how can I implement the fourth power of the norm

[Mark_L_Stone]

Only scalar quadratic forms can be specified in CVX toolbox

My guess is that you have the square from the Signal Processing Toolbox installed, and that is getting called by CVX’s square_pos instead of CVX’s square (see 2nd to last paragraph below for explanation). On my machine, which -all square_pos C:\cvx_2.2.2\functions\square_pos.m C:\cvx_2.2.2\functions@cvx\square_pos.m % cvx method The first of these is supposed to be called when called with a numeric argument, whether or not interspersed between other CVX statements. You can look at the sou…