Minimal information to make a universe

[wolram]

Is there a minimal amount of information that one could use to make a universe, is this what string theory tries to do, I mean how much information would one need to make all the elementary particles, and how would one input energy to them, and what rules would be needed to build this universe.
If one knew all this one could build a universe but how close can one get?

 

[ohwilleke]

Knowing is not doing. Even if you knew the minimum amount of information and had enough energy there is the difficult little bit about actually imposing the laws of nature implied by that minimum of information on the universe, which nobody I know has the superpowers to accomplish.

 

[rootone]

I guess a minimal description of any hypothetical universe describes a space containing a single Hydrogen atom.
(Assuming that baryonic matter needs to exist in order call something a universe)

 

[newjerseyrunner]

I guess a minimal description of any hypothetical universe describes a space containing a single Hydrogen atom.
(Assuming that baryonic matter needs to exist in order call something a universe)

By that definition there was about 10^-12 seconds between the Big Bang and the start of the universe.

Wouldn't you just need the geometry of spacetime, why does it have to have anything in it? Isn't space, time, and energy the only non reducible parts of our universe (according to current formulations)

Also, what is a universe? If I program QM and GR into a computer with some initial condition and simulate it, is that a universe? You have no way of knowing that's not what we are.

 

[rootone]

... What is a universe? ...

Yes, OP needs to define that.
What is 'a universe' in context of this thread wolram ?

 

[Urs Schreiber]

Is there a minimal amount of information that one could use to make a universe, is this what string theory tries to do,

One way to read this question might be: How much choice is there in the fundamental laws of nature, and in the value of the fundamental constants they depend on?

In different terminology, this is an ancient question, not unrelated to the search for ontological arguments , which tried to argue for the logical necessity of existence (of "god" in the terminology of those days) based only on pure logic. In the early 19th century Georg Hegel claimed a vast generalization of the ontological argument to metaphysics and eventually physics, claiming that from the assumption of, literally, nothingness, and following just a fundamental logical process of conceptual oppositions and unifications, first the metaphysical concepts and then eventually space, time, matter and then all the rest would emerge by logical necessity, from literal nothingness. Accordingly he called this the Science of Logic .
(While, clearly Hegel's account remains vague and unsatisfactory from a modern perspective, it is striking which insights he did gain. For instance after he argues that and how space and time emerge from pure logic, next he claims to find that they must necessarily be able to transform into each other and form a unity., see here )

While these deep considerations were mostly forgotten by the natural science community (and not appreciated for their scientific content by the philosophers) it indeed so happens that, back in the days of the 1980s, there was for a short but intensive while a meme alive that possibly string theory might give a way to see that, assuming just the principles of spacetime of stringy S-matrices, then the space of choices for the universe might be close to being a singleton. This meme originated from the seminal article Candelas-Horowitz-Strominger-Witten 85 on Calabi-Yau compactifications of string backgronds, and from the initial ignorance among string theorists about Calabi-Yau manifolds, resulting in the infamous initial idea that there might be only very few of them, each encoding one of a very small number of kinds of possible 4-dimensional "universes". The later surprise when the community as a whole realized that there are in general many possibilities for compactifications (a "landscape" of them) has to be understood on the backdrop of this initial hope for a stringy version of the "ontological argument".

What has not been considered much is a systematic re-analysis, using modern mathematics and modern insights into fundamental physics, of the idea of Hegelian ontology. I have once tried to give such, laid out in

• Urs Schreiber, Modern Physics formalized in Modal Homotopy Type Theory, to appear in S. Centrone, D. Kant, D. Sarikaya (eds.) What are Suitable Criteria for a Foundation of Mathematics? (2017) Springer Synthese Library

This starts with giving a mathematical formalization of something like Hegel's ontological Proceß , then demonstrates that from this process the super-point emerges, and then demonstrates that from the super-point emerges spacetime, gravity, strings and branes (reviewed now in more detail here). Notice that, besides some basic assumptions on how the process is to proceed, this is a sequence of mathematical theorems. It remains to see what exactly to make of these results, but the result itself is just a fact.