PDEs on the Homogeneous Space of Positions and Orientations
By Remco Duits
We solve and analyze PDEs on the homogeneous space of positions and orientations. This homogeneous space is given by $\mathbb M=SE(d)/H$ where $SE(d)$ is the roto-translation Lie group and $H\equiv SO(d−1)$ the subgroup of rotations around a reference axis. We consider $d\in{2,3}$ with emphasis on $d=3$.
We solve the following PDEs on $\mathbb M$ analytically:
– Degenerate and non-degenerate (convection-)diffusion systems on $\mathbb M$, cf. [1] – Forward Kolmogorov PDEs of $\alpha$-stable Lévy processes on $\mathbb M$, cf. [2].
this is done by a Fourier transform on $\mathbb M$, cf. [2].
We solve the following PDEs on $\mathbb M$ numerically:
– Nonlinear Diffusions on $\mathbb M$, cf. [3], – Mean Curvature Flows and Total Variation Flows on $\mathbb M$, cf. [4] ($d= 2,3$), [5, 6] ($d= 2$), – Eikonal PDEs for sub-Riemannian and Finslerian geodesic front propagation on $\mathbb M$, cf. [7, 8],
via anisotropic fast-marching [10], left-invariant finite difference techniques [11] or Monte-Carlo simula-tions [2] of the underlying SDEs. The numerics is tested to our new exact solutions of the PDEs [2, 12] and of the sub-Riemannian geodesics in $\mathbb M$ [13].
We show their applications in medical image analysis in enhancement of fibers/blood vessels in 2D and 3D medical images [3, 4], and in fiber-enhancement [14], denoising [4], fiber-tracking [15], and structuralconnectivity quantification [16] in DW-MRI.