tag:blogger.com,1999:blog-2846514233477399562.post6112556890591000275..comments2024-01-08T09:37:04.406+01:00Comments on RÉSONAANCES: Weekend Plot: axing axionsJesterhttp://www.blogger.com/profile/08947218566941608850noreply@blogger.comBlogger24125tag:blogger.com,1999:blog-2846514233477399562.post-60179611711717244682014-03-29T22:14:38.054+01:002014-03-29T22:14:38.054+01:00Just to reply to this, our conclusions are not in ...Just to reply to this, our conclusions are not in conflict with Fox et al. While there is an overall variance of the misalignment angle when f>H, it is still possible for the misalignment to be less than this in a particular horizon volume post inflation. This always allows you to tune the actual contribution to the dark matter down and avoid the isocurvature constraint, but you need a double fine tuning. Not only is the misalignment small, but you are also in an atypical Hubble patch. This is consistent with Hertzberg et al and the anthropic axion window, to my knowledge. I understand that Fox et al use the variance as a minimum displacement and don't allow this additional tuning. Of course, as Gondolo and Visinelli point out, if f is really huge, much super-Planckian, then you can get around that, but no one wants super-Planckian f, do they :)<br />Tories Smellhttps://www.blogger.com/profile/15622660682213487917noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-65431241553733329642014-03-27T07:40:29.173+01:002014-03-27T07:40:29.173+01:00no:)no:)Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-51454871019655588152014-03-27T00:47:38.205+01:002014-03-27T00:47:38.205+01:00OK, so it's like this ... either we kill strin...OK, so it's like this ... either we kill string theory by keeping r around 0.2 as observed ... or we kill LCDM by bringing r down and letting A_L go above 1. Yes? Marni Dee Sheppeardhttps://www.blogger.com/profile/08188528831432604162noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-79448333762122841582014-03-26T23:27:09.638+01:002014-03-26T23:27:09.638+01:00It seems their upper limit is 10^-5 eV: http://www...It seems their upper limit is 10^-5 eV: http://www.phys.washington.edu/groups/admx/images/admxboundary.jpg<br />We need a bigger cavity. Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-27032816961840976672014-03-26T22:32:11.399+01:002014-03-26T22:32:11.399+01:00Anyone know if ADMX can be made sensitive down to ...Anyone know if ADMX can be made sensitive down to axions as light as10^-4 eV?Samhttps://twitter.com/qftmenoreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-16538386382493046552014-03-26T14:50:37.055+01:002014-03-26T14:50:37.055+01:00Another way to relax the isocurvature bound on the...Another way to relax the isocurvature bound on the axion CDM is to assume that the saxion (or the radial component of the PQ scalar) evolves after inflation. From Fig.1 of 1403.4186, it looks still difficult to totally get rid of the tension even if the initial position of the saxion is close to the Planck scale, though...Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-46605223740262963622014-03-25T22:37:39.084+01:002014-03-25T22:37:39.084+01:00Anon, it seems you're right, Marsh et al disag...Anon, it seems you're right, Marsh et al disagrees with the rest of the literature. So the conclusion is that even fine-tuning cannot save high-scale axions. I'll put an update to the post later today. Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-41635756247635887972014-03-25T21:23:13.286+01:002014-03-25T21:23:13.286+01:00Sterile neutrinos, gravitinos, neutralinos, minima...Sterile neutrinos, gravitinos, neutralinos, minimalinos, anyinos, wimpzillas, babyzillas, hooperons, mini-black holes, old newspapers... it's a long list. Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-83774298202892038182014-03-25T12:55:05.062+01:002014-03-25T12:55:05.062+01:00Gravitons, inflatons, and axions might lead the li...Gravitons, inflatons, and axions might lead the list of undiscovered particles in free space. What might be other leading candidates?David Brownhttps://www.blogger.com/profile/10537922851243581921noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-59508310741893436362014-03-25T00:54:33.523+01:002014-03-25T00:54:33.523+01:00A small initial misalignment angle wouldn't he...A small initial misalignment angle wouldn't help because the axion field picks up fluctuations *around its misalignment value* during inflation (set by H_I/2 pi) in the usual way, which seed the isocurvature perturbations.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-35903297283275765462014-03-25T00:25:01.100+01:002014-03-25T00:25:01.100+01:00It's a valid possibility. One needs to ensure ...It's a valid possibility. One needs to ensure these particles were never in thermal equilibrium, and then invoke a non-thermal production mechanism, but otherwise there is no problem. There are models along these lines on the market (WIMPzillas, godzillas, babyzillas, and so on). Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-37140882480368110702014-03-25T00:03:13.587+01:002014-03-25T00:03:13.587+01:00So, with significant problems for any theory that ...So, with significant problems for any theory that has axions as the dominant constituent of dark matter, and with no sighting of WIMPs, let me ask this:<br /><br />The new physics scale in these observations is 10^14-10^16 GeV. You've said that neutrino experiment suggest some possible physics at 10^15 GeV. With our only hints of new physics at those scales, is there any problem with a model in which dark matter's mass is ~10^14 GeV or larger? Is there any problem with a model where a bunch of the mass in the universe is composed of particles that become non-relativistic when the temperature is ~10^14 GeV?Alexnoreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-13215516395263077842014-03-24T23:25:28.741+01:002014-03-24T23:25:28.741+01:00That's right physicsphile. A high-scale axion...That's right physicsphile. A high-scale axion would generically overclose the universe, unless you fine-tune the initial displacement angle. People argued this fine-tuning could be anthropic. Up to the caveats mentioned in the next this idea is now dead: one needs much more fine-tuning of clearly non-anthropic sort to suppress the isocurvature perturbations. Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-57689969857019760402014-03-24T23:20:45.271+01:002014-03-24T23:20:45.271+01:00Thanks, I see, I need to think why a small axion m...Thanks, I see, I need to think why a small axion misalignment angle wouldn't help. Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-12956568649954018522014-03-24T22:42:27.791+01:002014-03-24T22:42:27.791+01:00> Jester said...
