  Given an integer $n\geq 1$ and an irreducible character $\chi_{\lambda}$ of
$S_{n}$ for some partition $\lambda$ of $n$, the immanant
$\mathrm{imm}_{\lambda}:\mathbb{C}^{n\times n}\to\mathbb{C}$ maps matrices
$A\in\mathbb{C}^{n\times n}$ to $\mathrm{imm}_{\lambda}(A)=\sum_{\pi\in
S_{n}}\chi_{\lambda}(\pi)\prod_{i=1}^{n}A_{i,\pi(i)}$. Important special cases
include the determinant and permanent, which are the immanants associated with
the sign and trivial character, respectively.
  It is known that immanants can be evaluated in polynomial time for characters
that are close to the sign character: Given a partition $\lambda$ of $n$ with
$s$ parts, let $b(\lambda):=n-s$ count the boxes to the right of the first
column in the Young diagram of $\lambda$. For a family of partitions $\Lambda$,
let $b(\Lambda):=\max_{\lambda\in\Lambda}b(\lambda)$ and write Imm$(\Lambda)$
for the problem of evaluating $\mathrm{imm}_{\lambda}(A)$ on input $A$ and
$\lambda\in\Lambda$. If $b(\Lambda)<\infty$, then Imm$(\Lambda)$ is known to be
polynomial-time computable. This subsumes the case of the determinant. On the
other hand, if $b(\Lambda)=\infty$, then previously known hardness results
suggest that Imm$(\Lambda)$ cannot be solved in polynomial time. However, these
results only address certain restricted classes of families $\Lambda$.
  In this paper, we show that the parameterized complexity assumption FPT
$\neq$ #W[1] rules out polynomial-time algorithms for Imm$(\Lambda)$ for any
computationally reasonable family of partitions $\Lambda$ with
$b(\Lambda)=\infty$. We give an analogous result in algebraic complexity under
the assumption VFPT $\neq$ VW[1]. Furthermore, if $b(\lambda)$ even grows
polynomially in $\Lambda$, we show that Imm$(\Lambda)$ is hard for #P and VNP.
This concludes a series of partial results on the complexity of immanants
obtained over the last 35 years.
