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Mar 3, 2016 at 17:59 comment added Benjamin This is common in the physics literature and I've never understood why it is used.
Apr 9, 2012 at 14:59 history edited AlexArvanitakis CC BY-SA 3.0
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Apr 9, 2012 at 2:20 vote accept AlexArvanitakis
Apr 9, 2012 at 1:45 comment added Robert Bryant But, if you take my $1$-variable solution, your $2$-variable solution is expressed as $U(t,t_0) = U(t)U(t_0)^{-1}$, so there's no need for a $2$-variable expression.
Apr 9, 2012 at 1:43 answer added Robert Bryant timeline score: 8
Apr 9, 2012 at 1:19 comment added AlexArvanitakis The point of using $U(t,t_0)$ is that the matrices $U(t_1,t_2)$ possess the semigroup property $U(t,t_0)=U(t,t_1)U(t_1,t_0)$.
Apr 9, 2012 at 1:15 comment added Robert Bryant Still, what is the point of having two arguments for $U$?
Apr 9, 2012 at 1:14 history edited AlexArvanitakis CC BY-SA 3.0
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Apr 9, 2012 at 1:14 comment added AlexArvanitakis Sorry, I was being sloppy. I meant $U(t_0,t_0)=\mathbf{1}_n$. Fixing...
Apr 9, 2012 at 1:06 comment added Robert Bryant I don't understand your notation $U(t,t_0)$, and I'm sure you don't mean to have $U(t,t_0) = \mathbf{1}_n$, which doesn't make sense. Don't you just mean $U'(t) = A(t)U(t)$ with initial condition $U(t_0)=\mathbf{1}_n$?
Apr 8, 2012 at 20:14 history edited AlexArvanitakis CC BY-SA 3.0
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Apr 8, 2012 at 19:52 history asked AlexArvanitakis CC BY-SA 3.0