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José Navarro
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Recently, I came across a beautiful paper by Arnol'd and Krylov (Uniform distribution of points on a sphere...) that contains the following theorem:

Theorem: Let A and B be two rotations of the sphere $S_2$ and let $x$ be a point of the sphere. If the sequence of points $$x, Ax, Bx, A^2x, ABx, BAx, B^2x, \ldots $$ is dense on the sphere, then it is uniformly distributed.

Here, uniformly distributed means that, if we consider the $2^n$ points produced with exactly $n$ iterations of the rotations, namely $$ A^nx , A^{n-1}Bx , A^{n-2}BAx , \ldots , B^nx \ , $$ and we count the proportion of them that lie inside a region $\Delta$ (bounded by a piecewise smooth curve), then these ratios converge to the measure of $\Delta$; that is to say: $$ \lim_{n\to \infty} \frac{\mbox{Number of points among } \{A^nx , \ldots , B^nx \} \mbox{ inside } \Delta}{2^n} = \frac{\mu(\Delta)}{\mu(S_2)}.$$

A quick search has shown to me that there have been many developments of the ideas behind this result, in many different directions.

But I was wondering what is the state of the art concerning the uniform distribution of points under the action of semigroups of isometries in a more general situation.

To be precise,

Question: Is there a similar result for the action of a (finitely generated) semigroup of isometries of a compact Riemannian manifold?

As an example (on a non-compact manifold), there is a theorem by Kazhdan (Uniform distribution on a plane) that concerns the action on the Euclidean plane of the semigroup generated by a rotation and an arbitrary motion.

Nevertheless, mostMost of the references I see are too specialized for me and, although they seem very general, I am not able to understand whether they cover the situation I am interested in or not.

Edit 1

In the following reference:

Guivarc'h, Y.: Equirépartition dans les espaces homogènes, in Théorie Ergodique, LNM 532, Springer, Berlin (1976) pp. 131--142.

the author seems to comment in the introduction that an analogous result to that of Arnol'd-Krylov holds for the sequence of probabilities $p_n = \frac{1}{n} \sum_{k=0}^{n-1} p^k$ on a compact Lie group.

Here, $p$ is a sum of Dirac deltas, its power $p^k$ is made via the convolution product and the equidistribution statement is written in terms of convergence of probabilities.

As the group of isometries of a compact Riemannian manifold is a compact Lie group, I assume that the answer to my question is yes, but I am not sure yet (there are many assumptions on Guivarc'h's note and very few details...).

Recently, I came across a beautiful paper by Arnol'd and Krylov (Uniform distribution of points on a sphere...) that contains the following theorem:

Theorem: Let A and B be two rotations of the sphere $S_2$ and let $x$ be a point of the sphere. If the sequence of points $$x, Ax, Bx, A^2x, ABx, BAx, B^2x, \ldots $$ is dense on the sphere, then it is uniformly distributed.

Here, uniformly distributed means that, if we consider the $2^n$ points produced with exactly $n$ iterations of the rotations, namely $$ A^nx , A^{n-1}Bx , A^{n-2}BAx , \ldots , B^nx \ , $$ and we count the proportion of them that lie inside a region $\Delta$ (bounded by a piecewise smooth curve), then these ratios converge to the measure of $\Delta$; that is to say: $$ \lim_{n\to \infty} \frac{\mbox{Number of points among } \{A^nx , \ldots , B^nx \} \mbox{ inside } \Delta}{2^n} = \frac{\mu(\Delta)}{\mu(S_2)}.$$

A quick search has shown to me that there have been many developments of the ideas behind this result, in many different directions.

But I was wondering what is the state of the art concerning the uniform distribution of points under the action of semigroups of isometries in a more general situation.

To be precise,

Question: Is there a similar result for the action of a (finitely generated) semigroup of isometries of a compact Riemannian manifold?

As an example (on a non-compact manifold), there is a theorem by Kazhdan (Uniform distribution on a plane) that concerns the action on the Euclidean plane of the semigroup generated by a rotation and an arbitrary motion.

Nevertheless, most of the references I see are too specialized for me and, although they seem very general, I am not able to understand whether they cover the situation I am interested in or not.

Recently, I came across a beautiful paper by Arnol'd and Krylov (Uniform distribution of points on a sphere...) that contains the following theorem:

Theorem: Let A and B be two rotations of the sphere $S_2$ and let $x$ be a point of the sphere. If the sequence of points $$x, Ax, Bx, A^2x, ABx, BAx, B^2x, \ldots $$ is dense on the sphere, then it is uniformly distributed.

