tag:blogger.com,1999:blog-22973357.post4781683284200391509..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: The origin of mass. Or, the pion’s PR problem.Sabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger30125tag:blogger.com,1999:blog-22973357.post-72085809921639392012015-08-25T00:09:54.391-04:002015-08-25T00:09:54.391-04:00kashyap,
First, I didn't say there's anyt...kashyap,<br /><br />First, I didn't say there's anything new about nonlinear sigma model, I said the new thing is that we might be able to find a way to measure details of the chiral phase transition. Besides this though you didn't understand my answer, so let me try it again. It's an effective model. It's an approximation that is valid in the limit used. Yes, that simplifies Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-35664793621617204582015-08-24T14:14:20.442-04:002015-08-24T14:14:20.442-04:00Hi Bee,
My complaint is that in old days, before k...Hi Bee,<br />My complaint is that in old days, before knowing about quarks and gluons, people used to talk about nuclear forces coming from pion exchanges etc.I suppose they are assuming quark gluon condensate as pions to simplify the calculation. But as a fundamental theory of masses, it does not impress me. There are already numerical lattice gauge calculations which reproduce masses of many kashyap vasavadahttps://www.blogger.com/profile/10732897306667764590noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-29808625623986164222015-08-24T10:29:32.627-04:002015-08-24T10:29:32.627-04:00Kashyap,
It's an effective model. It's a ...Kashyap,<br /><br />It's an effective model. It's a low energy approximation to QCD. I don't understand your comment. It *is* quarks and gluons, just in a simpler description, roughly speaking. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-85783964535612753712015-08-24T09:39:13.640-04:002015-08-24T09:39:13.640-04:00Hi Bee,
Pion model may be ok as a temporary interm...Hi Bee,<br />Pion model may be ok as a temporary intermediate model, but as a fundamental theory of masses it is going backwards.We already know about quarks and gluons.So in principle, everything should be explained in terms of quarks and gluons.What is your thought on this?kashyap vasavadahttps://www.blogger.com/profile/10732897306667764590noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-8844300086931836312015-08-23T20:06:13.113-04:002015-08-23T20:06:13.113-04:00http://hyperphysics.phy-astr.gsu.edu/hbase/particl...http://hyperphysics.phy-astr.gsu.edu/hbase/particles/haddia.html<br /> It is like turning one baseball bat from a whole 20-foot tree trunk. Sawdust.<br />http://www.curtismeyer.com/material/lecture.pdf<br /> If this was designed by a supreme being, and it was hired, Personnel needs a performance review.<br /><br />Until somebody has a better way to fill the Periodic Table, I suppose we'Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12286118975353834472015-08-23T11:56:51.090-04:002015-08-23T11:56:51.090-04:00Any book on lattice gauge theories, e.g., that by ...Any book on lattice gauge theories, e.g., that by Mike Creutz.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-71420099137371675172015-08-23T11:54:46.398-04:002015-08-23T11:54:46.398-04:00Most reviews on lattice gauge theories (like Mike ...Most reviews on lattice gauge theories (like Mike Creutz' book) discuss it.<br /><br />I wrote a second version of this comment, because I had trouble publishing the first (entirely my fault).Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-35548388738793018322015-08-23T11:52:19.387-04:002015-08-23T11:52:19.387-04:00Bee,
Thanks for presenting this. I often shock my...Bee,<br /><br />Thanks for presenting this. I often shock my nonscientist friends when I tell them most of the mass in the Universe is not from the Higgs.<br /><br />Having said that, there are limits to your statement. The quark-antiquark-condensate mechanism gives masses only for low-lying baryons (which make up most of the mass in the Universe), but not other strongly-interacting particles. ByAnonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-53658576429916928242015-08-23T11:48:22.930-04:002015-08-23T11:48:22.930-04:00Hi Peter,
Interesting, thanks, I didn't know ...Hi Peter,<br /><br />Interesting, thanks, I didn't know this! Do you have some reference where I could read up on this? Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59102255672811452472015-08-23T11:45:40.480-04:002015-08-23T11:45:40.480-04:00Hi Bee,
I hope I'm not out of line pointing o...Hi Bee,<br /><br />I hope I'm not out of line pointing out a subtlety in your discussion. The masses of the low-lying baryons can be understood as generated from the quark-antiquark condensate, in an effective description (sorry for my inelegant statement, which you summarized more clearly). While this accounts for most of the mass of the visible universe, the masses of heavy hadrons are not Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-22973357.post-81601286523873263072015-08-22T11:06:47.664-04:002015-08-22T11:06:47.664-04:00Jim,
As Sky pointed out in a comment above, you&#...Jim,<br /><br />As Sky pointed out in a comment above, you're mistaken in thinking that the pions (the particles) increase the mass of the nucleons. Note how carefully I vaguely said they "generate" it. The pion plays the same role as the Higgs particle (they are both bosons). The particle is an excitation over a background, but it's the (coupling to the) background (the Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24681873371226979942015-08-22T10:54:03.417-04:002015-08-22T10:54:03.417-04:00Nicolas,
