Bang/Crunch Revisited

[modest]

It sounds vaguely like Michael's making reference to the Hartle-Hawking wave function which replaces the idea of the singularity in classical general relativity (the point at which the physics breaks down) with a kind of quantum analogue to a singularity. Read page 251-253. Is this what you're referring to, Michael? Are you saying you support Hawking's model? Or, are you talking about something else?

Links, please.

~modest

[Michael Mooney]

Originally Posted by modest

It sounds vaguely like Michael's making reference to the Hartle-Hawking wave function which replaces the idea of the singularity in classical general relativity (the point at which the physics breaks down) with a kind of quantum analogue to a singularity. Read page 251-253. Is this what you're referring to, Michael? Are you saying you support Hawking's model? Or, are you talking about something else?

Links, please.

~modest

Hawking wrote an intro endorsing Endless Universe by Neil Turok and Paul Steinhardt on M-theory cosmology, and I assumed this meant he was abandoning his singularity model of cosmic origin. This a few months after my criticism of the singularity quote (above) in Myspace. I doubt he or his team saw my posts there, but never the less....

Other refs of a similar nature:

Hawking Loses Bet; Changes Mind on Black Holes

Introduction to M-theory - Wikipedia, the free encyclopedia

"However, many cosmologists, including Stephen Hawking, are drawn to M-Theory because of its mathematical elegance and relative simplicity."

Amazon.com: Wesley L. Janssen's review of The Universe in a Nutshell

Quantum Cosmology, M-theory and the Anthropic Principle

Theories of Everything

"Can Everything Come to Be Without a Cause?"
Can Everything Come to Be Without a Cause?

Some papers on black holes without singularities:

[gr-qc/0504029] Black hole evaporation: A paradigm
[gr-qc/0503041] A black hole mass threshold from non-singular quantum gravitational collapse
[gr-qc/0504043] Quantum Gravitational Collapse
[gr-qc/0411032] The Kantowski-Sachs Space-Time in Loop Quantum Gravity
[gr-qc/0407097] Disappearance of Black Hole Singularity in Quantum Gravity
[gr-qc/0412039] Quantum black holes from null expansion operators
[gr-qc/0410125] Quantum resolution of black hole singularities

"The Great Singularity Debate"
The great Singularity debate | Between the Lines | ZDNet.com

Hope this fulfills the request for links.
Michael

[maddog]

Originally Posted by Michael Mooney

Hawking wrote an intro endorsing Endless Universe by Neil Turok and Paul Steinhardt on M-theory cosmology, and I assumed this meant he was abandoning his singularity model of cosmic origin. This a few months after my criticism of the singularity quote (above) in Myspace. I doubt he or his team saw my posts there, but never the less....

What about Hawking's interest in M-theory would make you think he was abandoning
anything ?

Originally Posted by Michael Mooney

Hawking Loses Bet; Changes Mind on Black Holes

I do hope you are not claiming to be who he made the bet with...
This would have nothing to do with your interaction on MySpace. Really!

Originally Posted by Michael Mooney

Introduction to M-theory - Wikipedia, the free encyclopedia

Good expose on M-theory. I hear Ed Witten has now been considering using Twistor
Theory combined with M-Theory (last five years).

Originally Posted by Michael Mooney

Quantum Cosmology, M-theory and the Anthropic Principle

What is wrong here ?

Originally Posted by Michael Mooney

Theories of Everything

or here ? Posting links with out discussion is worse than not. What is the point of the
link. To what does it relate to (for / against) or what ?

Originally Posted by Michael Mooney

Some papers on black holes without singularities:
[gr-qc/0504029] Black hole evaporation: A paradigm
[gr-qc/0503041] A black hole mass threshold from non-singular quantum gravitational collapse
[gr-qc/0504043] Quantum Gravitational Collapse
[gr-qc/0411032] The Kantowski-Sachs Space-Time in Loop Quantum Gravity
[gr-qc/0407097] Disappearance of Black Hole Singularity in Quantum Gravity
[gr-qc/0412039] Quantum black holes from null expansion operators
[gr-qc/0410125] Quantum resolution of black hole singularities

I will read these papers, they look interesting. Most seem to be addressing qualification
issues for Loop Quantum Gravity (LQG). I am not sure how these links support or not
any point you are attempting to make. BTW, what is your point ???

maddog

[enorbet2]

Now that this thread has apparently hit a stride that is more scientifically based I think it is worthwhile to remind all concerned that nomenclature here is paramount. There is an extreme difference between Quantum Gravity theories and Loop Quantum Gravity theories, somewhat analagous to the boost that Ed Witten gave String theory with supersymmetry resulting in M Theory. In popular terms referring to them interchangeably is akin to equating Ron Howard with Ritchie Cunningham or even Opie.

