Null test for cosmic curvature using Gaussian process. (arXiv:2209.08502v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Wu_P/0/1/0/all/0/1">Peng-Ju Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Qi_J/0/1/0/all/0/1">Jing-Zhao Qi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_X/0/1/0/all/0/1">Xin Zhang</a>
The cosmic curvature $Omega_{K,0}$, which determines the spatial geometry of
the universe, is an important parameter in modern cosmology. Any deviation from
$Omega_{K,0}=0$ would have a profound impact on primordial inflation paradigm
and fundamental physics. In this work, we adopt a cosmological
model-independent method to test whether $Omega_{K,0}$ deviates from zero. We
use the Gaussian process to reconstruct the reduced Hubble parameter $E(z)$ and
the derivative of distance $D'(z)$ from observational data, and then determine
$Omega_{K,0}$ with a null test relation. The cosmic chronometer (CC) Hubble
data, baryon acoustic oscillation (BAO) Hubble data, and supernovae Pantheon
sample are considered. Our result is consistent with a spatially flat universe
within the domain of reconstruction $0<z<2.3$, at the $1sigma$ confidence
level. In the redshift interval $0<z<1$, the result favors a flat universe,
while at $z>1$, it tends to favor a closed universe. In this sense, there is
still a possibility for a closed universe. We also carry out the null test of
the cosmic curvature at $0<z<4.5$ using the simulated gravitational wave
standard sirens, CC+BAO and redshift drift Hubble data. The result shows that
in the future, with the synergy of multiple high-quality observations, we can
tightly constrain the spatial geometry or exclude the flat universe.
The cosmic curvature $Omega_{K,0}$, which determines the spatial geometry of
the universe, is an important parameter in modern cosmology. Any deviation from
$Omega_{K,0}=0$ would have a profound impact on primordial inflation paradigm
and fundamental physics. In this work, we adopt a cosmological
model-independent method to test whether $Omega_{K,0}$ deviates from zero. We
use the Gaussian process to reconstruct the reduced Hubble parameter $E(z)$ and
the derivative of distance $D'(z)$ from observational data, and then determine
$Omega_{K,0}$ with a null test relation. The cosmic chronometer (CC) Hubble
data, baryon acoustic oscillation (BAO) Hubble data, and supernovae Pantheon
sample are considered. Our result is consistent with a spatially flat universe
within the domain of reconstruction $0<z<2.3$, at the $1sigma$ confidence
level. In the redshift interval $0<z<1$, the result favors a flat universe,
while at $z>1$, it tends to favor a closed universe. In this sense, there is
still a possibility for a closed universe. We also carry out the null test of
the cosmic curvature at $0<z<4.5$ using the simulated gravitational wave
standard sirens, CC+BAO and redshift drift Hubble data. The result shows that
in the future, with the synergy of multiple high-quality observations, we can
tightly constrain the spatial geometry or exclude the flat universe.
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