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The kind of completely regular space you are looking for is an $F$-space.

Suppose that $X$ is a completely regular space. Then we say that a subset $A\subseteq X$ is $C^*$-embedded if whenever $f:A\rightarrow\mathbb{R}$ is bounded and continuous, there is a continuous $g:X\rightarrow\mathbb{R}$ with $g|_A=f$. We say that a subset of $X$ of the form $f^{-1}[\{0\}]^c$ for some continuous $f:X\rightarrow\mathbb{R}$ is a cozero set. An $F$-space is a space where every cozero set is $C^*$-embedded.

Proposition: Let $X$ be a completely regular space. Then the following are equivalent:

  1. $X$ is an $F$-space

  2. whenever $f,g:X\rightarrow\mathbb{R}$ are continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

  3. whenever $f,g:X\rightarrow\mathbb{R}$ are bounded and continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

Proof: $2\rightarrow 3$ follows since in (3) we strengthen the premises.

$1\rightarrow 2$ Suppose that $X$ is an $F$-space, and $0\leq f\leq g$. Then let $\ell:g^{-1}[\{0\}]^c\rightarrow\mathbb{R}$ be the function defined by letting $\ell(x)=f(x)/g(x)$. Then $g^{-1}[\{0\}]^c$ is a cozero set, and $\ell$ is bounded, so $\ell$ extends to a bounded continuous function $h:X\rightarrow\mathbb{R}$. Observe that $f=gh$.

$3\rightarrow 1$. Let $U$ be a cozero set, and let $\ell:U\rightarrow[0,1]$ be a continuous function. Let $g:X\rightarrow[0,1]$ be a continuous function where $U=g^{-1}[\{0\}]$$U=g^{-1}[\{0\}]^c$. Then let $f:X\rightarrow[0,1]$ be the continuous function such that $f(x)=g(x)\ell(x)$ whenever $x\in U$ and $f(x)=0$ elsewhere. We observe that $0\leq f\leq g\leq 1$, so there must be a continuous function $h:X\rightarrow[0,1]$ with $f=gh$. However, this means that $h(x)=\ell(x)$ whenever $x\in U$, so $h$ is a continuous extension of the function $\ell$.

Q.E.D.

There are plenty of other characterizations of the $F$-spaces. If $X$ is a completely regular space, then let $C(X)$ denote the ring of all continuous functions $f:X\rightarrow\mathbb{R}$. If $A,B\subseteq X$, then we say that $A,B$ are completely separated if there is a continuous function $f:X\rightarrow[0,1]$ with $A\subseteq f^{-1}[\{0\}],B\subseteq f^{-1}[\{1\}]$.

The following fact can be found in the standard text Rings of Continuous Functions by Gillman and Jerison.

Let X be a completely regular space. The following are equivalent:

  1. $X$ is an $F$-space.

  2. The Stone-Cech compactification $\beta X$ is an $F$-space.

  3. Every finitely generated ideal in $C(X)$ is principal.

  4. Every ideal in $C(X)$ is convex.

  5. For all $f\in C(X)$, there is a $g\in C(X)$ with $f=g\cdot |f|$.

  6. If $f\in C(X)$, then the sets $\{x\in X\mid f(x)>0\}$ and $\{x\in X\mid f(x)<0\}$ are completely separated.

  7. If $M\subseteq C(X)$ is a maximal ideal, then the set of all prime ideals $P$ in $C(X)$ with $P\subseteq M$ is linearly ordered.

  8. If $f,g\in C(X),$ then $\langle f,g\rangle=\langle|f|+|g|\rangle.$

Comparison with other properties

If $X$ is an $F$-space, then every countable subset of $X$ is $C^*$-embedded. Therefore, every compact $F$-space has a homeomorphic copy of $\beta\omega$. A basically disconnected space is a completely regular space where every cozero set has open closure. Every basically disconnected space is an $F$-space, but $(\beta\omega)\setminus\omega$ is an $F$-space that is not basically disconnected. There are also some connected $F$-spaces.

The kind of completely regular space you are looking for is an $F$-space.

Suppose that $X$ is a completely regular space. Then we say that a subset $A\subseteq X$ is $C^*$-embedded if whenever $f:A\rightarrow\mathbb{R}$ is bounded and continuous, there is a continuous $g:X\rightarrow\mathbb{R}$ with $g|_A=f$. We say that a subset of $X$ of the form $f^{-1}[\{0\}]^c$ for some continuous $f:X\rightarrow\mathbb{R}$ is a cozero set. An $F$-space is a space where every cozero set is $C^*$-embedded.

