tag:blogger.com,1999:blog-22973357.post682137661443561402..comments2019-04-20T17:40:22.935-04:00Comments on Backreaction: A philosopher's take on “naturalness” in particle physicsSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger18125tag:blogger.com,1999:blog-22973357.post-37528900286148308932019-02-04T16:09:08.173-05:002019-02-04T16:09:08.173-05:00which BSM physics moves the SM away from criticali...which BSM physics moves the SM away from criticality is ruled out, for example does SUSY or strings do this?neohttps://www.blogger.com/profile/16769182614452171312noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72593072785502623652019-02-04T03:30:25.037-05:002019-02-04T03:30:25.037-05:00According to a well-known joke, there are only thr...According to a well-known joke, there are only three natural numbers: zero, one, and infinity. From this perspective an infinitely fine-tuned SM with a Higgs mass at 125.x GeV is natural. I find it quite intriguing that the Higgs mass seems to sit exactly at the boundary of vacuum stability, rather than a few GeV away from it in either direction.<br /><br />If there is an underlying reason for Thomas Larssonhttps://www.blogger.com/profile/01207766078592840926noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-36083211208913985872019-02-03T19:10:05.458-05:002019-02-03T19:10:05.458-05:00Bee,
couldn't naturalness, specifically UV-cu...Bee,<br /><br />couldn't naturalness, specifically UV-cutoff of the Higgs mass, the null results from LHC on favored BSM, and QFT be used to <br /><br />1- to suggest no new physics from fermi to planck scale and<br />2- single out QG theories that does not affect the Higgs mass at the fermi scale?<br /><br />and i have in mind asymptotic safety which was used to predict the Higgs mass at neohttps://www.blogger.com/profile/16769182614452171312noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-58471916646556907802019-02-03T16:57:31.080-05:002019-02-03T16:57:31.080-05:00I think this is tricky. Coupling constants and run...I think this is tricky. Coupling constants and running parameters have been argued to converge to unity at quantum gravity, Hagedorn temperature etc. The fine structure constant α = e^2/4πεħc is experimentally known to be around 1/128 at the TeV scale and this as a running parameter is thought to converge to unity. For an elementary particle of mass m the gravitational constant is α_g(m) = Gm^2/Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8159799915305845252019-02-03T16:31:01.622-05:002019-02-03T16:31:01.622-05:00I find the whole concept of a multiverse to be an ...I find the whole concept of a multiverse to be an admission of defeat, not worthy of science to use as a basis for grandiose experiments. It is not disturbance about the output of money that informs my objections, just the idea that grown up physicists would waste their brains on such silly ideas. Jack Bidnikhttps://www.blogger.com/profile/05238506372280414520noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44635081112432043042019-02-03T12:29:55.290-05:002019-02-03T12:29:55.290-05:00The argument goes that that's a bad thing beca...The argument goes that that's a bad thing because if you assume a probability distribution on the initial parameters (at high energies) that has a typical (normalized) width of 1 you are unlikely to end up near the measured values.<br /><br />The problem with this argument is that you put in the number 1 to justify that parameters of order 1 are natural. It's a circular argument. You can Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-75377873394276170792019-02-03T12:26:20.854-05:002019-02-03T12:26:20.854-05:00Pavel,
The SM does not predict any of the particl...Pavel,<br /><br />The SM does not predict any of the particle masses. In that the Higgs is not any different from the other particles. That the cancellation is huge has absolutely no consequences for the predictability exactly because it cancels qua assumption. It does not enter any predictions. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25811391383113972792019-02-03T11:12:41.964-05:002019-02-03T11:12:41.964-05:00I started thinking, and as usual confused myself. ...I started thinking, and as usual confused myself. If in abstract QFT space, a large range for a parameter in the low energy theory flows towards a fixed point for that parameter in the high energy theory, then if we sit a little off the fixed point and consider the flows down to the low energy theory,a very small change in the high energy theory parameter will move the low energy parameter a lotArunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-69238623220980835742019-02-03T10:48:54.441-05:002019-02-03T10:48:54.441-05:00Sabine, sure, the SM is highly explanatory and pre...Sabine, sure, the SM is highly explanatory and predictive, except for the Higgs mass that receives a huge cancellation between physically and structurally distinct radiative contributions. [A clever renormalization may hide away the cancellation, still I am pretty confident there will be large derivatives of the likelihood with respect to the parameters for some (quasi-)observables, in some Pavel