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Greg Muller
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My guess is this is the kind of algebra you don't care about (since they contain no geometric informationaren't subrings of real-valued functions), but algebras of the form $\mathbb{R}[x]/x^n$ will have your property. When looking for a flow corresponding to a derivation $\xi$, consider the formal power series $$ \sum_i \frac{t^i\xi^i}{i!} $$ The problem, of course, is showing that this power series converges in the algebra of appropriate endomorphisms. However However, a lazy trick for guaranteeing its convergence is to hope that $\xi^n=0$ for some $n$. This happens for every derivation in the ring $\mathbb{R}[x]/x^n$, or more generally when the nilradical is maximal.

Edit: As is pointed out in the comments, this is a lazy trick for guaranteeing its convergencecorrect claim but the wrong reason. The real reason flows exponentiate in these rings, as well as all finite dimensional ones, is to hope that a derivation is given by a matrix $\xi^n=0$ for(after some $n$. This happens for every derivation in the ringchoice of basis), and all matrices can be exponentiated $\mathbb{R}[x]/x^n$(that is, or more generally when the nilradical is maximalabove series converges).

My guess is this is the kind of algebra you don't care about (since they contain no geometric information), but algebras of the form $\mathbb{R}[x]/x^n$ will have your property. When looking for a flow corresponding to a derivation $\xi$, consider the formal power series $$ \sum_i \frac{t^i\xi^i}{i!} $$ The problem, of course, is showing that this power series converges in the algebra of appropriate endomorphisms. However, a lazy trick for guaranteeing its convergence is to hope that $\xi^n=0$ for some $n$. This happens for every derivation in the ring $\mathbb{R}[x]/x^n$, or more generally when the nilradical is maximal.

My guess is this is the kind of algebra you don't care about (since they aren't subrings of real-valued functions), but algebras of the form $\mathbb{R}[x]/x^n$ will have your property. When looking for a flow corresponding to a derivation $\xi$, consider the formal power series $$ \sum_i \frac{t^i\xi^i}{i!} $$ The problem, of course, is showing that this power series converges in the algebra of appropriate endomorphisms. However, a lazy trick for guaranteeing its convergence is to hope that $\xi^n=0$ for some $n$. This happens for every derivation in the ring $\mathbb{R}[x]/x^n$, or more generally when the nilradical is maximal.

Edit: As is pointed out in the comments, this is a correct claim but the wrong reason. The real reason flows exponentiate in these rings, as well as all finite dimensional ones, is that a derivation is given by a matrix (after some choice of basis), and all matrices can be exponentiated (that is, the above series converges).

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Greg Muller
  • 13k
  • 7
  • 53
  • 79

My guess is this is the kind of algebra you don't care about (since they contain no geometric information), but algebras of the form $\mathbb{R}[x]/x^n$ will have your property. When looking for a flow corresponding to a derivation $\xi$, consider the formal power series $$ \sum_i \frac{t^i\xi^i}{i!} $$ The problem, of course, is showing that this power series converges in the algebra of appropriate endomorphisms. However, a lazy trick for guaranteeing its convergence is to hope that $\xi^n=0$ for some $n$. This happens for every derivation in the ring $\mathbb{R}[x]/x^n$, or more generally when the nilradical is maximal.