arXiv 2007.139802020-07gr-qcastro-ph.HEhep-th

从黑洞连续谱看Einstein-Maxwell介子-轴子引力

Implications of Einstein-Maxwell dilaton-axion gravity from the black hole continuum spectrum

Indrani Banerjee, Bhaswati Mandal, Soumitra SenGupta

备注：: 14 pages, 6 figures, 1 Table (accepted for publication in MNRAS)
DOI：: 10.1093/mnras/staa3232

摘要：

弦激发的模型可以作为潜在的候选人，以取代GR在高能量制度，量子引力预计将发挥至关重要的作用。这种模型不仅可以解释引力的紫外性质，而且在解决暗物质和暗能量等问题上也显示出很好的前景，这些问题在GR的框架内无法得到充分的解决。这是这项工作的核心是一个这样的字符串启发模型产生的低能量有效作用的杂波弦论与有趣的影响，暴胀宇宙学和宇宙后期加速。因此，重要的是要调查的作用，这样的理论在解释天体物理观测，例如，连续谱的黑洞，预计将持有丰富的信息有关的背景度量。Kerr-Sen时空对应于EMDA引力中精确的、静止的、轴对称的黑洞解，具有源自轴场的轴荷和角动量。本文采用Novikov \& Thorne的薄吸积盘模型，计算了Kerr-Sen背景下类星体周围吸积盘的理论能谱。然后用它来评估80个帕洛马-格林类星体样本的光学亮度的理论估计，随后将其与可用的观测结果进行比较。我们基于$χ^2$分析的结果表明，类星体的光学观测更倾向于使用介子参数$r_2\sim 0.2$，这一结果也得到了其他误差估计的进一步证实，Nash-Sutcliffe效率、一致性指数及其修正版本。我们进一步报道了类星体的光学数据不支持强自旋荷（$r_2>1.6$），并估计了类星体的自旋。

英文摘要：

String inspired models can serve as potential candidates to replace GR in the high energy regime where quantum gravity is expected to play a vital role. Such models not only subsume the ultraviolet nature of gravity but also exhibit promising prospects in resolving issues like dark matter and dark energy, which cannot be adequately addressed within the framework of GR. The Einstein-Maxwell dilaton-axion (EMDA) theory, which is central to this work is one such string inspired model arising in the low energy effective action of the heterotic string theory with interesting implications in inflationary cosmology and in the late time acceleration of the universe. It is therefore important to survey the role of such a theory in explaining astrophysical observations, e.g. the continuum spectrum of black holes which is expected to hold a wealth of information regarding the background metric. The Kerr-Sen spacetime corresponds to the exact, stationary, and axisymmetric black hole solution in EMDA gravity, possessing dilatonic charge and angular momentum originating from the axionic field. In this work, we compute the theoretical spectrum from the accretion disk around quasars in the Kerr-Sen background assuming the thin accretion disk model due to Novikov \& Thorne. This is then used to evaluate the theoretical estimates of optical luminosity for a sample of eighty Palomar-Green quasars which are subsequently compared with the available observations. Our results based on $χ^2$ analysis indicate that the dilaton parameter $r_2\sim 0.2$ is favored by optical observations of quasars which is further corroborated by other error estimators e.g., the Nash-Sutcliffe efficiency, the index of agreement, and their modified versions. We further report that strong dilaton charges ($r_2>1.6$) are disfavored by quasar optical data and the spins associated with the quasars are also estimated.

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