Why Do We Seek a Universe Born from 'Almost Nothing'?

[wolram]

I came across this in the AandC reference library posted by Marcus
http://www.astrosociety.org/pubs/mercury/31_02/nothing.html
My question is,Why do we seem to want a universe that started from
"almost", nothing, or reduce our existence and our Us existence
to as close to 0 as possible?

 

[Chronos]

Personal preference is not an issue. Observation shows we live in an expanding universe [at least according to most theorists]. If you run the movie backwards, the opening scene is a dimensionless point. Once Hubble discovered the universe was expanding, theorists pretty much jumped straight to such a scenario and proposed a radical theory - that the universe began in a Big Bang [which is an admittedly poor choice of words - the Big Unfolding would have been better but marketing felt BB was sexier]. They then, like all good scientists, began pondering the consequences of such a theory and came up with some startling predictions - notably primordial elemental abundance and a thing called background radiation. Years later, these predictions were confirmed, which explains the current popularity of the theory.

 

[wolram]

By Cronos
Personal preference is not an issue. Observation shows we live in an expanding universe [at least according to most theorists]. If you run the movie backwards, the opening scene is a dimensionless point. Once Hubble discovered the universe was expanding, theorists pretty much jumped straight to such a scenario and proposed a radical theory - that the universe began in a Big Bang [which is an admittedly poor choice of words - the Big Unfolding would have been better but marketing felt BB was sexier]. They then, like all good scientists, began pondering the consequences of such a theory and came up with some startling predictions - notably primordial elemental abundance and a thing called background radiation. Years later, these predictions were confirmed, which explains the current popularity of the theory.
All the above is understood, but now the singularity is is on the limb of popular
science, and other universe theories are marginal, it seems to me that
some form of energy, matter, has always been in existence in our" vicinity",
and to go beyond that statement is unprovable to date, and may stay
that way until we can send a probe to the edge of a black hole to gather
real data. This is not a dig at popular science, it is just a search for a
fruitful way forward.

 

[NeutronStar]

What are they calling "Nothing"?

Quantum theory, and specifically Heisenberg’s uncertainty principle, provide a natural explanation for how that energy may have come out of nothing. Throughout the universe, particles and antiparticles spontaneously form and quickly annihilate each other without violating the law of energy conservation. These spontaneous births and deaths of so-called "virtual particle" pairs are known as "quantum fluctuations."

Where these people get off using the word "nothing" is beyond me!

Let's say that the universe did start from a "quantum fluctuation" as the theory goes. That's hardly starting from "nothing".

I mean, you can't have a quantum fluctuation if you don't have a quantum field to begin with. The quantum field with all of its properties (i.e. what we see as mathematical rules and regulations) must have been there to "fluctuate" in the first place.

Field theory are not merely human abstractions, fields are necessarily "real" properties of the universe. In other words, the properties and behavior of a field is just as real as the particles or other phenomena that it gives rise to. In fact, it may very well be (and it's my personal opinion) that the universe and everything in it is nothing more the fluctuating fields.

We can hardly claim that "Quantum theory, and specifically Heisenberg's uncertainty principle, provide a natural explanation for how energy may have come out of nothing." If we are using quantum theory and Heisenberg's uncertainty principle, then we are already talking about the properties of a quantum field. So the quantum field must have then existed prior to any "fluctuations".

Why people insist on calling a quantum field "nothing" is beyond me. It obviously has very specific behavioral properties, and even if that's all that it has, at least it has "something". That's more than "nothing".

In other words, some type of "information" must have existed prior to the fluctuation. Or to look at it another way,… there simply must have been "something" there to fluctuate in the first place!

So this conclusion that things are starting from "nothing" is just a little bit absurd to me. But then the mere fact that anything exists at all is quite absurd to me too, so I guess it really doesn’t matter one way or the other.

 

[turbo]

Where these people get off using the word "nothing" is beyond me!

Let's say that the universe did start from a "quantum fluctuation" as the theory goes. That's hardly starting from "nothing".

I mean, you can't have a quantum fluctuation if you don't have a quantum field to begin with. The quantum field with all of its properties (i.e. what we see as mathematical rules and regulations) must have been there to "fluctuate" in the first place.

