  A detailed comparison is presented of analytical and particle-in-cell (PIC)
simulation investigation of the transverse instability, in two dimensions, of
initially one-dimensional electron phase-space hole equilibria. Good
quantitative agreement is found between the shift-mode analysis and the
simulations for the magnetic field ($B$) threshold at which the instability
becomes overstable (time-oscillatory) and for the real and imaginary parts of
the frequency. The simulation $B$-threshold for full stabilization exceeds the
predictions of shift-mode analysis by 20 to 30\%, because the mode becomes
substantially narrower in spatial extent than a pure shift. This threshold
shift is qualitatively explained by the kinematic mechanism of instability.
