June 15th, 2017, 09:33 PM  #1 
Senior Member Joined: May 2015 From: Arlington, VA Posts: 258 Thanks: 23 Math Focus: Number theory  Connecting spacetime curvatures
Can the connected curvatures of the universe be more than one of flat, positive or negative?

June 17th, 2017, 09:20 AM  #2 
Math Team Joined: Jan 2015 From: Alabama Posts: 2,647 Thanks: 680 
I really have no idea what you are thinking here. "Curvature" is, by definition, a real number. All real numbers are one and only one of "zero", "positive", or "negative". There is no other possibilities!

June 17th, 2017, 10:24 AM  #3 
Senior Member Joined: Sep 2015 From: Southern California, USA Posts: 1,403 Thanks: 713 
I'm thinking this might be a good place to start. Perhaps you can refine your question. If you're asking can spacetime locally take on any value of curvature the answer is probably yes though it might take theoretical negative mass to achieve it. 
June 17th, 2017, 03:43 PM  #4 
Senior Member Joined: May 2015 From: Arlington, VA Posts: 258 Thanks: 23 Math Focus: Number theory 
"The curvature of space is a geometric description of length relationships in spatial coordinates. In mathematics, any geometry has three possible curvatures, so the geometry of the universe has the same three possible curvatures. Flat (A drawn triangle's angles add up to 180° and the Pythagorean theorem holds) Positively curved (A drawn triangle's angles add up to more than 180°) Negatively curved (A drawn triangle's angles add up to less than 180°)" __________ I am asking whether two or all three of such spaces can exist as one. I.e., can different curvatures connect continuously? (E.g., saddles to spheres to planes or combinations thereof?) 
June 17th, 2017, 04:58 PM  #5  
Senior Member Joined: Aug 2012 Posts: 1,521 Thanks: 364  Quote:
What if mathematics itself tells us more about us than it does the universe? The ant crawling on a leaf on a tree in a forest has a theory too, at its level of being able to form theories. Arguably same as us.  
June 17th, 2017, 06:06 PM  #6 
Senior Member Joined: May 2015 From: Arlington, VA Posts: 258 Thanks: 23 Math Focus: Number theory 
Maschke, The statement was from the wiki article that romsek referred to, and which I glanced at. Can one construct microscopically any of the three curvatures from the others? Could a fractal universe arise with two or three curvatures? How about if spatial curvature was relative to the observer's curvature? Maybe then a saddle universe would seem flat to a saddle observer. Fourdimensionality (spacetime) has been explored extensively with regard to curvature. Do higher dimensions like CalabiYau involve more concepts of curvature? A peculiar universe (like that of polyhedra) with singularities might require a discontinuous treatment. 

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