Dark matter axion clump resonance of photons
Dark matter axion clump resonance of photons
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DOI：
10.1088/1475-7516/2018/11/004
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发表时间：
2018-05
影响因子：
6.4
通讯作者：
M. Hertzberg;E. D. Schiappacasse
中科院分区：
文献类型：
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作者：
M. Hertzberg;E. D. Schiappacasse
最近，人们对暗物质轴子凝聚体的物理性质产生了兴趣。由于引力和自相互作用，它们可以组织成空间局部团块，我们在参考文献中检查了其属性。 [1, 2]。由于轴子凝聚体是相干振荡的，因此可以想象它会导致光子的参量共振，从而导致光子占据数呈指数增长以及随后的无线电波发射。我们表明，虽然空间均匀凝聚体总是存在共振，但空间局部团块凝聚体的共振的存在敏感地取决于团块的大小、轴子-光子耦合的强度和场振幅。通过将电磁场分解为矢量球谐函数，我们能够以数值方式计算任意参数的团块共振。我们发现，对于真正的 BEC 基态球对称团块，QCD 轴子-光子耦合的常规值不存在共振，但对于具有中等大耦合的轴子，或进入隐藏扇形光子，或来自具有排斥相互作用的标量暗物质，则存在共振。我们将这些结果扩展到由有限角动量组织的非球对称团块，并发现即使具有传统耦合的 QCD 轴子团块也可以在足够大的角动量下发生共振衰减。我们讨论了这些结果可能产生的天体物理后果，包括团块堆积和合并导致天空中快速电磁发射的想法。
Recently there has been interest in the physical properties of dark matter axion condensates. Due to gravitational attraction and self-interactions, they can organize into spatial localized clumps, whose properties were examined by us in refs. [1, 2]. Since the axion condensate is coherently oscillating, it can conceivably lead to parametric resonance of photons, leading to exponential growth in photon occupancy number and subsequent radio wave emission. We show that while resonance always exists for spatially homogeneous condensates, its existence for a spatially localized clump condensate depends sensitively on the size of clump, strength of axion-photon coupling, and field amplitude. By decomposing the electromagnetic field into vector spherical harmonics, we are able to numerically compute the resonance from clumps for arbitrary parameters. We find that for spherically symmetric clumps, which are the true BEC ground states, the resonance is absent for conventional values of the QCD axion-photon coupling, but it is present for axions with moderately large couplings, or into hidden sector photons, or from scalar dark matter with repulsive interactions. We extend these results to non-spherically symmetric clumps, organized by finite angular momentum, and find that even QCD axion clumps with conventional couplings can undergo resonant decay for sufficiently large angular momentum. We discuss possible astrophysical consequences of these results, including the idea of a pile-up of clump masses and rapid electromagnetic emission in the sky from mergers.