Twisted Radio Waves and Twisted Thermodynamics
  We present and analyze a gedanken experiment and show that the assumption that an antenna operating at a single frequency can transmit more than two independent information channels to the far field violates the Second Law of Thermodynamics. Transmission of a large number of channels, each associated with an angular momentum "twisted wave" mode, to the far field in free space is therefore not possible. 
Laszlo B. Kish, Robert D. Nevels
physics.class-ph cs.IT math.IT