We study the shadows of four-dimensional black holes in M-theory inspired models. We first inspect the influence of M2-branes on such optical aspects for nonrotating solutions. In particular, we show that the M2-brane number can control the circular shadow size. This geometrical behavior is distorted for rotating solutions exhibiting cardioid shapes in certain moduli space regions. Implementing a rotation parameter, we analyze the geometrical shadow deformations. Among others, we recover the circular behaviors for a large M2-brane number. Investigating the energy emission rate at high energies, we find, in a well-defined approximation, that the associated peak decreases with the M2-brane number. Moreover, we investigate a possible connection with observations (from Event Horizon Telescope or future devices) from a particular M-theory compactification by deriving certain constraints on the M2-brane number in the light of the M87⋆ observational parameters.

中文翻译：

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M理论场景中的黑洞阴影

我们在受 M 理论启发的模型中研究四维黑洞的阴影。我们首先考察影响米用于非旋转解决方案的此类光学方面的 2 膜。特别是，我们表明米2-brane number 可以控制圆形阴影的大小。对于在某些模空间区域中呈现心形形状的旋转解决方案，这种几何行为是扭曲的。实施旋转参数，我们分析几何阴影变形。其中，我们恢复了大范围的循环行为米2-膜数。研究高能量下的能量发射率，我们发现，在一个明确的近似值中，相关的峰值随着米2-膜数。此外，我们通过推导对 M 的某些约束，研究与特定 M 理论紧凑化的观测（来自事件视界望远镜或未来设备）的可能联系。2- 根据光的膜数米87⋆观测参数。