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Life in a 2D +1 Universe:

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https://phys.org/news/2019-06-physics-life-d-universe.html

Researcher shows physics suggests life could exist in a 2-D universe

by Bob Yirka , Phys.org

James Scargill, a physicist at the University of California, has written a paper reporting that the laws of physics allow for the existence of a life-supporting two-dimensional universe. MIT's Technology Review has reviewed the paper and found that the work does show that such a 2+1 universe could exist.

Because we live in three-dimensions, it is difficult for us to envision a universe in which the third dimension does not exist—or one in which there is a fourth or fifth dimension. But philosophers and physicists have spent a lot of time and work trying to figure out if life could exist in anything but the three dimensions we know. In such discussions, time is also included, which has led to the description of what we experience as a 3+1-dimensional universe.

more at link.....

the paper:

https://arxiv.org/pdf/1906.05336.pdf

Can Life Exist in 2 + 1 Dimensions?

Abstract: 

There are anthropic reasons to suspect that life in more than three spatial dimensions is not possible, and if the same could be said of fewer than three, then one would have an anthropic argument for why we experience precisely three large spatial dimensions. There are two main arguments levelled against the possibility of life in 2 + 1 dimensions: the lack of a local gravitational force and Newtonian limit in 3D general relativity, and the claim that the restriction to a planar topology means that the possibilities are ‘too simple’ for life to exist. I will examine these arguments and show how a purely scalar theory of gravity may evade the first one, before considering certain families of planar graphs which share properties which are observed in real-life biological neural networks and are argued to be important for their functioning.

Conclusions:

In this paper I have considered the two main arguments which are commonly presented against the possibility of complex life in 2 + 1 dimensions: the absence of a local gravitational force in three-dimensional general relativity, and that the topological restrictions placed by requiring planarity are too severe to allow complex life. The first can be avoided by changing the gravitational theory. As a proof-of-principle I have presented a purely scalar theory of gravity which allows stable orbits around point sources, and has a not-obviously-fatal (though unusual) cosmology; it could potentially be improved by making the whole metric dynamical. One could also imagine a brane-world scenario in which the massless graviton is not localised to the brane, thus allowing two-dimensional life to enjoy fully four-dimensional gravity. To deal with the second objection I have turned to research that has been conducted into the properties of biological neural networks, and created a family of planar graphs (the ‘cycle-based’ ones from section 3.1.3) which seem to exhibit many of the properties which have been conjectured to be important for complex brains. In particular they are approximately ‘small-world,’ they have a hierarchical and modular construction, and they show evidence of the stretching (in parameter space) of a critical point into a finite critical region for certain stochastic processes. It should be noted that whilst this is certainly suggestive of the possibility of complex brains in two dimensions, it is not conclusive, as it likely that the properties described above are not sufficient on their own. Therefore more work is needed to compare the graphs presented here with real-life neural networks (and also to include edge weights and directions, which have been neglected here), as well as to consider further families of planar graphs, in order to arrive at a more complete understanding of the possibility of complex brains in two dimensions. Overall it would seem that if one wishes to use anthropic reasoning to explain the observed dimensionality of space-time, then the possibility of life in 2+1 dimensions requires further investigation. In particular it would be interesting to determine if there might be other impediments to life which have so far been overlooked, as well as to continue to search for non-anthropic explanations for the dimensionality of space-time.

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Don't like it, but hey! it's only me! 

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Posted (edited)

We could put it in the drawer along with reversed entropy, parallel universes and supersymmetry :D

Edited by QuantumT

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