show/hide this revision's text 2 added 15 characters in body

Let T $T$ be an algebraic torus defined over Q$\mathbb Q$, $T_infinity$ T_\infty$ be its reals real points and $\pi_0(T_infinity)$ \pi_0(T_\infty)$ be the group of connected components of $T_infinity$. T_\infty$.

Why is the homomorphism $T(Q)\ra T(\mathbb Q)\to \pi_0(T_infinity)$ pi_0(T_\infty)$ surjective?

Thanks

show/hide this revision's text 1

A question on algebraic torus

Let T be an algebraic torus defined over Q, $T_infinity$ be its reals points and $\pi_0(T_infinity)$ be the group of connected components of $T_infinity$. Why is the homomorphism $T(Q)\ra \pi_0(T_infinity)$ surjective?

Thanks