Sorgenfrey Plane

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The Sorgenfrey Plane is an example of a product space of two Lindelöf spaces that is not itself Lindelöf.[1] It should be noted that the Sorgenfrey plane is not normal.


The Sorgenfrey Plane, named after mathematician Robert Sorgenfrey, is defined as the product topology of two Lindelöf spaces: $$\mathbb{R}_\ell \times \mathbb{R}_\ell = \mathbb{R}^2_\ell$$

Further Reading

External Links


  1. Munkres, James R. Topology, 2015. pg. 191.