Skip to main content
added 33 characters in body
Source Link

Starting point. For every simple, undirected graph $G=(V,E)$ there is $E_0\subseteq E$ such that $(V,E_0)$ is minimally connected: the spanning tree. The goal of this question is to find out whether the same thing holds for "graph-like" hypergraphs.

Formulation for hypergraphs. We call a hypergraph $H=(V,E)$ with $V\neq \emptyset$ connected if for all non-empty $X\subseteq V$ with $X\neq V$ there is $e\in E$ with $$e\cap X \neq \emptyset \neq e \cap (V\setminus X).$$

(Trivially, for every connected hypergraph, we have $\bigcup E = V$.)

We say that $H=(V,E)$ is linear if the cardinality of the intersection of any two distinct edges is at most $1$.

Question. If $H =(V,E)$ is a linear connected hypergraph, is there $E_0\subseteq E$ with the following properties?

  1. $(V, E_0)$ is connected, and
  2. whenever $e_0\in E_0$, the hypergraph $\big(V, (E_0\setminus\{e_0\})\big)$ is no longer connected.

Note. There is an easy example showing that if we consider all connected hypergraphs, the answer is negative.

Starting point. For every simple, undirected graph $G=(V,E)$ there is $E_0\subseteq E$ such that $(V,E_0)$ is minimally connected: the spanning tree. The goal of this question is to find out whether the same thing holds for "graph-like" hypergraphs.

We call a hypergraph $H=(V,E)$ with $V\neq \emptyset$ connected if for all non-empty $X\subseteq V$ with $X\neq V$ there is $e\in E$ with $$e\cap X \neq \emptyset \neq e \cap (V\setminus X).$$

(Trivially, for every connected hypergraph, we have $\bigcup E = V$.)

We say that $H=(V,E)$ is linear if the cardinality of the intersection of any two distinct edges is at most $1$.

Question. If $H =(V,E)$ is a linear connected hypergraph, is there $E_0\subseteq E$ with the following properties?

  1. $(V, E_0)$ is connected, and
  2. whenever $e_0\in E_0$, the hypergraph $\big(V, (E_0\setminus\{e_0\})\big)$ is no longer connected.

Note. There is an easy example showing that if we consider all connected hypergraphs, the answer is negative.

Starting point. For every simple, undirected graph $G=(V,E)$ there is $E_0\subseteq E$ such that $(V,E_0)$ is minimally connected: the spanning tree. The goal of this question is to find out whether the same thing holds for "graph-like" hypergraphs.

Formulation for hypergraphs. We call a hypergraph $H=(V,E)$ with $V\neq \emptyset$ connected if for all non-empty $X\subseteq V$ with $X\neq V$ there is $e\in E$ with $$e\cap X \neq \emptyset \neq e \cap (V\setminus X).$$

(Trivially, for every connected hypergraph, we have $\bigcup E = V$.)

We say that $H=(V,E)$ is linear if the cardinality of the intersection of any two distinct edges is at most $1$.

Question. If $H =(V,E)$ is a linear connected hypergraph, is there $E_0\subseteq E$ with the following properties?

  1. $(V, E_0)$ is connected, and
  2. whenever $e_0\in E_0$, the hypergraph $\big(V, (E_0\setminus\{e_0\})\big)$ is no longer connected.

Note. There is an easy example showing that if we consider all connected hypergraphs, the answer is negative.

added 1 character in body
Source Link

Starting point. For every simple, undirected graph $G=(V,E)$ there is $E_0\subseteq E$ such that $(V,E_0)$ is minimally connected: the spanning tree. The goal of this question is to find out whether the same thing holdholds for "graph-like" hypergraphs.

We call a hypergraph $H=(V,E)$ with $V\neq \emptyset$ connected if for all non-empty $X\subseteq V$ with $X\neq V$ there is $e\in E$ with $$e\cap X \neq \emptyset \neq e \cap (V\setminus X).$$

(Trivially, for every connected hypergraph, we have $\bigcup E = V$.)