Field theory are not merely human abstractions, fields are necessarily "real" properties of the universe. In other words, the properties and behavior of a field is just as real as the particles or other phenomena that it gives rise to. In fact, it may very well be (and it's my personal opinion) that the universe and everything in it is nothing more the fluctuating fields.

Shh! You'll scare the children! The pre-existence of a field in which such a fluctuation could have arisen seems essential, doesn't it? A field with real (or at least potential) properties. Hardly nothing.

Going back to Wolram's initial question and Chronos' follow-up: I believe that we humans are hard-wired to prefer absolute answers and closure over open questions. It is comforting to have a sense of certainty over something, and I believe the psychological appeal of a "beginning of it all" is a major factor in the popularity of the Big Bang theory. Not a reasoned "personal choice" perhaps but a deeply ingrained preference for closure.

Einstein, Hubble, Hoyle and others (both theorists and observational astronomers) were comfortable with the concept of a steady-state universe - in fact Einstein inserted the cosmological constant into GR to ensure that the universe did not expand or collapse. It was not until the concepts of "constant speed of light in a vacuum" and "redshift/distance relationship" were combined to produce the idea of "cosmological expansion" that the Big Bang theory evolved. Yes, some of the predictions of the theory have been borne out, but there are a lot of fudge factors required to keep BB viable in the face of discordant observations. Still, it is an attractive theory to many because it gives us a "nailed down" beginning.

The constancy of the speed of light in a vacuum is a fundamental concept to standard cosmology. One significant problem with this is that according to quantum theory, a vacuum cannot exist in our universe. Instead the "vacuum" through which light waves propagate in space is a seething, frothy sea of virtual EM particles and anti-particles. It is a real field, and we must expect it to behave like one, susceptible to polarizing influences and capable of existing at a range of energy densities. Given the absolute theoretical energy of the ZPE field (summed over all wavelengths), this range could be very large, depending on the degree to which the field can be polarized. If EM waves interact with this field to any degree, we must be prepared to expect some measurable effects, like perhaps seeing the light refracted by the field and/or perhaps being redshifted as it traverses great distances.

Hubble "found" the redshift/distance relationship (actually, he demonstrated its linearity), but he was not comfortable with the idea that redshift was caused by the expansion of the universe. It may be that the proponents of a "tired light" concept are correct, since there is no true vacuum in space. Time will tell.

 

[marcus]

I came across this in the AandC reference library posted by Marcus
http://www.astrosociety.org/pubs/mercury/31_02/nothing.html
My question is,Why do we seem to want a universe that started from
"almost", nothing, or reduce our existence and our Us existence
to as close to 0 as possible?

Hi wolram, about that statement (by Filippenko and Pasachoff) of the
"universe is the ultimate free lunch" idea...

Alex is an acquaintance and both he and Ray pasachoff are great teachers and textbook writers---they know how to communicate to undergrad non-majors. So I thought their account of the idea might be a good one to have even tho it is just pedagogical exposition for general audience.

but I don't want to hold it up as an authority!

the universe that bootstraps itself into existence
or begins with a comparatively small fluctuation
is a common idea. Alan Guth also has a good exposition of it IIRC.

but ideas change with time and no one can say This Is It.

It is worth knowing about but maybe it's wrong.

==============
you ask a provocative question about it.
you say, Why are people so drawn to this idea? what is so attractive about free lunch, or getting something from nothing?
========
one thing is it is catchy, it gets your attention because of the paradoxical character. we all know energy conservation and that you DONT get all the matter and energy in the universe from comparatively small beginnings.
but the idea is that it really can happen that way

so the surprise and paradox appeals to people
=========

another appeal is the fact that it takes off some of the constraints and frees the theory up

It is really hard to picture how the universe got started and it makes it easier to come up with descriptions if they don't have to explain where all the huge amount of energy came from.

