tag:blogger.com,1999:blog-22973357.post890591841977154100..comments2021-04-19T12:32:15.583-04:00Comments on Sabine Hossenfelder: Backreaction: Schrödinger meets NewtonSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger29125tag:blogger.com,1999:blog-22973357.post-42062342621849540542012-04-24T07:47:11.915-04:002012-04-24T07:47:11.915-04:00Sigh, the realm where the only physical thing is t...Sigh, the realm where the only physical thing is the S-matrix....Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-86690211856084025442012-04-24T00:39:42.697-04:002012-04-24T00:39:42.697-04:00Dear Arun,
Well, it's quantum mechanics, it d...Dear Arun,<br /><br />Well, it's quantum mechanics, it doesn't actually include interactions. You can either make a mean field approximation for the background and end up with the Schroedinger equation with a gravitational potential for the background. Or you include additional graviton-interactions, for which you need the perturbative quantization. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-46369576636832611412012-04-23T13:11:16.287-04:002012-04-23T13:11:16.287-04:00Dear Bee,
So what would the Schrodinger equation ...Dear Bee,<br /><br />So what would the Schrodinger equation (non-relativistic, but with quantum source) look like when taking the appropriate limit of the naive perturbative quantization of gravity?<br /><br />The small metric perturbations should presumably all wind up in the potential term of the Schrodinger equation. How the metric dynamically changes because of the quantum source is less Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-38772280889836587172012-04-23T11:01:55.840-04:002012-04-23T11:01:55.840-04:00Philip, please, that was addressed to you too: It&...Philip, please, that was addressed to you too: It's off-topic. If you want to discuss Robert's theory of something or other, please do it elsewhere. Thanks,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-50865498837473861182012-04-23T07:28:55.722-04:002012-04-23T07:28:55.722-04:00@RLO:
Let me quote from the abstract of your pape...@RLO:<br /><br />Let me quote from the abstract of your paper (in a refereed journal, by the way): "Two definitive predictions are also pointed out: (1) the model predicts that the electron will be found to have structure with radius of about 4 x 10 to the -17th cm".<br /><br />This is a definitive prediction (your words) which has been experimentally ruled out. End of story.<br /><br Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-41557020211189462372012-04-22T11:08:57.527-04:002012-04-22T11:08:57.527-04:00Dear Arun,
No, that's not what it means.
Th...Dear Arun,<br /><br />No, that's not what it means. <br /><br />There's a perfectly fine non-relativistic limit as long as the background curvature remains small because then you can use the "naive" perturbative quantization of gravity as an effective theory. That should cover everything we can plausibly observe on Earth, including interfering molecules. The effect described Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56432125999044103762012-04-22T10:49:49.757-04:002012-04-22T10:49:49.757-04:00Dear Bee,
Does this mean that whatever the real ...Dear Bee, <br /><br />Does this mean that whatever the real theory of quantum gravity is, it has no meaningful limit where there is a non-relativistic quantum source of gravity?Arunhttps://www.blogger.com/profile/03451666670728177970noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-77945282600481763502012-04-20T19:14:52.407-04:002012-04-20T19:14:52.407-04:00Thanks Bee and Jim.
