On the second variation of the biharmonic Clifford torus in S^4

Stefano Montaldo, Cezar Oniciuc, Andrea Ratto

The flat torus $\mathbb{T}={\mathbb{S}}^1\left(\frac{1}{2}\right)\times {\mathbb{S}}^1\left(\frac{1}{2}\right)$ admits a proper biharmonic isometric immersion into the unit $…