Freethought & Rationalism Archive

Shadowy Man · 02-27-2003, 08:24 PM

This afternoon I attended a seminar on the implications of the recent WMAP results on inflationary theory.

There were more people at this seminar than ever attended that series of seminars.

The speaker was presenting the results from one of the WMAP papers, but to give context for the results he ran us through some "elementary" inflationary theory.

My brain hurt after that seminar, and I think I might have understood 25-30% of what he said. Many of the faculty members were noticeably perplexed as well (except for a few particle physicists who understand things like gauge theory, etc.)

I feel like I know a little bit more about inflationary theory, but I still plan on reading Guth's book, which I recently purchased, hoping that it is not so technical that I'm hopelessly lost, but technical enough to still be accurate.

I came out of that seminar thinking that there's maybe a couple of dozen people around who really understand inflationary theory - the rest of us are just talking out of our asses!

Wow!

Friar Bellows · 02-27-2003, 09:38 PM

I know how to spell inflation!

Here are three review papers on this topic which you might find useful:

Cosmology, Inflation and the Physics of Nothing by William H. Kinney (60 pages)

An Introduction to Cosmological Inflation by Andrew R Liddle (36 pages)

An Exposition on Inflationary Cosmology by Gary Scott Watson (93 pages)

Shadowy Man · 02-28-2003, 07:36 AM

Quote:

Originally posted by Friar Bellows
I know how to spell inflation!

But do you understand what impact scale-invariant adiabatic fluctuations, as opposed to isocurvature ones, with a Gaussian amplitude distribution have on the temperature-polarization correlation and acoustic mode angular power spectrum due to the difference in times between when they reenter the horizon and the time of decoupling?

The speaker showed some equations, calling it a "cartoon" of the math - which brought a chuckle out of everyone in the room because it was a second order differential equation. That was the cartoon version!!

I'll take a look at those references... thanks. It's been a while since I've done heavy math, but I did take a class in gravitational physics so I'm somewhat familiar with Einstein's equations, etc.

butswana · 02-28-2003, 08:58 AM

It takes quite a bit of effort to wrap your brian around this stuff. I understand it but I have one hell of a time if I try to explain it to someone.
I find that most people can't get it. It is just not possible for them to comprehend. It makes them feel stupid, so they get pissed off.

Tom Sawyer · 02-28-2003, 01:55 PM

Quote:

But do you understand what impact scale-invariant adiabatic fluctuations, as opposed to isocurvature ones, with a Gaussian amplitude distribution have on the temperature-polarization correlation and acoustic mode angular power spectrum due to the difference in times between when they reenter the horizon and the time of decoupling?

As long as you have absolutely no followup questions, yes, I understand it completely.

lpetrich · 02-28-2003, 11:19 PM

I'm fairly sure that I understand what inflationary cosmology is, even though peteyh's stumper quote is a bit difficult for me to follow. It would be more convenient to break it up into several sentences. Like:

Fluctuations can be scale-invariant adiabatic or isocurvature; they will be assumed to have a Gaussian amplitude distribution. They will produce distinctive signatures of acoustic-mode angular power spectrum and of temperature-polarization correlation -- which can be observed. Their producing different signatures is a result of different times of their re-entering the horizon relative to the time of matter-radiation decoupling.

Shadowy Man · 03-01-2003, 05:51 AM

Like I said.. I'm very skeptical now of anyone who claims to understand inflationary theory.

Can you tell my why the WMAP data rule out theories with isocurvature fluctuations instead of adiabatic ones?

Answerer · 03-01-2003, 07:52 PM

Just curious guys, what causes vaccum fluctuations? I heard that it is a random process.

Deep Junior · 03-02-2003, 05:09 PM

Inflationary Theory? haha ok... man just look at the pictures...
"A picture is worth a thousand words."
If I haven't learned much, I have learned that people tend to take things out of proportion...

Oh, and yes.. I was scared out of my mind when I saw those pictures from WMAP - in fact, I immediately showed them to all my friends and family.

lpetrich · 03-02-2003, 10:01 PM

Those fluctuations are a quantum-mechanical effect; they get frozen in place as the Universe expands and stretches them beyond the event-horizon size.

