Israel Gelfand famously chided his students to declare that they didn’t study differential geometry or representation theory etc but that they studied mathematics. I was witness to the unity of mathematics in a rather stunning way. Working with the linearized Euler equations of hydrodynamics on the two dimensional torus, if one studies the spectrum of the linearization about a steady state, one is naturally led into counting problems associated with the integer lattice, stuff that shows up in number theory. To see this connection, between problems in the stability theory of fluid dynamics on the one hand and counting problems and number theory on the other hand, is startling to say the least, at least to the mathematically naive person such as me. At a deeper level, one is led then to wonder at such things as the Platonic nature of mathematical reality.

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