&gt; <i>and radiate all waste heat toward a black hole (maximum cooling).</i><p>It&#x27;s comparatively inefficient to radiate heat into a narrow cone, and there is little advantage to radiating it into a black hole. On the contrary, matter falling into the black hole will form an accretion disk that radiates heat back to you. In order to maximize dissipation, they would simply radiate it away into all directions uniformly.<p>However, there might be other considerations to take into account here besides physics. It might be important to such an isolated civilization to avoid detection. In that case they would gladly take the hit on efficiency and radiate their heat in narrow cones into the gaps where no nearby stars are located.<p>&gt; <i>An advanced alien civilization will probably have very low radiation signature. To afford the maximum amount of computation</i><p>Maybe. We can&#x27;t say what the goals are of any advanced civilization. The reason why we like to talk about this <i>specific</i> type of civilization is that they are the type that we can actually <i>look for</i> right now.<p>But as I said above, if you&#x27;re an isolationist population of computer brains, it makes sense to go through the effort of avoiding other people showing up on your doorstep. Such a culture might deem it acceptable to invest most of their energy budget into avoiding detection, as opposed to computation only.