Here, uniformly distributed means that, if we consider the $2^n$ points produced with exactly $n$ iterations of the rotations, namely $$ A^nx , A^{n-1}Bx , A^{n-2}BAx , \ldots , B^nx \ , $$ and we count the proportion of them that lie inside a region $\Delta$ (bounded by a piecewise smooth curve), then these ratios converge to the measure of $\Delta$; that is to say: $$ \lim_{n\to \infty} \frac{\mbox{Number of points among } \{A^nx , \ldots , B^nx \} \mbox{ inside } \Delta}{2^n} = \frac{\mu(\Delta)}{\mu(S_2)}.$$

A quick search has shown to me that there have been many developments of the ideas behind this result, in many different directions.

But I was wondering what is the state of the art concerning the uniform distribution of points under the action of semigroups of isometries in a more general situation.

To be precise,

Question: Is there a similar result for the action of a (finitely generated) semigroup of isometries of a compact Riemannian manifold?

Most of the references I see are too specialized for me and, although they seem very general, I am not able to understand whether they cover the situation I am interested in or not.

Edit 1

In the following reference:

Guivarc'h, Y.: Equirépartition dans les espaces homogènes, in Théorie Ergodique, LNM 532, Springer, Berlin (1976) pp. 131--142.

the author seems to comment in the introduction that an analogous result to that of Arnol'd-Krylov holds for the sequence of probabilities $p_n = \frac{1}{n} \sum_{k=0}^{n-1} p^k$ on a compact Lie group.

Here, $p$ is a sum of Dirac deltas, its power $p^k$ is made via the convolution product and the equidistribution statement is written in terms of convergence of probabilities.

As the group of isometries of a compact Riemannian manifold is a compact Lie group, I assume that the answer to my question is yes, but I am not sure yet (there are many assumptions on Guivarc'h's note and very few details...).

Notice added Draw attention by José Navarro
Bounty Started worth 50 reputation by José Navarro
Improved explanation (with only one change).
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José Navarro
  • 1.1k
  • 10
  • 20

Recently, I came across a beautiful paper by Arnol'd and Krylov (Uniform distribution of points on a sphere...) that contains the following theorem:

Theorem: Let A and B be two rotations of the sphere $S_2$ and let $x$ be a point of the sphere. If the sequence of points $$x, Ax, Bx, A^2x, ABx, BAx, B^2x, \ldots $$ is dense on the sphere, then it is uniformly distributed.

Here, uniformly distributed means that, if we consider the $2^n$ points produced with exactly $n$ iterations of the rotations, namely $$ A^nx , A^{n-1}Bx , A^{n-2}BAx , \ldots , B^nx \ , $$ and we count the proportion of them that lie inside a region $\Delta$ (bounded by a piecewise smooth curve), then these ratios converge to the measure of $\Delta$; that is to say: $$ \lim_{n\to \infty} \frac{\mbox{Number of points among } \{A^nx , \ldots , B^nx \} \mbox{ inside } \Delta}{2^n} = \frac{\mu(\Delta)}{\mu(S_2)}.$$

A quick search has shown to me that there have been many developments of the ideas behind this result, in many different directions.

But I was wondering what is the state of the art concerning the uniform distribution of points under the action of semigroups of isometries in a more general situation.

To be precise,

Question: Is there a similar result for the action of a (finitely generated) semigroup of isometries of a compact Riemannian manifold?

As an example (on a non-compact manifold), there is a theorem by Kazhdan (Uniform distribution on a plane) that concerns the action on the Euclidean plane of the semigroup generated by a rotation and an arbitrary motion.

Nevertheless, most of the references I see are too specialized for me and, although they seem very general, I am not able to understand whether they cover the situation I am interested in or not.

Recently, I came across a beautiful paper by Arnol'd and Krylov (Uniform distribution of points on a sphere...) that contains the following theorem:

Theorem: Let A and B be two rotations of the sphere $S_2$ and let $x$ be a point of the sphere. If the sequence of points $$x, Ax, Bx, A^2x, ABx, BAx, B^2x, \ldots $$ is dense on the sphere, then it is uniformly distributed.

