human
I am working on the file "Arahanov-Bohm Oscillations/Cylindrical Shell and Arahanov-Bohm Oscillations.ipynb".
The first task is:
I now want to introduce a magnetic field in the simulation. I think one way to do it is to add a phase to t_phi parameter.
Can you write Python code for it?

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Can you provide a the Python code you requested?
assistant
#Here is the Python code you requested.

for i in range(10):
    params = Parameters()
    params.N_z = 1
    params.N_phi = 50
    params.flux = 5*i
    params.t_z = 1
    params.t_phi = 1*np.exp(1j*2*np.pi*params.flux/N_phi)
    params.mu = 2

    H = calc_H(params)
    E_linspace = np.linspace(0,4,1000)
    dos = np.array([calc_DOS(E,H) for E in E_linspace])

    #plt.figure(i)
    plt.plot(E_linspace,dos)
    plt.xlabel('Energy (E)')
    plt.ylabel('Density of States(E) [a.u.]')
    #plt.title("flux" + str(params.flux))

# code for transport

def calc_current(E,params):
    if params.N_z < 2:
        raise Exception("Calculation of current requires atleast two logitudianl points in the device.")
    eta = 1e-10
    # calcualtion of the surface functions
    def surface_g(E,parmas):
        dummy_contact_params = Parameters()
        dummy_contact_params.N_z = 2
        dummy_contact_params.N_phi = params.N_phi
        dummy_contact_params.flux = params.flux
        dummy_contact_params.t_z = params.t_z
        dummy_contact_params.t_phi = params.t_phi
        dummy_contact_params.mu = params.mu
       
        H_mat = calc_H(dummy_contact_params)
        N_dof_lat = params.N_phi
        alpha = H_mat[:N_dof_lat,:N_dof_lat]
        beta = H_mat[:N_dof_lat,N_dof_lat:2*N_dof_lat]

        err = 1.0
        iter_count = 0
        iter_limit = 100000
        err_limit = 1e-6

        g = np.linalg.inv((E + 1j*eta)*np.eye(alpha.shape[0]) - alpha)
        g_old = np.linalg.inv((E + 1j*eta)*np.eye(alpha.shape[0]) - alpha)
        # iterate over iter_limit iterations or until err < err_limit
        for i in range(iter_limit):
            g = np.linalg.inv((E + 1j*eta)*np.eye(alpha.shape[0]) - alpha - np.dot(np.dot(np.conj(beta.T),g),beta))
            g = 0.5*(g + g_old)

            err = np.linalg.norm(g-g_old)/np.sqrt(np.linalg.norm(g)*np.linalg.norm(g_old))
            g_old = g
            if(err < err_limit):
                #print("Finished at",i,"Error :",err)
                break;
            if(i == (iter_limit - 1)):
               ...