We say that $H=(V,E)$ is linear if the cardinality of the intersection of any two distinct edges is at most $1$.

Question. If $H =(V,E)$ is a linear connected hypergraph, is there $E_0\subseteq E$ with the following properties?

  1. $(V, E_0)$ is connected, and
  2. whenever $e_0\in E_0$, the hypergraph $\big(V, (E_0\setminus\{e_0\})\big)$ is no longer connected.

Note. There is an easy example showing that if we consider all connected hypergraphs, the answer is negative.

Starting point. For every simple, undirected graph $G=(V,E)$ there is $E_0\subseteq E$ such that $(V,E_0)$ is minimally connected: the spanning tree. The goal of this question is to find out whether the same thing hold for "graph-like" hypergraphs.

We call a hypergraph $H=(V,E)$ with $V\neq \emptyset$ connected if for all non-empty $X\subseteq V$ with $X\neq V$ there is $e\in E$ with $$e\cap X \neq \emptyset \neq e \cap (V\setminus X).$$

(Trivially, for every connected hypergraph, we have $\bigcup E = V$.)

We say that $H=(V,E)$ is linear if the cardinality of the intersection of any two distinct edges is at most $1$.

Question. If $H =(V,E)$ is a linear connected hypergraph, is there $E_0\subseteq E$ with the following properties?

  1. $(V, E_0)$ is connected, and
  2. whenever $e_0\in E_0$, the hypergraph $\big(V, (E_0\setminus\{e_0\})\big)$ is no longer connected.

Note. There is an easy example showing that if we consider all connected hypergraphs, the answer is negative.

Starting point. For every simple, undirected graph $G=(V,E)$ there is $E_0\subseteq E$ such that $(V,E_0)$ is minimally connected: the spanning tree. The goal of this question is to find out whether the same thing holds for "graph-like" hypergraphs.

We call a hypergraph $H=(V,E)$ with $V\neq \emptyset$ connected if for all non-empty $X\subseteq V$ with $X\neq V$ there is $e\in E$ with $$e\cap X \neq \emptyset \neq e \cap (V\setminus X).$$

(Trivially, for every connected hypergraph, we have $\bigcup E = V$.)

We say that $H=(V,E)$ is linear if the cardinality of the intersection of any two distinct edges is at most $1$.

Question. If $H =(V,E)$ is a linear connected hypergraph, is there $E_0\subseteq E$ with the following properties?

  1. $(V, E_0)$ is connected, and
  2. whenever $e_0\in E_0$, the hypergraph $\big(V, (E_0\setminus\{e_0\})\big)$ is no longer connected.

Note. There is an easy example showing that if we consider all connected hypergraphs, the answer is negative.

Source Link

"Spanning trees" for connected linear hypergraphs

Starting point. For every simple, undirected graph $G=(V,E)$ there is $E_0\subseteq E$ such that $(V,E_0)$ is minimally connected: the spanning tree. The goal of this question is to find out whether the same thing hold for "graph-like" hypergraphs.

We call a hypergraph $H=(V,E)$ with $V\neq \emptyset$ connected if for all non-empty $X\subseteq V$ with $X\neq V$ there is $e\in E$ with $$e\cap X \neq \emptyset \neq e \cap (V\setminus X).$$

(Trivially, for every connected hypergraph, we have $\bigcup E = V$.)

We say that $H=(V,E)$ is linear if the cardinality of the intersection of any two distinct edges is at most $1$.

Question. If $H =(V,E)$ is a linear connected hypergraph, is there $E_0\subseteq E$ with the following properties?

  1. $(V, E_0)$ is connected, and
  2. whenever $e_0\in E_0$, the hypergraph $\big(V, (E_0\setminus\{e_0\})\big)$ is no longer connected.

Note. There is an easy example showing that if we consider all connected hypergraphs, the answer is negative.