I guess I'm just saying the obvious here
========

My own personal take: I think everybody should read the latest
Ambjorn Jurkiewicz Loll
Semiclassical Universe from First Principles
because it that paper they have the universe come into existence by itself IN THE COMPUTER, that is, in a computer simulation.

in every one of their runs, there is this long "stalk" of time when the universe has essentially zero size and when growth hasnt started.

and then at some unpredictable moment the thing begins to expand and burgeon out.

they say their model recovers the equation that hawking etc. postulated about the scale factor. and they say they get out of their computer model the business that Villenkin was promoting about the universe coming into existence from littler or nothing.

the AJL paper does bear looking at. I'll be back after lunch.

 

[turbo]

I think everybody should read the latest
Ambjorn Jurkiewicz Loll
Semiclassical Universe from First Principles
because it that paper they have the universe come into existence by itself IN THE COMPUTER, that is, in a computer simulation.

in every one of their runs, there is this long "stalk" of time when the universe has essentially zero size and when growth hasnt started.

and then at some unpredictable moment the thing begins to expand and burgeon out.

they say their model recovers the equation that hawking etc. postulated about the scale factor. and they say they get out of their computer model the business that Villenkin was promoting about the universe coming into existence from littler or nothing.

the AJL paper does bear looking at. I'll be back after lunch.

After your free lunch. In the final reckoning, does not there have to be a field or ground state in which this universe suddenly comes into being? We are back to defining initial conditions.

Indeed, it's turtles all the way down.

 

[Chronos]

All the above is understood, but now the singularity is is on the limb of popular science, and other universe theories are marginal, it seems to me that some form of energy, matter, has always been in existence in our" vicinity", and to go beyond that statement is unprovable to date, and may stay that way until we can send a probe to the edge of a black hole to gather real data. This is not a dig at popular science, it is just a search for a fruitful way forward.

The singularity has always been out on a limb. It has always been generally recognized as the point where the mathematical model breaks down, not reality. The pre-BB state is hidden from view by the Planck wall [the first tick of Planck time] and we may never penetrate that veil. So yes, it is purely speculative to predict or describe the nature of the pre-emergent state. To call it nothing is as good as any other description. It certainly has no known counterpart in the post emergent universe, save perhaps a black hole as you suggested. Of course we can't see inside those either. Just another one of nature's tantalizing little practical jokes.

But was it 'nothing' in the purest philosophical sense? That's not very appealing and gives rise to the most intractable paradox of all. By the strictest logical standard, nothing is omnipotent. How can nothing be destabilized? By what? When you take this into consideration, it is easy to see why the quantum fluctuation proposal is attractive. What do we know about nothing? In this universe nothing is a pure vacuum state. But even a pure vacuum state does not just lay there doing nothing. It continuously churns out stuff [virtual particles] from literally nothing. How can that be? It uses no energy, no matter, but keeps itself amused by popping out little somethings then promptly destroying them. Has that always been the nature of nothing, or did nothing get bored after something crashed the party and decided to take up a hobby?

 

[marcus]

My question is,Why do we seem to want a universe that started from
"almost", nothing, ...

Turbo, read the original post on the thread.
we are not talking about U arising from nothing
but from a comparatively little something

the turtles-all-the-way-down business is of no concern

what apparently concerns a lot of us is our deeprooted notion of Conservation of Energy.

People find it strange that the mass of a billion billion stars could come from, say, a black hole with a mass of no more than few solar masses.

How could the mass-energy of the universe multiply itself a quintillion-fold?

this question needs addressing no matter whatever and however you imagine the original fluctuation or original field or original turtle.

This is why I hope that at least a few people will actually READ the
new AJL article Semiclassical Universe from First Principles

the universe in their simulation, running by their model, bootstraps itself into existence (not from nothing but) from NEARLY nothing, and does so at an unpredicatble time.

and in the process follows a semiclassical equation that was not put into the model, but just happens to be followed.

and the beginnings, in their model, are NOT A FIELD and have no pre-existing spacetime! The kernel from which it begins and burgeons out is purely combinatorial

Indeed the whole model is combinatorial and consists of bunches of n-tuples of natural numbers----space and time and geometry are just
things that emerge at largescale.

And, impressively enough, for the first 10 years or so they were trying to do this stuff, macroscopic space and time did not emerge. what emerged was too fractal-branchy or else too crumpled. In other words they finally got it to work right.

