Non-quasiparticle microwave absorption in   $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$
  We show that a non-quasiparticle charge collective mode, in parallel and coincident with the d-wave pair conductivity, leads to a quantitative understanding of microwave surface impedance measurements on superconducting $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$. The analysis suggests an inhomogeneous charge ground state in $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$ and other HTS. 
S. Sridhar and Z. Zhai