Punatalk
Punatalk
Home | Profile | Register | Active Topics | Members | Search | FAQ | Donate
Username:
Password:
Save Password
Forgot your Password?

 All Forums
 Punaweb Forums
 Punatalk
 Discoveries by the telescopes on Mauna Kea
 New Topic  Reply to Topic
 Printer Friendly
Previous Page | Next Page

Please note: All postings, business listings and advertisements are made available here, without charge, as a public service by Punaweb. No recommendations or endorsements of any specific posting, business listing or advertisement are made or implied by Punaweb.

Author Topic
Page: of 43

oink
Punatic

USA
2708 Posts

Posted - 01/12/2018 :  22:01:17  Show Profile  Reply with Quote
quote:
"By comparing the Bayesian evidence for the models, we find that (Lambda)CDM does a better job globally, while the holographic models provide a (marginally) better fit to data without very low multipoles (i.e. l<=30), where the dual QFT becomes non-perturbative."

Say what?

Pua`a
S. FL
Big Islander to be.
Go to Top of Page

TomK
Punatic

USA
6922 Posts

Posted - 01/12/2018 :  22:29:42  Show Profile  Visit TomK's Homepage  Reply with Quote
As I said, it was written by a cosmologist. That's actually the "easiest" sentence to understand, you're fortunate I didn't quote the whole abstract, which says:

"We test a class of holographic models for the very early universe against cosmological observations and find that they are competitive to the standard (Lambda)CDM model of cosmology. These models are based on three dimensional perturbative super-renormalizable Quantum Field Theory (QFT), and while they predict a different power spectrum from the standard power-law used in (Lambda)CDM, they still provide an excellent fit to data (within their regime of validity). By comparing the Bayesian evidence for the models, we find that (Lambda)CDM does a better job globally, while the holographic models provide a (marginally) better fit to data without very low multipoles (i.e. l<=30), where the dual QFT becomes non-perturbative. Observations can be used to exclude some QFT models, while we also find models satisfying all phenomenological constraints: the data rules out the dual theory being Yang-Mills theory coupled to fermions only, but allows for Yang-Mills theory coupled to non-minimal scalars with quartic interactions. Lattice simulations of 3d QFT's can provide non-perturbative predictions for large-angle statistics of the cosmic microwave background, and potentially explain its apparent anomalies."

Maybe that's a little clearer? ;)

Personally, I prefer not being a cosmologist, I think it can do harm to your mental health...
Go to Top of Page

TomK
Punatic

USA
6922 Posts

Posted - 01/13/2018 :  02:02:17  Show Profile  Visit TomK's Homepage  Reply with Quote
This should clear things up.

Bzowksi et al, 2012:

"We provide a precise and quantitative holographic description of a class of inflationary slow-roll models. The dual QFT is a deformation of a three-dimensional CFT by a nearly marginal operator, which, in the models we consider, generates an RG flow to a nearby IR fixed point. These models describe hilltop inflation, where the inflaton rolls from a local maximum of the potential in the infinite past (corresponding to the IR fixed point of the dual QFT) to reach a nearby local minimum in the infinite future (corresponding to the UV of the dual QFT). Through purely holographic means, we compute the spectra and bispectra of scalar and tensor cosmological perturbations. The QFT correlators to which these observables map holographically may be calculated using conformal perturbation theory, even when the dual QFT is strongly coupled. Both the spectra and the bispectra may be expressed this way in terms of CFT correlators that are fixed, up to a few constants, by conformal invariance. The form of slow-roll inflationary correlators is thus determined by the perturbative breaking of the de Sitter isometries away from the fixed point. Setting the constants to their values obtained by AdS/CFT at the fixed point, we find exact agreement with known expressions for the slow-roll power spectra and non-Gaussianities."

QED. Any questions?
Go to Top of Page

oink
Punatic

USA
2708 Posts

Posted - 01/13/2018 :  05:50:47  Show Profile  Reply with Quote
Thanks for taking time for such a through response, I think. I only have one thing to say. Uncle!

Pua`a
S. FL
Big Islander to be.
Go to Top of Page

HereOnThePrimalEdge
Punatic

South Sandwich Islands
5924 Posts

Posted - 02/06/2018 :  13:29:54  Show Profile  Reply with Quote
TomK,
Do you know if anyone on Mauna Kea will look for a space-Tesla Roadster tonight? Would it be large enough to spot while it's trajectory is a day out from earth?

Recycle Puna. Humans, although probably not you personally, have already left 400,000 pounds of trash on the moon. - YouTube's Half As Interesting
Go to Top of Page

TomK
Punatic

USA
6922 Posts

Posted - 02/06/2018 :  16:11:27  Show Profile  Visit TomK's Homepage  Reply with Quote
Right now, if it were dark and the clouds disappeared, we'd be able to track and spot it very easily!

http://www.n2yo.com/?s=43205

What an amazing sight watching it launch this morning and then seeing the two boosters simultaneously returning to the ground.
Go to Top of Page

oink
Punatic

USA
2708 Posts

Posted - 02/06/2018 :  19:20:56  Show Profile  Reply with Quote
Crap! I forgot to go out and watch the shot.

Pua`a
S. FL
Big Islander to be.
Go to Top of Page

TomK
Punatic

USA
6922 Posts

Posted - 02/06/2018 :  23:44:34  Show Profile  Visit TomK's Homepage  Reply with Quote
Were you near enough to hear the sonic booms when the boosters landed? I heard all four as the boosters landed (on the live TV feed) and as the shock waves had a long way to travel, they arrived just after the boosters actually landed.

