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arXiv 1806.07779gr-qc
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Proca星的Head-on collisions和轨道合并

Head-on collisions and orbital mergers of Proca stars

Nicolas Sanchis-Gual, Carlos Herdeiro, José A. Font, Eugen Radu, Fabrizio Di Giovanni

摘要:

Proca星是自引力的玻色-爱因斯坦凝聚体,它是爱因斯坦-(复)-Proca系统的数值定态解。这些孤子既可以是稳定的,又可以通过引力冷却机制从一般的初始数据动态地形成。在本文中,我们进一步探索这些孤子对象的动力学性质,通过执行迎面碰撞和轨道合并的等质量Proca星,使用完全非线性数值演化。对于迎面碰撞,我们表明,这些碰撞的终点和引力波形取决于Proca星的紧凑性。紧凑度足够小的Proca星碰撞后留下稳定的Proca星残骸。但是更紧凑的Proca星碰撞形成一个短暂的${\it hypermassive}$ Proca星,它最终衰变成一个黑洞,尽管暂时被Proca准束缚态包围。不稳定的中间阶段会在波形中留下印记,使其与黑洞正面碰撞的波形不同。最后的准正常振铃相匹配的史瓦西黑洞,即使小的偏差可能会发生,作为充分的非线性和长寿命的Proca准束缚态的签名。对于轨道合并,结果也取决于恒星的紧凑性。对于大多数紧凑型恒星,双星合并形成一个克尔黑洞,它保留了部分初始轨道角动量,被短暂的Proca场残余所包围;在较低紧凑度的情况下,双星合并形成一个大质量的Proca星,有角动量,但不平衡。与先前对(标量)玻色子星的研究一样,当接近最终的平衡态时,这些物体的角动量似乎收敛到零。

英文摘要:

Proca stars are self-gravitating Bose-Einstein condensates obtained as numerical stationary solutions of the Einstein-(complex)-Proca system. These solitonic can be both stable and form dynamically from generic initial data by the mechanism of gravitational cooling. In this paper we further explore the dynamical properties of these solitonic objects by performing both head-on collisions and orbital mergers of equal mass Proca stars, using fully non-linear numerical evolutions. For the head-on collisions, we show that the end point and the gravitational waveform from these collisions depends on the compactness of the Proca star. Proca stars with sufficiently small compactness collide leaving a stable Proca star remnant. But more compact Proca stars collide to form a transient ${\it hypermassive}$ Proca star, which ends up decaying into a black hole, albeit temporarily surrounded by Proca quasi-bound states. The unstable intermediate stage can leave an imprint in the waveform, making it distinct from that of a head-on collision of black holes. The final quasi-normal ringing matches that of Schwarzschild black hole, even though small deviations may occur, as a signature of sufficiently non-linear and long-lived Proca quasi-bound states. For the orbital mergers, the outcome also depends on the compactness of the stars. For most compact stars, the binary merger forms a Kerr black hole which retains part of the initial orbital angular momentum, being surrounded by a transient Proca field remnant; in cases with lower compactness, the binary merger forms a massive Proca star with angular momentum, but out of equilibrium. As in previous studies of (scalar) boson stars, the angular momentum of such objects appears to converge to zero as a final equilibrium state is approached.

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