L. Susskind -- The "Megaverse"

[lpetrich]

Now for some nuclear fine tuning.

Let's consider the first nuclides up from the nucleons.

The deuteron (pn): binding energy +2.2 MeV

From Weizsäcker's semi-empirical mass formula, the binding-energy volume effect is +16 MeV/nucleon, so a deuteron has a low binding energy by nuclear standards.

The dineutron (nn) and the diproton (pp) are borderline unstable. The Effect of Hypothetical Diproton Stability on the Universe If the strong interaction was about 2% stronger, then diprotons would be stable.

This could come about by the pion having lower mass, thus extending the reach of the nucleon-nucleon interaction. The pions' masses are, to first approximation,
sqrt( E_QCD * (m_up + m_down) )

So lowering the up and down quarks' masses should do it.

R. A. W. Bradford calculates that increasing the strength of the strong interaction by 2% should be enough to make diprotons stable. But once a diproton or a dineutron is formed, it will decay to a deuteron. So deuterium may be the most common form of hydrogen in the Universe.


There's also the interesting conundrum of what would happen if the proton is more massive than the neutron, or even if (proton + electron) is more massive than the neutron. This means that neutrons will wander free until they encounter nuclei, including other neutrons. A dineutron will make a deuteron, and here also, deuterium may be the most common hydrogen isotope.


So we get weird universes rather than necessarily-sterile ones.

 

[Farsight]

Looks like lpetrich going to ignore me and start throwing out non-real what-if scenarios in order to start peddling the multiverse again.

Good luck guys.

 

[lpetrich]

Oh boy, now it isn't just the multiverse, now it's intelligent design. Sheesh. lpetrich, look at what you're saying.

These are *speculations*. Farsight, if you can't tell the difference between speculations and well-established theories, then that's your problem, not mine.

By the way, I haven't ignored discussions about why the fine structure constant is variable. That's physics, that's science. The multiverse isn't.

I don't see any evidence of that awareness.

Re topologies, look to TQFT, and think along these lines: different particles are different topologies, or different "field structures".

TQFT is an interesting "toy model", but it's NOT well-established. And no, argumentum ex bellis picturis does not count.

I can't talk much.

Argumentum ex inopiâ temporis
(I can't say that I really know Latin -- I just find it fun to invent Latin names for fallacies)

 

[Farsight]

You carry on with your multiverse and your intelligent design, lpetrich. I've got more important things to do.

 

[Toontown]

That apart, yes, if the fine structure constant had a different value, things would be different.

Different in a Farsight-excluding way, more specifically.

Do you really believe the only possible one-off popgun anomaly of a universe just happens to be the only one that doesn't specifically exclude you?

But one thing wouldn't be different: there would still be some Perpetual Student warbling on about the multiverse.

Some narthok, warbling on about the multiverse, maybe. But no you, specifically. Your specific existence requires, among a large number of other specifics, one particular fine structure constant value, plus or minus a little bit.

Do you really believe you can explain your specific existence by warbling on about how something else would exist if you didn't?

Edit: Or do you believe that your specific existence doesn't need explaining because something else would exist if you didn't, but nothing else can possibly exist, because there ain't no Goldilocks multiverse?

 

[lpetrich]

Then there is the famous Hoyle resonance, a bit of fine tuning that helps form carbon and heavier elements.

Here's what's behind it. Sir Fred Hoyle was considering how heavy elements can be formed in stars. An important link in the chain of reactions was helium to carbon.

He4 + He4 -> Be8 - 93.7 keV
Be8 + He4 -> C12 + 7.367 MeV

But there were some problems. Be8 is unstable, decaying back into 2 He4's, so it could not accumulate. The Be+He->C reaction took place too slowly to form observed amounts of the heavy elements.

So he proposed that C12 had an excited state at about the right energy for Be8 + He4. This excited state, the "Hoyle resonance", was later discovered at an energy of 7.65 MeV, about the right energy. Without such an excited state, it would have been hard to form carbon from helium.

