‎In this paper we study the residual spectrum of the quasi-split unitary group $G=U(n,n)$ defined over a number field $F$‎, ‎coming from the Borel subgroups‎, ‎$L_{dis}^2(G(F)backslash G(Bbb A))_T$‎. ‎Due to lack of information on the local results‎, ‎that is‎, ‎the image of the local intertwining operators of the principal series‎, ‎our results are incomplete‎. ‎However‎, ‎we describe a conjec...

Basic relation between numerical range and Davis-Wielandt shell of an operator $A$ acting on a Hilbert space with orthonormal basis $xi={e_{i}|i in I}$ and its conjugate $bar{A}$ which is introduced in this paper are obtained. The results are used to study the relation between point spectrum, approximate spectrum and residual spectrum of $A$ and $bar{A}$. A necessary and sufficient condition fo...

In this paper, we propose an opportunistic channel access scheme based on weighted residual entropy function in cognitive radio networks. This central decision scheme significantly improves spectrum utilization compared with random and first opportunistic spectrum access schemes. Particularly, in this mechanism, appropriate spectrum opportunity will be selected based on the usefulness of idle c...