tag:blogger.com,1999:blog-22973357.post3487687659001387744..comments2019-06-17T10:40:38.581-04:00Comments on Sabine Hossenfelder: Backreaction: Quantum Mechanics is wrong. There, I’ve said it.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger88125tag:blogger.com,1999:blog-22973357.post-86324492740776849382019-05-25T03:34:55.193-04:002019-05-25T03:34:55.193-04:00Lawrence,
in d=1+1, large N expansion, sigma mode...Lawrence,<br /><br />in d=1+1, large N expansion, sigma model, <i>dimensional transmutation</i> generates a mass by trading a dimensionless coupling for a dimensional mass scale, the UV cut-off. See <a href="http://www.damtp.cam.ac.uk/user/tong/sft.html" rel="nofollow">David Tong</a> eq. (4.28) or <a href="https://books.google.de/books?id=n8Mmbjtco78C&pg=PA404&lpg=PA404&dq=%22Note+Reimondhttps://www.blogger.com/profile/04669340425105889539noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-34102579679397101702019-05-20T13:46:43.188-04:002019-05-20T13:46:43.188-04:00blackswan,
Sabine and Louis are trying to tell yo...blackswan,<br /><br />Sabine and Louis are trying to tell you diplomatically that physicists will not take you seriously unless and until you go to the trouble to learn a great deal of physics.<br /><br />Same thing in medicine, civil engineering, and most other fields.<br /><br />Sorry, but that is reality.<br /><br />Dave <br /><br />(usually "PhysicistDave," but am having trouble Dave Millerhttps://www.blogger.com/profile/10255057779449383067noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91535017628711058622019-05-20T13:08:29.789-04:002019-05-20T13:08:29.789-04:00mh, could you provide one or more examples of theo...mh, could you provide one or more examples of theories which provide "a viable physical explanation"?patrickd314https://www.blogger.com/profile/05007570959862325152noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-19055550851804059972019-05-20T02:50:14.527-04:002019-05-20T02:50:14.527-04:00Souvik,
Rovelli talks about the “… relational str...Souvik,<br /><br />Rovelli talks about the <i>“… <b>relational</b> structure of physical quantities.”</i> <br />Your <i>“… minimize Feynman's path integral …”</i> does not make much sense. You either mean you vary the Lagrangian to get the equations of motion or you might mean the classical limit ℏ→0 again giving you the classical equations of motion. E.g. varying the Dirac Lagrangian gives Reimondhttps://www.blogger.com/profile/04669340425105889539noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-17024729634447512182019-05-20T00:35:47.107-04:002019-05-20T00:35:47.107-04:00Textbooks on quantum mechanics beyond high school,...Textbooks on quantum mechanics beyond high school, i.e. at an undergraduate level introduces the theoretical formalism early on, like Sakurai motivates it through Stern Gerlach and EPR experiments. Quantum mechanics applied to the hydrogen atom or quantum chemistry in general is merely the opening gambit for some pedagogical paths to the subject. In that case, quantum mechanics of 1 d.o.f. is notSouvikhttps://www.blogger.com/profile/07991325103104780113noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-36992316491736519332019-05-19T14:39:43.660-04:002019-05-19T14:39:43.660-04:00It is not too difficult to develop General Relativ...It is not too difficult to develop General Relativity using axioms and fundamental assumptions. What's hard is combining it with quantum mechanics.Peter Shorhttps://www.blogger.com/profile/13823970640202949073noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5635218755098095012019-05-19T13:06:30.228-04:002019-05-19T13:06:30.228-04:00Hello Ajit,
I’d like to give your question a try ...Hello Ajit, <br />I’d like to give your question a try (which should in no way hinder Dr. Hossenfelder from correcting each of us if she likes). If someone today were to figure some things out regarding QM in a way that’s experimentally verified, they’d actually be revered as strongly as any physicist might be. No worries there! <br /><br />To me the theme of this post gets to something that Philosopher Erichttps://www.blogger.com/profile/11126076811765843302noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24741543223016030222019-05-19T03:47:14.318-04:002019-05-19T03:47:14.318-04:00Souvik,
I've been taught an axiomatic approac...Souvik,<br /><br />I've been taught an axiomatic approach to quantum mechanics, so the answer to your question is "no." Look, I am using the word "quantum mechanics" to mean "that what is the content of almost all textbooks on quantum mechanics". And also what popular science articles on quantum mechanics are about. As I said, I have no interest in debating what Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56954564341148408282019-05-19T03:16:49.338-04:002019-05-19T03:16:49.338-04:00Are you sure what you're thinking of as quantu...Are you sure what you're thinking of as quantum mechanics is not just quantum chemistry? You wouldn't call classical mechanics a study of the simple pendulum, would you? Classical mechanics is a framework of kinematics and dynamics, expressed in Newtonian, Hamiltonian or Lagrangian form, that is broader than its use case for analyzing a pendulum. Similarly, quantum mechanics is a Souvikhttps://www.blogger.com/profile/07991325103104780113noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-71916004621556510452019-05-19T01:40:46.387-04:002019-05-19T01:40:46.387-04:00Souvik,
