Abstract
In the context of forthcoming galaxy surveys, to ensure unbiased constraints
on cosmology and gravity when using non-linear structure information,
percent-level accuracy is required when modelling the power spectrum. This
calls for frameworks that can accurately capture the relevant physical effects,
while allowing for deviations from $Łambda$CDM. Massive neutrino and baryonic
physics are two of the most relevant such effects. We present an integration of
the halo model reaction frameworks for massive neutrinos and
beyond-$Łambda$CDM cosmologies. The integrated halo model reaction, combined
with a pseudo power spectrum modelled by HMCode2020 is then compared against
$N$-body simulations that include both massive neutrinos and an $f(R)$
modification to gravity. We find that the framework is 5% accurate down to at
least $k3 \, h/Mpc$ for a modification to gravity of $|f_\rm
R0|10^-5$ and for the total neutrino mass $M_m_łeq
0.15$ eV. We also find that the framework is 4(1)% consistent with the Bacco
(EuclidEmulator2) emulator for $w$CDM cosmologies down to at least $k
3 \, h$/Mpc. Finally, we compare against hydrodynamical simulations
employing HMCode2020's baryonic feedback modelling on top of the halo model
reaction. For $Łambda$CDM cosmologies we find 2% accuracy for $M_łeq
0.48$eV down to at least $k5h$/Mpc. Similar accuracy is found when
comparing to $w$CDM hydrodynamical simulations with $M_= 0.06$eV. This
offers the first non-linear and theoretically general means of accurately
including massive neutrinos for beyond-$Łambda$CDM cosmologies, and further
suggests that baryonic effects can be reliably modelled independently of
massive neutrino and dark energy physics. These extensions have been integrated
into the publicly available ReACT code.
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