Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A comment on a controversial issue: a Generalized Fractional Derivative
  cannot have a regular kernel   The problem whether a given pair of functions can be used as the kernels of a
generalized fractional derivative and the associated generalized fractional
integral is reduced to the problem of existence of a solution to the Sonine
equation. It is shown for some selected classes of functions that a necessary
condition for a function to be the kernel of a fractional derivative is an
integrable singularity at 0. It is shown that locally integrable completely
monotone functions satisfy the Sonine equation if and only if they are singular
at 0.

17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
13
The categories of this paper are: quant-ph
20
The categories of this paper are: acc-phys
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
37
The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
29
The categories of this paper are: funct-an