Proposition: Let $X$ be a completely regular space. Then the following are equivalent:

  1. $X$ is an $F$-space

  2. whenever $f,g:X\rightarrow\mathbb{R}$ are continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

  3. whenever $f,g:X\rightarrow\mathbb{R}$ are bounded and continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

Proof: $2\rightarrow 3$ follows since in (3) we strengthen the premises.

$1\rightarrow 2$ Suppose that $X$ is an $F$-space, and $0\leq f\leq g$. Then let $\ell:g^{-1}[\{0\}]^c\rightarrow\mathbb{R}$ be the function defined by letting $\ell(x)=f(x)/g(x)$. Then $g^{-1}[\{0\}]^c$ is a cozero set, and $\ell$ is bounded, so $\ell$ extends to a bounded continuous function $h:X\rightarrow\mathbb{R}$. Observe that $f=gh$.

$3\rightarrow 1$. Let $U$ be a cozero set, and let $\ell:U\rightarrow[0,1]$ be a continuous function. Let $g:X\rightarrow[0,1]$ be a continuous function where $U=g^{-1}[\{0\}]$. Then let $f:X\rightarrow[0,1]$ be the continuous function such that $f(x)=g(x)\ell(x)$ whenever $x\in U$ and $f(x)=0$ elsewhere. We observe that $0\leq f\leq g\leq 1$, so there must be a continuous function $h:X\rightarrow[0,1]$ with $f=gh$. However, this means that $h(x)=\ell(x)$ whenever $x\in U$, so $h$ is a continuous extension of the function $\ell$.

Q.E.D.

There are plenty of other characterizations of the $F$-spaces. If $X$ is a completely regular space, then let $C(X)$ denote the ring of all continuous functions $f:X\rightarrow\mathbb{R}$. If $A,B\subseteq X$, then we say that $A,B$ are completely separated if there is a continuous function $f:X\rightarrow[0,1]$ with $A\subseteq f^{-1}[\{0\}],B\subseteq f^{-1}[\{1\}]$.

The following fact can be found in the standard text Rings of Continuous Functions by Gillman and Jerison.

Let X be a completely regular space. The following are equivalent:

  1. $X$ is an $F$-space.

  2. The Stone-Cech compactification $\beta X$ is an $F$-space.

  3. Every finitely generated ideal in $C(X)$ is principal.

  4. Every ideal in $C(X)$ is convex.

  5. For all $f\in C(X)$, there is a $g\in C(X)$ with $f=g\cdot |f|$.

  6. If $f\in C(X)$, then the sets $\{x\in X\mid f(x)>0\}$ and $\{x\in X\mid f(x)<0\}$ are completely separated.

  7. If $M\subseteq C(X)$ is a maximal ideal, then the set of all prime ideals $P$ in $C(X)$ with $P\subseteq M$ is linearly ordered.

  8. If $f,g\in C(X),$ then $\langle f,g\rangle=\langle|f|+|g|\rangle.$

Comparison with other properties

If $X$ is an $F$-space, then every countable subset of $X$ is $C^*$-embedded. Therefore, every compact $F$-space has a homeomorphic copy of $\beta\omega$. A basically disconnected space is a completely regular space where every cozero set has open closure. Every basically disconnected space is an $F$-space, but $(\beta\omega)\setminus\omega$ is an $F$-space that is not basically disconnected. There are also some connected $F$-spaces.

The kind of completely regular space you are looking for is an $F$-space.

Suppose that $X$ is a completely regular space. Then we say that a subset $A\subseteq X$ is $C^*$-embedded if whenever $f:A\rightarrow\mathbb{R}$ is bounded and continuous, there is a continuous $g:X\rightarrow\mathbb{R}$ with $g|_A=f$. We say that a subset of $X$ of the form $f^{-1}[\{0\}]^c$ for some continuous $f:X\rightarrow\mathbb{R}$ is a cozero set. An $F$-space is a space where every cozero set is $C^*$-embedded.

Proposition: Let $X$ be a completely regular space. Then the following are equivalent:

  1. $X$ is an $F$-space

  2. whenever $f,g:X\rightarrow\mathbb{R}$ are continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

  3. whenever $f,g:X\rightarrow\mathbb{R}$ are bounded and continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

Proof: $2\rightarrow 3$ follows since in (3) we strengthen the premises.

