I thought it might be useful, at least at the beginning of the site, to make a list of some canonical forms of subfield tags. Obviously it's impossible to create a comprehensive list of tags, but my idea is to have a set such that any question which is appropriate for the site could be tagged with at least one tag from the set. This will also help us out later when people get enough rep to vote on tag synonyms, since we'll already know what the community thinks the canonical forms of certain tags should be.
To begin with, these tags are already used on the site and I think they would make good subject tags:
acoustics
astrophysics
atmospheric-science
(physical aspects of meteorology and climatology)
classical-mechanics
(when lagrangian-mechanics
and hamiltonian-mechanics
and newtonian-mechanics
are too specific)
cosmology
education
(could be renamed to physics-education
)
electro-magnetism
(needs to have the hyphen removed though)
fluid-dynamics
general-relativity
geophysics
(physical aspects of geology and seismology)
gravity
(when general-relativity
and newtonian-gravity
are too specific)
hamiltonian-mechanics
high-energy-physics
kinematics
(basic relationships between position, velocity, and acceleration)
lagrangian-mechanics
magnetohydrodynamics
mathematical-physics
medical-physics
newtonian-mechanics
nuclear-physics
optics
(when quantum-optics
is either too specific or inappropriate)
particle-physics
(although this might fit under high-energy-physics
)
physical-chemistry
quantum-field-theory
quantum-mechanics
quantum-optics
rotational-dynamics
special-relativity
string-theory
(also might fit under high-energy-physics
)
thermodynamics
wave-theory
These have not been used on the site, but I think they would be appropriate subject tags:
atomic-physics
computational-physics
condensed-matter-physics
newtonian-gravity
The tags in the following list are in use, and I can see how they could be good subject tags, but I think they're either too broad or too specific, or redundant with the preceding lists. Note that I am not advocating that these tags be renamed or deleted. They're fine as tags (well most of them are fine), but I just think that any question that uses them still should have a tag from one of the previous lists. Others may disagree.
mechanics
: too broad
climate-science
: subset of atmospheric-science
applied-physics
: too broad
experimental-physics
: too broad
standard-model
: subset of high-energy-physics
aerodynamics
: subset of fluid-dynamics
sound
: typically equivalent to acoustics
philosophy
: probably off-topic, or there should be another applicable tag
large-hadron-collider
: subset of high-energy-physics
accelerator-physics
: subset of high-energy-physics
software
: equivalent to computational-physics
nuclear-engineering
: equivalent to nuclear-physics
material-science
: either equivalent to condensed-matter-physics
, or the question may be off topic for this site
electrostatics
: subset of electromagnetism
Comments and suggestions are welcome and encouraged. I'm making this CW so it can be collaboratively edited (although if you change something other than fixing a typo, please leave a comment).