function S=uskewHMat(v,n)
%function H=uskewHMat(v,n)
% form skew symmetric matrix from vector
%Input:  v  in R^(t(n)-n)  
% Output:  S  skew-symmetric with zero diagonal
%svind: linear indices of the **strictly** upper triangle by columns
svindu = logical(triu(ones(n),1));
S=zeros(n);
S(svindu)=v/sqrt(2);
S=S-S';
