tag:blogger.com,1999:blog-7315236707728759521.post1975496010967227182..comments2024-03-28T21:52:52.100-06:00Comments on Dispatches From Turtle Island: LUX Dark Matter Detection Experiment Gets An UpgradeAndrew Oh-Willekehttp://www.blogger.com/profile/02537151821869153861noreply@blogger.comBlogger16125tag:blogger.com,1999:blog-7315236707728759521.post-79287702167566888902016-02-01T14:22:47.584-07:002016-02-01T14:22:47.584-07:00This said, there is good reason to think that if d...<i>This said, there is good reason to think that if dark matter is the correct hypothesis that it is simply made up of particles that don't interact except via gravity with other stuff in he same universe. </i><br /><br />Wouldn't that be a description of matter tat exists on a different brane? Wouldn't the Standard Model Lagrangian (subject to corrections) be more or less the definition of our brane?Ryanhttps://www.blogger.com/profile/07906194112935320590noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-1941285333624389142016-01-31T01:45:53.567-07:002016-01-31T01:45:53.567-07:00Thanks for answering, Andrew.
1. I just discover...Thanks for answering, Andrew. <br /><br />1. I just discovered the basic ideas of the work of Laura Mersini-Houghton and she actually challenges the supposed homogeneity of the background radiation field at large scales and that's probably why Brian Green doesn't invite her to debates: she would challenge Linden and Guth. However she is not only supportive of the multiverse but also of entangled universes and of course M theory - but also quantum mechanics at its best: she's a radical factualist and that looks very promising. I have to learn more though but it seems a very good lead.<br /><br />2. Does that objection takes in consideration that we'd be dealing not with one but several parallel universes, whose gravitational effects we perceive only cumulatively (and maybe also filtered by whatever alterations the "gravitational leaking" process may cause)? Anyhow, of course there is no strict need that other universes are like ours at all except at macro-gravitational level, i.e. general organization or clumping of matter at galactic scale (don't need to be galaxies though, it may be different). <br /><br />However you claim that "no solid states of matter would be possible, only diffuse cold gas cloud like fluid structures". As the organization of matter in the parallel universes is tightly interconnected since day one (big bang or primordial inflation or whatever) that should behave similarly in all the parallel universes... unless the laws of physics (not gravitation, I guess, but maybe others) change between them.<br /><br />3. Can you explain again this objection in ways I can understand? I'm very much unfamiliar with what you say, sorry. As far as I can discern the interactions between the dark matter (and not "dark sector": dark energy would be something else, totally unrelated to what I say) and conventional matter, i.e. between the parallel universes and ours in my model, are purely gravitational. <br /><br />"Occam's Razor strongly disfavors that explanation since it isn't necessary to describe the evidence to date". <br /><br />Listen to Mersini: she argues that the data demands parallel universes, and she's only talking about the background radiation, not even dark matter as far as I can tell. IMO dark matter seems to demand also parallel universes with at least a significant degree of probability, particularly as the solidity of WIMP (and MACHO) tentative pseudo-conventional explanations become less and less likely. <br /><br />We actually should not talk about "dark matter", as nobody has ever observed it in any way, but about "dark gravity", whatever its source. This source is very possibly some sort of matter, but whatever else that alters the curvature of space-time (or emits gravitons if we go quantum) would do: that's the only constraint, there is no box. Majuhttps://www.blogger.com/profile/12369840391933337204noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-23944346479161891322016-01-30T20:07:56.070-07:002016-01-30T20:07:56.070-07:00"I know Andrew won't like this kind of th..."I know Andrew won't like this kind of thinking: parallel universes, extra dimensions, bleh! But in fact, if correct, it would allow us for the first time to get information from outside our universe via "dark matter" analysis, something unthinkable by any other conceivable means."<br /><br />You are right, and I'll explain why, but first off, I want to make clear that the general kind of ideas you are having about parallel universes such as the braneworld scenarios of string theory are mostly within the range of mainstream speculation and aren't definitively ruled out.<br /><br />This said, there is good reason to think that if dark matter is the correct hypothesis that it is simply made up of particles that don't interact except via gravity with other stuff in he same universe. Some of the key points:<br /><br />1. The very large scale structure of matter in the universe with long filaments of matter rich strands forming cells around large empty areas are exactly what you would expect from a homogeneous Big Bang with exceedingly early post-Big Bang quantum fluctuations accounting for the patterns of varied density. If there were a parallel universe without the same focal Big Bang at exactly the same time one would expect an inhomogeneous distribution of matter clumps in our own universe that wasn't spherically symmetric. In contrast, if there was a parallel universe at exactly the same time and the same place, you would expect the initial quantum fluctuations in each universe to differ producing blurred out filaments of matter rather than rather well defined narrow ones.