Who knows what is the classification standard of American mathematics? There seems to be three levels, and the first level of classification is represented by a two-digit number. It's better to list all these forms. The classification standard of mathematics discipline adopts a three-level hierarchical classification scheme.

The first level of classification is represented by a two-digit number, the second level is represented by a letter, and the third level is represented by another two-digit number. For example:

53 stands for differential geometry

53A stands for classical differential geometry.

53A45 stands for vector and tensor analysis.

[Editor] The 64 top mathematics disciplines in the first-level classification are identified by unique two digits, including some special mathematics research, such as "History and Biography", "Mathematics Education" and some interdisciplinary subjects. In particular, it includes many interdisciplinary subjects related to physics:

mechanics

Spectral theory

physical geography

optics

Electromagnetic theory

All valid MSC classification codes must contain the first-class identification.

[Editor] The secondary identification code of the secondary classification is a single Latin letter, which represents a specific mathematical field under the primary classification. The secondary identification code is different from the primary discipline classification.

For example, the primary identification code of differential geometry is 53, and the secondary identification code is:

Classical differential geometry

Local differential geometry

C global differential geometry

Three-dimensional symplectic geometry and contact geometry

In addition, the secondary identification code "-"is used to indicate a specific type of file. This code has the following form:

53-00 General reference materials (manuals, dictionaries, reference materials, etc.). )

53-0 1 textbooks (textbooks, teaching reference articles, etc. )

53-02 Research discussion (monograph, investigation article)

53-03 History (at least one classification number must also be assigned from 0 1

53-04 explicit machine calculation and program (non-calculation or programming theory)

53-06 meetings, papers, etc.

The second and third levels of this code are always the same, that is, only the first level identifier can be changed. 53- and 53 are invalid classifications.

[Editor] Three-level classification Three-level identification codes are very detailed, usually corresponding to a specific mathematical object, research direction or well-known problems.

A tertiary identification code 99 exists in each category to indicate that it is not in the previous category.