What I am saying is, it matters what kind of turtle.

 

[marcus]

Semiclassical Universe from First Principles
http://arxiv.org/hep-th/0411152

 

[turbo]

I did read it. The BB universe cannot have arisen out of nothing in a field devoid of rules or potentials. "Essentially nothing", "almost nothing", "really close to nothing", etc are all equivalent to SOMETHING. Where did the "tiny little something" come from?

This cannot be addressed logically, any more than the creationists' God can be addressed. If you need a prime mover, a creator, or an initial fluctuation to jump-start your cosmos, you are all in the same boat.

 

[turbo]

What do we know about nothing? In this universe nothing is a pure vacuum state. But even a pure vacuum state does not just lay there doing nothing. It continuously churns out stuff [virtual particles] from literally nothing. How can that be? It uses no energy, no matter, but keeps itself amused by popping out little somethings then promptly destroying them. Has that always been the nature of nothing, or did nothing get bored after something crashed the party and decided to take up a hobby?

Indeed! And the energy level that our universe maintains as its ground state seems to be very high indeed, if quantum field theorists can be believed. Everything that we see, feel, experience, etc, etc, is a fluctuation relative to that ground state. Ain't existence fun?

 

[wolram]

Marcus
This is something i have not read yet but it sounds interesting

My own personal take: I think everybody should read the latest
Ambjorn Jurkiewicz Loll
Semiclassical Universe from First Principles
because it that paper they have the universe come into existence by itself IN THE COMPUTER, that is, in a computer simulation.

 

[wolram]

By Tubo1


Indeed! And the energy level that our universe maintains as its ground state seems to be very high indeed, if quantum field theorists can be believed. Everything that we see, feel, experience, etc, etc, is a fluctuation relative to that ground state. Ain't existence fun?

NO its the most perplexing enigmatic itchy subject i have ever stuck my foot in
Maybe an eternal ZPE field is the answer, i can think of nothing better, but what
about the special turtles Marcus mentions?

 

[wolram]

Marcus.
Semiclassical Universe from First Principles
http://arxiv.org/hep-th/0411152
I may be missing something, but to run this simulation," computer power", is used
is this not cheating?

 

[turbo]

Marcus.
Semiclassical Universe from First Principles
http://arxiv.org/hep-th/0411152
I may be missing something, but to run this simulation," computer power", is used is this not cheating?

Well, it's not as if they just turned on the computer and watched model universes spontaneously arise. They modeled a minisuperspace "stage" that conformed to some very specific laws, as explained in this earlier paper:

http://arxiv.org/PS_cache/hep-th/pdf/0105/0105267.pdf

Unlike previous approaches, we use a space of piecewise linear Lorentzian space-times as our starting point. That this procedure is in general inequivalent to path integrals over bona fide Euclidean geometries has already been demonstrated in two dimensions [7, 8].
The reason why previous discrete path-integral approaches have been formulated for Euclidean gravity 3 is often a technical one, rather than the conviction that Euclidean space-times are more fundamental physical quantities than Lorentzian.

There is a preferred notion of a discrete “time”, namely, the parameter labelling successive spatial slices. Note that this has nothing to do with a gauge choice, since we were not using coordinates in the first place. This “proper time” is simply part of the invariant geometric data common to each of the Lorentzian geometries. We choose particular sets of simplicial building blocks in three and four dimensions. Unlike in the Euclidean case, we cannot make the simplest possible choice of making all d -simplices equilateral. Instead, we fix all spatial (squared) link lengths to 1, l 2 space = 1, and all time-like links to have a squared length l 2 time = −α , α >0. Keeping α variable allows for a relative scaling of space- and time-like lengths and is convenient when discussing the Wick rotation later. As usual, the simplices are taken to be pieces of at Minkowski space, and a simplicial manifold acquires non-trivial curvature through the way the individual building blocks are glued together.

The initial conditions for these simulations were set rather stringently, with lots of decision-making along the way. An analogy to this would seem to favor the "intelligent design" folks and the creationists, for how did our universe arise in the absence of similar initial conditions?