Triple-alpha process^WP

Fred Hoyle was an advocate of steady-state cosmology, which meant that the Big Bang had not happened. So he had to consider the interiors of stars. Big Bang advocates hoped that heavy elements could be produced when the Universe was hot and dense enough for nucleosynthesis.

It turns out that the Big-Bang nucleosynthesis phase could not have produced much of anything much heavier than helium, so the steady-staters were right about the origin of every element much heavier than helium.


A problem with the Hoyle-resonance argument is that there are numerous possible nuclear reactions. In the absence of that excited state and similar ones, it's likely that some other ones may have existed.

 

[Perpetual Student]

You carry on with your multiverse and your intelligent design, lpetrich. I've got more important things to do.

As stated in another thread, a hallmark characteristic of crackpots is the inability to distinguish between scientifically based speculation and woo.

 

[Farsight]

No, the hallmark of a quack is that he starts a thread peddling unscientific snake-oil woo that's been kicking around for fifty years and has no experimental evidential empirical support whatsoever.

And then when somebody expresses their scepticism and explains that the Goldilocks multiverse is a castle-in-the-air because "fine tuned constants" are running constants, the hallmark of a quack is to try to dismiss and disregard it, and call people names.

 

[Perpetual Student]

No, the hallmark of a quack is that he starts a thread peddling unscientific snake-oil woo that's been kicking around for fifty years and has no experimental evidential empirical support whatsoever.

And then when somebody expresses their scepticism and explains that the Goldilocks multiverse is a castle-in-the-air because "fine tuned constants" are running constants, the hallmark of a quack is to try to dismiss and disregard it, and call people names.

Your reading comprehension of these threads is as sloppy as your reading comprehension of physics and cosmology.
Your comment that I "peddled" the multiverse conjecture is patently false as all can see, since I merely presented it as an interesting subject for discussion as a cosmological conjecture -- something that seems to be beyond the ken of crackpots. As for fine tuning, you have yet to show how or why fine-tuning is negated by the "running" of these constants, since they are still within a range one could describe as fine-tuned -- your desperate hand waving to the contrary.
Cherry picking texts, speeches, titles and pretty pictures is not doing physics.
Saddly, I'm afraid it's all beyond your grasp.

 

[lpetrich]

No, the hallmark of a quack is that he starts a thread peddling unscientific snake-oil woo that's been kicking around for fifty years and has no experimental evidential empirical support whatsoever.

Without any attempt to show that someone would have observed it by now.

And then when somebody expresses their scepticism and explains that the Goldilocks multiverse is a castle-in-the-air because "fine tuned constants" are running constants, the hallmark of a quack is to try to dismiss and disregard it, and call people names.

Farsight seems to think that the fine structure constant varies like crazy over the extent of the Universe, and that some parts thus have "good" values and some parts have "bad" values.

That is not absolutely impossible, but there is no good evidence that it happens in the observable parts of our Universe -- there are strong upper limits on how much it varies, something like a few times 10^-4. Not enough to create significantly different values. Strictly speaking, that is the the variation of its zero-momentum limit, since that's what's usually called the fine structure constant. Farsight makes a big fuss about how it is a "running" constant:

FSC = function of FSC0, p
FSC0 = zero-momentum limit
p = interaction momentum

Farsight seems to be arguing that because FSC is known to vary, that FSC0 must also vary. That seems like the fallacy of ambiguity to me.

 

[sol invictus]

And then when somebody expresses their scepticism and explains that the Goldilocks multiverse is a castle-in-the-air because "fine tuned constants" are running constants, the hallmark of a quack is to try to dismiss and disregard it, and call people names.

Actually, you already admitted you were wrong about that. Short memory?

That apart, yes, if the fine structure constant had a different value, things would be different.

 

[Farsight]

Actually, I didn't admit I was wrong about that. Memory playing tricks?