Here, uniformly distributed means that, if we consider the $2^n$ points produced with $n$ iterations of the rotations, namely $$ A^nx , A^{n-1}Bx , A^{n-2}BAx , \ldots , B^nx \ , $$ and we count the proportion of them that lie inside a region $\Delta$ (bounded by a piecewise smooth curve), then these ratios converge to the measure of $\Delta$; that is to say: $$ \lim_{n\to \infty} \frac{\mbox{Number of points among } \{A^nx , \ldots , B^nx \} \mbox{ inside } \Delta}{2^n} = \frac{\mu(\Delta)}{\mu(S_2)}.$$

A quick search has shown to me that there have been many developments of the ideas behind this result, in many different directions.

But I was wondering what is the state of the art concerning the uniform distribution of points under the action of semigroups of isometries in a more general situation.

To be precise,

Question: Is there a similar result for the action of a (finitely generated) semigroup of isometries of a compact Riemannian manifold?

As an example (on a non-compact manifold), there is a theorem by Kazhdan (Uniform distribution on a plane) that concerns the action on the Euclidean plane of the semigroup generated by a rotation and an arbitrary motion.

Nevertheless, most of the references I see are too specialized for me and, although they seem very general, I am not able to understand whether they cover the situation I am interested in or not.

Recently, I came across a beautiful paper by Arnol'd and Krylov (Uniform distribution of points on a sphere...) that contains the following theorem:

Theorem: Let A and B be two rotations of the sphere $S_2$ and let $x$ be a point of the sphere. If the sequence of points $$x, Ax, Bx, A^2x, ABx, BAx, B^2x, \ldots $$ is dense on the sphere, then it is uniformly distributed.

Here, uniformly distributed means that, if we consider the $2^n$ points produced with exactly $n$ iterations of the rotations, namely $$ A^nx , A^{n-1}Bx , A^{n-2}BAx , \ldots , B^nx \ , $$ and we count the proportion of them that lie inside a region $\Delta$ (bounded by a piecewise smooth curve), then these ratios converge to the measure of $\Delta$; that is to say: $$ \lim_{n\to \infty} \frac{\mbox{Number of points among } \{A^nx , \ldots , B^nx \} \mbox{ inside } \Delta}{2^n} = \frac{\mu(\Delta)}{\mu(S_2)}.$$

A quick search has shown to me that there have been many developments of the ideas behind this result, in many different directions.

But I was wondering what is the state of the art concerning the uniform distribution of points under the action of semigroups of isometries in a more general situation.

To be precise,

Question: Is there a similar result for the action of a (finitely generated) semigroup of isometries of a compact Riemannian manifold?

As an example (on a non-compact manifold), there is a theorem by Kazhdan (Uniform distribution on a plane) that concerns the action on the Euclidean plane of the semigroup generated by a rotation and an arbitrary motion.

Nevertheless, most of the references I see are too specialized for me and, although they seem very general, I am not able to understand whether they cover the situation I am interested in or not.

Source Link
José Navarro
  • 1.1k
  • 10
  • 20

Uniform distribution of points on Riemannian manifolds

Recently, I came across a beautiful paper by Arnol'd and Krylov (Uniform distribution of points on a sphere...) that contains the following theorem:

Theorem: Let A and B be two rotations of the sphere $S_2$ and let $x$ be a point of the sphere. If the sequence of points $$x, Ax, Bx, A^2x, ABx, BAx, B^2x, \ldots $$ is dense on the sphere, then it is uniformly distributed.

Here, uniformly distributed means that, if we consider the $2^n$ points produced with $n$ iterations of the rotations, namely $$ A^nx , A^{n-1}Bx , A^{n-2}BAx , \ldots , B^nx \ , $$ and we count the proportion of them that lie inside a region $\Delta$ (bounded by a piecewise smooth curve), then these ratios converge to the measure of $\Delta$; that is to say: $$ \lim_{n\to \infty} \frac{\mbox{Number of points among } \{A^nx , \ldots , B^nx \} \mbox{ inside } \Delta}{2^n} = \frac{\mu(\Delta)}{\mu(S_2)}.$$

A quick search has shown to me that there have been many developments of the ideas behind this result, in many different directions.

But I was wondering what is the state of the art concerning the uniform distribution of points under the action of semigroups of isometries in a more general situation.

To be precise,

Question: Is there a similar result for the action of a (finitely generated) semigroup of isometries of a compact Riemannian manifold?

As an example (on a non-compact manifold), there is a theorem by Kazhdan (Uniform distribution on a plane) that concerns the action on the Euclidean plane of the semigroup generated by a rotation and an arbitrary motion.

Nevertheless, most of the references I see are too specialized for me and, although they seem very general, I am not able to understand whether they cover the situation I am interested in or not.