What Makes the Hilbert Cube Cubelike?

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Discussion Overview

The discussion centers around the properties and definitions of the Hilbert cube, particularly what makes it "cubelike." Participants explore various definitions and visualizations of the Hilbert cube, including its relationship to homeomorphism and product topology.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions the meaning of "cubelike" in relation to the Hilbert cube and suggests it may be due to its homeomorphism to I^inf.
  • Another participant notes that the Hilbert cube can be defined in various ways, specifically referencing a definition involving the subset of l^2 space.
  • A participant explains that the Hilbert cube is the product [0,1]^{\mathbb{N}} with the product topology and mentions that taking the product of three intervals resembles a cube, which contributes to the naming.
  • Another participant adds that a cube can be defined as a product of any closed intervals and suggests that using the definition involving [0,1] x [0,1/2] x [0,1/3] x ... is preferred in Hilbert space contexts due to its isometric properties.

Areas of Agreement / Disagreement

Participants express differing definitions and perspectives on the Hilbert cube, indicating that multiple competing views remain without a consensus on a singular definition or understanding.

Contextual Notes

Limitations include the ambiguity in definitions of the Hilbert cube and the varying interpretations of what constitutes "cubelike." There are also unresolved aspects regarding the implications of homeomorphism versus isometry in this context.

Cincinnatus
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So, what exactly is "cubelike" about the hilbert cube?

I think I am having trouble "visualizing" it. Is it just called that because it it homeomorphic to I^inf. ?
 
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I realize there are different ways of defining the hilbert cube, so this question probably doesn't make much sense.

My class defined it to be the subset of l^2 space given by 0<x_n<1/n (actually less than or equal to).
 
the hilbert cube is the product [tex][0,1]^{\mathbb{N}}[/tex] with the product topology. if you take the product of just 3 of them it looks like a cube, hence the name. some people like to define it as [0,1] x [0,1/2] x [0,1/3] x ... x [0, 1/n] x ... just because it's easier to work with, but it doesn't really matter since all closed intervals are homeomorphic to [0,1]
 
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actually a cube is a product of any closed intervals. someone working in a hilbert space would rather use [0,1] x [0,1/2] x [0,1/3] x ... x [0, 1/n] x ... as the definition since it is isometric, rather than just homeomorphic, to a subspace of itself.
 

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