That should teach me to not j...Thanks Bee and Jim.<br /><br />That should teach me to not jump the preliminar section.Marcoshttps://www.blogger.com/profile/11822417314224471848noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-24295183549205084302012-04-20T16:20:26.440-04:002012-04-20T16:20:26.440-04:00Matti: The above equations are for a single parti...Matti: The above equations are for a single particle. The appearance of probability density playing the role of gravitational mass density here comes from the assumption that the expectation value of the stress-energy tensor couples to gravity:<br /><T00>=<psi|mdelta(x-x')|psi>=m|psi|^2<br /><br />Marcos: Weinberg has previously investigated the possibility of a nonlinear Jimhttps://www.blogger.com/profile/06253172808198955308noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27904608344222251992012-04-20T13:54:57.017-04:002012-04-20T13:54:57.017-04:00Oops, there should be expectation value of Phi bef...Oops, there should be expectation value of Phi before "instead of Phi". My hope to write here without using codes of symbols is destroyed :'(Fizeghttps://www.blogger.com/profile/16004276374246182173noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-20201716090746313132012-04-20T13:51:57.586-04:002012-04-20T13:51:57.586-04:00By the way, there is huge difference between the s...By the way, there is huge difference between the semiclassical gravity and these SN equations. In semiclassical gravity the source is quantum field and in SN equations it is one particle. And while equations on expectation value of this field (and we talk then not about one particle but about quantum soup of particles) quite possibly take this form (I have serious doubts without honest Fizeghttps://www.blogger.com/profile/16004276374246182173noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-42862780800940682692012-04-20T11:27:32.922-04:002012-04-20T11:27:32.922-04:00Hi!
Great blog, I can't say the same about th...Hi!<br /><br />Great blog, I can't say the same about the papers in question.<br /><br />I think there's quite easy way to see that there are problems with their credibility. We can in some situations consider electromagnetic field in the same semiclassical way, however nobody (at least as far as I know) perform absolutely the same calculations with electric potential instead of Fizeghttps://www.blogger.com/profile/16004276374246182173noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-63314279211114020682012-04-20T10:36:48.798-04:002012-04-20T10:36:48.798-04:00Well, as I wrote in my earlier post, there are goo...Well, as I wrote in <a href="http://backreaction.blogspot.de/2012/01/real-thought-experiment-that-shows.html" rel="nofollow">my earlier post</a>, there are good reasons to think the SN equation doesn't actually make sense. In any case, the Schroedinger equation is normally linear, in case that's what you're asking. The SN equation is a non-linear modification and is, as I wrote, in Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-53434278610147201602012-04-20T10:32:37.339-04:002012-04-20T10:32:37.339-04:00Does it even makes sense to use Quantum Mechanics ...Does it even makes sense to use Quantum Mechanics with a non-linear Schrödinger equation? Is there a non-linear version of it? (Yep, I don't know that much of physics)<br /><br />I mean, if the equation is non-linear, how can you reach conclusions like that the wave packet tends to spread?Marcoshttps://www.blogger.com/profile/11822417314224471848noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-51313542615439884252012-04-20T10:32:01.692-04:002012-04-20T10:32:01.692-04:00Robert: If you have anything scientific to say, wr...Robert: If you have anything scientific to say, write a paper, publish it, win a Nobel prize. Good luck. All further off-topic comments will be deleted. Have a nice weekend,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-17215759068839171902012-04-20T10:26:54.912-04:002012-04-20T10:26:54.912-04:00Bee,
And you continue to completely ignore the di...Bee,<br /><br />And you continue to completely ignore the distinction of:<br /><br />1. WITHIN BOUND atomic systems<br /><br />2. BETWEEN UNBOUND atomic systems<br /><br />Only #2 has been measured and this this measurement is not relevant to what I am talking about, as I have explained before several times and in several places.<br /><br />Helbig,<br /><br />I have answered your misleading Robert L. Oldershawhttps://www.blogger.com/profile/15396555790655312393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-29555709002272611822012-04-20T09:37:47.713-04:002012-04-20T09:37:47.713-04:00Hi Bee,