<br /><br />2. At the galactic cluster and galaxy level, there are very significant qualitative differences between the particle interactions in the dark sector and the particle interactions in the ordinary matter sector. While there is feedback between them, ordinary matter is much, much more clumpy than dark matter, so if there are parallel universes the laws of physics and kinds of particles in the dark universe(s) is profoundly different from that found in ours. In particular, it would be essentially impossible for the dark sector to have plants, animals or rocks. No solid states of matter would be possible, only diffuse cold gas cloud like fluid structures.<br /><br />3. Another qualitative difference between our universe and any parallel dark universe is that the degrees of freedom in the dark universe have to be much smaller than in the ordinary matter universe. The entire physics of the dark matter universe as experienced in our world can be summed up with not more than three physical constants. It takes far more physical constants than that to model the gravitational effects that our world has on the dark sector.<br /><br />Parallel universes aren't strictly impossible, but Occam's Razor strongly disfavors that explanation since it isn't necessary to describe the evidence to date. andrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-14332182910441290192016-01-29T22:02:57.588-07:002016-01-29T22:02:57.588-07:00I must correct: the dark:normal matter ratio is sl...I must correct: the dark:normal matter ratio is slightly above 5:1 (not 6:1), so, considering that a small fraction of DM can perfectly be "conventional" invisible matter such as neutrinos or black holes, would make the "local multiverse" sized 6 and not 7. So forget about my previous ranting re. the 11 dimensions of M theory, unless the extra remaining dimension is needed to give curvature (curling) to the others - anyhow we do not know the exact "trans-universal" effect of gravity, so it was very speculative to begin with.<br /><br />I've found that the theory is known as "parallel dark matter" or PDM and has been floating around for many years now. It does not strictly depend on the existence of gravitons (which would need to be closed strings, what is under debate but would explain the "weakness" of gravity) but only on gravity being weak because it "leaks".<br /><br />The behavior of DM as dissociated (lagging behind) from its parent galaxy in at least one case (http://www.dailygalaxy.com/my_weblog/2015/09/unknown-nature-of-our-dark-matter-universe-could-contain-rich-physics-and-potentially-complex-behavi.html) is suggestive, as much as the Bullet Cluster but in opposite meaning, of PDM. <br /><br />One question: do we know the amount of DM in our immediate vicinity (Earth's orbit, Solar System)? I'm curious about how many potential transdimensional neighbors we may have locally, probably none, else DM would have been described earlier in one way or another, as it would affect gravitation in the Solar System itself.Majuhttps://www.blogger.com/profile/12369840391933337204noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-10594090885653257732016-01-29T15:08:42.019-07:002016-01-29T15:08:42.019-07:00I just googled for "dark matter gravitons par...I just googled for "dark matter gravitons parallel universes" and there seems to be a lot of articles on this issue. I still do not grasp all the implications but it seems that, well, DM doesn't fit cold WIMP models (it does interact with something other than just gravity but we do not know what is it yet, just that some dark matter clusters lag behind their corresponding galaxies) and that it fits well with the brane model of "closed string" gravitons and string-related hypotheses of multiverses or "folded" universe. So I found only support for what I was saying above (the lagging DM cluster could have been affected by non-gravitational interactions affecting only another universe, just as the Bullet Cluster is only affected in ours, so DM keeps going ahead).<br /><br />A related though or speculation:<br /><br />The overall ratio of DM seems to be 6:1, implying in my interpretation 7 parallel universes (including ours) in the same "multiverse cluster", maybe originated in the same Big Bang and therefore strongly entangled with each other through gravity since day one. If my maths are correct (very possibly not, I'm awful at that), this fits perfectly with the notion of 11 dimensions that M theory demands: you actually need 7 dimensions to allow for 7 parallel universes, the other four dimensions are "sliced" in each universe (the three spatial ones) and time (which may be essentially the same for all the cluster). <br /><br />Does this coincidence between the dark:normal matter ratio and the restriction on the number of strictly parallel universes in M theory somehow prove the latter? Or am I imagining things?