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Direct Evidence of a Dual Cascade in Gravitational Wave Turbulence
Physical Review Letters ( IF 8.6 ) Pub Date : 2021-09-20 , DOI: 10.1103/physrevlett.127.131101
Sébastien Galtier 1, 2, 3 , Sergey V Nazarenko 4
Affiliation  

We present the first direct numerical simulation of gravitational wave turbulence. General relativity equations are solved numerically in a periodic box with a diagonal metric tensor depending on two space coordinates only, gijgii(x,y,t)δij, and with an additional small-scale dissipative term. We limit ourselves to weak gravitational waves and to a freely decaying turbulence. We find that an initial metric excitation at intermediate wave number leads to a dual cascade of energy and wave action. When the direct energy cascade reaches the dissipative scales, a transition is observed in the temporal evolution of energy from a plateau to a power-law decay, while the inverse cascade front continues to propagate toward low wave numbers. The wave number and frequency-wave-number spectra are found to be compatible with the theory of weak wave turbulence and the characteristic timescale of the dual cascade is that expected for four-wave resonant interactions. The simulation reveals that an initially weak gravitational wave turbulence tends to become strong as the inverse cascade of wave action progresses with a selective amplification of the fluctuations g11 and g22.

中文翻译:

引力波湍流中双级联的直接证据

我们提出了引力波湍流的第一个直接数值模拟。广义相对论方程在具有对角线度量张量的周期框中进行数值求解,仅取决于两个空间坐标,G一世jG一世一世(X,,)δ一世j,以及一个额外的小规模耗散项。我们将自己限制在微弱的引力波和自由衰减的湍流中。我们发现中间波数处的初始度量激发导致能量和波作用的双重级联。当直接能量级联达到耗散尺度时,在能量从平台到幂律衰减的时间演变中观察到转变,而反级联前沿继续向低波数传播。发现波数和频率-波数谱与弱波湍流理论兼容,并且双级联的特征时间尺度是四波共振相互作用预期的时间尺度。G11G22.
更新日期:2021-09-20
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