 

[marcus]

... They modeled a minisuperspace "stage" that conformed to some very specific laws, as explained in this earlier paper:

http://arxiv.org/PS_cache/hep-th/pdf/0105/0105267.pdf

Hi turbo. It is really helpful to see relevant passages quoted from the paper, as in your post.
The 2001 paper you give a link for, and quote from, is
hep-th/0105267 "Dynamically Triangulating Lorentzian Q. G."

I agree that this is a really basic paper, and when you read later ones you need to refer back to it for specific detail---so I printed it out.

But I can't find any mention of "minisuperspace" in the paper.
Maybe my eyesight is poor. Do you have a quote from the paper talking about this?

Could you perhaps be mistaken that, in fact:
"They modeled a minisuperspace "stage" that conformed to some very specific laws, as explained in this earlier paper..."

A minisuperspace model----something with a very small number of degrees of freedom, like in the classic Friedmann model where there are just a couple of parameters that evolve and a lot of symmetry is assumed----is different from a full model cosmology.

I would rather say that AJL programmed a FULL model cosmology than that they did a minisuperspace.

However in their recent paper "Semiclassical Universe..." they GOT RESULTS which, if you integrate out other information, BOIL DOWN to a wave function for some other people's earlier minisuperspace.

So they do a full model, but it runs right, and so in gross outlines it reproduces the largescale behavior of an earlier simpler minisuperspace model. But that part was precisely what they DID NOT BUILD IN.

At any rate that is my take on it---maybe you can find some passage that contradicts this. And I think it is a really important distinction.
they start with a comparatively simple and general model. they get results by running it that they did not put in. some evidence of verisimilitude.

For sure there's more to do. They can hopefully make their model
more simple, more general, and more true-to-life in the features that come out of running it.

BTW Martin Bojowald, in Loop Quantum Cosmology, DOES use minisuperspace models derived by simplifying down the full LQG model.
But that is something different---it is Loop, and not Dynamical Triangulations.

You probably are well aware, but i want to emphasize the distinction for clarity, between Loop and CDT.

 

[marcus]

... conformed to some very specific laws, as explained in...

... initial conditions for these simulations were set rather stringently, with lots of decision-making along the way.

specific laws: the question is not how specific the laws, but whether the laws are the right laws.

this is an ontology discussion----bout what is there---and there is a chance that some laws are the right laws because they generate realistic behavior
(given limited computing, like they only had at most 360 thousand 4D blocks to play with, and no matterfields as yet, etc)

stringent initial conditions: I am not sure I would agree.
the initial condition is about as unimposing as I can imaging----just start out with essentially zero volume and wait for something to happen

the initial conditons were so un-demanding that for 10 years or so they couldn't even get a 4D spacetime to emerge---kept getting feathery 2D fractal-like things, or heavily ingrown compacted infinite dimensional crunches.

just because the building block you use is 4D doesn't guarantee the macro assemblage will be 4D----because it is not built in any surrounding space,
the assembly of blocks can happen any way allowed by the model and it IS space

so I would say the initial conditions are rather MINIMAL and UNconstraining, 'cause they don't even guarantee familiar 4D results till you get the evolution rules right

lots of decision-making along the way I think you may be mistaken here also. My impression is that there was no human intervention during runs.
The rules of geometric evolution were set, the minimal initial conditions imposed, and the thing was run repeatedly-----to let an idea of typical geometric evolution emerge.

they accumulated statistics of various types, from hundreds of different runs, which would have been meaningless had they been making decisions by hand---or otherwise interfering

if they had been inclined to put stuff in by hand they could have published (I would say much less valuable) results 10 years ago

 

[turbo]

But I can't find any mention of "minisuperspace" in the paper.
Maybe my eyesight is poor. Do you have a quote from the paper talking about this?

You are correct - the term is inappropriate in this context, and I used it loosely.

So they do a full model, but it runs right, and so in gross outlines it reproduces the largescale behavior of an earlier simpler minisuperspace model. But that part was precisely what they DID NOT BUILD IN.

At any rate that is my take on it---maybe you can find some passage that contradicts this. And I think it is a really important distinction.
they start with a comparatively simple and general model. they get results by running it that they did not put in. some evidence of verisimilitude.