$1\rightarrow 2$ Suppose that $X$ is an $F$-space, and $0\leq f\leq g$. Then let $\ell:g^{-1}[\{0\}]^c\rightarrow\mathbb{R}$ be the function defined by letting $\ell(x)=f(x)/g(x)$. Then $g^{-1}[\{0\}]^c$ is a cozero set, and $\ell$ is bounded, so $\ell$ extends to a bounded continuous function $h:X\rightarrow\mathbb{R}$. Observe that $f=gh$.

$3\rightarrow 1$. Let $U$ be a cozero set, and let $\ell:U\rightarrow[0,1]$ be a continuous function. Let $g:X\rightarrow[0,1]$ be a continuous function where $U=g^{-1}[\{0\}]^c$. Then let $f:X\rightarrow[0,1]$ be the continuous function such that $f(x)=g(x)\ell(x)$ whenever $x\in U$ and $f(x)=0$ elsewhere. We observe that $0\leq f\leq g\leq 1$, so there must be a continuous function $h:X\rightarrow[0,1]$ with $f=gh$. However, this means that $h(x)=\ell(x)$ whenever $x\in U$, so $h$ is a continuous extension of the function $\ell$.

Q.E.D.

There are plenty of other characterizations of the $F$-spaces. If $X$ is a completely regular space, then let $C(X)$ denote the ring of all continuous functions $f:X\rightarrow\mathbb{R}$. If $A,B\subseteq X$, then we say that $A,B$ are completely separated if there is a continuous function $f:X\rightarrow[0,1]$ with $A\subseteq f^{-1}[\{0\}],B\subseteq f^{-1}[\{1\}]$.

The following fact can be found in the standard text Rings of Continuous Functions by Gillman and Jerison.

Let X be a completely regular space. The following are equivalent:

  1. $X$ is an $F$-space.

  2. The Stone-Cech compactification $\beta X$ is an $F$-space.

  3. Every finitely generated ideal in $C(X)$ is principal.

  4. Every ideal in $C(X)$ is convex.

  5. For all $f\in C(X)$, there is a $g\in C(X)$ with $f=g\cdot |f|$.

  6. If $f\in C(X)$, then the sets $\{x\in X\mid f(x)>0\}$ and $\{x\in X\mid f(x)<0\}$ are completely separated.

  7. If $M\subseteq C(X)$ is a maximal ideal, then the set of all prime ideals $P$ in $C(X)$ with $P\subseteq M$ is linearly ordered.

  8. If $f,g\in C(X),$ then $\langle f,g\rangle=\langle|f|+|g|\rangle.$

Comparison with other properties

If $X$ is an $F$-space, then every countable subset of $X$ is $C^*$-embedded. Therefore, every compact $F$-space has a homeomorphic copy of $\beta\omega$. A basically disconnected space is a completely regular space where every cozero set has open closure. Every basically disconnected space is an $F$-space, but $(\beta\omega)\setminus\omega$ is an $F$-space that is not basically disconnected. There are also some connected $F$-spaces.

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The kind of completely regular space you are looking for is an $F$-space.

Suppose that $X$ is a completely regular space. Then we say that a subset $A\subseteq X$ is $C^*$-embedded if whenever $f:A\rightarrow\mathbb{R}$ is bounded and continuous, there is a continuous $g:X\rightarrow\mathbb{R}$ with $g|_A=f$. We say that a subset of $X$ of the form $f^{-1}[\{0\}]^c$ for some continuous $f:X\rightarrow\mathbb{R}$ is a cozero set. An $F$-space is a space where every cozero set is $C^*$-embedded.

Proposition: Let $X$ be a completely regular space. Then the following are equivalent:

  1. $X$ is an $F$-space

  2. whenever $f,g:X\rightarrow\mathbb{R}$ are continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

  3. whenever $f,g:X\rightarrow\mathbb{R}$ are bounded and continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

Proof: $2\rightarrow 3$ follows since in (3) we strengthen the premises.

$1\rightarrow 2$ Suppose that $X$ is an $F$-space, and $0\leq f\leq g$. Then let $\ell:g^{-1}[\{0\}]^c\rightarrow\mathbb{R}$ be the function defined by letting $\ell(x)=f(x)/g(x)$. Then $g^{-1}[\{0\}]^c$ is a cozero set, and $\ell$ is bounded, so $\ell$ extends to a bounded continuous function $h:X\rightarrow\mathbb{R}$. Observe that $f=gh$.

