function BdGVec = BdGMatrix(gVec, psi, Params, VDk, VParams, Transf, muchem) gs = Params.gs; gdd = Params.gdd; gammaQF = Params.gammaQF; KEop = 0.5*(Transf.KX.^2+Transf.KY.^2); g_pf_2D = 1/(sqrt(2*pi)*VParams.ell); gQF_pf_2D = sqrt(2/5)/(pi^(3/4)*VParams.ell^(3/2)); Ez = (0.25/VParams.ell^2) + (0.25*Params.gz*VParams.ell^2); muchem_tilde = muchem - Ez; % eigs only works with column vectors psi = psi.'; KEop = KEop.'; VDk = VDk.'; % Interaction Potential frho = fftn(abs(psi).^2); Phi = real(ifftn(frho.*VDk)); % Operators H = @(w) real(ifft(KEop.*fft(w))); C = @(w) (((g_pf_2D*gs*abs(psi).^2) + (g_pf_2D*gdd*Phi)).*w) + (gQF_pf_2D*gammaQF*abs(psi).^3.*w); muHC = @(w) (-muchem_tilde * w) + H(w) + C(w); X = @(w) (psi.*real(ifft(VDk.*fft(psi.*w)))) + (3/2)*(gQF_pf_2D*gammaQF*abs(psi).^3).*w; g = reshape(gVec, size(psi)); % Operate in order on g BdG = muHC(muHC(g) + (2.*X(g))); BdGVec = reshape(BdG, [], 1); end