The Multiverse, the Initial Conditions, the Laws and, Mathematics by Laura Mersini-Houghton

"Thus, until we find a criterion that forbids the existence of more than one spacetime, we have to allow for a plurality of spacetimes."

Not a single spacetime exists:

WHAT SCIENTIFIC IDEA IS READY FOR RETIREMENT? Steve Giddings: "Spacetime. Physics has always been regarded as playing out on an underlying stage of space and time. Special relativity joined these into spacetime... (...) The apparent need to retire classical spacetime as a fundamental concept is profound..."

Nima Arkani-Hamed 06:11 : "Almost all of us believe that space-time doesn't really exist, space-time is doomed and has to be replaced by some more primitive building blocks."

Einstein's space-time is an absurd consequence of Einstein's 1905 false constant-speed-of-light postulate.

Pentcho Valev

You curtail the kind zeal high-end in most interpreted form of jargon.

With Regards,

Miss. Sujatha Jagannathan

Dear Laura Mersini-Houghton:

In your essay you wrote, "The open debate Fqxi has initiated through these essays on the structure of reality and the place mathematics occupies in it, is very timely. For the first time this decade, we are in a position where the possibility of a vaster and complex cosmos - the multiverse - has not only moved firmly into the realm of scientific exploration, but can potentially be detected in our sky." I think it is likely that evidence for the multiverse is not merely potentially detectable but has ALREADY been detected according to 3 independent lines of evidence: Milgrom's MOND verifications, the space roar, and the photon underproduction crisis. Have you carefully studied the space roar and/or the photon underproduction crisis? -- D. Brown

Hi Laura --

I found this a very interesting essay, partly because your notion of a hierarchy of levels gives a clear framework on which to hang a variety of difficult questions, and partly because you deal with the questions so thoughtfully, explaining how your thinking has changed and what you still find unclear. I found your Notes on Time on arXiv, and I'm glad to find such a clear, not-too-technical treatment of this issue in the multiverse picture.

I'm not convinced of the multiverse idea, though, mainly because it presumes a vast array of definite structure out there, that's just given to begin with. You ask -- if there's no multiverse, "How else can we meaningfully ask how the initial conditions of our universe were selected from an underlying theory, if that theory does not provide an ensemble of possible initial conditions to choose from?" But this assumes that these possible initial conditions are all somehow well-defined in and of themselves.

The point of my essay is that at least in our universe, we have physical contexts that meaningfully define all the relevant laws and conditions that constitute physics, including the structure of spacetime. So the set of physical structures in our world is not an arbitrary selection from an infinite collection of random possibilities. It's a system that works something like a language, to provide contexts in which all its own elements are meaningful in relation to each other. In essays for FQXi contests in 2012 and 2013, I've considered how this kind of self-defining system might have been able to evolve from an initial "state" with no definite rules or conditions. So there is at least a conceivable alternative to an initial landscape of predefined universes.

Thanks -- Conrad

Dear Laura Mersini-Houghton,

While I tend to reject the idea of a multiverse, I found your open and honest description of your thought processes well-written and fascinating. Thank you for writing it as you did. For some reason few people describe how they have changed their mind on basic issues. It is refreshing to read this.

Unless I missed it, you do not treat the topic of entanglement in your multiverse. I invite you to read my essay and consider the possibility that you may not need to do so.

My best regards,

Edwin Eugene Klingman

Laura -

Though I have difficulty reading electronic screens and despite my disagreeing with your essay, I found it FASCINATING!! You came to my attention when I saw the program "Which universe are we in?" on Australian TV last month. I don't think you're EXACTLY correct when you say anomalies in the Cosmic Microwave Background can be explained by gravitation from other universes affecting us. It'd be more correct to say "other SUBuniverses".

I don't believe there was any Big Bang or Inflation, and I'm not a fan of a multiverse that supposes different parts of that multiverse could have different laws of physics or differing laws of nature. Details of my views and alternatives to the big bang / inflation (which, though I avoid equations, do have a powerful foundation in mathematics) are best expressed in the more recent of the short articles I've posted at vixra.org.

I'd recommend #63 ("No Big Bang or Inflation" - http://vixra.org/abs/1410.0196} and #73 ("The Cosmos According To FQXi From A Parallel Universe" - http://vixra.org/abs/1502.0052). The latter has a link to my FQXi essay in the abstract.

Our 13.8-billion-year-old subuniverse is expanding by displacing "old" space-time, and is just one of an infinite number in a single infinite and eternal cosmos which cannot undergo overall expansion (details in the above articles).

Interesting essay, but I have one question. You wrote:

An analogous case can be found in the role language plays on the human mind. Questions such as: 'can the human mind operate without a language?', seem to already be settled with the reply: 'yes'. There still exist tribes in our planet whose members communicate with each other without language.

Please, could you write just one example of tribe communicating without a language? Because I really find difficult to imagine how would it be possible to communicate without any kind of language. Perhaps, there is a problem of translation. Do you mean that "language" is a "spoken language"? Is the gesture communication of deaf-mutes a language or not? Is a road sign (without words - say - just the arrow of one-way direction sign) the sign of a language or not?

Thanks and good luck for the competition.

LF

Dear Professor Mersini-Houghton,

this is a very interesting and thought provoking essay. I'm not sure if the results of Gödel and Cantor should make us quite that pessimistic about using mathematics to model nature. There is a difference between a set of axioms and a model that satisfies those axioms. Incompleteness of a set of axioms means that we can always add another axiom to the set without making things inconsistent. I'm not sure that models have the same incompleteness property, so maybe these results say more about the limitations of thinking of mathematics as sets of axioms than they say about a mathematical model as an adequate model of nature.