After the inflationary phase ends, the Universe's expansion slows down, and larger and larger fluctuations re-enter the event horizon. These fluctuations can be seen in the Cosmic Microwave Background; galaxies form from matter attracted to them when the Universe gets sufficiently cold.

02-27-2003, 08:24 PM	#1
Shadowy Man Veteran Member Join Date: Jun 2002 Location: A Shadowy Planet Posts: 7,585	No one here understands inflationary theory This afternoon I attended a seminar on the implications of the recent WMAP results on inflationary theory. There were more people at this seminar than ever attended that series of seminars. The speaker was presenting the results from one of the WMAP papers, but to give context for the results he ran us through some "elementary" inflationary theory. My brain hurt after that seminar, and I think I might have understood 25-30% of what he said. Many of the faculty members were noticeably perplexed as well (except for a few particle physicists who understand things like gauge theory, etc.) I feel like I know a little bit more about inflationary theory, but I still plan on reading Guth's book, which I recently purchased, hoping that it is not so technical that I'm hopelessly lost, but technical enough to still be accurate. I came out of that seminar thinking that there's maybe a couple of dozen people around who really understand inflationary theory - the rest of us are just talking out of our asses! Wow!

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02-27-2003, 09:38 PM	#2
Friar Bellows Veteran Member Join Date: Apr 2001 Location: arse-end of the world Posts: 2,305	I know how to spell inflation! Here are three review papers on this topic which you might find useful: Cosmology, Inflation and the Physics of Nothing by William H. Kinney (60 pages) An Introduction to Cosmological Inflation by Andrew R Liddle (36 pages) An Exposition on Inflationary Cosmology by Gary Scott Watson (93 pages)

02-28-2003, 08:58 AM	#4
butswana Veteran Member Join Date: Sep 2001 Location: Indianapolis, IN Posts: 1,804	It takes quite a bit of effort to wrap your brian around this stuff. I understand it but I have one hell of a time if I try to explain it to someone. I find that most people can't get it. It is just not possible for them to comprehend. It makes them feel stupid, so they get pissed off.

02-28-2003, 11:19 PM	#6
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	I'm fairly sure that I understand what inflationary cosmology is, even though peteyh's stumper quote is a bit difficult for me to follow. It would be more convenient to break it up into several sentences. Like: Fluctuations can be scale-invariant adiabatic or isocurvature; they will be assumed to have a Gaussian amplitude distribution. They will produce distinctive signatures of acoustic-mode angular power spectrum and of temperature-polarization correlation -- which can be observed. Their producing different signatures is a result of different times of their re-entering the horizon relative to the time of matter-radiation decoupling.

03-01-2003, 05:51 AM	#7
Shadowy Man Veteran Member Join Date: Jun 2002 Location: A Shadowy Planet Posts: 7,585	Like I said.. I'm very skeptical now of anyone who claims to understand inflationary theory. Can you tell my why the WMAP data rule out theories with isocurvature fluctuations instead of adiabatic ones?

03-01-2003, 07:52 PM	#8
Answerer Veteran Member Join Date: Feb 2002 Location: Singapore Posts: 3,956	Just curious guys, what causes vaccum fluctuations? I heard that it is a random process.

03-02-2003, 05:09 PM	#9
Deep Junior Junior Member Join Date: Mar 2003 Location: Underground Posts: 12	Inflationary Theory? haha ok... man just look at the pictures... "A picture is worth a thousand words." If I haven't learned much, I have learned that people tend to take things out of proportion... Oh, and yes.. I was scared out of my mind when I saw those pictures from WMAP - in fact, I immediately showed them to all my friends and family.

03-02-2003, 10:01 PM	#10
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	Those fluctuations are a quantum-mechanical effect; they get frozen in place as the Universe expands and stretches them beyond the event-horizon size. After the inflationary phase ends, the Universe's expansion slows down, and larger and larger fluctuations re-enter the event horizon. These fluctuations can be seen in the Cosmic Microwave Background; galaxies form from matter attracted to them when the Universe gets sufficiently cold.

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