From the post "Spin First Run Later" and "Photon Emission After Absorption" dated 15 Jul 2015, for 0≤x<xz
d2xdt2=1mψc−uψc+u1eu(e2u−1)1/2(dxdt)2
and for x>xz, where ψ(xz)=ψmax,
−d2xdt2=1mψc+uψc+u1eu(e2u−1)1/2(dxdt)2
Although,
d2xdt2=0 is trivial in most cases, it is not so here, especially in the latter equation where,
0=1mψc+uψc+u1eu(e2u−1)1/2(dxdt)2
(dxdt)2=v2=−1mψcψc+uueu(e2u−1)1/2
which means v=dxdt is complex and is perpendicular to x, the radial line joining the particle and the center of the ψ cloud.
In that expression,
ψc=ψn−ψmax
u=ln(cosh(x−xa2))
which suggests that for each value of x there is a corresponding value of v by which the particle orbits about the center of the particle cloud at radius rorbit=x.
The centrifugal force,
F=mv2x
This force is provided for by the difference in ψ between the orbiting particle and the ψ cloud. This force points in the direction of higher ψ towards ψmax at x=xz.
ψn−ψ(x)=F=mv2x
which leads to,
ψn−ψ(x)=F=mv2x=−1xψcψc+uueu(e2u−1)1/2
ψn{1+1xψc+uueu(e2u−1)1/2}=−ln(cosh(x−xa2)+ψmax{1+1xψc+uueu(e2u−1)1/2}
{ψn−ψmax+ln(cosh(x−12xa)}{1+1xψc+uueu(e2u−1)1/2}=0
which is true as,
d2xdt20+1mψ(x)=1mψn
implies,
ψn−ψ(x)=0
ψn−ψmax+ln(cosh(x−12xa)=0
We have just verified the possibility of d2xdt2=0 for x>xz. When d2xdt2>0, −d2xdt2 points towards the origin and acts to provide for the centrifugal force. v2 is negative, v is complex, iv is in the direction perpendicular to x. The particle is in orbit around the origin. Orbiting around the center of the particle ψ cloud is the natural thing to do.
For the former case, 0≤x<xz, d2xdt2=0 just implies that the particle can instantaneously experience zero acceleration.
Note: First we verify the possibility of v changing direction to iv at d2xdt2=0 then assert that when d2xdt2>0, −d2xdt2 provides for the centrifugal force and the particle is thus in circular motion. For x>xz, where ψ(xz)=ψmax, the force on the particle is towards ψmax, as such in the negative x direction.