tag:blogger.com,1999:blog-1513704378254120283.post8401642221051014073..comments2024-01-23T13:58:48.688-08:00Comments on The Trenches of Discovery: Planck: All we need is six numbers to describe the universeShaun Hotchkisshttp://www.blogger.com/profile/04832423210563130467noreply@blogger.comBlogger7125tag:blogger.com,1999:blog-1513704378254120283.post-67853803724031343402013-04-03T02:09:58.711-07:002013-04-03T02:09:58.711-07:00Hi Torbjörn, thanks for the comment.
I have to a...Hi Torbjörn, thanks for the comment. <br /><br />I have to admit, I'm not entirely sure I understand what your intended point was. I called \(\Lambda\) (i.e. dark energy) "poorly named" because it isn't really "dark" at all. That word implies something to do with light and dark energy, whatever it is, has nothing to do with light at all.<br /><br />I also happen to think dark matter is poorly named. The much better name would be transparent matter.<br /><br />Dark just sounds more mysterious and exciting, so the names have caught on.Shaun Hotchkisshttps://www.blogger.com/profile/04832423210563130467noreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-21644037428797325222013-04-02T14:49:36.779-07:002013-04-02T14:49:36.779-07:00"The model of cosmology that has been gaining..."The model of cosmology that has been gaining traction over the last decade and a bit is called ΛCDM. This stands for Λ Cold Dark Matter, where the Λ represents the poorly named "dark energy"."<br /><br />Noo... I write this as interested in astrobiology. (And boy, do the standard cosmology help, with definite age, structure evolution and basis for chemical evolution, and what not.) I'm just trying to unconfuse terminology for us borders:<br /><br />This is fluid, but Planck should congeal it: DE and DM should stand for the observational properties or entities as we now know them. When we get to the now well tested 5+1 parameter model they turn out to be some cold DM (CDM) and a cosmological constant (Lambda). (After looking at '100s of millions of models' in some cases I think the ESA press conference said, with DE & DM of various kinds.)<br /><br />(And at the current time I take it the "cold" DM is well constrained. But time and other possible variation of the presumed CC is still somewhat open, so DE will be an observational term for the time being.)<br /><br />And thanks for the intended coverage!Torbjörn Larssonhttps://www.blogger.com/profile/13304729731231255545noreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-27271983477228489522013-03-25T14:41:57.793-07:002013-03-25T14:41:57.793-07:00Thanks a lot Shaun. Have a nice time.Thanks a lot Shaun. Have a nice time.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-83760764269121657162013-03-25T14:35:33.648-07:002013-03-25T14:35:33.648-07:00Thanks for the question (and please, just call me ...Thanks for the question (and please, just call me Shaun!).<br /><br />If you stick around, hopefully exactly this sort of question will come up a lot next week at the conference in Noordiwjk (it looks like the inflation talks will come on Thursday). So hopefully I get to address it in detail then. If I don't, please ask the question again.<br /><br />I'll give you a brief answer now though. The original, hybrid inflation model was ruled out when the spectral index was seen to be red tilted, rather than blue tilted (i.e. that the amplitude of primordial fluctuations is greater on large scales than on small scales). However, nowadays, "hybrid inflation" has come to mean any inflationary model that ends via a hybrid transition (a hybrid transition here means a second field becomes unstable when the inflaton reaches a particular value and suddenly causes the end of inflation). Using this definition of "hybrid inflation" there will be many models that have survived Planck.<br /><br />Your question is a nice one though, so even if I do write some brief points about inflation models next week, I might try to tackle the problem with another, more detailed, post after the conference (or find an appropriate guest poster).<br /><br />I hope that helps...Shaun Hotchkisshttps://www.blogger.com/profile/04832423210563130467noreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-43140285116285672302013-03-25T13:47:24.247-07:002013-03-25T13:47:24.247-07:00Thank you very much Dr.Shaun.
I would be grateful ...Thank you very much Dr.Shaun.<br />I would be grateful if you shed light on inflation models after Planck and especially Hybrid inflation and its extensions.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-18156592484962634692013-03-25T09:27:13.609-07:002013-03-25T09:27:13.609-07:00Thanks! And sure, no problem. It is paper XIX (in ...Thanks! And sure, no problem. It is paper XIX (in particular, section 5). The arXiv link is here: <a href="http://arxiv.org/abs/1303.5079" rel="nofollow">http://arxiv.org/abs/1303.5079</a><br /><br />Figure 7 of that paper is the relevant one for the original measurement by Granett et al.Shaun Hotchkisshttps://www.blogger.com/profile/04832423210563130467noreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-4320449311555353782013-03-25T09:08:36.897-07:002013-03-25T09:08:36.897-07:00Hi, I just recently started reading your blog -- l...Hi, I just recently started reading your blog -- love it! Can you direct me to the paper in the Planck Legacy Archive that confirms that the ISW mystery is still present?Mathewhttps://www.blogger.com/profile/16387298704270562707noreply@blogger.com