It isn't that Quantum Gravity has just led directly to Loop Quantum Gravity after the former "hit a wall" in 2004, it's that the "crash" branched out into many theories, with some saying LQG being the most simple, elegant and well-developed. Ifo one hasn't the time to read complete books (which are often years getting to press, but are vastly more complete) it is at least worthwhile for wiki goers to be certain to view both

Quantum gravity - Wikipedia, the free encyclopedia
and
Loop quantum gravity - Wikipedia, the free encyclopedia

Even better see this:

YouTube - Loop quantum gravity 01

be sure to use HQ if your comp supports it, definitely go fullscreen, possibly keep a hand on "brightness" control for reading projected text and don't miss parts 2 and 3. It's superb and points out the "non-perturbative" vs/ "perturbative" differences between the two and the considerable split that results in substantial progress in one of the few Background Independent theories in quest of understanding our Universe. Number geeks will not be disappointed but it is by no means above the heads of the math impaired.

It is said that Quantum Gravity replaces the Big Bang with the Big Bounce but Loop Quantum Gravity does not require it. So this thread goes on, soon to be "quantum leaped" by several new experiments and instruments as divers as LHC and numerous new space telescopes, some at LaGrange points, such as Herschel-Planck. This is a very exciting time!

[enorbet2]

Oh yeah and only very slightly OT but this thread could benefit greatly from some humour

YouTube - TBBT S02E02. Loop Quantum Gravity Vs...

enjoy

[enorbet2]

Distinctly on topic but also worthy of News is progress on a completely different kind of experimental approach based on the smaller AMANDA project. Amanda II Project- Official Site

The ICE CUBE project will ultimately take up over a kilometer square section in ice at Antarctica to track neutrinos. IceCube In Depth

As a particle physics detector capable of detecting neutrinos with energies far above those produced at accelerators, IceCube will search for super-symmetric particles and the topological defects created during grand unified phase transitions in the early universe. The detection of cosmic neutrino beams will also make it possible to study neutrino oscillations over megaparsec baselines.

It's purpose is to do and see things the LHC cannot and consider effects telescopes and colliders cannot, specifically to track the distribution of ancient neutrinos. If said distribution shows that gravity breaks down the quantum nature of neutrinos this would be a serious game changer for all forms of Quantum Gravity as well as String Theory. Obviously this will utterly change this thread, whatever the results, and ICE CUBE will go progressively online since it employs some 4200 receptors and can operate independently and as a sub collective before all are installed, with results just getting better all the time. ICE CUBE is expected to operate over 20 years, which may humble a few in this thread as to just how far away we are from anything really conclusive. Getting out on the edge may be exciting and fun, but it can also be frivolous and/or disappointing to those who stake their reputations prematurely on edgy concepts. As stated in Sagan's "Contact".... "Small steps!" are best.

[Pluto]

G'day from the land of ozzzzz

Observation local and deep field show that both contraction and expansion is occuring at the same time. We look at the motions of galaxies whether cluster or single, star formations and what ever, matter is moving towards a gravity sink and that from this gravity sink, jets eject matter away and in the extreme cases huge jets expell matter, thousands (M87) to millions of lights years ( super black holes located centre of clusters of galaxies )from their origin.

Chandra Press Room :: Extended X-Ray Jet in Nearby Galaxy Reveals Energy Source :: October 25, 1999
Chandra :: Photo Album :: 3C273 :: 06 Nov 00
HubbleSite - NewsCenter - Megastar-Birth Cluster is Biggest, Brightest and Hottest Ever Seen (10/30/2003) - Release Text
HubbleSite - NewsCenter - Images from Hubble's ACS Tell a Tale of Two Record-Breaking Galaxy Clusters (01/01/2004) - Release Text
HubbleSite - NewsCenter - Very Long Baseline Array Reveals Formation Region of Giant Cosmic Jet Near a Black Hole (10/27/1999) - Introduction
Chandra Press Room :: X-ray Arcs Tell The Tale Of Giant Eruption :: August 7, 2002

[gr-qc/0109038] Has the Universe always expanded ?
Has the Universe always expanded ?

