Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Auxiliary matrix formalism for interaction representation
  transformations, optimal control and spin relaxation theories   Auxiliary matrix exponential method is used to derive simple and numerically
efficient general expressions for the following, historically rather cumbersome
and hard to compute, theoretical methods: (1) average Hamiltonian theory
following interaction representation transformations; (2)
Bloch-Redfield-Wangsness theory of nuclear and electron relaxation; (3)
gradient ascent pulse engineering version of quantum optimal control theory. In
the context of spin dynamics, the auxiliary matrix exponential method is more
efficient than methods based on matrix factorizations and also exhibits more
favourable complexity scaling with the dimension of the Hamiltonian matrix.

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The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics