# \#slepc **URL:** https://fenicsproject.discourse.group/tag/slepc/68.md [Latest](https://fenicsproject.discourse.group/latest.md) · [Categories](https://fenicsproject.discourse.group/categories.md) · [Tags](https://fenicsproject.discourse.group/tags.md) --- ## [Why do I obtain inaccurate mode shapes from SLEPc PEP-solver for 3D elasticity problem with periodic BC?](https://fenicsproject.discourse.group/t/why-do-i-obtain-inaccurate-mode-shapes-from-slepc-pep-solver-for-3d-elasticity-problem-with-periodic-bc/19753)
**Author:** [@nadine](https://fenicsproject.discourse.group/u/nadine)\ **Replies:** 6\ **Last updated:** [July 3, 2026, 9:53am UTC](https://fenicsproject.discourse.group/t/why-do-i-obtain-inaccurate-mode-shapes-from-slepc-pep-solver-for-3d-elasticity-problem-with-periodic-bc/19753 "2026-07-03T09:53:13Z")
Hi everyone, I’m implementing an inverse dispersion solver in DOLFINx that computes complex wavenumbers k(ω) for waves in a periodic elastic 3D structure, using the SLEPc PEP-solver and Bloch periodic boundary condition… --- ## [Modal analysis using dolfin-x](https://fenicsproject.discourse.group/t/modal-analysis-using-dolfin-x/7349)
**Author:** [@Shubham\_Saurabh](https://fenicsproject.discourse.group/u/Shubham_Saurabh)\ **Replies:** 11\ **Last updated:** [May 13, 2026, 3:46pm UTC](https://fenicsproject.discourse.group/t/modal-analysis-using-dolfin-x/7349 "2026-05-13T15:46:08Z")
Hello, I am trying to do modal analysis using dolfin-x. I have assembled mass and stiffness matrix. but not able to use eigen solver in it. I have to compute natural frequencies and mode shapes of a system. The below c… --- ## [Why is my quadratic eigenvalue solver for inverse dispersion in a periodic rod not converging to the expected eigenvalues? (DOLFINx + SLEPc)](https://fenicsproject.discourse.group/t/why-is-my-quadratic-eigenvalue-solver-for-inverse-dispersion-in-a-periodic-rod-not-converging-to-the-expected-eigenvalues-dolfinx-slepc/19673)
**Author:** [@nadine](https://fenicsproject.discourse.group/u/nadine)\ **Replies:** 2\ **Last updated:** [May 11, 2026, 8:49am UTC](https://fenicsproject.discourse.group/t/why-is-my-quadratic-eigenvalue-solver-for-inverse-dispersion-in-a-periodic-rod-not-converging-to-the-expected-eigenvalues-dolfinx-slepc/19673 "2026-05-11T08:49:51Z")
Hello everyone, I’m implementing an inverse dispersion solver in DOLFINx that computes complex wavenumbers k(\\omega) for waves in a periodic elastic 3D structure. Instead of solving the forward eigenvalue problem \\omega… --- ## [Cumulative failures after many MPC construction + SLEPc solve cycles in one process (dolfinx\_mpc 0.8.0, DOLFINx 0.8.0, complex PETSc)](https://fenicsproject.discourse.group/t/cumulative-failures-after-many-mpc-construction-slepc-solve-cycles-in-one-process-dolfinx-mpc-0-8-0-dolfinx-0-8-0-complex-petsc/19670)
**Author:** [@Kashf13\_Kashf](https://fenicsproject.discourse.group/u/Kashf13_Kashf)\ **Replies:** 1\ **Last updated:** [April 24, 2026, 12:53pm UTC](https://fenicsproject.discourse.group/t/cumulative-failures-after-many-mpc-construction-slepc-solve-cycles-in-one-process-dolfinx-mpc-0-8-0-dolfinx-0-8-0-complex-petsc/19670 "2026-04-24T12:53:24Z")
I’m computing elastic Bloch band structures using dolfinx\_mpc.MultiPointConstraint for periodic boundary conditions. Each k-point builds an MPC with the appropriate Bloch phase, assembles K and M, and solves a generalize… --- ## [FFCX compiler files size limit with petsc.assemble\_matrix](https://fenicsproject.discourse.group/t/ffcx-compiler-files-size-limit-with-petsc-assemble-matrix/19654)