With respect to your “d|psi>/dt = iH|...Souvik,<br /><br />With respect to your <i>“d|psi>/dt = iH|psi> is always *exactly* true …”</i> you might want to consider what is more “*exactly* true”: a Hamiltonian <i>H</i>, the time component of a four-vector and a time variable <i>t</i>, which both are different in different reference frames OR a Lorentz invariant Lagrangian in QFT.<br />And with respect to gauge and redundancy I Reimondhttps://www.blogger.com/profile/04669340425105889539noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-78768518275077262162019-05-19T00:31:20.017-04:002019-05-19T00:31:20.017-04:00Souvik,
What you want to call quantum mechanics i...Souvik,<br /><br />What you want to call quantum mechanics is simply not what is taught today as quantum mechanics. If you want, you can of course keep your vocabulary. I have no problem with that. I have zero interest to discuss the definition of words Souvik-style. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-55563185612449729532019-05-18T16:54:27.235-04:002019-05-18T16:54:27.235-04:00There is, of course, a relativity of wrong (someth...There is, of course, a relativity of wrong (something any diatribe like this would do well to acknowledge), but Ptolemaic cosmology was NOT more useful than Copernican. It only seemed to be to the people using it. But it was all a delusion.Archimedes218https://www.blogger.com/profile/12242764583554426760noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9172932693861180612019-05-18T15:10:47.514-04:002019-05-18T15:10:47.514-04:00The potential in the treatment of a hydrogen atom ...The potential in the treatment of a hydrogen atom is classical. That makes *the potential an approximation*, but not quantum mechanics! The 1/r potential emerges from a deeper theory, but given a 1/r potential, quantum mechanics is an exact theory of the evolution of ONE DEGREE OF FREEDOM. I'm sorry, this is not semantics. This does not mean QM is an approximation to QED. d|psi>/dt = iH|Souvikhttps://www.blogger.com/profile/07991325103104780113noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-84929275671976062019-05-18T12:05:05.601-04:002019-05-18T12:05:05.601-04:00Thanks for the explanation,I got the gist of QM no...Thanks for the explanation,I got the gist of QM not being useful for applications were particles get destroyed or created (vacuum modeling issues) and the Lamb shift is related to vacuum interactions so it"s covered by QFT. I had just used it as an example of how a mathematical model can be very accurate numerically without providing a viable physical explanation. I agree that QM is an mhhttps://www.blogger.com/profile/03582678489140510042noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-40677780078331136822019-05-18T11:33:44.528-04:002019-05-18T11:33:44.528-04:00Suppose, someone does find some good way to resolv...Suppose, someone does find some good way to resolve all the known riddles of quantum mechanics (such as the measurement problem) using some new approach which is even backed by sound enough a maths (like differential equations, dynamical theory, and computational simulations based on them). Suppose you get convinced that such an approach should work. <br /><br />Even then, such a development Ajit R. Jadhavhttps://www.blogger.com/profile/02194541129055576042noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89361103801885707602019-05-18T06:10:58.719-04:002019-05-18T06:10:58.719-04:00Souvik,
The potential comes from the interaction ...Souvik,<br /><br />The potential comes from the interaction terms, not the other way round, though this is of course to some extent semantics. Look, think of the treatment of the hydrogen atom in quantum mechanics. It has a potential, but no exchange particles. It's an approximation. You can't derive QED from it. QED will give corrections to this treatment. To get QED, you need additionalSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-5811117923618102692019-05-18T04:31:27.526-04:002019-05-18T04:31:27.526-04:00What do you think any interaction term in a field ...What do you think any interaction term in a field theory, or even a mass term really is? Deep down it is a potential. This becomes clear if you discretize the field into a lattice and think again about the mechanics of a single node in relation to the field Lagrangian you're writing. The mass term is quadratic in the field strength for a point in spacetime and quite literally a potential Souvikhttps://www.blogger.com/profile/07991325103104780113noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-7168700520351774092019-05-18T00:39:31.289-04:002019-05-18T00:39:31.289-04:00Interesting topic.
