论文标题
CMB B模式模板删除的局限性
Limitations of CMB B-mode template delensing
论文作者
论文摘要
在通货膨胀引力波产生的CMB极化的原始$ b $ mode的努力中，应该减轻与重力镜头产生的$ b $ modes相关的较大差异，这是一个称为删除的过程。通过使用高分辨率$ e $ mmode观测值和某些镜头潜力的代理，一种流行的方法是通过模仿镜头操作（以梯度订单或非扰动）来构建镜头$ b $ mmode模板。通过明确计算对两循环订单的所有贡献，以镜头上的$ b $ themodes的功率谱，并在无噪声限制中删除了这样的模板，我们可以证明：（i）校正：（i）校正了$ b $ mode Power Spectrum在$ o（$ o（$ o）$ o（1）的范围\ level caine can $ o（1）\％（\ f efor）\％（\ of）的范围内，因为 命令; （ii）如果要通过未放大或删除的$ e $ modes构建梯度订购模板，这些取消将消失，从而产生$ O（10）\，\％原始功率的剩余删除地板； （iii）当在梯度订单模板中使用镜头$ e $码时，会产生新的取消，从而使删除楼层的原始功率低至$ o（1）\％\％\％$ $ o（1）\％\％$ $ $ o（1）\％\％$ $ o（1）\％\％$； （iv）对于由镜头$ e $ modes构建的非扰动模板，这些新的取消将消失，重新引入了$ o（10）\，\％$的残留删除地板。我们进一步表明，在现实情况下，梯度订购模板的表现优于非扰动的模板，对$ e $ mmode偏振和镜头潜力的噪声估计。因此，我们建议在$ b $ mode模板删除的实际应用中，其中模板是直接从（过滤的）观察到的$ e $ modes构造的，应使用梯度订购方法，而不是非扰动重新映射。
Efforts to detect a primordial $B$-mode of CMB polarization generated by inflationary gravitational waves ought to mitigate the large variance associated with the $B$-modes produced by gravitational lensing, a process known as delensing. A popular approach to delensing entails building a lensing $B$-mode template by mimicking the lensing operation, either at gradient order or non-perturbatively, using high-resolution $E$-mode observations and some proxy of the lensing potential. By explicitly calculating all contributions to two-loop order in lensing to the power spectrum of $B$-modes delensed with such a template in the noise-free limit, we are able to show that: (i) corrections to the leading-order calculation of the lensing $B$-mode power spectrum only enter at the $O(1)\,\%$ level because of extensive cancellations between large terms at next-to-leading order; (ii) these cancellations would disappear if a gradient-order template were to be built from unlensed or delensed $E$-modes, giving rise to a residual delensing floor of $O(10)\,\%$ of the original power; (iii) new cancellations arise when the lensed $E$-modes are used in the gradient-order template, allowing for the delensing floor to be as low as $O(1)\,\%$ of the original power in practical applications of this method; and (iv) these new cancellations would disappear for a non-perturbative template constructed from the lensed $E$-modes, reintroducing a residual delensing floor of $O(10)\,\%$. We further show that the gradient-order template outperforms the non-perturbative one in realistic scenarios with noisy estimates of the $E$-mode polarization and lensing potential. We therefore recommend that in practical applications of $B$-mode template delensing, where the template is constructed directly from the (filtered) observed $E$-modes, the gradient-order approach should be used rather than a non-perturbative remapping.
