Let $A$ be a complex Banach algebra with identity 1. Define the exponential spectrum $e(x)$ of an element $xin A$ by $$e(x)= {lambdainmathbb{C}: x-lambda1 notin G_1(A)},$$ where $G_1(A)$ is the connected component of the group of invertibles $G(A)$ that contains the identity.
Is it true that $e(ab)cup{0} = e(ba)cup{0}$ for all $a,b in A$?
Equivalently, is it true that
$1-ab$ is in $G_1(A)$ if and only if $1-ba$ is in $G_1(A)$, for all $a,b in A$?
Note: The usual spectrum has this property.
Just an additional note:
We have $e(ab)cup{0} = e(ba)cup{0}$ for all $a,b in A$ if
1) The group of invertibles of $A$ is connected, because then the exponential spectrum of any element is just the usual spectrum of that element.
2) The set $Z(A)G(A) = {ab: a in Z(A), bin G(A)}$ is dense in $A$, where $Z(A)$ is the center of $A$. (One can prove this). In particular, we have $e(ab)cup{0} = e(ba)cup{0}$ for all $a,b in A$ if the invertibles are dense in $A$.
3) $A$ is commutative, clearly.
But what about other Banach algebras? Can someone provide a counterexample?
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