**Author:** [@mariom121](https://fenicsproject.discourse.group/u/mariom121)\ **Replies:** 11\ **Last updated:** [April 17, 2026, 2:52pm UTC](https://fenicsproject.discourse.group/t/ffcx-compiler-files-size-limit-with-petsc-assemble-matrix/19654 "2026-04-17T14:52:21Z")
Dear Fenics community: 'm building a fenicsx / dolfinx code for a physical equation built with sympy, which is very intrincate. The physics of the equation are fine but I need to emulate spectral methods and thus I need … --- ## [Non periodic corner - eigenvalue problem with Slepc](https://fenicsproject.discourse.group/t/non-periodic-corner-eigenvalue-problem-with-slepc/19580)
**Author:** [@Felipe\_Rocha](https://fenicsproject.discourse.group/u/Felipe_Rocha)\ **Replies:** 2\ **Last updated:** [March 10, 2026, 3:06pm UTC](https://fenicsproject.discourse.group/t/non-periodic-corner-eigenvalue-problem-with-slepc/19580 "2026-03-10T15:06:43Z")
import numpy as np from mpi4py import MPI from dolfinx import mesh, fem, plot import ufl import pyvista as pv from petsc4py import PETSc from slepc4py import SLEPc from dolfinx\_mpc import MultiPointConstraint, assemble\_m… --- ## [Why do I obtain ~185 near-zero eigenvalues in a clamped 3D elasticity eigenproblem (DOLFINx + SLEPc)?](https://fenicsproject.discourse.group/t/why-do-i-obtain-185-near-zero-eigenvalues-in-a-clamped-3d-elasticity-eigenproblem-dolfinx-slepc/19539)
**Author:** [@nadine](https://fenicsproject.discourse.group/u/nadine)\ **Replies:** 3\ **Last updated:** [February 24, 2026, 3:38pm UTC](https://fenicsproject.discourse.group/t/why-do-i-obtain-185-near-zero-eigenvalues-in-a-clamped-3d-elasticity-eigenproblem-dolfinx-slepc/19539 "2026-02-24T15:38:12Z")
Hello everyone, I am solving a 3D linear elasticity eigenvalue problem in DOLFINx for the dynamic case of a simple cylindrical rod. The geometry is imported from a STEP file (exported from COMSOL), meshed in Gmsh, and t… --- ## [Structural Modal Analysis](https://fenicsproject.discourse.group/t/structural-modal-analysis/19479)
**Author:** [@Finn\_Hansen](https://fenicsproject.discourse.group/u/Finn_Hansen)\ **Replies:** 1\ **Last updated:** [February 10, 2026, 2:57pm UTC](https://fenicsproject.discourse.group/t/structural-modal-analysis/19479 "2026-02-10T14:57:48Z")
I am trying to replecate the eigenfrequencies from this paper: Modal Analysis of Single Rectangular Cantilever Plate by Mathematically, FEA and Experimental Ashish R. Sonawane, Poonam S. Talmale I cant get to achive re… --- ## [Scaling of condition number in 1D, 2D, and 3D](https://fenicsproject.discourse.group/t/scaling-of-condition-number-in-1d-2d-and-3d/18462)
**Author:** [@Haydel\_Collins](https://fenicsproject.discourse.group/u/Haydel_Collins)\ **Replies:** 6\ **Last updated:** [December 15, 2025, 8:56pm UTC](https://fenicsproject.discourse.group/t/scaling-of-condition-number-in-1d-2d-and-3d/18462 "2025-12-15T20:56:26Z")
My understanding is that the condition number (for stiffness matrix of poisson) should scale like h^-2. Here is a MWE, more or less from the demos, where I run this for a few levels of refinement using nx = \[10,20,40,80…