>
>Which conclusions? At...> Jester said...<br />><br />>Which conclusions? At least the main message (the paragraphs in italics in Fox et al.) seems to match.<br /><br />The conclusions as summarized in the abstract:<br /><br />"[...] such a compact modulus can not play the role of a QCD axion and solve the strong CP problem if gravitational waves interpreted as arising from inflation with Hubble constant $H_inf \gsim 10^{13}$ GeV are observed by the PLANCK polarimetry experiment. In this case axion fluctuations generated during inflation would leave a measurable isocurvature and/or non-Gaussian imprint in the spectrum of primordial temperature fluctuations. <i>This conclusion is independent of any assumptions about the initial axion misalignment angle, how much of the dark matter is relic axions, or possible entropy release by a late decaying particle such as the saxion; it relies only on the mild assumption that the Peccei-Quinn symmetry remains unbroken in the early universe</i>."Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-84867400387926364222014-03-24T22:27:40.104+01:002014-03-24T22:27:40.104+01:00I was under the impression the axion DM was a nice...I was under the impression the axion DM was a nice alternative to the WIMP "miracle" as during inflation there would be different sub-Universes generated, each with different proportions of dark matter. Only those ones which had a suitably small \theta would be inhabitable as discussed in http://arxiv.org/abs/0807.1726 . I was wondering whether this new paper, you are discussing, now rules out this possibility, assuming no entropy production etc., and so makes the wimp "miracle" a more likely explanation of the DM abundance?physicsphilenoreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-54877792280442488702014-03-24T21:38:55.052+01:002014-03-24T21:38:55.052+01:00Are you going to comment on B-L phase transitions ...Are you going to comment on B-L phase transitions (with inflation or not)? Because some of these people predicted the right scale. Marni Dee Sheppeardhttps://www.blogger.com/profile/08188528831432604162noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-35364523289640767982014-03-24T15:48:26.863+01:002014-03-24T15:48:26.863+01:00" the QCD axion is still viable."
And a...<br />" the QCD axion is still viable."<br /><br />And always will be?Robert L. Oldershawhttps://www.blogger.com/profile/15396555790655312393noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-37081563325139552452014-03-24T09:04:59.195+01:002014-03-24T09:04:59.195+01:00Only a part of the parameter space of the QCD axio...Only a part of the parameter space of the QCD axion is constrained by BICEP2. For 10^9 GeV < f < 10^14 GeV the QCD axion is still viable. Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-51266779804945593092014-03-24T08:03:32.058+01:002014-03-24T08:03:32.058+01:00Axing of axions should direct our attention to non...Axing of axions should direct our attention to non-axionic solutions to the strong CP problem -- that use discrete space time symmetries P and CP.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-82322644571082857762014-03-24T05:47:01.143+01:002014-03-24T05:47:01.143+01:00No. The plot shows the axion mass m which is diffe...No. The plot shows the axion mass m which is different from the axion scale f (the scale where the global symmetry whose spontaneous breaking gives rise to a Goldstone boson - the axion). For QCD axions the two are related by m~0.01 GeV^2/f. For more general axions the mass can be considered a free parameter. Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-33810830813946799702014-03-24T05:40:32.702+01:002014-03-24T05:40:32.702+01:00You keep mentioning 10^14 GeV, but the masses show...You keep mentioning 10^14 GeV, but the masses shown on this plot only go up to a value 41 orders of magnitude smaller than that. Is there a typo?Xezlecnoreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-41706156444998867802014-03-24T05:27:34.659+01:002014-03-24T05:27:34.659+01:00Which conclusions? At least the main message (the ...Which conclusions? At least the main message (the paragraphs in italics in Fox et al.) seems to match. Jesterhttps://www.blogger.com/profile/08947218566941608850noreply@blogger.comtag:blogger.com,1999:blog-2846514233477399562.post-36246933034246106682014-03-24T05:07:53.153+01:002014-03-24T05:07:53.153+01:00Hi Adam,
I'm no expert but I'm under the ...Hi Adam,<br /><br />I'm no expert but I'm under the impression that some of the conclusions of Marsh et. al. are in conflict with Fox et. al. in hep-th/0409059. Could you explain?<br /><br />Thanks!Anonymousnoreply@blogger.com