Authors: Patrick Peter (IAP), Nelson Pinto-Neto (CBPF)
(Submitted on 11 Sep 2001)

Abstract: We consider a cosmological setting for which the currently expanding era is preceded by a contracting phase, that is, we assume the Universe experienced at least one bounce. We show that scalar hydrodynamic perturbations lead to a singular behavior of the Bardeen potential and/or its derivatives (i.e. the curvature) for whatever Universe model for which the last bounce epoch can be smoothly and causally joined to the radiation dominated era. Such a Universe would be filled with non-linear perturbations long before nucleosynthesis, and would thus be incompatible with observations. We therefore conclude that no observable bounce could possibly have taken place in the early universe if Einstein gravity together with hydrodynamical fluids is to describe its evolution, and hence, under these conditions, that the Universe has always expanded.

[Pluto]

G'day from the land of ozzzzz

This link was posted in the last post, just drawing your attention to the power of the jet that expands matter reforming its surroundings not just within a galaxy but also to near galaxies. A very important process in galaxy evolution.

X-ray Arcs Tell The Tale Of Giant Eruption August 7, 2002

Chandra Press Room :: X-ray Arcs Tell The Tale Of Giant Eruption :: August 7, 2002

Other authors have suggested that the merger of a small spiral galaxy with Centaurus A about a hundred million years ago triggered the high-energy jets and the ongoing violent activity in the nucleus of the galaxy. The tremendous energy released when a galaxy is "turned on" by a collision can have a profound influence on the subsequent evolution of the galaxy and its neighbors. The mass of the central black hole can increase, the gas reservoir for the next generation of stars can be expelled, and the space between the galaxies can be enriched with heavier elements.

We are just leaning about the universe and yet we know all.

[Michael Mooney]

Maddog,
The sub-topic was on cosmic origin... clapping membranes (M-Theory) or singularity (all cosmic "stuff" originally in a "point of zero volume.")

Hawking abandon the latter in favor of the former. Whether or not my debunking of "infinite matter density in a point of zero volume" had anything to do with this particular change of his mind was a side issue and only a chronological sequence of events, not a debate between us, as I clarified before.

Another sub-issue was about the existence (or not) of "singularities" (plural... in general... of all sizes) in black holes. The list of similar links addresses that question.

Modest asked what I was talking about and requested links.

My post answered him honestly and to the best of my ability short of composing and extensive paper on the subject.

Do you have an unresolved problem with me personally which ensures that your every reply will be framed as a personal attack?

Michael

[modest]

Originally Posted by Michael Mooney

Hawking wrote an intro endorsing Endless Universe by Neil Turok and Paul Steinhardt on M-theory cosmology, and I assumed this meant he was abandoning his singularity model of cosmic origin. This a few months after my criticism of the singularity quote (above) in Myspace. I doubt he or his team saw my posts there, but never the less....

Ok. I think I see what happened. When you mentioned Turok it clicked. Hawking bet Turok that the Plank satellite would find relic gravitational waves from inflation supporting a more classical type singularity over a M-theory / colliding brane scenario (which Turok's model is). The exchange is described in the book you mention (page 213):

Endless universe: beyond the Big Bang - Google Books

I don't know if the bet has been settled, but I doubt it because Plank has only just been launched in May.

It certainly has *not* been established by any stretch of the imagination that inflation did not happen while colliding branes did happen. These are very much open questions. The thing you should realize is that the big bang singularity is where general relativistic physics breaks down. So, we need some kind of new physics to understand what (if anything) came before the big bang.

What that new physics will be is a very open question in cosmology and it is certainly not possible as of yet to say conclusively if inflation vs. M-Theory is correct (if indeed either are).

Here Turok talks about his theory and some discussion of the bet with Hawking:

It's a strange idea, though Turok would say it's no stranger than the standard explanation of the Big Bang: a singular point that defies our laws of physics, where all equations go to infinity and "all the properties we normally use to describe the universe and its contents just fail." That inconsistency led Turok to see if the Big Bang could be explained within the framework of string theory, a controversial and so-far untested explanation of the universe as existing in at least 10 dimensions and being formed from one-dimensional building blocks called strings. Within a school of string theory known as m-theory, Turok said, "the seventh extra dimension of space is the gap between two parallel objects called branes. It's like the gap between two parallel mirrors. We thought, What happens if these two mirrors collide? Maybe that was the Big Bang...

Turok: "If the universe sprung into existence and then expanded exponentially, you get gravitational waves traveling through space-time. These would fill the universe, a pattern of echoes of the inflation itself. In our model, the collision of these two branes doesn't make waves at all. So if we could measure the waves, we could see which theory is right.

Stephen Hawking bet me that we'll see the signal from inflation. I said that we won't, and he can take it for any amount of money at even odds. So far he hasn't named an amount. He's richer than me, so he's being nice. "

Physicist Neil Turok: Big Bang Wasn't the Beginning

~modest