The finite element method is adopted to give concrete bounds for eigenvalue of differential operators. The upper bound for eigenvalues has been well done in the history. However, to give lower bound eigenvalue is quite a difficult task. Compared with the classical research on eigenvalue evaluation, which only focused on approximate value of eigenvalue, new theories and computation methods are developed to give exact and sharp lower and upper bounds for the eigenvalues.
The classical error analysis theory for finite element method mainly focuses on the qualitative one, such as the convergence order, the stability. However, in many cases, for example the computer-assisted mathematical proof, we need the concrete values of approximation errors. For this purpose, we need to challenge the following problems, which have close relation with the eigenvalue problem of differential operators.
- to give not only the boundedness but also the concrete values of many error constants in the error analysis.
- to deal with the singularity of PDE solutions in case that the domain has an re-entrant corner.
I have interest in studying the finite element methods including,
- conforming FEM, non-conforming FEM, mixed FEM and hybrid FEM.
"Verified computation" means solving various problems to provide veirified solutions, i.e., mathematically correct results.
In floating-point number based numerical computation, there comes rounding error, which makes the computation result to be an approximate solution. To give mathematically exact result, the interval airthmetic proves to be powerful tool to bound the rounding error.
One application of verified computaton is to investigate the existence and uniqueness of solution to non-linear partial differential equations.
The Four-probe measurement of resistivity of semi-product material is related to the following Poisson's boundary value problem.
\( -\Delta u = f \text{ in } \Omega, {\partial{u}}/{{\partial n}} =0 \text{ on } \partial \Omega \)
By solving the above problem in 3D with proper processing of singularities, the resistivity can be calculated. See detail.
- This is research is supported by JKA RING!RING! Project.