tag:blogger.com,1999:blog-22973357.post2494861370375581931..comments2019-03-21T01:04:31.382-04:00Comments on Backreaction: No, negative masses have not revolutionized cosmologySabine Hossenfelderhttps://plus.google.com/111136225362929878171noreply@blogger.comBlogger123125tag:blogger.com,1999:blog-22973357.post-71034969052883131522018-12-25T03:40:20.548-05:002018-12-25T03:40:20.548-05:00"Please correct me if I am wrong"
"..."Please correct me if I am wrong"<br /><br />"4-dimensional space-time" -<br /><br />The mistake is in this part of the wording, for example. We know the properties of 4-dimensional models from mathematics, and we do not observe these properties in reality. If we observe the properties of another model, then we must use the mathematical writing of this model. The diagnosis is Anatol Sevashkohttps://www.blogger.com/profile/14658939824936548070noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-42460862574886700572018-12-25T02:35:43.581-05:002018-12-25T02:35:43.581-05:00and if you try to define "anti-geodesic"...and if you try to define "anti-geodesic" <a href="https://arxiv.org/abs/0807.2838" rel="nofollow">that's what you get</a>Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-27164591305540371202018-12-24T23:35:22.392-05:002018-12-24T23:35:22.392-05:00In Einstein's GRT the motion of a small positi...In Einstein's GRT the motion of a small positive mass point test particle is ruled by the geodesic equation in curved 4-dimensional space-time. But what I believe I have learned from my friend and GRT expert Heinz Dehnen (Ret. U. Konstanz),the motion of a small negative mass point test particle would be ruled by an anti-geodesic, which together with geodesics is not possible in a Riemannian Unknownhttps://www.blogger.com/profile/01830984381732921837noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-82658800461105110912018-12-16T08:40:00.990-05:002018-12-16T08:40:00.990-05:00@Axil: it was meant as a joke, hence the ;-) Yeah,...@Axil: it was meant as a joke, hence the ;-) Yeah, I know, everyone tells me my jokes are not funny. I should stop trying to make them.<br /><br />As Sabine has noted, GR says nothing about things like quarks, photons, atoms, even fluids (liquids and gases) and dust. In the everyday sense of those words. However, both fluid and dust are used in GR, where they have quite narrow meanings; there’s aJeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-43960142695914657622018-12-16T01:20:11.566-05:002018-12-16T01:20:11.566-05:00Axil,
A superfluid does not form by "a proce...Axil,<br /><br />A superfluid does not form by "a process of quantum mechanical entanglement with photons, plasmons, and phonons in which cold plasma forms". To begin with a superfluid isn't a plasma. Also, it doesn't come about by entanglement with photons. Plasmons and phonons are quasi particles, the latter of which can exist once a superfluid has formed, but it does not Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-61547550820923791492018-12-16T00:45:24.239-05:002018-12-16T00:45:24.239-05:00I observe "dark" phenomena in my mathema...I observe "dark" phenomena in my mathematical model. "Dark" phenomena exist, but the "dark" name is unfortunate is no good for combine all the properties of these phenomena.<br /><br />Math GR is not perfect. Mathematics GR is not a criterion of truth.<br /><br />The error of the article under discussion, the error of your criticism, the error of GR and the correct Anatol Sevashkohttps://www.blogger.com/profile/14658939824936548070noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-28531998314060373462018-12-15T15:00:35.317-05:002018-12-15T15:00:35.317-05:00@ JeanTate
Dust and gas can be transformed into ...@ JeanTate<br /><br /><br />Dust and gas can be transformed into a Super fluid by a process of quantum mechanical entanglement with photons, plasmons, and phonons in which cold plasma forms. This Bose Einstein condensate can extend for cosmological distances and fill up the space in and between galaxies. This condensate can exist in a “Dark” state where it absorbs energy and does not radiate any Axilhttps://www.blogger.com/profile/07190120527431077518noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-57265298717473432072018-12-15T09:01:41.352-05:002018-12-15T09:01:41.352-05:00Thanks again Sabine.
