Formatting Guidelines

Constants should be written in upright font. However, constants such as $c$ (speed of light), $h$ (Planck constant), and $G$ (gravitational constant) are considered variable symbols. Despite their unchanging values, they are treated as physical quantities and should be written in italic font. Mathematical constants with fixed values (e.g., $\rm{e} = 2.7182818\ldots$, $\rm{\pi} = 3.1415926\ldots$, $\rm{i}^2 = -1$, etc.) should be written in upright font. Regarding $\pi$, the writing guidelines of Chinese Physics B conflict with the international standard ISO 80000-2. The author believes the international standard should be followed, using upright font.

• Variables should be written in italic font.
• Units should be written in upright font.
• Mathematical functions should be written in upright font. This refers to special functions like $\rm{sin}(x)$, not general functions like $f(x)$.

Pay special attention to the following rules:

• Neutron mass $m_n$ and proton mass $m_p$ are italic, but atomic mass $\rm{u}$ is upright.
• Electron charge $e$ is italic, but electronvolt $\rm{eV}$ is upright.
• The natural constant $\rm{e}$ is upright.
• The differential operator $\rm{d}$ should be written in upright font (according to the 2019 revision of the international standard ISO 80000-2). However, in AMS (American Mathematical Society) journals, the differential symbol is often written as $d x$, which is a traditional practice. In fact, many journals or publishers do not strictly follow these rules and instead adhere to the author's preferences.
• In mathematics, points and lines (e.g., point A, line AB) are written in upright font. Axes and planes are written in italic font. The origin of coordinates is written in upright font as $\rm{O}$. There is considerable debate on this point, and no unified standard seems to exist.

Additionally:

• Uppercase English letters generally represent matrices, while lowercase letters represent variables or vectors. (This point is debatable, as references often provide conflicting guidelines.)

Miscellaneous

The rules for upright and italic Greek letters seem even more complicated. It appears that this issue has not been thoroughly considered.

The conclusion might be that the "guidelines" are not truly standardized.

References

• Quantities and Units in Atomic and Nuclear Physics
• Chinese Physics B Writing Guidelines
• LaTeX Guidelines

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Last update: 2025-04-15
Created: 2025-04-15