Does multiverse really explain fine-tuning?

[Chalnoth]

Except that outcome has arisen from incomplete physics which does not have a quantum gravity theory and that does not know what the Inflaton or Dark Matter, or Dark Energy are.

The extrapolation of theory into the infinite landscape of string and inflation hypotheses may be nothing more than the outcome of our ignorance.,

Maybe, but there is absolutely no reason to think this. And how would ruling out a class of models dissuade investigations into physical causes? Are multiverse models somehow unphysical?

 

[Haelfix]

Except that outcome has arisen from incomplete physics which does not have a quantum gravity theory and that does not know what the Inflaton or Dark Matter, or Dark Energy are.
The extrapolation of theory into the infinite landscape of string and inflation hypotheses may be nothing more than the outcome of our ignorance.
Garth

Without a doubt there is much more to be discovered, but note that one of the great theoretical virtues of inflation is that (unlike its competitors) it arises from the physics of weak coupling. In other words we can reliably make many statements (but not all) about what it predicts, without knowing too much about messy unknown details of what happens in the deep UV (it is sensitive to these details, but not so much that we can't still make reliable predictions about certain aspects) This is one of the reasons it is so deeply studied.

Now, of course, if you asked me whether this is the final say on the matter I would tell you probably not, but nevertheless this is what we have, its quite successful so let's go with it and see where it leads, rather than throwing the baby out with the bathwater. As far as I'm concerned the question of whether the multiverse exists or not, is basically a spectator that comes along for the ride of this much deeper question.

 

[Garth]

Maybe, but there is absolutely no reason to think this. And how would ruling out a class of models dissuade investigations into physical causes? Are multiverse models somehow unphysical?

'Physical causes' in the sense that such hypotheses can be tested by experiment.

I'm not ruling out a class of models, I just find explanations unsatisfactory when they explain global properties of this universe by invoking others.

Garth

 

[Chalnoth]

'Physical causes' in the sense that such hypotheses can be tested by experiment.

I'm not ruling out a class of models, I just find explanations unsatisfactory when they explain global properties of this universe by invoking others.

And many multiverse models are testable. Your point?

 

[Garth]

And many multiverse models are testable. Your point?

Testable? Exactly how?

Garth

 

[Chalnoth]

Testable? Exactly how?

Garth

Testable. If anybody was claiming that a specific multiverse model were true, then you might have a point.

 

[Garth]

So are you saying that only specific models are testable and that the 'multiverse paradigm' itself is not?

We have an questioned theory of Inflation that predicts a multiverse.

As I said above while there are crucial and pertinent elements of fundamental physics still unknown such a prediction may well be just the outcome of an extrapolation of our ignorance.

Garth

 

[Chalnoth]

So are you saying that only specific models are testable and that the 'multiverse paradigm' itself is not?

Of course. It's typically not possible to test something that isn't specific, and the term "multiverse" isn't specific.

We have an questioned theory of Inflation that predicts a multiverse.

Even without inflation, if you have a theory of high-energy physics that includes any spontaneous symmetry breaking, you have a multiverse.

As I said above while there are crucial and pertinent elements of fundamental physics still unknown such a prediction may well be just the outcome of an extrapolation of our ignorance.

Maybe, but that's hardly a convincing argument. High-energy physics theories are pushing in the opposite direction, towards more types of spontaneous symmetry breaking. Sure, it's conceivable that this is misleading, that a deeper understanding of high-energy physics will validate notions of the universe that were popular before we started delving into high-energy physics, but why should we expect that to be the case?