The thing I find most notable is the lack of any concrete information on how these things are to be cooled, other than quotes like "space cooling is free".

If you want to radiate away the heat, you are either limited by the Stefan-Boltzmann equation which requires extraordinarily large radiators at any reasonable operating temperature, or have to develop a "super-Planckian" radiator technology, something which while it may be theoretically possible doesn't seem to actually exist yet as a practical technology.

The only other plausible technology I can think of would be to use evaporative or sublimation-based cooling, but that would consume vast quantities of mass in the process, every bit of which would have to be delivered to space first.

Has anyone seen any published work that suggests it is actually anywhere near economically feasible to dissipate megawatts of power in space, using either these or any other technology?