Register | Sign In


Understanding through Discussion


EvC Forum active members: 65 (9162 total)
4 online now:
Newest Member: popoi
Post Volume: Total: 915,817 Year: 3,074/9,624 Month: 919/1,588 Week: 102/223 Day: 13/17 Hour: 1/1


Thread  Details

Email This Thread
Newer Topic | Older Topic
  
Author Topic:   Big Bounce, instead of Big Bang
JIM
Inactive Member


Message 1 of 7 (59520)
10-05-2003 2:31 PM


Really should call it "Big Bounce" instead of Big Bang.
Yesterday another paper was posted at the Los Alamos arxiv
about getting rid of the Big Bang glitch by quantizing General Relativity.
Martin Bojowald started this line of research but more people are getting into it, the new paper is by a guy at Hamilton College and someone in the Czech Republic
http://arxiv.org/abs/gr-qc/0309035
"Isotropic Loop Quantum Cosmology with Matter II: the Lorentzian Constraint"
Franz Hinterleitner (Masaryk University, Brno) and Seth Major (Hamilton College)
The essential thing here is that (by failing at certain points) classical theories sometimes predict their own replacement by quantized versions. GR does this by breaking down at the time zero singularity (BB) and failing to compute.
There are historical parallels-----in 1900 Planck came up with a theory of thermal radiation (the first quantum theory of anything) that cured a "singularity" in the classical theory of how hot objects radiate-----the classical unquantized theory suffered from infinities, failing to compute sensible answers at either very short or very long wavelengths. Not too long after that Bohr came up with a quantum theory of the hydrogen atom which cured another classical glitch---the unquantized theory predicted absurd results at a certain point and he fixed the bug.
Sometimes by having glitches, a classical theory will show it needs to be quantized, and quantizing it sometimes fixes the bugs. The Big Bang is a glitch in GR. Quantizing GR in a minimal way (not adding new structure besides what is necessary to quantize the basic equations of GR) gets rid of the trouble at time zero (and also predicts inflation without having to add any new particle or field, just from a quantum geometrical effect of ordinary matter)
So there are a bunch of papers cropping up about this and more people getting into it. Here are some names in no particular order of people who (since Bojowald started it) have published about loop quantum cosmology getting rid of the big bang singularity and/or deriving inflation as a result of loop-quantizing GR
Ashtekar
Lewandowski
Bojowald
Smolin
Stephon Alexander (SLAC)
Golam Hossain (Chennai, India)
Gambini
Pullin
Seth Major
Franz Hinterleitner
Doubtless I've missed some.
Hossain's paper was mainly about getting inflation
by loop-quantizing GR, but incidentally gets rid of BB singularity.
------------------
"If A equals success, then the formula is A = X + Y + Z. X is work. Y is play. Z is keep your mouth shut." -- Albert Einstein

Replies to this message:
 Message 5 by w_fortenberry, posted 10-11-2003 9:54 PM JIM has not replied

  
Beercules
Inactive Member


Message 2 of 7 (59773)
10-06-2003 2:29 PM


LQG does not make any testible predictions, and even if it did, there is no built in mechanism to bring an ever expanding universe to contract in the first place. So for now, the bang will not be replaced.

Replies to this message:
 Message 3 by wesir1, posted 10-07-2003 9:16 AM Beercules has not replied

  
wesir1
Inactive Member


Message 3 of 7 (59881)
10-07-2003 9:16 AM
Reply to: Message 2 by Beercules
10-06-2003 2:29 PM


re beercules
Hi there,
"LQG does not make any testible predictions, and even if it did, there is no built in mechanism to bring an ever expanding universe to contract in the first place. So for now, the bang will not be replaced."
on the contary it does, for one the photons traveling from distant Galaxies, ones with a higher energetic level, will travel slighty faster than its lower engergy counterparts, can't recall why this is so... I am guessing its a result of the (higher engertic) photon taken a the path of shortest distance - or ligh cone (LQG spacetime is not consitanty smooth, but rather bubbly)

This message is a reply to:
 Message 2 by Beercules, posted 10-06-2003 2:29 PM Beercules has not replied

  
Beercules
Inactive Member


Message 4 of 7 (59921)
10-07-2003 12:03 PM


The speed of light of various wavelengths does not vary. Where are you getting this from?

  
w_fortenberry
Member (Idle past 6107 days)
Posts: 178
From: Birmingham, AL, USA
Joined: 04-19-2002


Message 5 of 7 (60568)
10-11-2003 9:54 PM
Reply to: Message 1 by JIM
10-05-2003 2:31 PM


GR does this by breaking down at the time zero singularity (BB) and failing to compute.
In your own words, what do you believe to be the reason for the supposed break down of general relativity at the "time zero singularity"?

This message is a reply to:
 Message 1 by JIM, posted 10-05-2003 2:31 PM JIM has not replied

Replies to this message:
 Message 6 by John, posted 10-12-2003 4:30 AM w_fortenberry has not replied

  
John
Inactive Member


Message 6 of 7 (60601)
10-12-2003 4:30 AM
Reply to: Message 5 by w_fortenberry
10-11-2003 9:54 PM


In my words, our math can't handle infinity.
------------------
No webpage found at provided URL: www.hells-handmaiden.com

This message is a reply to:
 Message 5 by w_fortenberry, posted 10-11-2003 9:54 PM w_fortenberry has not replied

Replies to this message:
 Message 7 by NosyNed, posted 10-12-2003 4:40 AM John has not replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 7 of 7 (60603)
10-12-2003 4:40 AM
Reply to: Message 6 by John
10-12-2003 4:30 AM


I don't think it is the math that is the problem. But any theory which produces infinity for an answer somewhere has a problem with the physical interpretation of the math.
It is my weak understanding that currently the idea is that by quantizing GR we get rid of the possibility of a zero sized massive object and so get rid of infinite density.

This message is a reply to:
 Message 6 by John, posted 10-12-2003 4:30 AM John has not replied

  
Newer Topic | Older Topic
Jump to:


Copyright 2001-2023 by EvC Forum, All Rights Reserved

™ Version 4.2
Innovative software from Qwixotic © 2024