Cosmological parameter constraints from observations of time-delay lenses are
becoming increasingly precise. However, there may be significant bias and
scatter in these measurements due to, among other things, the so-called
mass-sheet degeneracy. To estimate these uncertainties, we analyze strong
lenses from the largest EAGLE hydrodynamical simulation. We apply a mass-sheet
transformation to the radial density profiles of lenses, and by selecting
lenses near isothermality, we find that the bias on H0 can be reduced to 5%
with an intrinsic scatter of 10%, confirming previous results performed on a
different simulation data set. We further investigate whether combining lensing
observables with kinematic constraints helps to minimize this bias. We do not
detect any significant dependence of the bias on lens model parameters or
observational properties of the galaxy, but depending on the source--lens
configuration, a bias may still exist. Cross lenses provide an accurate
estimate of the Hubble constant, while fold (double) lenses tend to be biased
low (high). With kinematic constraints, double lenses show bias and intrinsic
scatter of 6% and 10%, respectively, while quad lenses show bias and intrinsic
scatter of 0.5% and 10%, respectively. For lenses with a reduced $\chi^2 > 1$,
a power-law dependence of the $\chi^2$ on the lens environment (number of
nearby galaxies) is seen. Lastly, we model, in greater detail, the cases of two
double lenses that are significantly biased. We are able to remove the bias,
suggesting that the remaining biases could also be reduced by carefully taking
into account additional sources of systematic uncertainty.

利用大型 EAGLE 模拟，通过给透镜的径向密度剖面施加质量纸张变换，选择一些近等温性的透镜，将 H0 的偏差降低到 5% 并减小自身的内在散射率到 10%。本文进一步调查了将透镜观测值与动力学限制相结合是否有助于将偏差降到最小，同时还发现了在不同的源 - 透镜配置下仍可能存在偏差。

利用强引力透镜和星系动力学减少 $H_0$ 测量上的偏差：来自 EAGLE 模拟的结果

Reducing biases on $H_0$ measurements using strong lensing and galaxy  dynamics: results from the EAGLE simulation

Cosmological parameter constraints from the CMB power spectra alone suffer
several well-known degeneracies. These degeneracies can be broken by numerical
artefacts and also a variety of physical effects that become quantitatively
important with high-accuracy data e.g. from the Planck satellite. We study
degeneracies in models with flat and non-flat spatial sections, non-trivial
dark energy and massive neutrinos, and investigate the importance of various
physical degeneracy-breaking effects. We test the CAMB power spectrum code for
numerical accuracy, and demonstrate that the numerical calculations are
accurate enough for degeneracies to be broken mainly by true physical effects
(the integrated Sachs-Wolfe effect, CMB lensing and geometrical and other
effects through recombination) rather than numerical artefacts. We quantify the
impact of CMB lensing on the power spectra, which inevitably provides
degeneracy-breaking information even without using information in the
non-Gaussianity. Finally we check the numerical accuracy of sample-based
parameter constraints using CAMB and CosmoMC. In an appendix we document recent
changes to CAMB's numerical treatment of massive neutrino perturbations, which
are tested along with other recent improvements by our degeneracy exploration
results.

通过对 CMB 功率谱的研究，我们探讨了在平坦和非平坦空间环境，非平凡暗能量和有质量的中微子等模型中消除已知退化现象的重要性，以及采用真实物理效应和数值精度检验非高斯性中的损失信息。