I'm also interested in your comments on laws of initial conditions. Though classically we talk about initial conditions, there is no time asymmetry involved since conditions at a time t0 can classically be used both to predict for all times after t0 and to "retrodict" for all times before t0. But a big bang that is classically singular attains such high spacetime curvature that a quantum gravity treatment is necessary. However, the same can be said for the future spacetime singularities that occur inside black holes. Do your theories of the initial conditions also provide "final conditions" for black hole singularities? Also do these theories allow for a "big crunch" and provide final conditions for that? In addition, do the theories allow for white holes? and if so, do they provide initial conditions for the white hole singularity?

Laura -

Thanks for a very fine essay. It seems you have come to a two-level hierarchy for reality - the level of laws (mathematics) and the level of physical reality (the multiverse). But you also have a sense that there is something missing in terms of complexity giving rise to spontaneous transitions.

While I've approached the question using a quite different language, I've ended up with the same two-level hierarchy for laws (Form) and physical reality (Cosmos). And, as I noted in one of the comments, there is actually a third level which I refer to as intentionality. I'm not sure this speaks to quite the same functionality that you ascribe to complexity, but it addresses the same issue - that the world has unfolded through time in a series of transitions of increasing diversity (broken symmetry).

I would be interested to know if you are comfortable with my formulation.

Thanks - George Gantz

Dear Laura

Thanks for the warning about confusion. I do remain confused, but less so than the SM. A well written and original essay, but I may be a little more interested in how you derive the large scale Planck anisotropies via entanglement, largely as I've worked on the same (from the 'observational cosmology' view). I hope you'll study some of the the valuable (Green/Red) fruits in my essay.

On the multiverse; do you consider that anything so mundane as 'multiverses' in separate spatial and temporal domains may be a solution? 'Temporal' merely as sequential recycling of ours, and spatial at a far greater scale range than human minds can normally conceive, in fractal-like 'steps'. i.e. in the 'big' direction we then have 'infinitely' many universes like galaxies with perhaps true vacuum between?

If you feel we need more (after reading my essay) can you identify why?

Many thanks

Peter

I found this an extremely stimulating article. It boldly goes beyond the frontiers of established physics and does so in a reasonable understandable way. However, I had great difficulty making sense of the layer of laws as something with some kind of separated existence beyond space-time. prescriptive laws may have an existence separate from the matter to which gthey are applie. But the laws of physics are not prescriptive. I can't make sense of a separate layer of lws for any branch of established physics. So I see no basis for extrapolating this to idealized future physics

Ed. MacKinnon

Dear Professor L. Mersini-Houghton,

Great thought provoking essay, I have a couple of comments/observations if you dont mind.

I would have to agree your answer to "Does the multiverse exist?" given your definition of the multiverse "contains all the universes, domains, matter and particles, energy and vacua, and any other object you can think of embedded in its spacetimes.". If the multiverse doesn't exist, where are the particles?

Regarding "If there is a multiverse, what does it look like?", you provide a significant amount of material for the reader to digest, but perhaps I am left a little confused. We all want answers, just tell us what it looks like so we dont have to think so hard about it. I am joking of course, not all question in physics have been complete answers at this time, otherwise there would be no jobs for physicists.

WRT the role of mathematics in physics, I thought your comment "can nature contain laws and axioms that cannot be written in a mathematical language, yet still exist?" provided a solid basis to think about the role of mathematics in physics.

Best of luck in the contest, and if so inclined, you can read my essay here. You will see a view of the world that quite different from yours. Regardless of the difference, I really enjoyed your essay and thought it was very well done and a pleasure to read.

Regards, Ed Unverricht

Dear Professor Mersini-Houghton,

I posted a comment at your site that was unnecessarily contemptuous and devoid of the civility all contributors are entitled to. I deeply regret having done so, and I do hope that you can forgive my slurring of your fully deserved reputation.

I suspect that I may be suffering a relapse of Asperger's Disorder. While this might explain my distasteful action, it cannot in any way justify it.

Respectfully,

Joe Fisher

Dear Laura,

Marvelous essay, and one that hits the bull's-eye of today's most profound issues.

Besides holding steadfastly to extending the general relativity solution ("Scientific progress is incremental and at this time we have reached the stage of investigation into fundamental aspects of spacetime") I agree that the multiverse model naturally follows from the identification of time with information theory.

Where we might diverge, is in our opinions on the origin of branching universes. You favor hierarchies -- what I find, on the other hand, is that nature cannot respect any vacuum state without respecting all vacuum states. No hierarchy.

Deserved highest mark from me. I look forward to dialogue.

All best,

Tom

Dear Laura,

It is intriguing that, as you write, the multiverse paradigm agrees with three major physical theories: QM, cosmic inflation and string theory. I like that you describe your point very elegantly, without technicalities and in connection with Planck satellite experiments. As I am a pedestrian in cosmology, I cannot judge if one needs the multiverse hypothesis for the CMB giant cold spot and the CMB additional anisotropies. I heard that another 'church' propose a Poincaré dodecahedral space for the latter effect (J.P. Luminet).

My impression is that many enigma (not in a philosophical range) as the dark energy or the smallness of cosmological constant need an unifying scheme. I am not (yet?) convinced that one needs the many worlds for QM (except for restoring the classical space time). I am also reluctant to accept that the 'laws' are a layer in real world, I tend to favour a cognitive process of humans

in their evolution without further ado. But I agree that it is again a credo without proofs.

Thank you for guiding me into the multiverse hypothesis and good luck (I try to boost your essay). I hope you will have enough time to follow me into the Monstrous World of finite groups.

Michel