<br /><br />And then a fundamental question:<br /><br />If gravitons do exist, how are they different from space-time itself or rather its curvature? If both explain gravity, then both must be the same or tightly related (function of each other). Thoughts?Majuhttps://www.blogger.com/profile/12369840391933337204noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-3219760224055741452016-01-28T16:29:04.264-07:002016-01-28T16:29:04.264-07:00I just realized that Wikipedia mentions by passing...I just realized that Wikipedia mentions by passing a similar hypothesis to mine, referencing <a href="http://home.cern/about/physics/extra-dimensions-gravitons-and-tiny-black-holes" rel="nofollow">the CERN</a> and T. Siegfred 1999 (but the link does not work properly and I cannot find the paper itself). So I guess I'm 17 years late for the party... but that the hypothesis has never been discarded either.Majuhttps://www.blogger.com/profile/12369840391933337204noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-61515240870093734632016-01-28T16:09:41.390-07:002016-01-28T16:09:41.390-07:00Note: when I wrote "... universes separated f...Note: when I wrote "... universes separated from us in the "curled up" "higher" dimensions but otherwise sharing space-time proper with us"... I have the impression that I'm not using the correct words, feel free to correct me.Majuhttps://www.blogger.com/profile/12369840391933337204noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-42466803953798187022016-01-28T16:06:25.537-07:002016-01-28T16:06:25.537-07:00I was rescuing that idea from my memory, so only a...I was rescuing that idea from my memory, so only after writing I realized that it is directly related with M Theory, because all other particles are "open strings", attached to our "brane" by the ends but gravitons are not (closed strings instead) and therefore they do leak all the time between universes. I knew that much from M theory but it's not consolidated knowledge, so hard to connect with other stuff, as I'm not physicists nor cosmologist at all, except in rare days. <br /><br />However until considering "dark matter" in the context of the "Bullet Cluster" (particularly the animations that show how dark matter is totally unaffected by the collision) it didn't dawn to me that it looked like dark matter was traveling in parallel spaces, rather than ours. <br /><br />So then I loosely linked it with the problem of inflation (also related to dark matter) and early galaxy formation and vague ideas about the Big Bang producing maybe many parallel universes instead of just one (there are theories out there, just not sure which one is it, my knowledge is quite fragmentary), universes separated from us in the "curled up" "higher" dimensions but otherwise sharing space-time proper with us. My idea is that, as dark matter is needed for inflation and galaxy formation, the formation of galaxies in the parallel universes should be roughly the same as in hours: variance may and should exist in detail but not in the overall structure of the universes. <br /><br />Another issue is that, per Chaos Theory, small differences in the initial conditions can and should produce large unpredictable differences in the long run. But this would probably not affect the general gravitational structure, the big scale of things, because "dark matter", being in my interpretation the "transdimensional" gravity of many universes (~6 per the estimated universal ratio but local rations may be much greater, so uncertain), would keep the structure glued. I may well be wrong on this but it should still work as basic principle of understanding on top of which to describe the local differences and ponder about the implications of the irregularity of DM distribution for the parallel universes and the multiverse set of all them, which is by virtue of all this interconnected ("only" by gravity but that's no petty matter in the big picture). <br /><br />I'm sure that someone else has described all this better than I can but I haven't really found the reference that talks of all this in a single coherent theory, so I have to use my own words and ideas.Majuhttps://www.blogger.com/profile/12369840391933337204noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-16595725881310469902016-01-28T10:35:14.290-07:002016-01-28T10:35:14.290-07:00Maju - that's called brane cosmology. I actual...Maju - that's called brane cosmology. I actually came here just now to ask Andrew how seriously he takes that as an option lol.Ryanhttps://www.blogger.com/profile/07906194112935320590noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-56539669617758017712016-01-28T02:12:36.191-07:002016-01-28T02:12:36.191-07:00I have been watching too many dark matter and othe...I have been watching too many dark matter and other cosmological mysteries documentaries in the last months and one day, when contemplating the behavior of dark matter in the Bullet Cluster, it dawned to me this hypothesis about dark matter: it behaves as it would the sum of many parallel universes, as it if it would not be "here" at all, yet it is "here" in a way only gravitons leaking between universes can. <br /><br />What if it doesn't just behave like that but actually is that?