Author Topic: David Tong on the Big Bang  (Read 1697 times)

David Tong on the Big Bang
« on: October 16, 2013, 11:56:59 AM »
If you want to know about the real deal, you'll get it from Tong.

You are not allowed to view links. Register or Login

Offline Solitary

Re: David Tong on the Big Bang
« Reply #1 on: October 16, 2013, 11:10:38 PM »
Quote from: "josephpalazzo"
If you want to know about the real deal, you'll get it from Tong.

You are not allowed to view links. Register or Login




Thanks josephpalazzo!  =D>  The best explanation of the theory I have heard so far because it makes sense and he gives good evidence for it.  :-D  Solitary
There is nothing more frightful than ignorance in action.

Re: David Tong on the Big Bang
« Reply #2 on: October 17, 2013, 09:20:47 AM »
He has a series of lectures on QFT well worth watching. Here's the first one -- you can get the others from the sidebar.

[youtube:1o2o1t2e]http://www.youtube.com/watch?v=8yplCob7_Ck[/youtube:1o2o1t2e]

His lectures notes are at: You are not allowed to view links. Register or Login

Offline entropy

Re: David Tong on the Big Bang
« Reply #3 on: October 17, 2013, 04:40:11 PM »
Nice. I like his enthusiasm. You can tell that this information excites him and he is jazzed to have the opportunity to share it. He's a good story teller - especially for a geek. He understands how to express the ideas in a way that the audience can comprehend and weaves it expertly together into an interesting narrative.

Thanks for the link.

Offline entropy

Re: David Tong on the Big Bang
« Reply #4 on: October 17, 2013, 08:02:38 PM »
josephpalazzo, I have an odd question that you may know the answer to without much thought - in Tong's lecture about the Big Bang, he shows an image which I think is of the cosmic microwave background radiation and I'm wondering if it is conceptually valid to think of that map as being a glimpse of the basic energy density distribution throughout the observable universe? If so, is it conceptually valid to think of the regions that are cooler as having more entropy (as being more entropic?) and the regions where it is warmer as having lower entropy?


I have an astronomy map app for my iPhone - one of those where you just hold your iPhone up and it figures out where it is pointed and the app gives a view of the night sky on the screen with star names and constellations and planets and other astronomical objects labeled. I think it would be cool to have an app like that, that would superimpose an image of the part of the microwave background radiation map onto the the screen as it was pointed toward a particular region of the sky.

Re: David Tong on the Big Bang
« Reply #5 on: October 18, 2013, 10:11:33 AM »
Quote from: "entropy"
josephpalazzo, I have an odd question that you may know the answer to without much thought - in Tong's lecture about the Big Bang, he shows an image which I think is of the cosmic microwave background radiation and I'm wondering if it is conceptually valid to think of that map as being a glimpse of the basic energy density distribution throughout the observable universe? If so, is it conceptually valid to think of the regions that are cooler as having more entropy (as being more entropic?) and the regions where it is warmer as having lower entropy?

No, that map looks at quantum fluctuations. This is given in QFT as:

?[sub:7rah7wec]?[/sub:7rah7wec] = k[sup:7rah7wec]3[/sup:7rah7wec]?V[sub:7rah7wec]k[/sub:7rah7wec]?[sup:7rah7wec]2[/sup:7rah7wec]/4pi[sup:7rah7wec]2[/sup:7rah7wec]a[sup:7rah7wec]2[/sup:7rah7wec]

Where

?[sub:7rah7wec]?[/sub:7rah7wec] = power spectrum of the quantum fluctuations
k = energy of the inflaton particle
V[sub:7rah7wec]k[/sub:7rah7wec]= the potential of the inflaton field
a = the cosmic scale factor which determines how fast the universe is expanding.

What people do is contruct models that would explain the distribution of these quantum fluctuations - the map in that video is the data to be explained if the model is correct.



Quote
I have an astronomy map app for my iPhone - one of those where you just hold your iPhone up and it figures out where it is pointed and the app gives a view of the night sky on the screen with star names and constellations and planets and other astronomical objects labeled. I think it would be cool to have an app like that, that would superimpose an image of the part of the microwave background radiation map onto the the screen as it was pointed toward a particular region of the sky.

That would be great. Don't know if the people making those apps are aware of QFT and what it would take to write the software for those quantum fluctuations.