In a "phenomenological way" cou...Hi Bee,<br /><br />In a "phenomenological way" could you apply what you are saying to "something real" so as to get a sense of the meeting other then the way yo are saying it is taking place?<br /><br />So I guess the <a href="http://backreaction.blogspot.com/2012/01/real-thought-experiment-that-shows.html?showComment=1327325648328#c7753835943424367356" rel="nofollow">The<br /PlatoHagelhttps://www.blogger.com/profile/00849253658526056393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1439701311536095522012-04-20T06:33:08.379-04:002012-04-20T06:33:08.379-04:00Hi Bee,
Thanks for a nice piece outlining the fea...Hi Bee,<br /><br />Thanks for a nice piece outlining the features and virtues of an equation regarding an approach I wasn’t familiar with before. I find this particularly interesting as I think you’re aware I like this idea of looking at the older concepts to consider what elements of them might be fundamental and those which can be discarded, as I find that’s how truly meaningful physics so Phil Warnellhttps://www.blogger.com/profile/15671311338712852659noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-30405309430681907962012-04-20T05:44:19.877-04:002012-04-20T05:44:19.877-04:00I realized that the proposed equations cannot desc...I realized that the proposed equations cannot describe single particle. It does not make sense to assume that a solution of Schrodinger equation -in this case non-linear - describes something behaving like classical distribution of matter which is many particle state. <br /><br />The equations could however describe order parameter for many particle system such as condensate of Cooper pairs.Matti Pitkänenhttps://www.blogger.com/profile/13512912323574611883noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-78943389468924432562012-04-20T03:17:10.883-04:002012-04-20T03:17:10.883-04:00Also note that RLO predicted substructure for the ...Also note that RLO predicted substructure for the electron at a level well above that which is now routinely probed. This falsification of a "definitive prediction" of his theory hasn't stopped him from peddling said theory. What use is a "definitive prediction" then?Phillip Helbighttps://www.blogger.com/profile/12067585245603436809noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-47353640349808922732012-04-20T01:17:29.709-04:002012-04-20T01:17:29.709-04:00Robert,
You do not only repeat yourself, you also...Robert,<br /><br />You do not only repeat yourself, you also continue to ignore my reply. Particle collisions are now routinely testing interactions down to a thousands of a fermi, that's well below any subatomic distances. No deviation from the standard model has been found, the gravitational interaction has not played any role. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-56684111860096792512012-04-19T21:19:38.513-04:002012-04-19T21:19:38.513-04:00With sincere apologies for repeating myself, but I...With sincere apologies for repeating myself, but I am hoping that open-minded readers will please consider the following argument.<br /><br />Whenever someone states, as if it were a fact, that 'gravitational interactions within the atom are weak', I feel that it is scientifcally required of me to point out that this is decidedly an untested assumption.<br /><br />The value of G has neverRobert L. Oldershawhttps://www.blogger.com/profile/15396555790655312393noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-28965633646362627582012-04-19T15:13:30.381-04:002012-04-19T15:13:30.381-04:00arxiv:1105.1579 "by solving Eq. (3) with the...arxiv:1105.1579 "<i>by solving Eq. (3) with the Green's function</i>" Physical chirality is excluded. "<i>sigma = 4.4x10^(-9) m ...mass is given in units of 3.33x10^(-17) kg (2x10^10 u)</i>" <br /><br />4.47 nm diameter is 4.68x10^(-26) m^3. One vaccinia virus masses 9.5x10^(-18) kg in 2.5x10^(-25) m^3. That looks like 3.5 vaccinia viruses in the volume of 0.187 Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12100221584662728592012-04-19T09:27:18.583-04:002012-04-19T09:27:18.583-04:00Hi Bee,
Sure, I've scanned the articles, but I...Hi Bee,<br />Sure, I've scanned the articles, but I have an exam on condensed matter physics coming up tomorrow, so a thourough read will have to wait :) I am originally from a place close to Maastricht (actually quite close to Aachen, which you probably know). At the moment I'm living in Eindhoven, where I study applied physics. Next year (or the year after that) I'll be going to theErikhttps://www.blogger.com/profile/14629571445007334997noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25824102443574736512012-04-19T06:11:37.008-04:002012-04-19T06:11:37.008-04:00Danke, oh Georg, ein Loch war im Eimer. I've f...Danke, oh Georg, ein Loch war im Eimer. I've fixed that.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.com