I'm not trying to downplay the importance of their work or call it into question. It's just that I am not tremendously surprised by the results in the November paper. Here's why: It may be that they did not explicitly put in functions that would cause the model to produce the behavior that it exhibited, but we must admit that the functions may be implicit in the initial conditions that they set up. After all, if you want to make a computer model of how the universe arose, and you start by defining space-time using the geometries by which standard cosmologies define space-time, using the same conventions and assumptions, you should expect that your model will mimic the behavior of the universe whose "rules" you put in. If build your model with different rules and assumptions it will behave differently.

For sure there's more to do. They can hopefully make their model more simple, more general, and more true-to-life in the features that come out of running it.

They may be able to make the model simpler and more general - that would be nice. I am quite impressed that they managed to accomplish what they have, so far. At some level, though, (assuming finer divisions of time and space in their model), they will run out of processing power and time. Modeling continuous processes (like weather) by simulation at finer and finer resolutions is what super-computers are built for, after all.

 

[turbo]

specific laws: the question is not how specific the laws, but whether the laws are the right laws.

Absolutely! If the laws are those commonly accepted by standard cosmology, we should expect the model to generate behavior consistent with that cosmology, once the model is set running. Change the laws, and the model will yeild different results.

stringent initial conditions: I am not sure I would agree.
the initial condition is about as unimposing as I can imaging----just start out with essentially zero volume and wait for something to happen

the initial conditons were so un-demanding that for 10 years or so they couldn't even get a 4D spacetime to emerge---kept getting feathery 2D fractal-like things, or heavily ingrown compacted infinite dimensional crunches.

The inability of the model to produce 4D spacetime may have been due to the model's incompleteness, or incorrect assumptions, but I doubt that it was due to a lack of constraint. On the contrary, the model probably had to be "tightened up" a lot over that 10 year period before it could produce the desired results.

lots of decision-making along the way I think you may be mistaken here also. My impression is that there was no human intervention during runs.
The rules of geometric evolution were set, the minimal initial conditions imposed, and the thing was run repeatedly-----to let an idea of typical geometric evolution emerge.

they accumulated statistics of various types, from hundreds of different runs, which would have been meaningless had they been making decisions by hand---or otherwise interfering

if they had been inclined to put stuff in by hand they could have published (I would say much less valuable) results 10 years ago

I did not say (nor did I mean to imply) that the authors intervened during runs. I also did not mean that they explicitly put in functions that would guarantee the subsequent behavior of the model. They made many choices as they built their model, though, and one or more of those choices may have implicitly guaranteed the behavior of the model. I'm not saying this as a perjorative - we must consider that the assumptions underlying the choices may have consequences that are not explicit in the choice. Understanding these consequences and how they arose could be the most valuable part of this study! To the authors' credit, they often explain in the paper why they made those choices and why (in some cases) the choices should not cause problems for the applicability of the model. An example:

As usual in the study of critical phenomena, we expect the final continuum theory (if it exists) to be largely independent of the details of the chosen discretization 6 . Our choice of building blocks is simple and allows for a straightforward Wick rotation. However, other types of fundamental building blocks may sometimes be more convenient. For example, a combination of pyramids and tetrahedra is used in [19] in a three-dimensional context. In general, one should be careful not to restrict the local curvature degrees of freedom too much. With our choice of building blocks, the (discretized) local curvatures around given bones (simplices of dimension d −2) can always take both positive and negative values.

I certainly hope that the final continuum theory is independent of the details of the chosen discretization. To model the emergence of the universe a smooth continuous fashion, they would need a computer bigger than the universe.

 

[wolram]

Well i asked for it and got it, nothing but theory and counter theory, i must say
i count Marcus as a doyen in this subject, but Turbo 1 is also powerful in
rebuttal, I have no problem in thinking that "something" has always existed, and to
be honest i can not see an alternative,.