Offline entropy

Re: David Tong on the Big Bang
« Reply #6 on: October 18, 2013, 10:43:13 AM »
Quote from: "josephpalazzo"
Quote from: "entropy"
josephpalazzo, I have an odd question that you may know the answer to without much thought - in Tong's lecture about the Big Bang, he shows an image which I think is of the cosmic microwave background radiation and I'm wondering if it is conceptually valid to think of that map as being a glimpse of the basic energy density distribution throughout the observable universe? If so, is it conceptually valid to think of the regions that are cooler as having more entropy (as being more entropic?) and the regions where it is warmer as having lower entropy?

No, that map looks at quantum fluctuations. This is given in QFT as:

?[sub:fet3dc4k]?[/sub:fet3dc4k] = k[sup:fet3dc4k]3[/sup:fet3dc4k]?V[sub:fet3dc4k]k[/sub:fet3dc4k]?[sup:fet3dc4k]2[/sup:fet3dc4k]/4pi[sup:fet3dc4k]2[/sup:fet3dc4k]a[sup:fet3dc4k]2[/sup:fet3dc4k]

Where

?[sub:fet3dc4k]?[/sub:fet3dc4k] = power spectrum of the quantum fluctuations
k = energy of the inflaton particle
V[sub:fet3dc4k]k[/sub:fet3dc4k]= the potential of the inflaton field
a = the cosmic scale factor which determines how fast the universe is expanding.

What people do is contruct models that would explain the distribution of these quantum fluctuations - the map in that video is the data to be explained if the model is correct.



Quote
I have an astronomy map app for my iPhone - one of those where you just hold your iPhone up and it figures out where it is pointed and the app gives a view of the night sky on the screen with star names and constellations and planets and other astronomical objects labeled. I think it would be cool to have an app like that, that would superimpose an image of the part of the microwave background radiation map onto the the screen as it was pointed toward a particular region of the sky.

That would be great. Don't know if the people making those apps are aware of QFT and what it would take to write the software for those quantum fluctuations.

I see that Tong was positing that quantum fluctuations (along with inflation) could explain the cosmic background microwave radiation map, but the map has information that is independent of whether or not it can be explained by quantum fluctuations. I was wondering about that information.

I don't understand why the app makers would have to do QFT calculations - couldn't they just electronically imprint the map as it is onto the scene just like the app I have now imprints the map of the Milky Way onto the scene if I ask it to?

Re: David Tong on the Big Bang
« Reply #7 on: October 18, 2013, 12:04:30 PM »
Quote
Quote from: "entropy"

Quote from: "josephpalazzo"
No, that map looks at quantum fluctuations. This is given in QFT as:

?[sub:3u35s24o]?[/sub:3u35s24o] = k[sup:3u35s24o]3[/sup:3u35s24o]?V[sub:3u35s24o]k[/sub:3u35s24o]?[sup:3u35s24o]2[/sup:3u35s24o]/4pi[sup:3u35s24o]2[/sup:3u35s24o]a[sup:3u35s24o]2[/sup:3u35s24o]

Where

?[sub:3u35s24o]?[/sub:3u35s24o] = power spectrum of the quantum fluctuations
k = energy of the inflaton particle
V[sub:3u35s24o]k[/sub:3u35s24o]= the potential of the inflaton field
a = the cosmic scale factor which determines how fast the universe is expanding.

What people do is contruct models that would explain the distribution of these quantum fluctuations - the map in that video is the data to be explained if the model is correct.



Quote
I have an astronomy map app for my iPhone - one of those where you just hold your iPhone up and it figures out where it is pointed and the app gives a view of the night sky on the screen with star names and constellations and planets and other astronomical objects labeled. I think it would be cool to have an app like that, that would superimpose an image of the part of the microwave background radiation map onto the the screen as it was pointed toward a particular region of the sky.

That would be great. Don't know if the people making those apps are aware of QFT and what it would take to write the software for those quantum fluctuations.

I see that Tong was positing that quantum fluctuations (along with inflation) could explain the cosmic background microwave radiation map, but the map has information that is independent of whether or not it can be explained by quantum fluctuations. I was wondering about that information.
Quote
I don't understand why the app makers would have to do QFT calculations - couldn't they just electronically imprint the map as it is onto the scene just like the app I have now imprints the map of the Milky Way onto the scene if I ask it to?

I'm no expert in that field. Perhaps someone who dabbles in programming could answer you.

Offline entropy

Re: David Tong on the Big Bang
« Reply #8 on: October 18, 2013, 01:18:51 PM »
Thanks for the feedback. I meant the cosmic background radiation map app comment to be a general one to everyone - just to express that I think an app like that would be cool. I suspect that the creators of the astronomy app I have could do it without a great deal of difficulty if they decided it was worthwhile.

 

SMF spam blocked by CleanTalk