$3\rightarrow 1$. Let $U$ be a cozero set, and let $\ell:U\rightarrow[0,1]$ be a continuous function. Let $g:X\rightarrow[0,1]$ be a continuous function where $U=g^{-1}[\{0\}]$. Then let $f:X\rightarrow[0,1]$ be the continuous function such that $f(x)=g(x)\ell(x)$ whenever $x\in U$ and $f(x)=0$ elsewhere. We observe that $0\leq f\leq g\leq 1$, so there must be a continuous function $h:X\rightarrow[0,1]$ with $f=gh$. However, this means that $h(x)=\ell(x)$ whenever $x\in U$, so $h$ is a continuous extension of the function $\ell$.

Q.E.D.

There are plenty of other characterizations of the $F$-spaces. If $X$ is a completely regular space, then let $C(X)$ denote the ring of all continuous functions $f:X\rightarrow\mathbb{R}$. If $A,B\subseteq X$, then we say that $A,B$ are completely separated if there is a continuous function $f:X\rightarrow[0,1]$ with $A\subseteq f^{-1}[\{0\}],B\subseteq f^{-1}[\{1\}]$.

The following fact can be found in the standard text Rings of Continuous Functions by Gillman and Jerison.

Let X be a completely regular space. The following are equivalent:

  1. $X$ is an $F$-space.

  2. The Stone-Cech compactification $\beta X$ is an $F$-space.

  3. Every finitely generated ideal in $C(X)$ is principal.

  4. Every ideal in $C(X)$ is convex.

  5. For all $f\in C(X)$, there is a $g\in C(X)$ with $f=g\cdot |f|$.

  6. If $f\in C(X)$, then the sets $\{x\in X\mid f(x)>0\}$ and $\{x\in X\mid f(x)<0\}$ are completely separated.

  7. If $M\subseteq C(X)$ is a maximal ideal, then the set of all prime ideals $P$ in $C(X)$ with $P\subseteq M$ is linearly ordered.

  8. If $f,g\in C(X),$ then $\langle f,g\rangle=\langle|f|+|g|\rangle.$

Comparison with other properties

If $X$ is an $F$-space, then every countable subset of $X$ is $C^*$-embedded. Therefore, every compact $F$-space has a homeomorphic copy of $\beta\omega$. A basically disconnected space is a completely regular space where every cozero set has open closure. Every basically disconnected space is an $F$-space, but $(\beta\omega)\setminus\omega$ is an $F$-space that is not basically disconnected. There are also some connected $F$-spaces.

The kind of completely regular space you are looking for is an $F$-space.

Suppose that $X$ is a completely regular space. Then we say that a subset $A\subseteq X$ is $C^*$-embedded if whenever $f:A\rightarrow\mathbb{R}$ is bounded and continuous, there is a continuous $g:X\rightarrow\mathbb{R}$ with $g|_A=f$. We say that a subset of $X$ of the form $f^{-1}[\{0\}]^c$ for some continuous $f:X\rightarrow\mathbb{R}$ is a cozero set.

Proposition: Let $X$ be a completely regular space. Then the following are equivalent:

  1. $X$ is an $F$-space

  2. whenever $f,g:X\rightarrow\mathbb{R}$ are continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

  3. whenever $f,g:X\rightarrow\mathbb{R}$ are bounded and continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

Proof: $2\rightarrow 3$ follows since in (3) we strengthen the premises.

$1\rightarrow 2$ Suppose that $X$ is an $F$-space, and $0\leq f\leq g$. Then let $\ell:g^{-1}[\{0\}]^c\rightarrow\mathbb{R}$ be the function defined by letting $\ell(x)=f(x)/g(x)$. Then $g^{-1}[\{0\}]^c$ is a cozero set, and $\ell$ is bounded, so $\ell$ extends to a bounded continuous function $h:X\rightarrow\mathbb{R}$. Observe that $f=gh$.

$3\rightarrow 1$. Let $U$ be a cozero set, and let $\ell:U\rightarrow[0,1]$ be a continuous function. Let $g:X\rightarrow[0,1]$ be a continuous function where $U=g^{-1}[\{0\}]$. Then let $f:X\rightarrow[0,1]$ be the continuous function such that $f(x)=g(x)\ell(x)$ whenever $x\in U$ and $f(x)=0$ elsewhere. We observe that $0\leq f\leq g\leq 1$, so there must be a continuous function $h:X\rightarrow[0,1]$ with $f=gh$. However, this means that $h(x)=\ell(x)$ whenever $x\in U$, so $h$ is a continuous extension of the function $\ell$.