Physics in action. I loved it!
Go to Top of Page

oink
Punatic

USA
2708 Posts

Posted - 02/07/2018 :  07:44:01  Show Profile  Reply with Quote
I doubt it but I don't know where it came down. As the crow flies we're a little over 100 miles South of the launch point. We can see launches but we're too far away for it to be spectacular. It's just interesting. My childhood home, which I still have to sell should anyone want a small waterfront fixerupper, was close enough to see the big Vehicle Assembly Building and actually feel the vibrations from the Saturn 5s and hear the windows rattle. I have heard sonic booms from the landing shuttles from that house when they were still flying. And we did hear the boom from the landing boosters one time when we were up checking on the old house.

Pua`a
S. FL
Big Islander to be.
Go to Top of Page

TomK
Punatic

USA
6922 Posts

Posted - 02/07/2018 :  19:27:59  Show Profile  Visit TomK's Homepage  Reply with Quote
The beauty of galactic cannibalism

Some recent stunning images from the CFHT on MK have shown that was once thought to be a relatively quiescent group of galaxies shows that there's a little more going on, specifically described as "galactic cannibalism".

https://goo.gl/NkeRjH

"Due to its unique features, Stephan's Quintet has been widely observed across the entire electromagnetic spectrum, and has been the subject of many complex numerical simulations. The team detected a red halo composed of old stars centered on a galaxy, NGC 7317. NGC 7317 was thought to be in a stable state or recently arrived near the group. The detection of red stars implies the contrary, that this galaxy has been interacting for a very long time with the other members of the group. Interactions such as the one seen in these observations are called galactic cannibalism. Galactic cannibalism occurs when the gravitational forces from a larger galaxy or group of galaxies slowly tear apart a smaller galaxy. Characteristic features of galactic cannibalism are streams or halos of stars orbiting the larger galaxy, like the halo of red stars seen around NGC 7317. A first implication is that Stephan's Quintet is far older than currently admitted. The models of formation and evolution of this emblematic system will have to be revised. This global case of galactic cannibalism should eventually lead to the formation of a giant elliptical galaxy."

Edited by - TomK on 02/07/2018 19:28:42
Go to Top of Page

HereOnThePrimalEdge
Punatic

South Sandwich Islands
5924 Posts

Posted - 02/08/2018 :  07:48:53  Show Profile  Reply with Quote
Rob Weryk, the Hawaiian astronomer who discovered Oumuamua, has provided a few updates on the red Tesla Roadster's orbit for Atlantic Magazine. The car will still head out to Mars, but is no expected to travel even farther (intentionally? unintentionally?) into the asteroid belt. When it's path brings it back towards earth in 11 years, telescopes here in Hawaii may be able to spot it:

“Musk’s message is a bit ambiguous,” Rob Weryk, a postdoctoral researcher at the University of Hawaii Institute for Astronomy, said in an email.

Weryk has some experience in tracking unusual-looking objects in the solar system. He was the first to lay eyes on ‘Oumuamua, the first known interstellar object to visit our solar system.

Powerful telescopes like Pan-STARRS may be able to see the Tesla if it crosses their field of view—and if it’s not too cloudy—“at least for a time until it is too faint,” Weryk said. If they don’t see it now, they can try again in 11 years, when the Tesla should approach the Earth, according to corrected data.
https://www.theatlantic.com/science/archive/2018/02/tesla-elon-musk-mars-spacex-asteroid-belt/552719/


Recycle Puna. Humans, although probably not you personally, have already left 400,000 pounds of trash on the moon. - YouTube's Half As Interesting
Go to Top of Page

TomK
Punatic

USA
6922 Posts

Posted - 02/08/2018 :  17:53:07  Show Profile  Visit TomK's Homepage  Reply with Quote
"The car will still head out to Mars, but is no expected to travel even farther (intentionally? unintentionally?)"

My understanding is that they just burned the second stage as long as they could to demonstrate it could be restarted after being turned off in low earth orbit. In addition, it showed that it would be capable of taking a satellite into geosynchronous orbit (without a satellite having to do it itself). I think they originally estimated this would put it into a solar orbit that extended out to the distance of Mars but it actually went on a little longer and sent it into an even larger orbit.
Go to Top of Page

TomK
Punatic

USA
6922 Posts

Posted - 02/09/2018 :  19:12:46  Show Profile  Visit TomK's Homepage  Reply with Quote
The Asteroid Terrestrial-impact Last Alert System (ATLAS) used its telescope on Mauna Loa last night to image the Tesla Roadstar. They determined its distance at about 0.005 AU (about 465,000 miles) moving away from us at 2.2 miles/sec.

The dark patches are electronic artifacts on a small part of the detector:

https://goo.gl/Df8vgC
Go to Top of Page

Rob Tucker
Kama'aina

9190 Posts

Posted - 02/09/2018 :  19:17:34  Show Profile  Reply with Quote
That was brilliant marketing....
Go to Top of Page

HereOnThePrimalEdge
Punatic

South Sandwich Islands
5924 Posts

Posted - 02/09/2018 :  21:29:30  Show Profile  Reply with Quote
telescope on Mauna Loa last night to image the Tesla Roadstar
Thanks TomK!

That was brilliant marketing....
Definitively. I already saw a photo of a Tesla yesterday with a bumper sticker that said "My Other Car Is In Orbit."

Recycle Puna. Humans, although probably not you personally, have already left 400,000 pounds of trash on the moon. - YouTube's Half As Interesting
Go to Top of Page
Page: of 43 Topic  
Previous Page | Next Page
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
Punatalk © 2003 to 2014 Punaweb Go To Top Of Page
Powered By: Snitz Forums 2000 Version 3.4.06