tensorExp -- Compute a component of the exponential of a tensor.

Let $T((\mathbb{R}^d))$ denote the dual of the tensor algebra on $\mathbb{R}^d$, i.e., the space $\prod_k (\mathbb{R}^d)^{\otimes k}$. Given $x \in T(\mathbb{R}^d)$ its exponential is $$\exp(x) := \sum_{k \geq 0} \frac{1}{k!} x^{\otimes k} \in T((\mathbb{R}^d)). $$ $\texttt{tensorExp(x,k)}$ computes the degree $k$ component of $\exp(x)$.

If the constant term of the input is not $0$, the exponential can not be expressed with algebraic coefficients. To avoid this case, the method is only implemented for tensors with constant term equal to $0$.

The method is implemented only for tensors with constant term $0$.