Does there exist an elliptic curve over a number field $K$ such that $WC(E/K)\cong H^1(G\_K, E)$ is trivial?



Trivial Weil-Châtelet group
Weil-Chatelet groups are huge. A theorem of Shafarevich states that if $n \ge 2$ and if $E$ is an elliptic curve (or an abelian variety) over a number field $k$ then $H^1(G\_k,E)$ has infinitely many elements of order $n$. See Section 5 of Pete Clark's lecture on WC groups:
[http://alpha.math.uga.edu/~pete/wcnotes.pdf](http://alpha.math.uga.edu/%7Epete/wcnotes.pdf)


