

I guess you cannot falsify a dogma which states that the world is not classic.
Either it's classic or it's not, but if it's not classical, then is this reality depends on a specific observer?
Who is he?

The invisible hand of fate(initial conditions). Or the invisible observer if you like. Either way, we can usually offset the effects of this misfortune by intelligence as it seems to make quite a noticeable difference to what is unfolding. Most times at least.