Q.E.D.

There are plenty of other characterizations of the $F$-spaces. If $X$ is a completely regular space, then let $C(X)$ denote the ring of all continuous functions $f:X\rightarrow\mathbb{R}$. If $A,B\subseteq X$, then we say that $A,B$ are completely separated if there is a continuous function $f:X\rightarrow[0,1]$ with $A\subseteq f^{-1}[\{0\}],B\subseteq f^{-1}[\{1\}]$.

The following fact can be found in the standard text Rings of Continuous Functions by Gillman and Jerison.

Let X be a completely regular space. The following are equivalent:

  1. $X$ is an $F$-space.

  2. The Stone-Cech compactification $\beta X$ is an $F$-space.

  3. Every finitely generated ideal in $C(X)$ is principal.

  4. Every ideal in $C(X)$ is convex.

  5. For all $f\in C(X)$, there is a $g\in C(X)$ with $f=g\cdot |f|$.

  6. If $f\in C(X)$, then the sets $\{x\in X\mid f(x)>0\}$ and $\{x\in X\mid f(x)<0\}$ are completely separated.

  7. If $M\subseteq C(X)$ is a maximal ideal, then the set of all prime ideals $P$ in $C(X)$ with $P\subseteq M$ is linearly ordered.

  8. If $f,g\in C(X),$ then $\langle f,g\rangle=\langle|f|+|g|\rangle.$

The kind of completely regular space you are looking for is an $F$-space.

Suppose that $X$ is a completely regular space. Then we say that a subset $A\subseteq X$ is $C^*$-embedded if whenever $f:A\rightarrow\mathbb{R}$ is bounded and continuous, there is a continuous $g:X\rightarrow\mathbb{R}$ with $g|_A=f$. We say that a subset of $X$ of the form $f^{-1}[\{0\}]^c$ for some continuous $f:X\rightarrow\mathbb{R}$ is a cozero set. An $F$-space is a space where every cozero set is $C^*$-embedded.

Proposition: Let $X$ be a completely regular space. Then the following are equivalent:

  1. $X$ is an $F$-space

  2. whenever $f,g:X\rightarrow\mathbb{R}$ are continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

  3. whenever $f,g:X\rightarrow\mathbb{R}$ are bounded and continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

Proof: $2\rightarrow 3$ follows since in (3) we strengthen the premises.

$1\rightarrow 2$ Suppose that $X$ is an $F$-space, and $0\leq f\leq g$. Then let $\ell:g^{-1}[\{0\}]^c\rightarrow\mathbb{R}$ be the function defined by letting $\ell(x)=f(x)/g(x)$. Then $g^{-1}[\{0\}]^c$ is a cozero set, and $\ell$ is bounded, so $\ell$ extends to a bounded continuous function $h:X\rightarrow\mathbb{R}$. Observe that $f=gh$.

$3\rightarrow 1$. Let $U$ be a cozero set, and let $\ell:U\rightarrow[0,1]$ be a continuous function. Let $g:X\rightarrow[0,1]$ be a continuous function where $U=g^{-1}[\{0\}]$. Then let $f:X\rightarrow[0,1]$ be the continuous function such that $f(x)=g(x)\ell(x)$ whenever $x\in U$ and $f(x)=0$ elsewhere. We observe that $0\leq f\leq g\leq 1$, so there must be a continuous function $h:X\rightarrow[0,1]$ with $f=gh$. However, this means that $h(x)=\ell(x)$ whenever $x\in U$, so $h$ is a continuous extension of the function $\ell$.

Q.E.D.

There are plenty of other characterizations of the $F$-spaces. If $X$ is a completely regular space, then let $C(X)$ denote the ring of all continuous functions $f:X\rightarrow\mathbb{R}$. If $A,B\subseteq X$, then we say that $A,B$ are completely separated if there is a continuous function $f:X\rightarrow[0,1]$ with $A\subseteq f^{-1}[\{0\}],B\subseteq f^{-1}[\{1\}]$.

The following fact can be found in the standard text Rings of Continuous Functions by Gillman and Jerison.

Let X be a completely regular space. The following are equivalent:

  1. $X$ is an $F$-space.

