tag:blogger.com,1999:blog-1513704378254120283.post8875132656150837478..comments2024-01-23T13:58:48.688-08:00Comments on The Trenches of Discovery: The ISW Mystery IV: Where does the evidence lead?Shaun Hotchkisshttp://www.blogger.com/profile/04832423210563130467noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-1513704378254120283.post-63750972716721779422012-05-23T03:30:07.708-07:002012-05-23T03:30:07.708-07:00Hah, as we both know indeed. Subir probably wouldn...Hah, as we both know indeed. Subir probably wouldn't approve of how lazily I am lumping the apparent accelerated expansion under the label <i>dark energy</i>. I don't really approve either, but it is easier, for now.<br /><br />I guess the significance of the discoveries depends on the perspective. I wasn't trying to make a strong claim about the comparison between the two discoveries. I was just trying to stress that n-G would be a big discovery.<br /><br />Non-Gaussianity would be telling us something non-trivial about the universe 14 billion years ago. Not necessarily something mysterious, I agree, but definitely something interesting. It would also be telling us, very indirectly (unfortunately), about how nature behaves at energies that aren't able to be probed by any other means.<br /><br />Dark energy is more mysterious because we think we better know what to expect from it. So, yes, in that sense it was a big discovery because it required something of a paradigm shift. And yes, because we don't have quite as clear expectations for inflation, n-G wouldn't require so much of a paradigm shift. But both discoveries would be revealing just as much new stuff about the universe. <br /><br />When I claimed that n-G might be a bigger discovery I was coming from the perspective that learning <i>anything</i> about nature at 10^(any number bigger than 3) GeV would be incredible.Shaun Hotchkisshttps://www.blogger.com/profile/04832423210563130467noreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-69426433151932979022012-05-23T03:07:29.099-07:002012-05-23T03:07:29.099-07:00Both these points are really good points. I'm ...Both these points are really good points. I'm going to link to this comment where I mention the fluke option.<br /><br />And, for anyone reading, it's actually quite a bit less than 0.3% once you take into account how conservative we were in our calculation.Shaun Hotchkisshttps://www.blogger.com/profile/04832423210563130467noreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-70380330248284923552012-05-23T02:17:39.926-07:002012-05-23T02:17:39.926-07:00Shaun, why do you think that the discovery of non-...Shaun, why do you think that the discovery of non-Gausssianity "would be as big a discovery as the discovery of dark energy 14 years ago, if not bigger"?<br /><br />Ok, so single-field inflation would be wrong. But there are many models of inflation with more than one field. And if we are going to have to postulate new scalar fields at higher energy scales, it is not clear to me why we should not expect more than one. On the other hand, having a tiny but non-zero cosmological constant did present a fine-tuning problem, which many people still take very seriously (as we both know!).Sesh Nadathurhttps://www.blogger.com/profile/07155102110438904961noreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-72391009020875668962012-05-23T02:08:38.820-07:002012-05-23T02:08:38.820-07:00I see that someone has voted for the answer to be ...I see that someone has voted for the answer to be "a statistical fluke". I'd just like to point out that there is a less than 0.3% chance of it being a statistical fluke (that's what it means to be more than 3 sigma away from the expectation). That's not to say it can't be a statistical fluke of course - and this is why 3 sigma evidence is not regarded as conclusive in fields where it is possible to have better standards, say in particle physics - but do you really think that the chance of any of the other explanations being right is less than 0.3%?<br /><br />I'd understand a position that said "yeah, looks odd on the face of it, but Shaun, you and your collaborators probably made a mistake in your calculations so it isn't a mystery after all" (I'd disagree, but I'd understand it). But that's not the same as saying it is a statistical fluke.<br /><br />I voted for "other", by the way, because this includes the possibility that we made a mistake or some over-simplifying assumption, the possibility that the actual observation had some (undetected) flaw in it, and every other possibility that we might not yet have thought of. On balance I thought that won.Sesh Nadathurhttps://www.blogger.com/profile/07155102110438904961noreply@blogger.comtag:blogger.com,1999:blog-1513704378254120283.post-41063404364248830992012-05-22T03:48:03.186-07:002012-05-22T03:48:03.186-07:00Seeing as at least one other person has now voted ...Seeing as at least one other person has now voted in the poll... if you do have a guess, feel free to write here why you chose the option you chose.<br /><br />I chose "noisy foregrounds", partially because this would be the least interesting real solution and it's best not to get one's hopes up and partially because it is the solution that I understand the physics of the least, so I probably also just don't understand all the reasons why it won't work. Some people who do know more of that stuff than me are sure it can't be foregrounds (some aren't).<br /><br />Time will tell...Shaun Hotchkisshttps://www.blogger.com/profile/04832423210563130467noreply@blogger.com