Cold spot still baffles scientists

[wolram]

https://www.sciencedaily.com/releases/2016/10/161012095819.htm

Date:
October 12, 2016
Source:
University of Portsmouth
Summary:
Astrophysicists have created the largest ever map of voids and superclusters in the Universe, which helps solve a long-standing cosmological mystery.

So what is causing this cold spot?

 

[PeterDonis]

Have you googled "Integrated Sachs-Wolfe effect" (the effect that the article you linked to says causes the difference in CMB temperature)? If not, do so. If you have, what don't you understand about it?

 

[GeorgeDishman]

I think the O.P. may have been thinking that this text from the article (quoting one of the authors) suggested that the ISW is not the cause of the cold spot:

Dr Nadathur said: "Our results resolve one long-standing cosmological puzzle, but doing so has deepened the mystery of a very unusual 'Cold Spot' in the CMB.

"It has been suggested that the Cold Spot could be due to the ISW effect of a gigantic 'supervoid' which has been seen in that region of the sky. But if Einstein's gravity is correct, the supervoid isn't big enough to explain the Cold Spot.

"It was thought that there was some exotic gravitational effect contradicting Einstein which would simultaneously explain both the Cold Spot and the unusual ISW results from Hawai'i. But this possibility has been set aside by our new measurement -- and so the Cold Spot mystery remains unexplained."

 

[Chronos]

On page 5 of the subject paper, the authors note "The value of A_ISW we obtain is larger than the [lambda]CDM expectation but consistent with it at 1.2[sigma] similar to other results using luminous red galaxies in cross-correlation (e.g. Giannantonio et al. 2012). This is in contrast to the high-signifcance detections of the stacked ISW signal reported by Granett et al. (2008); Planck Collaboration et al. (2015b), which exceed the CDM expectation by a factor of ~5 or more, corresponding to a 3[sigma] discrepancy (see Nadathur et al. 2012; Flender et al. 2013; Cai et al. 2014; Hotchkiss et al. 2015; Aiola et al. 2015). Such a large discrepancy has been hard to explain in any alternative theoretical models. Our result is therefore an important step towards the resolution of this apparent anomaly." This appears to defeat any claim of an anomalous ISW effect, as suggested by the article. An off hand remark by the author may have merely been cut and pasted on the editor's table in the spirit of journalistic license.

 

[GeorgeDishman]

Ouch, thank you. So the article essentially states the opposite of what the paper says, even though they quoted the author. I hadn't had a chance to go through it properly but I didn't expect the pop-sci version to be that far off.