I might have something. I created a Metamath database for Walsh's fourth axiom
https://github.com/GinoGiotto/w4.mm and my proof for luk1 seems shorter than the current one.
Preliminary information:
- All theorems are complete and verified with metamath.exe.
- I saved all proofs in the normal format because the compressed one shows a lower step count (yes, this makes the database very big).
- The command "SHOW TRACE_BACK luk1 /COUNT /ESSENTIAL" says that "The proof would have 9513 steps if fully expanded back to
axiom references." which is lower than the 11989 step count in the table.
So, if the metamath.exe count is correct and if I have not made rookie mistakes then I have a shortening of luk1 in w4. I am not 100% confident that everything is fine until I translate it into condensed detachment and verify it with pmGenerator.
This email is just to claim my (potential) result before the new proofs arrive. I'm probably going to do the translation tomorrow or the day after tomorrow, and I will also attempt to shorten the proof further with the automatic compression algorithm. Hopefully everything is right. Fingers crossed.