ISO 80000 Part 13 gives some symbols within the scope of communication technology (its scope is more narrow than its title would suggest). The standard itself is copyrighted but the quantity symbols are listed on Wikipedia, https://en.wikipedia.org/wiki/ISO/IEC_80000#Part_13:_Informa...
Being careful to distinguish 'fundamental laws' from just 'quantities that we defined', information theory and queueing theory have some good examples of proven laws.
See also https://www.nist.gov/publications/quantities-and-units-softw...