Skip to main content
Changing title to help people find my question in future
Link

Nontrivial Are the polyhedral cones the only examples of cones $C$ that remains closed when they are added to vector subspaces?

formatting, added tag
Source Link
YCor
  • 63.9k
  • 5
  • 187
  • 286

Let $C \subset \mathbb{R}^{n}$ be a closed convex cone. If one wants to know whether the linear map $T:\mathbb{R}^{n} \mapsto\mathbb{R}^m$$T:\mathbb{R}^{n} \to\mathbb{R}^m$ sends the closed set $C$ to another closed one, $T(C)$, it is needed to prove that $\text{ker } T + C$ is closed.

My concern turns into to know whether there exist good examples of cones, other than polyhedral cones, that are mapped to closed sets by any linear map. Hence, the question is reduced to:

There exist a closed convex cone $C$, different from any polyhedral cone, such that, for every vector subspace $V$, $V+C$ is closed?

The article On the Closednessclosedness of the Linear Imagelinear image of a Closed Convex Coneclosed convex cone almost answers my question. If one can find an enlightening example of cone $C$ satisfying the condition (SUM-WE) for every every subspace, my example is constructed.

Let $C \subset \mathbb{R}^{n}$ be a closed convex cone. If one wants to know whether the linear map $T:\mathbb{R}^{n} \mapsto\mathbb{R}^m$ sends the closed set $C$ to another closed one, $T(C)$, it is needed to prove that $\text{ker } T + C$ is closed.

My concern turns into to know whether there exist good examples of cones, other than polyhedral cones, that are mapped to closed sets by any linear map. Hence, the question is reduced to:

There exist a closed convex cone $C$, different from any polyhedral cone, such that, for every vector subspace $V$, $V+C$ is closed?

The article On the Closedness of the Linear Image of a Closed Convex Cone almost answers my question. If one can find an enlightening example of cone $C$ satisfying the condition (SUM-WE) for every every subspace, my example is constructed.

Let $C \subset \mathbb{R}^{n}$ be a closed convex cone. If one wants to know whether the linear map $T:\mathbb{R}^{n} \to\mathbb{R}^m$ sends the closed set $C$ to another closed one, $T(C)$, it is needed to prove that $\text{ker } T + C$ is closed.

My concern turns into to know whether there exist good examples of cones, other than polyhedral cones, that are mapped to closed sets by any linear map. Hence, the question is reduced to:

There exist a closed convex cone $C$, different from any polyhedral cone, such that, for every vector subspace $V$, $V+C$ is closed?

The article On the closedness of the linear image of a closed convex cone almost answers my question. If one can find an enlightening example of cone $C$ satisfying the condition (SUM-WE) for every subspace, my example is constructed.

Problems with english, again
Source Link

Let $C \subset \mathbb{R}^{n}$ be a closed convex cone. If one wantwants to know whether the linear map $T:\mathbb{R}^{n} \mapsto\mathbb{R}^m$ sends the closed set $C$ to another closed one, $T(C)$, it'sit is needed to prove that $\text{ker } T + C$ is closed.

My concern turns into to know whether there exist good examples of cones, other than polyhedral cones, that are mapped to closed sets by any linear mapsmap. Hence, the questionsquestion is reduced to:

There exist a closed convex cone $C$, different from any polyhedral cone, such that, for every vector subspace $V$, $V+C$ is closed?

The article On the Closedness of the Linear Image of a Closed Convex Cone almost answers my question. If one can find an enlightening example of cone $C$ satisfying the condition (SUM-WE) for every every subspace, my example is constructed.

Let $C \subset \mathbb{R}^{n}$ be a closed convex cone. If one want to know whether the linear map $T:\mathbb{R}^{n} \mapsto\mathbb{R}^m$ sends the closed set $C$ to another closed one, $T(C)$, it's needed to prove that $\text{ker } T + C$ is closed.

My concern turns to know whether there exist good examples of cones other than polyhedral cones that are mapped to closed sets by linear maps. Hence, the questions is reduced to:

There exist a closed convex cone $C$, different from any polyhedral cone, such that, for every vector subspace $V$, $V+C$ is closed?

The article On the Closedness of the Linear Image of a Closed Convex Cone almost answers my question. If one can find an enlightening example of cone $C$ satisfying the condition (SUM-WE), my example is constructed.

Let $C \subset \mathbb{R}^{n}$ be a closed convex cone. If one wants to know whether the linear map $T:\mathbb{R}^{n} \mapsto\mathbb{R}^m$ sends the closed set $C$ to another closed one, $T(C)$, it is needed to prove that $\text{ker } T + C$ is closed.

My concern turns into to know whether there exist good examples of cones, other than polyhedral cones, that are mapped to closed sets by any linear map. Hence, the question is reduced to:

There exist a closed convex cone $C$, different from any polyhedral cone, such that, for every vector subspace $V$, $V+C$ is closed?

The article On the Closedness of the Linear Image of a Closed Convex Cone almost answers my question. If one can find an enlightening example of cone $C$ satisfying the condition (SUM-WE) for every every subspace, my example is constructed.

Fixing english
Source Link
Loading
Corrected symbol
Source Link
Loading
added 289 characters in body
Source Link
Loading
Source Link
Loading