PrivacyScanData/truncate/new2/hamiltonian-truncation-master/runQED.py

######################################################
# 
# Fock space Hamiltonian truncation for phi^4 theory in 2 dimensions
# Authors: Slava Rychkov (slava.rychkov@lpt.ens.fr) and Lorenzo Vitale (lorenzo.vitale@epfl.ch)
# December 2014
#
######################################################

import schwinger
import sys
import scipy
import numpy as np
import time
from scipy.constants import pi
from math import isclose
import matplotlib.pyplot as plt

def main(argv):
    
    #if there are too few arguments, print the right syntax and exit
    if len(argv) < 3:
        print("python runQED.py <R> <Emax>")
        sys.exit(-1)
    
    print("Beginning execution.")
    startTime = time.time()
    #circle circumference (p.5)
    R = float(argv[1])
    #maximum energy (compare Eq. 2.26)
    Emax = float(argv[2])
    #mass
    m = 0.
    verbose = False
    
    a = schwinger.Schwinger()
    
    a.buildFullBasis(2*pi*R, m, Emax, bcs="antiperiodic")

    print(f"Basis size: {a.fullBasis.size}")
    if verbose:
        print(f"Basis elements: {a.fullBasis}")

    #set the file name for saving the generated matrix
    fstr = "Emax="+str(a.fullBasis.Emax)+"_L="+str(a.L)

    a.buildMatrix()
    
    if verbose:
        print("Potential:")
        print(f"{a.potential.M.toarray()}")
    
    a.buildBasis(a.fullBasis.Emax)

    
    
    mass_gap = []
    for gval in [1]:# np.arange(1,15,0.5):
        computeVacuumEnergy(a,g=gval)
        spectrum = a.spectrum()
        #print(f"H: {a.H.toarray()}")
        print(f"Spectrum: {spectrum}")
        print(f"Normalized mass gap: {spectrum[1]/gval}")
        mass_gap.append(spectrum[1]/gval)
    
    # plt.xlabel("g")
    # plt.ylabel("m/g")
    # plt.title("R=1,lmax=5")
    # plt.plot(np.arange(1,15,0.5),mass_gap)
    # plt.savefig('normalized_mass_gap_vs_g.pdf')
    # plt.show()
    
    #for index in np.arange(1,len(spectrum),2):
    #    assert(isclose(spectrum[index],spectrum[index+1])), f"{spectrum[index]} !={spectrum[index+1]}"
    
    
    #print(a.h0)
    #print(a.fullBasis)
    print("Runtime:",time.time()-startTime)
    #a.saveMatrix(fstr)

def computeVacuumEnergy(schwinger, g):
    """
    

    Parameters
    ----------
    phi4 : Phi1234
        A Phi1234 object initialized with a suitable basis and the matrices
        for the various terms in the Hamiltonian.
    g : float
        Value of the coupling g.

    Returns
    -------
    A float representing the vacuum energy for this set of parameters.

    """
    sigma = -30.#-30.
    neigs = 10
    
    #print(schwinger.h0OffDiag.M.toarray())

    schwinger.setcouplings(g)

    print(f"Computing raw eigenvalues for g4 = {g}")

    schwinger.computeHamiltonian(ren=False)
    #print("Hamiltonian:")
    #print(schwinger.H.toarray())

    schwinger.computeEigval(sigma=sigma, n=neigs, ren=False)
        
    vacuumEnergy = schwinger.vacuumE(ren="raw")
    print("Raw vacuum energy: ", vacuumEnergy)
    
    return vacuumEnergy

if __name__ == "__main__":
    main(sys.argv)