Skip to main content
added 6 characters in body; added 21 characters in body
Source Link
Zarathustra
  • 1.4k
  • 12
  • 20

Let me write down the steps.

  1. Consider the case d=2, the generalization is straightforward.
  2. There is an open ball B that doesn't intersect E.
  3. Consider two families of geodesic circles F_1 and F_2. F_1 has slope 1/p and F_2 has slope 1-1/p. Number p is chosen in such a way that each circle from F_1 nd F_2 intersects B.
  4. Claim: $Leb(E\cap F_1(x))\le 1/2 length(F_1(x))$ OR $Leb(E\cap F_2(x))\le 1/2 length(F_1(x))$ for each x.
  5. Proof: $E\cap F_1(x)$ is a proper union of open intervals that are separated by gaps of length at leadleast $\sqrt{p^2+1}/2p$. So it remains to shoeshow that there are at least $p$ gaps. If there <pare less than $p$ gaps then there is an interval from $E\cap F_1(x)$ of length >greater than $\sqrt{p^2+1}/2p$. It follows that one can find a simple closed curve C_1 in E which is C^0 close to a horizontal generator. Assume that in the same way we also can find C_2 in E which is C^0 close to the vertical generator. Then one can easily see that E is the torus and the claim follows.
  6. Apply Fubini.

Let me write down the steps.

  1. Consider the case d=2, the generalization is straightforward.
  2. There is an open ball B that doesn't intersect E.
  3. Consider two families of geodesic circles F_1 and F_2. F_1 has slope 1/p and F_2 has slope 1-1/p. Number p is chosen in such a way that each circle from F_1 nd F_2 intersects B.
  4. Claim: $Leb(E\cap F_1(x))\le 1/2 length(F_1(x))$ OR $Leb(E\cap F_2(x))\le 1/2 length(F_1(x))$ for each x.
  5. Proof: $E\cap F_1(x)$ is a proper union of open intervals that are separated by gaps of length at lead $\sqrt{p^2+1}/2p$. So it remains to shoe that there are at least $p$ gaps. If there <p gaps then there is an interval from $E\cap F_1(x)$ of length > $\sqrt{p^2+1}/2p$. It follows that one can find a simple closed curve C_1 in E which is C^0 close to a horizontal generator. Assume that in the same way we also can find C_2 in E which is C^0 close to the vertical generator. Then one can easily see that E is the torus and the claim follows.
  6. Apply Fubini.

Let me write down the steps.

  1. Consider the case d=2, the generalization is straightforward.
  2. There is an open ball B that doesn't intersect E.
  3. Consider two families of geodesic circles F_1 and F_2. F_1 has slope 1/p and F_2 has slope 1-1/p. Number p is chosen in such a way that each circle from F_1 nd F_2 intersects B.
  4. Claim: $Leb(E\cap F_1(x))\le 1/2 length(F_1(x))$ OR $Leb(E\cap F_2(x))\le 1/2 length(F_1(x))$ for each x.
  5. Proof: $E\cap F_1(x)$ is a proper union of open intervals that are separated by gaps of length at least $\sqrt{p^2+1}/2p$. So it remains to show that there are at least $p$ gaps. If there are less than $p$ gaps then there is an interval from $E\cap F_1(x)$ of length greater than $\sqrt{p^2+1}/2p$. It follows that one can find a simple closed curve C_1 in E which is C^0 close to a horizontal generator. Assume that in the same way we also can find C_2 in E which is C^0 close to the vertical generator. Then one can easily see that E is the torus and the claim follows.
  6. Apply Fubini.
Source Link
Zarathustra
  • 1.4k
  • 12
  • 20

Let me write down the steps.

  1. Consider the case d=2, the generalization is straightforward.
  2. There is an open ball B that doesn't intersect E.
  3. Consider two families of geodesic circles F_1 and F_2. F_1 has slope 1/p and F_2 has slope 1-1/p. Number p is chosen in such a way that each circle from F_1 nd F_2 intersects B.
  4. Claim: $Leb(E\cap F_1(x))\le 1/2 length(F_1(x))$ OR $Leb(E\cap F_2(x))\le 1/2 length(F_1(x))$ for each x.
  5. Proof: $E\cap F_1(x)$ is a proper union of open intervals that are separated by gaps of length at lead $\sqrt{p^2+1}/2p$. So it remains to shoe that there are at least $p$ gaps. If there <p gaps then there is an interval from $E\cap F_1(x)$ of length > $\sqrt{p^2+1}/2p$. It follows that one can find a simple closed curve C_1 in E which is C^0 close to a horizontal generator. Assume that in the same way we also can find C_2 in E which is C^0 close to the vertical generator. Then one can easily see that E is the torus and the claim follows.
  6. Apply Fubini.