hi Luciano,

we've done something like this in https://arxiv.org/abs/1204.2019 you can indeed find cosmological apparent horizons using AHFinderDirect, the trick is to add the following parameter:

AHFinderDirect::surface_definition[1] = "inner expansion"

hope this helps.

cheers, Miguel

On 23/07/2022 06:48, Luciano Combi wrote:

Hi all,

I'm trying to use AHFinderDirect to find the apparent horizon in the de Sitter metric, implemented in the Exact thorn in comoving coordinates. I tried a few things but cannot get it to work. Have someone tried something similar, i.e. using the AHFD in cosmological spacetimes instead of BHs? Below I attach a typical parfile I used

Thanks!

# flesh cactus::cctk_itlast = 0

ActiveThorns = "PUGH" driver::ghost_size = 3 driver::global_nx = 120 driver::global_ny = 120 driver::global_nz = 120 ##57

ActiveThorns = "CoordBase SymBase CartGrid3D" grid::avoid_origin = "false" grid::type = "byspacing" grid::dxyz = 0.2

ActiveThorns = "ADMBase ADMCoupling StaticConformal CoordGauge SpaceMask Exact" ADMBase::initial_lapse = "exact" ADMBase::initial_shift = "exact" ADMBase::initial_data = "exact" ADMBase::lapse_evolution_method = "exact" ADMBase::shift_evolution_method = "exact" ADMBase::metric_type = "physical" Exact::exact_model = "de Sitter+Lambda" Exact::de_Sitter_Lambda__scale = 0.50

########################################

ActiveThorns = "IOUtil" IOUtil::parfile_write = "no"

########################################

ActiveThorns = "AEILocalInterp PUGHInterp PUGHReduce SphericalSurface AHFinderDirect"

AHFinderDirect::print_timing_stats = "true"

AHFinderDirect::output_Theta_every = 1 AHFinderDirect::h_base_file_name     = "dS.h" AHFinderDirect::Theta_base_file_name = "dS.Theta"

AHFinderDirect::N_horizons = 1 AHFinderDirect::origin_x[1] = 0.0 AHFinderDirect::origin_y[1] = 0.0 AHFinderDirect::origin_z[1] = 0.0

AHFinderDirect::initial_guess_method[1] = "coordinate sphere" AHFinderDirect::initial_guess__coord_sphere__x_center[1] =  0.0 AHFinderDirect::initial_guess__coord_sphere__y_center[1] =  0.0 AHFinderDirect::initial_guess__coord_sphere__z_center[1] =  0.0 AHFinderDirect::initial_guess__coord_sphere__radius[1] = 1.0

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-- *Luc Combi* CONICET PhD fellow (Buenos Aires, Argentina) Instituto Argentino de Radioastronomía

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