 

[marcus]

Well i asked for it and got it, nothing but theory and counter theory,...

yes he is, isn't he? powerful in rebuttal

good thread, wolram, not to mention the astute comment from the back bench

 

[marcus]

BTW wolram it would be nice if someone like selfAdjoint would explain how a scalar field creates all that energy to fill the universe with stars

it is just what we are seeing now, but much milder and slower and dilute. with our "dark energy" causing accelerated expansion.

for a split second they had a much stronger form of "dark energy" and it caused a brief episode of inflation and then it thermalized----fizzled, decayed went to pot turned to regular matter (plasma, light, gas) and eventually condensed to stars.

so the scenario goes---never seen it happen so can't be sure.

key thing is, as always the Friedmann equations, according to which if you ever have a CONSTANT ENERGY DENSITY FIELD that is, like, one joule per cubic meter, constant everwhere, or one calorie per cubic meter, constant everywhere

THEN EXPANDING SPACE TO CREATE MORE CUBIC METERS AUTOMATICALLY CREATES MORE ENERGY

and that constant field, if you study it carefully you find it has a negative pressure and actually has an antigravity effect on the expansion that you calculate with the Friedmann equations---which have a pressure term in them.

so all you need is a short-lived dark energy (except stronger than what we have which is only half a joule per cubic kilometer) with a constant or near-constant energy density, and you get inflation

and that brief episode of inflation creates almost all the energy in the universe----just by remaining roughly constant on a per-cubic-meter basis, while the friedmann equation creates more cubic meters.

Then it all thermalizes (turns to regular old matter and light and stuff) and then it begins condensing into stars.

Now obviously you wolram are too smart to believe that. You have never shown even a flicker of credulity all the time you've been posting PF.
However this is what Boffins tell us. what a disgusting word, excuse me for saying Boffin. It's all we have nowadays for a creation story, really.

So this is where it almost all came from. maybe there was a little bit to prime the pump and get started
but 99 percent came from this damned ridiculous scalar field during a splitsecond of inflation which was driven by the field itself.
(just like today's dark energy is actually creating energy, only more slowly, by remaining constant while causing space to expand

Frankly i think they can, and will, do better. But for now that's where 99 percent or more came from.
You asked about creation from nearly zero. so this scalar field thing had to be said. Ask selfAdjoint to confirm, just to be sure.

 

[meteor]

But I can't find any mention of "minisuperspace" in the paper

i think that turbo was really speaking of something that saw in hep-th/0411152
In page 2:

In [13] we reported that the approach of Causal Dynamical Triangulations, despite
its background independence, generates a four-dimensional universe around
which (small) quantum fluctuations take place. The purpose of this letter is to
identify the effective action which determines the shape of this macroscopic 4d
world. Rather surprisingly we find that the effective action which describes the
infrared, long-distance part of the universe is closely related to a simple minisuper-
space action frequently considered in quantum cosmology.

 

[wolram]

I guess this starting from as near to zero as possible depends what
"Mind set", sorry i could not think of the correct word, one has, is the
U infinite or finite, etc, etc.
As for scalar fields creating space and energy, i think that is maybe a
mathematical model that is untestable in the real world, like a few other
theories, Hawking radiation for one.
I have no problem with spook ie science, it is only when the spooks are
invisible that i start to worry that perchance we are going down the
wrong path.

 

[marcus]

I guess this starting from as near to zero as possible depends what
"Mind set", sorry i could not think of the correct word, one has, is the
U infinite or finite, etc, etc.
As for scalar fields creating space and energy, i think that is maybe a
mathematical model that is untestable in the real world, like a few other
theories, Hawking radiation for one.
I have no problem with spook ie science, it is only when the spooks are
invisible that i start to worry that perchance we are going down the
wrong path.

we are always going down the wrong paths frantically, I suppose, 98 percent of the time
but if we are smart we will not go down only one wrong path but go down
a lot of wrong paths
and like a spaghetti nightmare of a feynmann path integral all these wrong paths lead us to the next tavern or halfway house
and then we have a drink, get warmed by the fire and go on from there
it is called the history of science

did you mean to write "in" or "ie"?

You said: "...theories, Hawking radiation for one.
I have no problem with spook ie science, it is only when the spooks are invisible that i start to worry..."

I suppose spooks (plural, uncapitalized) is OK in science
what I can't stand is when they capitalize it and use it in the singular and explain everything with one Spook, this is too stupid even for me.

