New posts in Group Actions

$\text{SL}_2(\mathbb Z)$ acts on upper plane $\mathbb H$. What kind of points have non-trivial stabilizer? And how many orbits are there?

Is the identity axiom in the definition of group action redundant?

Orbit of a matrix can generates a basis?

How much of a group $G$ is determined by the category of $G$-sets?

Importance of group action in abstract algebra

Stabilizer of a Group Action

$SL(2,\mathbb{R})$ acts transitively on the upper half plane

How is the kernel of a group action defined?

Group action and orbit space

Show that giving a right-action of a group $G$ on a set $A$ is the same as giving a left-action of $G^{op}$ on A