  2. The Stone-Cech compactification $\beta X$ is an $F$-space.

  3. Every finitely generated ideal in $C(X)$ is principal.

  4. Every ideal in $C(X)$ is convex.

  5. For all $f\in C(X)$, there is a $g\in C(X)$ with $f=g\cdot |f|$.

  6. If $f\in C(X)$, then the sets $\{x\in X\mid f(x)>0\}$ and $\{x\in X\mid f(x)<0\}$ are completely separated.

  7. If $M\subseteq C(X)$ is a maximal ideal, then the set of all prime ideals $P$ in $C(X)$ with $P\subseteq M$ is linearly ordered.

  8. If $f,g\in C(X),$ then $\langle f,g\rangle=\langle|f|+|g|\rangle.$

Comparison with other properties

If $X$ is an $F$-space, then every countable subset of $X$ is $C^*$-embedded. Therefore, every compact $F$-space has a homeomorphic copy of $\beta\omega$. A basically disconnected space is a completely regular space where every cozero set has open closure. Every basically disconnected space is an $F$-space, but $(\beta\omega)\setminus\omega$ is an $F$-space that is not basically disconnected. There are also some connected $F$-spaces.

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The kind of completely regular space you are looking for is an $F$-space.

Suppose that $X$ is a completely regular space. Then we say that a subset $A\subseteq X$ is $C^*$-embedded if whenever $f:A\rightarrow\mathbb{R}$ is bounded and continuous, there is a continuous $g:X\rightarrow\mathbb{R}$ with $g|_A=f$. We say that a subset of $X$ of the form $f^{-1}[\{0\}]^c$ for some continuous $f:X\rightarrow\mathbb{R}$ is a cozero set.

Proposition: Let $X$ be a completely regular space. Then the following are equivalent:

  1. $X$ is an $F$-space

  2. whenever $f,g:X\rightarrow\mathbb{R}$ are continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

  3. whenever $f,g:X\rightarrow\mathbb{R}$ are bounded and continuous with $0\leq f\leq g$ there is some continuous $h:X\rightarrow\mathbb{R}$ with $f=gh$.

Proof: $2\rightarrow 3$ follows since in (3) we strengthen the premises.

$1\rightarrow 2$ Suppose that $X$ is an $F$-space, and $0\leq f\leq g$. Then let $\ell:g^{-1}[\{0\}]^c\rightarrow\mathbb{R}$ be the function defined by letting $\ell(x)=f(x)/g(x)$. Then $g^{-1}[\{0\}]^c$ is a cozero set, and $\ell$ is bounded, so $\ell$ extends to a bounded continuous function $h:X\rightarrow\mathbb{R}$. Observe that $f=gh$.

$3\rightarrow 1$. Let $U$ be a cozero set, and let $\ell:U\rightarrow[0,1]$ be a continuous function. Let $g:X\rightarrow[0,1]$ be a continuous function where $U=g^{-1}[\{0\}]$. Then let $f:X\rightarrow[0,1]$ be the continuous function such that $f(x)=g(x)\ell(x)$ whenever $x\in U$ and $f(x)=0$ elsewhere. We observe that $0\leq f\leq g\leq 1$, so there must be a continuous function $h:X\rightarrow[0,1]$ with $f=gh$. However, this means that $h(x)=\ell(x)$ whenever $x\in U$, so $h$ is a continuous extension of the function $\ell$.

Q.E.D.

There are plenty of other characterizations of the $F$-spaces. If $X$ is a completely regular space, then let $C(X)$ denote the ring of all continuous functions $f:X\rightarrow\mathbb{R}$. If $A,B\subseteq X$, then we say that $A,B$ are completely separated if there is a continuous function $f:X\rightarrow[0,1]$ with $A\subseteq f^{-1}[\{0\}],B\subseteq f^{-1}[\{1\}]$.

The following fact can be found in the standard text Rings of Continuous Functions by Gillman and Jerison.

Let X be a completely regular space. The following are equivalent:

  1. $X$ is an $F$-space.

  2. The Stone-Cech compactification $\beta X$ is an $F$-space.

  3. Every finitely generated ideal in $C(X)$ is principal.

  4. Every ideal in $C(X)$ is convex.

  5. For all $f\in C(X)$, there is a $g\in C(X)$ with $f=g\cdot |f|$.

  6. If $f\in C(X)$, then the sets $\{x\in X\mid f(x)>0\}$ and $\{x\in X\mid f(x)<0\}$ are completely separated.

  7. If $M\subseteq C(X)$ is a maximal ideal, then the set of all prime ideals $P$ in $C(X)$ with $P\subseteq M$ is linearly ordered.

  8. If $f,g\in C(X),$ then $\langle f,g\rangle=\langle|f|+|g|\rangle.$