acting on each vortex: $ {\bf F}_L\propto\phi_0
[{\bf z}_0,{\bf v}_s]=0$, where $\phi_0$ is a magnetic flux piercing the vortex and ${\bf v}_s$ is a a superfluid velocity induced in a given vortex core by other vortices and screening currents flowing along the boundaries. Thus, the local Doppler shift of the quasiparticle energy levels $\varepsilon_d=\hbar{\bf k}_F{\bf v}_s$ appears to vanish for trajectories passing through the vortex center. As a result, the position of the LDOS peaks coincide with the phase singularity points which are usually defined as vortex centers. However when the intervortex distance is comparable with (or less than) $\xi$ the part of the superfluid velocity induced by the neighboring vortex becomes strongly inhomogeneous inside the core region and the ${\bf v}_s$ value at a given vortex center diverges as $v_s\sim1/a$. As a consequence, the equilibrium size of the pair is no more determined by the condition of zero ${\bf v}_s$ at the vortex centers. The resulting nonvanishing Doppler shift for the trajectories passing through the vortex centers suppresses the LDOS at these points. Thus, for small $a$ the LDOS peak positions do not coincide with the vortex centers.

The Fig. \[Orbit\]b corresponds to the vortex-antivortex pair with the intervortex 