2 papers
math.GR2026
Colored Stallings graphs and Counterexamples to Stallings equalizer conjecture
Jialin Lei, Teng Zhang
The famous Stallings equalizer conjecture has remained open for more than 40 years, which states that, for any free group \(F_n\) of rank \(n\ge 2\), any free group \(F\), and any…
math.NA2026
Sharp condition-number bounds for growth factors of Higham matrices in Gaussian elimination
Teng Zhang
Higham's conjecture on the growth factor of complex symmetric positive definite matrices is a longstanding problem in the stability theory of Gaussian elimination without pivoting.…