Yes! the moment someone starts telling you about truly invisible spooks to solve their problems then he should be put somewhere he can be watched.
but it is all part of the nightmare venture along wrong paths that we call scientific progress.

 

[marcus]

i think that turbo was really speaking of something that saw in hep-th/0411152

Yes! and that is my point! Look on page 9 of THAT paper and there is even a whole section titled "3. Minisuperspace"

And there you will see that THEIR model is not a minisuperspace model, but a full model. And that their RESULT is that they recover behavior from runs of the full model which MIMICS the minisuperspace of some important people back in the 1980s.

Apparently Hawking, Hartle, Villenkin, did quantum cosmology using minisuperspace, and just one or two degrees of freedom and a really simple equation, like a basic schroedinger equation for the size of the universe. that was early 1980s.

that was semiclassical and it was all right as far as it went.

The point of the AJL paper is that they discovered that predicted semiclassical behavior, in doing their computer modeling. they found something they did not put in.

This is why the title of AJL most recent:
Semiclassical Universe from First Principles

the first principles is their full model
the semiclassical behavior they recover is the minisuperspace evolution of the earlier researchers

at first sight, at least, it means they scored a hit.

 

[turbo]

I suppose spooks (plural, uncapitalized) is OK in science
what I can't stand is when they capitalize it and use it in the singular and explain everything with one Spook, this is too stupid even for me.

Doesn't that characterize a lot of Cosmology today? When the model does not agree with observation, it seems permissable these days to measure the discrepancy, zero out the discrepancy with a new mathematical entity, and give the entity a snazzy name, like Dark Matter, Dark Energy, Chaplygin Gas, etc. Even though the entities cannot be detected, they take on an air of reality because they are psychologically attractive (like a narcotic) - they "fix" errors in our models, and therefore they must be "real", even if they are undetectable.

By the way, Wolram, Marcus, etc, this has been a very illuminating thread. I spent the better part of today merrily Googling and mining CiteBase for "inflation" "pre Big Bang" "scalar field+inflation" etc. Interestingly, in regard to the "pre Big Bang" links, I found quite a number of papers relating to inflation in String Theory, and a common theme seemed to be something like "how tightly constrained must be the initial conditions before inflation can occur". Not "must there be constraints on initial conditions?", but "what are the values of the constraints on initial conditions?". Something from nothing, indeed. It seems that in these models, even the "nothing" has to follow rules before "something" can emerge.

 

[marcus]

...String Theory, and a common theme seemed to be something like "how tightly constrained must be the initial conditions before inflation can occur". ... It seems that in these models, even the "nothing" has to follow rules before "something" can emerge.

right. this has led to some rather complicated speculation
in which you have infinite space and can afford to wait an unlimited time until something extremely improbable happens

but that takes some prior background spacetime to wait in!

a satisfactory QG theory should make inflation GENERIC with the bare minimum of prior structure-----it should just happen, without fine tuning parameters and without having to wait in a huge Waiting Room for the Unlikely Accident to happen.

For constrast, you might look at "Genericity of Inflation in Loop Quantum Cosmology" by Ganashyam Date. It is one of a bunch of papers pointing out that in Loop cosmology the early gravitational field is just inherently expansive---it does inflation robustly, without a fine tune, and also primes conditions for a second stage of usual inflation as well, if matter is included.

LQG has really been doing well in Cosmology, in the past few years. The stubborn difficulties are with the full theory.
Cosmologists simplify things by assuming some uniformity, so there is less to keep track of and the problems (whether you do classical or quantum) are apparently easier to solve.

 

[turbo]

For constrast, you might look at "Genericity of Inflation in Loop Quantum Cosmology" by Ganashyam Date. It is one of a bunch of papers pointing out that in Loop cosmology the early gravitational field is just inherently expansive---it does inflation robustly, without a fine tune, and also primes conditions for a second stage of usual inflation as well, if matter is included.

Interesting - their model has built-in inflation from a bounce (perhaps one of many), no particle horizon, and a universe that has always existed. A temporally infinite universe moots the "something from nothing" question, since the "something" has always existed anyway.