1. Malcolm Tobias Washington University mtobias@void.wustl.edu
CCTK Hydro
Malcolm Tobias
Washington University

2. CCTK Hydro: A Status Report
Contributors:
Miguel Alcubierre
Gabrielle Allen
Bernd Bruegmann
Teepanis Chachiyo
Thomas Dramlitsch
Ed Evans
Toni Font
Tom Goodale
Philip Gressman
Paul Lamping
Joan Masso
Mark Miller
Philippos Papadopoulos
Ed Seidel
Nikolaos Stergioulas
Wai-Mo Suen
Malcolm Tobias
Rob Young

3. Overview Cactus 3 Computational Modules (thorns) Initial data
MAHC hydro
Newtonian hydro
Boson stars
EOS tables
Analysis tools
Tests
Physics
Cactus 4 conversion

4. Initial data Single NS (TOV) Rotating NS Head-on colliding NS
Quasi-equil. Data (Meudon Data)
PN initial data
Test Data (FRW, shockwave)
IVP solver
Coupled Ham. & mom. Constraints!!!
No assumptions of conformal flatness!!!

5. MAHC hydro HRSC methods coupled to various evolution systems
Roe, Marquina, fluxsplit, ENO, HLLE
coupled to various evolution systems
ADM, Conformal systems, Bona-Masso
well tested (gr-qc/ )

6. Newtonian Hydro HRSC methods primarily Roe solver
tested on multiple systems
single NS
head-on NSs
orbiting NSs
multiple test indicators
angular momentum
mass
energy

7. Boson stars Coupled to a variety of GR evolution systems
stable over a long time scale

8. EOS tables 1D tables 2D tables tested for polytropic EOS
other EOS are in, but not yet tested
thermo. consistent interp.
2D tables
still under development
still need incorporated into evolution eqs.

9. Analysis tools Apparent horizon finders waveform extraction
Newman-Penrose quantities
constraint evaluators

10. Tests gr-qc/9811015 variety of initial data still fighting referee
shocktube
FRW
single static NS
boosted NS

11. Tests: GR-hydro coupling
3 hydro methods tested: Roe, fluxsplit and Marquina
3 GR evolution systems: ADM, BM-Einstein and BM Ricci
often different finite-difference schemes (leapfrog, icn, etc.)
TEST EVERY COMBINATION OF EACH!!!

12. Tests: GR-hydro coupling (2nd order time & space)

13. Tests: boosted NS

14. Tests: boosted NS

15. Tests: boosted NS

16. Physics
Phys. Rev. D (1998), gr-qc/ , gr- qc/ , Shapiro conjecture head-on collision of NS
evolution of quasi-equilibrium NS data (just beginning)
more on the way ;-)
How to do physics with cactus

17. Physics: head-on collision
Shapiro conjecture: can thermal pressure (from shock heating) delay the collapse in the head-on collision of NS s? Conjecture holds regardless of mass.
Take solar mass NS (polytropic EOS, G=2, K=1.16x105 cm5/g/s2), give them a velocity corresponding to Newtonian infall from infinity, solve the IVP and see what happens!

18. Physics: head-on collision

19. Physics: head-on collision

20. Physics: head-on collision

21. Physics: Meudon data

22. Physics: How to use Cactus
Cactus is not a black box
many untested combinations of parameters
top down approach
check all equations/routines
test for consistency of all terms
test for convergence
bottom up approach
make sure results look "reasonable"
make sure results are "right"

23. Cactus 4.0 Most hydro thorns still under conversion What we will gain:
AMR infrastructure
better interfacing between GR-hydro solvers
more users=more developers & debuggers