Nadolskyhttps://www.blogger.com/profile/02198856112442483856noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-51732533745016416732019-02-03T08:22:15.686-05:002019-02-03T08:22:15.686-05:00I should add that even though the last notion desc...I should add that even though the last notion described in my comment could be a useful notion, it doesn't mean that our current theories should satisfy it. Maybe the fundamental theory can't be described using the same semantics we have in QFT or string theory or any other currently known theory. So it could well be that currently known theories are not natural and yet they're Shayan javanihttps://www.blogger.com/profile/02962415306382491743noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-74963463936646333132019-02-03T08:12:02.836-05:002019-02-03T08:12:02.836-05:00Thanks Sabine, will be checking that out for sure....Thanks Sabine, will be checking that out for sure. Also yes, "believe" was badly worded by me.derdottehttps://www.blogger.com/profile/10588416166321871681noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-41064386355444138892019-02-03T07:48:51.087-05:002019-02-03T07:48:51.087-05:00Hi Daniel,
I don't want to speculate about wh...Hi Daniel,<br /><br />I don't want to speculate about what they believe to find because really I don't know what they believe. Let me instead tell you what they hope to find. <br /><br />They hope to find some new particles, notably some that would give them clues about new symmetries and/or a unification of the forces, or about dark matter/dark energy, or just something entirely new and Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-41031153721842855162019-02-03T07:37:22.395-05:002019-02-03T07:37:22.395-05:00Pavel,
That's just not how the word "nat...Pavel,<br /><br />That's just not how the word "natural" is used in the literature. In the common terminology, unnatural models can be both predictive and explanatory. General Relativity and the Standard Model are both unnatural, yet both are predictive and have high explanatory power. <br /><br />The UV-cutoff of the Higgs mass is not an observable. It's by assumption Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-71023038061523960922019-02-03T07:32:05.568-05:002019-02-03T07:32:05.568-05:00Sabine,
I find your latest blog entries quite inte...Sabine,<br />I find your latest blog entries quite interesting. However, I am not sure what people expect to find in particle physics nowdays, especially with you talking a lot about possible findings only achieveable at much higher energy than we can currently achieve. I am not a physicist (yet) but want to become one. I searched a bit but was unable to find what particle physicist actually Daniel Müllerhttps://www.blogger.com/profile/15548000651641012080noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89322763173518192852019-02-03T07:20:17.017-05:002019-02-03T07:20:17.017-05:00Dear Sabine, very helpful, then is it more convent...Dear Sabine, very helpful, then is it more conventional to say "Unnatural models are not explanatory", and that "not predictive" is a subcategory of "not explanatory"? I regretfully admit that I have not had a chance to get familiar with all relevant literature and terminology, including the interesting new paper by Williams.<br /><br />While indeed the Standard Pavel Nadolskyhttps://www.blogger.com/profile/02198856112442483856noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72587400224156668222019-02-03T07:16:51.602-05:002019-02-03T07:16:51.602-05:00Its obvious that a big problem in this situation, ...Its obvious that a big problem in this situation, is the fact that people don't really pay attention to what naturalness really means or what each author means by it. Its always a vague notion and people just assume other people know what they mean by it. But I think if we pay close attention, we can actually abandon useless notions of naturalness and find one useful meaning for it.<br />One Shayan javanihttps://www.blogger.com/profile/02962415306382491743noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27214300046535629792019-02-03T06:03:04.340-05:002019-02-03T06:03:04.340-05:00Pavel,
I cannot edit comments, I can only entirel...Pavel,<br /><br />I cannot edit comments, I can only entirely delete them, sorry.<br /><br />I get the impression that your notion of naturalness is different from the notion of technical naturalness that Porter is discussing. The standard model is clearly both technically unnatural and yet predictive. Your notion of naturalness seems to be what I would loosely speaking call explanatory power. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-85130697715322419232019-02-03T04:26:37.607-05:002019-02-03T04:26:37.607-05:00Dear Sabine, I have not read William's paper y...Dear Sabine, I have not read William's paper yet, but I will make a similar point re: the naturalness in my seminar in Tubingen on Tuesday. If the probability is defined in the epistemological, not ontological sense (that is, the probability quantifies a human's knowledge in light of experimental data), then the intuitive notion of naturalness is closely related, if not identical, to the Pavel Nadolskyhttps://www.blogger.com/profile/02198856112442483856noreply@blogger.com