points consist of elements $g \in
G$ such that $\underset{t \to 0}{\lim}~ \lambda(t)g\lambda(t)^{-1}$ exists. This is known as the [**instability parabolic**]{} associated to $\lambda$. If $\lambda$ is an instability 1-PS of $v$, then $P(\lambda)$ will also be known as the instability parabolic of $v$, denoted $P(v)$.

Now if $G$ acts on a projective variety $M$ defined over $K$ which is linearized by some very ample line bundle $\mathcal L$, then we get a $G$-equivariant embedding $i: M \hookrightarrow {\mathbb {P}}(H^\circ(M,{\mathcal L}))={\mathbb
{P}}(V)$. We then say that a point $m \in M$ is semistable for the $G$-action if the corresponding point in $V$ is semistable.

We recall some basic facts concerning instability 1-PS (See \[RR\] )

Suppose $G$ acts on a projective variety $M$ as above. Let $m \in M$ be a nonsemistable point for the action of $G$.\
(a) The function which sends every 1-PS $\lambda$ of $G$ to $\nu(\lambda,m)$ attains its maximum on the set of all 1-PS subgroups of G. Following \[RR\], we denote this value by $B$.\
(b) There exists a parabolic subgroup $P(m)$ of $G$, called the instability parabolic associated to the point $m$, such that for any instability 1-PS $\lambda$ associated to $m$, we have 