In contrast to early imprecise...Interesting topic.<br /><br />In contrast to early imprecise versions of quantum theory, QFT obtains precision by first assuming infinitesimal points as givens, even though it is fully recognized experimentally that such points cannot exist in the real universe. This abstract use of "not real" precision levels, ones that at best exist only at enormous energy levels, must then be Terry Bollingerhttps://www.blogger.com/profile/03915136249111338024noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12528201129110853932019-05-17T23:45:31.753-04:002019-05-17T23:45:31.753-04:00mh,
Unfortunately, you seem to have misunderstood...mh,<br /><br />Unfortunately, you seem to have misunderstood my blogpost. The Lamb shift is not a prediction of QM, it's a prediction of QFT. I am saying we know that QM is "wrong" in the sense that it is only an approximation. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-13877395501673747542019-05-17T17:08:13.058-04:002019-05-17T17:08:13.058-04:00Thank you, Sabine, for taking the time to answer m...Thank you, Sabine, for taking the time to answer me. I'm sure we would disagree on a lot of things, but I believe that's because the *things* are in disagreement. I think I can provide some insight into the recent disagreements about measuring the age of the universe in different ways as well. I just can't do anything with that insight by myself, and I don't have the resourcesblackswanhttps://www.blogger.com/profile/02277350682150547375noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-31865467666930339802019-05-17T17:06:12.271-04:002019-05-17T17:06:12.271-04:00Hi Sabine,
So are you saying that all the precise...Hi Sabine,<br /><br />So are you saying that all the precise, numerical results that come from predictions in quantum mechanics (like the Lamb shift) are not enough to make QM a completely accurate theory? Thank you for finally acknowledging that accurate measurements of predictions proposed by a theory does not make it a complete theory...it is really refreshing to hear that. I see QM as a mhhttps://www.blogger.com/profile/03582678489140510042noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-51631526624958856632019-05-17T06:33:14.236-04:002019-05-17T06:33:14.236-04:00Quantum Monte Carlo is one approach to relativisti...Quantum Monte Carlo is one approach to relativistic QM problems. This constructs a lattice with gauge potentials along the edgelinks. These can be computed according to differences between adjoint group actions at the vertices. These group actions g = e^{iθ}, with θ = ∫<b>A</b>·d<b>x</b> construct the pure gauge potentials δg = iδθg = iA<b>A</b>·δ<b>x</b>g and in the language of differential Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86768612259621232642019-05-17T01:49:51.558-04:002019-05-17T01:49:51.558-04:00Since Sabine recommended A. Zee: the electrostatic...Since Sabine recommended A. Zee: the electrostatic 1/r <a href="https://books.google.de/books?id=n8Mmbjtco78C&pg=PA28&lpg=PA28&dq=%22Yukawa+proposed+that+the+attraction+between+nucleons+in+the+atomic+nucleus+is+due+to+their+coupling+to+a+field%22" rel="nofollow">is an emergent property (one photon exchange) from QFT</a>.<br />And to bring this into the context of GR, the old Reimondhttps://www.blogger.com/profile/04669340425105889539noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74686192644067622572019-05-17T01:18:19.945-04:002019-05-17T01:18:19.945-04:00Sabine,
Since you said “… people who work on the ...Sabine,<br /><br />Since you said <i>“… people who work on the foundations of quantum mechanics never seem to be talking about quantum field theory”</i> I remember a comment to you, Tim and Carl <a href="http://backreaction.blogspot.com/2018/06/how-nature-became-unnatural.html?commentPage=2&showComment=1533099475371#c1909010804813207162" rel="nofollow">, see here (**)</a>:<br />… how to Reimondhttps://www.blogger.com/profile/04669340425105889539noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86793392758006268722019-05-16T23:49:38.283-04:002019-05-16T23:49:38.283-04:00Don,
Both QFT and QM are "solid". I am ...Don,<br /><br />Both QFT and QM are "solid". I am afraid I do not understand the comment. What I am saying is that QM is an approximation and in that sense the wrong theory to use for some situations.<br /><br />The most fundamental laws that I am referring to there are, as I say, differential equations. We currently get those from QFT and General Relativity. Please keep in mind that Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.com