Thanks for the reference, but I don'...Nicolas,<br /><br />Thanks for the reference, but I don't know the paper. First thing that comes to my mind is that pions are unstable, so not sure how this should work, but I'll have a look at this. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-22103735257880425512015-08-22T10:09:57.419-04:002015-08-22T10:09:57.419-04:00I didn't (mean to) imply the mass came from th...I didn't (mean to) imply the mass came from the valence quarks, I said my impression was the gluons cause an 'increase in the mass of nucleons from the constituent valence quarks,' corresponding with what you said.<br /><br />I thought pions were associated with the interactions between nucleons, while the gluons were associated with what held the hadrons together, and therefore <i>Anonymoushttps://www.blogger.com/profile/00999773798988643699noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-7677602501892290862015-08-22T08:19:35.802-04:002015-08-22T08:19:35.802-04:00Sabine what do you think of the idea that dark mat...Sabine what do you think of the idea that dark matter could be composed of pions: The SIMP Miracle (arXiv: 1402.5143) that has been accepted in Physical Review Letters.Nicolas Pouparthttps://www.blogger.com/profile/17722878242014554884noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1938929774636202482015-08-22T02:28:49.993-04:002015-08-22T02:28:49.993-04:00Jim,
No, the increased masses of the nucleons do ...Jim,<br /><br />No, the increased masses of the nucleons do not come from the masses of the valence quarks, that's the whole point, they come from the quark condensate. It's an effective model, and "effective" here isn't just a word but a technical term: There are no quarks and gluons in this description, instead there are pions and nucleons. They are fundamentally composed Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-48026017154594220042015-08-22T02:21:34.208-04:002015-08-22T02:21:34.208-04:00Sky,
I didn't want to make it more confusing ...Sky,<br /><br />I didn't want to make it more confusing as it is already. The pion gives rise to masses of nucleons as much or as little as the Higgs boson (!) gives rise to masses of quarks. You're right of course in that it's not the particle that is relevant, but the condensate (which I did mention). Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-16468542854132428132015-08-22T02:18:51.089-04:002015-08-22T02:18:51.089-04:00JimV,
Thanks for pointing it out, I've fixed ...JimV,<br /><br />Thanks for pointing it out, I've fixed that typo.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-19117031894066978762015-08-22T02:18:22.995-04:002015-08-22T02:18:22.995-04:00Wolbi,
I didn't say nothing can be calculated...Wolbi,<br /><br />I didn't say nothing can be calculated... Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-59701288681780388752015-08-21T21:01:19.833-04:002015-08-21T21:01:19.833-04:00Hi, I sort of wish you would refer to it as pion c...Hi, I sort of wish you would refer to it as pion condensate rather than just pions. Saying pions are responsible for mass of nucleons is technically correct, but it makes it sound like the nucleon mass is just mass of quarks + mass of pions which it is not. The pion condensate is the order parameter for chiral symmetry and when it goes to zero at high temperatures, the mass of nucleons disappear. Anonymoushttps://www.blogger.com/profile/13261699392174423329noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44081323515123634282015-08-21T18:12:59.178-04:002015-08-21T18:12:59.178-04:00Normally I would identify the pions with a decreas...Normally I would identify the pions with a decrease in the mass of a nucleus from the constituent nucleons, and the gluons with the increase in the mass of nucleons from the constituent valence quarks. <br /><br />It seems here you are implying the proton and neutron have increased masses from the sum of the masses of the constituent valence quarks not due to gluons or the fundamental degrees of Anonymoushttps://www.blogger.com/profile/00999773798988643699noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-57168512987421503042015-08-21T18:12:43.924-04:002015-08-21T18:12:43.924-04:00I think the statement:
"But at low energies, ...I think the statement:<br />"But at low energies, such as close by chiral symmetry breaking, little can be calculated from first principles. Instead, one works on the level of effective models, such as that based on pions and nucleons rather than quarks and gluons."<br />does not do justice to the results by lattice QCD: it can nowadays handle realistic pion masses, and it does provide wolbihttps://www.blogger.com/profile/10090706340303265150noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-50676056364648090432015-08-21T14:39:43.901-04:002015-08-21T14:39:43.901-04:00This is the first time I saw someone say that the ...This is the first time I saw someone say that the pion is the Higgs boson of hadronic mass. Usually they just talk vaguely about QCD. Kudos to Sabine for highlighting the real God particle. Mitchellhttps://www.blogger.com/profile/10768655514143252049noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-41507957920435288622015-08-21T13:19:02.806-04:002015-08-21T13:19:02.806-04:00I think "... a fruitful research direction ab...I think "... a fruitful research direction about which we will here more in the future" should be "... a fruitful research direction about which we will hear more in the future" ("here" should be "hear"). JimVhttps://www.blogger.com/profile/10198704789965278981noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1290497582688926002015-08-21T11:45:01.471-04:002015-08-21T11:45:01.471-04:00arXiv:1504.02175, "3×10^14 T" 10^10 T is...arXiv:1504.02175, "<i>3×10^14 T</i>" 10^10 T is 4×10^25 J/m^3, E/c^2 = 445,000 g/cm^3. u_B = (B^2)/2μ_o, 3×10^14 T, ~twice nuclear density. Vacuum birefringence arXiv:1212.1897 Footnotes become important.<br /><br />"<i>For me chirality has always been the most puzzling aspect of the standard model. It’s just so uncalled for.</i>" First observation, then theory. "<i>Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-80206869326945056142015-08-21T10:43:08.957-04:002015-08-21T10:43:08.957-04:00Right. Well, I did say that it's not an exact ...Right. Well, I did say that it's not an exact symmetry due to the small quark masses.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.com