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My interest is in topological monoids, but I think the question may make sense (in some fashion) for monoids of sets.

Let $M$ be a topological monoid, and let $X$ be a pointed space that $M$ acts on, on the right. The action divides $X$ into maximal orbits, which I think of as the equivalence classes with respect to the equivalence relation $\sim$ generated by the basic equivalences of the form $x \sim y \cdot m$ for $x, y\in x$ and $m\in M$. There is then a quotient space and quotient map $q:X\to X // M$, which the quotient of $X$ by the equivalence relation.

Roughly speaking, a principal fibration is a fibration sequence of the form $M \to X\to X//M$; this "definition" is good enough for the analogy I want to make. Here $M\to X$ sends $m$ to $*\cdot m$, where $*\in X$ is the basepoint.

Our favorite family of examples of fibrations (I say!) is the Moore path-loop fibrations, $\Omega_M (X) \to \mathcal{P}_M(X) \to X$. Here the fiber $\Omega_M(X)$ is a topological monoid acting on the total space $\mathcal{P}_M(X)$, but the quotient $\mathcal{P}_M(X)//\Omega_M (X)$ is not equal to $X$. However, there is a factorization $$ \mathcal{P}_M(X) \to \mathcal{P}_M(X)//\Omega_M (X) \to X . $$

QUESTION: Here is a concept: fibration sequences $M \to X\to B$ in which

  • $M$ is a topological monoid acting on $X$
  • there is a factorization $X\to X//M \to B$.

Is there an existing term for this? Or perhaps it is very close to some other concept that has a name? I don't want to go renaming the wheel, so I'd appreciate knowing what these are called, and especially references to places where the terminology is introduced, or at least used.

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    $\begingroup$ The terms weak orbits or connected components are used for what you can maximal orbit. I'm not sure how you get a sequence here. How does M map into X? Several points can be in the same orbit but not behave the same from the forward point of view. $\endgroup$ Commented Jun 2, 2021 at 12:03
  • $\begingroup$ $X$ has a basepoint! Adding information... $\endgroup$
    – Jeff Strom
    Commented Jun 2, 2021 at 12:15
  • $\begingroup$ What is your base point in your example.? Do you put any algebraic constraints on the action or just topological? For example is every action of a discrete monoid on a discrete space a principal fibration? When I hear the word principal I would think you want a free action in an appropriate sense. $\endgroup$ Commented Jun 2, 2021 at 13:05
  • $\begingroup$ @BenjaminSteinberg Moore paths and loops have real number lengths that are additive under products. In the Moore path and loop spaces, the basepoint is the unique trivial path, which has length zero. $\endgroup$
    – Jeff Strom
    Commented Jun 2, 2021 at 17:24

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