So it's a "fluid&qu...Thanks again Sabine.<br /><br />So it's a "fluid", but not "dust" ;-)<br /><br />Maybe one day someone will write a microscopic theory of DM, one that does not depend on the Standard Model ... perhaps they will also develop a microscopic model of Farnes' negative mass fluid, one that likewise does not depend on the Standard Model.<br /><br />Apart from the fact that JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-40116646151583684412018-12-15T01:33:48.713-05:002018-12-15T01:33:48.713-05:00Jean,
When cosmologists speak of "fluids&quo...Jean,<br /><br />When cosmologists speak of "fluids" they normally mean this as an effective bulk description of a collection of particles (I know it's confusing, but a fluid can be a gas). In principle this particle could be detected, but whether or not that's possible depends on how strong the interaction is. If it interacts very rarely, it might take a million years to catch Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-11527980884779614452018-12-14T23:15:45.626-05:002018-12-14T23:15:45.626-05:00Thanks Sabine.
Farnes, in his paper, does not con...Thanks Sabine.<br /><br />Farnes, in his paper, does not consider whether any negative mass can be in the form of particles (it’s a “fluid”). Just like in astrophysics, DM is not necessarily made of particles.<br /><br />But suppose, just suppose, that Farnes’ negative mass fluid could be made of particles, what could we say about them, other than they have negative mass?<br /><br />Just like DM JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-12375361938642496342018-12-14T11:19:28.915-05:002018-12-14T11:19:28.915-05:00@Axil,
A black hole sitting in a space with a con...@Axil,<br /><br />A black hole sitting in a space with a constant vacuum energy density might at first blush be thought to increase mass by frame dragging all this vacuum energy into it. That would in many ways be very troubling. However the condition that pressure p = wρ, for ρ the vacuum energy density and with w = -1, means the net energy gain by a black hole sitting in space is zero. This is Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72673553083157677942018-12-14T06:23:47.104-05:002018-12-14T06:23:47.104-05:00Axil,
What you say about black hole evaporation i...Axil,<br /><br />What you say about black hole evaporation is wrong back to front. I will not approve further comments of yours if you continue to spread such ill-informed statements.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-53190932803535547202018-12-14T03:48:51.555-05:002018-12-14T03:48:51.555-05:00@Peter Donis
I don’t understand why it is assumed...@Peter Donis<br /><br />I don’t understand why it is assumed that black holes evaporate. Most of the energy that they absorb from Hawking radiation comes in the form of photon pairs. The negative energy photon is a just like a positive energy photon except it has a negative frequency. Its mass is the same as the positive energy photon. Any black hole get bigger as time goes on as it extracts Axilhttps://www.blogger.com/profile/07190120527431077518noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-23398914904415663642018-12-14T02:33:47.940-05:002018-12-14T02:33:47.940-05:00@Sabine:
if you know the constant is constant you...@Sabine:<br /><br /><i>if you know the constant is constant you can solve the equation right away</i><br /><br />Yes, I see that, but in the proposed model where "negative mass" is supposed to act like a negative cosmological constant, the density of "negative mass" is not necessarily constant, is it? If it isn't, then there are dynamics that need to be solved, and I don&#Peter Donishttps://www.blogger.com/profile/09122769947782402203noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2568966597610766432018-12-13T10:47:50.833-05:002018-12-13T10:47:50.833-05:00JeanTate:
"I would like to ask what is perha...JeanTate:<br /><br />"<i>I would like to ask what is perhaps a very silly question. ...</i>"<br /><br />Actually that's a very good question. <br /><br />We can't find the Unicorns because the Faeries are hiding them.<br /><br />sean s.sean s.https://www.blogger.com/profile/04190153587965701495noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-10967840749809847022018-12-13T10:47:14.979-05:002018-12-13T10:47:14.979-05:00Jean,
