Lya multiple scattering #534
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jordanflitter
added
the
type: feature: physical
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Bencher Report
…d to introduce two new 4D arrays for LW flux as LW photons travel in straight lines). Also included USE_ADIABATIC_FLUCTUATIONS to allow the possibility to begin the simulation with homogeneous T_k
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Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #534 +/- ##
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+ Coverage 87.99% 88.25% +0.25%
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Files 31 31
Lines 4556 4597 +41
Branches 773 782 +9
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+ Hits 4009 4057 +48
+ Misses 388 381 -7
Partials 159 159 ☔ View full report in Codecov by Sentry. |
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Branch is finally ready to be reviewed. Unlike what my previous comment says, it is now possible to have In the code itself, I refer to equations from here: https://arxiv.org/pdf/2601.14360. |
This is a draft for the Lya multiple scattering branch.$\alpha$ and $\beta$ , are determined by the current redshift $z$ , the filter radius $R$ and the ionization fraction $x_\mathrm{HI}$ . Unfortunately GSL doesn't support computing 2F3 so I had to come up with my own implementation, which works pretty well based on the tests that I made.$\alpha\gg\beta$ , as in this limit 2F3 approaches the Bessel function. This configuration should be used only as a sanity check that the new window function (multiple scattering = MS) yields the same output as the old one (straight line = SL) in the appropriate limit.
There are now two new flags, called
LYA_MULTIPLE_SCATTERINGandTEST_SL_WITH_MS_FILTER, the latter becomes relevant only when the former is True, while the former is relevant only ifUSE_HALO_FIELD=True.When
LYA_MULTIPLE_SCATTERING=True, ifTEST_SL_WITH_MS_FILTER=False, the code uses a modified window function that replaces the window function of Eq. (22) in Davies, Mesinger, Murray 2025 (it replaces only the window function that is applied on the SFRD, not the one that is applied on X-ray luminosity). It is a subtraction of two hypergeometric functions 2F3 (instead of a subtraction of two Bessel functions) where the parameters of 2F3,When
LYA_MULTIPLE_SCATTERING=True, andTEST_SL_WITH_MS_FILTER=True, the code uses the same modified window function but withCurrently, this branch is designed to work only when
USE_MINI_HALOS=False. With mini-halos, the SFRD is also used for the Lyman-Werner feedback, but the applied filter should correspond to the old one (as LW photons travel in straight lines), which is not supported by the current implementation whenLYA_MULTIPLE_SCATTERING=True. In the future, two new more fields inXraySourceBox(likefiltered_sfr_lwandfiltered_sfr_lw_mini) should be introduced in this setting (thereby increasing the amount of used memory), or alternatively we can throw an error whenUSE_MINI_HALOSandLYA_MULTIPLE_SCATTERINGare both True.