A Dyson sphere around a black hole

The search for extraterrestrial intelligence (SETI) has been conducted nearly 60 years. A Dyson Sphere, a spherical structure that surrounds star and transports its radiative energy outward as an source advanced civilisation, is one of the main targets SETI. In this study, we discuss whether building Sphere around black hole effective. We consider six sources: (i) cosmic microwave background, (ii) Hawking radiation, (iii) accretion disk, (iv) Bondi accretion, (v) corona, (vi) relativistic jets. To develop future civilisations (for example, Type II civilisation), $4\times10^{26}\,{\rm W}$($1\,{\rm L_{\odot}}$) expected to be needed. Among (vi), largest luminosity can collected from reaching $10^{5}\,{\rm L_{\odot}}$, enough maintain civilisation. Moreover, if collects not only electromagnetic radiation but also other types (e.g., kinetic energy) jets, total would approximately 5 times larger. Considering emission our results show stellar-mass in Milky Way ($10\,\rm kpc$ away us) detectable ultraviolet$(\rm 10-400\,{\rm nm)}$, optical$(\rm 400-760\,{\rm near-infrared($\rm 760\,{\rm nm}-5\,{\rm \mu m}$), mid-infrared($\rm 5-40\,{\rm m}$) wavelengths via waste heat using current telescopes such Galaxy Evolution Explorer Ultraviolet Sky Surveys. Performing model fitting observed spectral distributions measuring variability radial velocity may help us identify these possible artificial structures.