<br /><br />I know Andrew won't like this kind of thinking: parallel universes, extra dimensions, bleh! But in fact, if correct, it would allow us for the first time to get information from outside our universe via "dark matter" analysis, something unthinkable by any other conceivable means. Majuhttps://www.blogger.com/profile/12369840391933337204noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-33081439312540786862016-01-27T17:36:58.641-07:002016-01-27T17:36:58.641-07:00"Any thoughts on the "dark" globula..."Any thoughts on the "dark" globular clusters around Centaurus A?"<br /><br />No.<br /><br />Some of the bullet cluster self-interaction data is http://arxiv.org/PS_cache/arxiv/pdf/0704/0704.0261v1.pdf although I don't find the comparison to EM which must be somewhere else.andrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-1394259130344955472016-01-27T12:48:21.892-07:002016-01-27T12:48:21.892-07:00"I don't think that the Bullet Cluster ar..."I don't think that the Bullet Cluster argues against DM not forming gravitationally bound objects beyond a certain scale."<br /><br />You're right. I was thinking if the Dark Matter didn't behave like stars that had been subject to gravitational scattering then that would tell us something about their mass distribution, but that's not the case here.<br /><br />"IIRC, there is evidence in the Bullet Cluster that suggests dark matter self-interaction with a force roughly comparable in magnitude to EM."<br /><br />Interesting. If you know the source I'd be interested in reading it. I'll dig for it myself.<br /><br />Any thoughts on the "dark" globular clusters around Centaurus A?Ryanhttps://www.blogger.com/profile/07906194112935320590noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-68598866822119888612016-01-27T02:04:44.767-07:002016-01-27T02:04:44.767-07:00IIRC, there is evidence in the Bullet Cluster that...IIRC, there is evidence in the Bullet Cluster that suggests dark matter self-interaction with a force roughly comparable in magnitude to EM.<br /><br />I don't think that the Bullet Cluster argues against DM not forming gravitationally bound objects beyond a certain scale. It is huge and its collision will probably eventually form a combined two cluster system. Clusters are especially rich in inferred DM.andrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-54401062182214179572016-01-26T16:18:37.005-07:002016-01-26T16:18:37.005-07:00One of the main ways that we know that dark matter...<i>One of the main ways that we know that dark matter, if it exists, is probably not baryonic, is because it does not exhibit the scattering that it would if it was charged under EM.</i><br /><br />Right. I would think the Bullet Cluster suggests that Dark Matter (if it exists) doesn't form gravitationally bound objects past a certain scale - or if it does, those objects are uncommon or easily disrupted. Though the microlensing searches for MACHOs suggests that too I guess. Obviously electromagnetism is essential to star formation for baryonic matter, but I think that's an additional constraint against something like electromagnetism.<br /><br />How about the Pauli exclusion principle? Could dark matter become trapped in compact objects?Ryanhttps://www.blogger.com/profile/07906194112935320590noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-34254356874010521922016-01-26T14:15:29.018-07:002016-01-26T14:15:29.018-07:00You could probably discern electromagnetism becaus...You could probably discern electromagnetism because it would affect the cross-section of interaction of non-dark matter with itself and would affect, for example, the scattering of interstellar gas. You might not get the form of the force law right, but it would probably be discernible in some respect.<br /><br />One of the main ways that we know that dark matter, if it exists, is probably not baryonic, is because it does not exhibit the scattering that it would if it was charged under EM.andrewhttps://www.blogger.com/profile/08172964121659914379noreply@blogger.comtag:blogger.com,1999:blog-7315236707728759521.post-17770229840607035982016-01-25T20:03:23.393-07:002016-01-25T20:03:23.393-07:00This doesn't mean that the dark sector is real...<i>This doesn't mean that the dark sector is really that simple if it exists (e.g. no one could guess from astronomy data alone, that there were second and third generation fermions, that there were W or Z bosons, that there were eight different kinds of gluons, or that protons and neutrons were composite particles), but it does mean that the dominant particle content of a dark sector must be very simple.</i><br /><br />Suppose you were living in a dark sector universe, trying to figure out the laws if our universe just through the effects of gravity, how much do you think one could figure out? Do you think the basics of electromagnetism would be within someone's reach? And would electromagnetism be relevant enough to have an effect on the overall structure we observe (ie through its effects on intergalactic and intragalactic gas clouds)?Ryanhttps://www.blogger.com/profile/07906194112935320590noreply@blogger.com