No experiment has ever seen evidence of neg...Jean,<br /><br />No experiment has ever seen evidence of negative masses of any kind, at least not of the fundamental kind. There is something called a "negative effective mass" in condensed matter systems, which is (loosely speaking) defined relative to a background medium and is not indeed negative. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-89350935315083637002018-12-13T07:41:43.091-05:002018-12-13T07:41:43.091-05:00I would like to ask what is perhaps a very silly q...I would like to ask what is perhaps a very silly question.<br /><br />Has any lab experiment, done here on Earth, ever found any hint of negative inertial mass? of negative active gravitational mass? of negative passive gravitational mass?<br /><br />How about outside the lab, any hint of any of these three forms of negative mass from studying rocks, air, water, cosmic rays, etc?<br /><br />What JeanTatehttps://www.blogger.com/profile/08737430572613792118noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33591618146209948402018-12-13T06:37:09.773-05:002018-12-13T06:37:09.773-05:00Bee wrote something I thought of writing and am go...Bee wrote something I thought of writing and am going to comment a bit in agreement. The Einstein field equation tells us that the traceless part of the Ricci tensor R_{ab} - 1/2Rg_{ab} equals the stress-energy tensor times a very small coupling constant 8πG/c^4 T_{ab}. To make things a bit confusing Einstein found that his equations predicted the universe, then thought to be just the Milky Way Lawrence Crowellhttps://www.blogger.com/profile/12090839464038445335noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-22694663626010916582018-12-13T06:05:53.427-05:002018-12-13T06:05:53.427-05:00But it is still unclear what exactly he means when...But it is still unclear what exactly he means when he says that constant negative mass density is similar to negative cosmological constant. He uses the first Friedman equation, but I don't see how he can claim that. And from the second equation it is obvious that negative mass density is similar to a positive cosmological constant.Space Timehttps://www.blogger.com/profile/06098439870046873701noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-30659066823830798142018-12-13T02:56:05.111-05:002018-12-13T02:56:05.111-05:00Peter,
It's debatable whether a cosmological ...Peter,<br /><br />It's debatable whether a cosmological constant counts as source or not, but imo it's not a very useful debate. What I meant to say is that if you know the constant is constant you can solve the equation right away.<br /><br /><i>"I also don't see energy conservation being used in lieu of the second Friedmann equation; it seems to me that one would still need to Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-85524052764594097282018-12-13T02:25:29.215-05:002018-12-13T02:25:29.215-05:00Sabine,
Regarding the Friedmann equations, you do...Sabine,<br /><br /><i>Regarding the Friedmann equations, you don't need the 2nd Friedmann equation if you use energy conservation instead, or if you don't have sources to begin with (which is the case in section 2.3.3.).</i><br /><br />In section 2.3.3 there is a nonzero density of negative mass, which is claimed to be equivalent to a negative cosmological constant. I don't see how Peter Donishttps://www.blogger.com/profile/09122769947782402203noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-55648879585351188972018-12-12T15:02:09.353-05:002018-12-12T15:02:09.353-05:00I'm just an average Joe construction worker re...I'm just an average Joe construction worker reading through this discussion. I must say this is over my head but I find it fascinating and I wish I understood more of it. I have been interested in the concept of this elusive matter and energy but that's as far as it goes. I was wondering how time fits into the picture. In my mind time is created by matter. If time does not exist at all Unknownhttps://www.blogger.com/profile/06065157059308361670noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-87382379150002698032018-12-12T11:41:04.324-05:002018-12-12T11:41:04.324-05:00I've read more of Jamie Farne's paper, whi...I've read more of Jamie Farne's paper, which has a clarity of language which makes it a rather enjoyable read. In the sections that I've read there's no mention of any (EM) radiation coupling between this negative-energy matter and our normal, positive-energy matter, though it's possible I overlooked an area where he addresses that. Now, the simplest extrapolation of the David Schroederhttps://www.blogger.com/profile/18048116250413347228noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-66824026448547888672018-12-12T08:47:23.294-05:002018-12-12T08:47:23.294-05:00"The AdS vacuum ..."
is your answer rela..."The AdS vacuum ..."<br />is your answer related to my own question or to the question of sbd else ? Frederic henry-couannierhttps://www.blogger.com/profile/13933350696243790692noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-90677999252860116442018-12-12T00:58:52.304-05:002018-12-12T00:58:52.304-05:00Brad,
The gravitational field for a black hole in...Brad,<br /><br />The gravitational field for a black hole in GR is a vacuum solution. (That's because the singularity is not part of space-time.) The mass is an integration parameter. You can chose it to be a negative number, if you wish, no problem. But the resulting space-time is no longer a black hole. It would repel all normally gravitating masses, including light, hence no horizon. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.com