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2 votes
0 answers
61 views

Ostrogradsky instability and fractional derivatives

Are fractional derivatives (or even more generally differentegrals) also under the scope of the Ostrogradsky instability theorem?
3 votes
0 answers
68 views

Lattice differentiation and Locality

Assume we define the locality of a theory in the following way: Assume we have a theory of real scalars, so this theory is non local if the action has terms like $$\int d^dx\,\phi(x)V(x-y)\phi(y).$$ ...
3 votes
3 answers
578 views

Infinite derivatives, Locality and Lagrangian

Providing the derivative of a single valued function $f(x)$ is like providing its value at two infinitesimally close points. My question consists of two parts: Can Higher derivatives be thought of as ...