Michael Zingale

some refs: https://arxiv.org/abs/1509.08609

this is also where the sponge is turning on, so I think there is a lot happening there. I can make it a bit better with: ``` maestro.use_linear_grav_in_beta0 = 1...

it also works with `init_iter=2` curiously With `init_iter = 3`, we get: ``` Timestep 1 starts with TIME = 0 DT = 8.675232218e-08 Cell Count: Level 0, 36864 cells inner...

I don't see this behavior in `reacting_bubble`

curiously, it still crashes at the same place if I run with `maestro.do_burning=0`

okay, curiously when I run it under valgrind, it runs fine. No crash :( (it's out to timestep 9)

when running with ``` ./Maestro2d.gnu.MPI.ex inputs_2d.rprox maestro.do_burning=0 maestro.evolve_base_state=0 ``` we have a divide by zero in `MaestroMakew0` because `p0_new_arr` is zero, and it is in the denominator for `delta_chi_w0`

somehow the new pressure is really getting messed up, in `MaestroAdvance.cpp`, but I am not sure why

see: https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-the-linkcheck-builder

addresses #1542