二元中子星在标量-张量理论中通过动能筛选的标量辐射
Scalar emission from binary neutron stars in scalar-tensor theories with kinetic screening
AI总结：
研究二元中子星在具有动能筛选（K-本质）的位移对称标量-张量理论中标量辐射的特性，通过3+1数值模拟在解耦极限下，揭示动能筛选对标量辐射非单调影响，对引力波测试引力理论有潜在意义。
摘要：
我们通过3+1数值模拟在解耦极限下，研究二元中子星在位移对称标量-张量理论中通过动能筛选（K-本质）的标量辐射。为构建静态二元初始数据，在屏蔽半径r*远大于轨道分离的范围内，我们引入了静态场方程的双曲化，以绕过影响直接时间演化的Keldysh型破裂。对于等质量二元系统，其中标量辐射主要由ℓ=m=2模式主导，动能筛选对标量辐射非单调作用，取决于r*与λ_{22}（λ_{22}为波长）的相对大小：当λ_{22}<<r*时，其相对于Fierz-Jordan-Brans-Dicke（FJBD）情况被抑制，而当λ_{22}≥r*时，其被放大超过FJBD。对于不等质量二元系统，标量偶极子重新出现，其随质量不对称性线性增长，而四极筛除在质量比~0.6下仍接近等质量情况。我们揭示的动能筛选非单调行为对引力波基于测试引力有潜在意义。特别是相对论双脉冲星要求r*>>10^9 km以有效抑制标量四极；对于宇宙学动机的Λ，r*~10^{11} km（对于太阳质量源），仅提供中等抑制。
英文摘要：
We investigate the scalar emission from binary neutron stars in shift-symmetric scalar-tensor theories with kinetic screening ($K$-essence), using 3+1 numerical simulations in the decoupling limit. To construct static binary initial data in the regime where the screening radius $r_*$ greatly exceeds the orbital separation, we introduce a hyperbolization of the static field equations that bypasses the Keldysh-type breakdown affecting direct time evolutions. For equal-mass binaries, where the scalar emission is dominated by the $\ell=m=2$ mode, kinetic screening acts non-monotonically on the scalar radiation, suppressing or enhancing the quadrupolar amplitude depending on the relative size of $r_*$ and $λ_{22}$ (with $λ_{22}$ the wavelength): for $λ_{22}\ll r_*$ it is suppressed relative to the Fierz-Jordan-Brans-Dicke (FJBD) case, while for $λ_{22}\gtrsim r_*$ it is amplified above FJBD. For unequal-mass binaries a scalar dipole re-emerges, growing linearly with the mass asymmetry, while the quadrupolar screening remains close to the equal-mass case down to mass ratios $\sim 0.6$. The non-monotonic behavior of kinetic screening that we uncover has potential implications for gravitational-wave-based tests of gravity. The relativistic double pulsar, in particular, requires $r_*\gg 10^9$~km to efficiently suppress the scalar quadrupole; for cosmologically-motivated $Λ$, $r_*\sim 10^{11}$~km (for a solar-mass source), giving only moderate suppression.
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