
// Make newform 960.3.c.e in Magma, downloaded from the LMFDB on 24 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_960_c();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_960_c_Hecke();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_960_3_c_e();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_960_3_c_e();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function ConvertToHeckeField(input: pass_field := false, Kf := [])
    if not pass_field then
        poly := [81, 0, 16, 0, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0], [0, 1, 0, 0], [0, 7, 0, 1], [8, 0, 1, 0]];
    Rf_basisdens := [1, 1, 9, 1];
    Rf_basisnums := ChangeUniverse([[z : z in elt] : elt in Rf_num], Kf);
    Rfbasis := [Rf_basisnums[i]/Rf_basisdens[i] : i in [1..Degree(Kf)]];
    inp_vec := Vector(Rfbasis)*ChangeRing(Transpose(Matrix([[elt : elt in row] : row in input])),Kf);
    return Eltseq(inp_vec);
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_960_c();"
function MakeCharacter_960_c()
    N := 960;
    order := 2;
    char_gens := [511, 901, 641, 577];
    v := [2, 2, 1, 1];
    // chi(gens[i]) = zeta^v[i]
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    F := CyclotomicField(order);
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),[F|F.1^e:e in v]);
    return MinimalBaseRingCharacter(chi);
end function;

// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_960_c_Hecke();"
function MakeCharacter_960_c_Hecke(Kf)
    N := 960;
    order := 2;
    char_gens := [511, 901, 641, 577];
    char_values := [[1, 0, 0, 0], [1, 0, 0, 0], [-1, 0, 0, 0], [-1, 0, 0, 0]];
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    values := ConvertToHeckeField(char_values : pass_field := true, Kf := Kf); // the value of chi on the gens as elements in the Hecke field
    F := Universe(values);// the Hecke field
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),values);
    return chi;
end function;


function ExtendMultiplicatively(weight, aps, character)
    prec := NextPrime(NthPrime(#aps)) - 1; // we will able to figure out a_0 ... a_prec
    primes := PrimesUpTo(prec);
    prime_powers := primes;
    assert #primes eq #aps;
    log_prec := Floor(Log(prec)/Log(2)); // prec < 2^(log_prec+1)
    F := Universe(aps);
    FXY<X, Y> := PolynomialRing(F, 2);
    // 1/(1 - a_p T + p^(weight - 1) * char(p) T^2) = 1 + a_p T + a_{p^2} T^2 + ...
    R<T> := PowerSeriesRing(FXY : Precision := log_prec + 1);
    recursion := Coefficients(1/(1 - X*T + Y*T^2));
    coeffs := [F!0: i in [1..(prec+1)]];
    coeffs[1] := 1; //a_1
    for i := 1 to #primes do
        p := primes[i];
        coeffs[p] := aps[i];
        b := p^(weight - 1) * F!character(p);
        r := 2;
        p_power := p * p;
        //deals with powers of p
        while p_power le prec do
            Append(~prime_powers, p_power);
            coeffs[p_power] := Evaluate(recursion[r + 1], [aps[i], b]);
            p_power *:= p;
            r +:= 1;
        end while;    
    end for;
    Sort(~prime_powers);
    for pp in prime_powers do
        for k := 1 to Floor(prec/pp) do
            if GCD(k, pp) eq 1 then
                coeffs[pp*k] := coeffs[pp]*coeffs[k];
            end if;
        end for;
    end for;
    return coeffs;
end function;


function qexpCoeffs()
    // To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
    weight := 3;
    raw_aps := [[0, 0, 0, 0], [0, -1, 0, 0], [0, 0, -2, -1], [0, -2, -1, 0], [0, 0, 0, -4], [0, 0, 0, 0], [0, 0, 8, 0], [12, 0, 0, 0], [0, 0, 17, 0], [0, 0, 0, 0], [32, 0, 0, 0], [0, -8, -4, 0], [0, 0, 0, 14], [0, -14, -7, 0], [0, 0, -25, 0], [0, 0, 48, 0], [0, 0, 0, -4], [16, 0, 0, 0], [0, -2, -1, 0], [0, 0, 0, 0], [0, 40, 20, 0], [72, 0, 0, 0], [0, 0, 31, 0], [0, 0, 0, 16], [0, -56, -28, 0], [0, 0, 0, 32], [0, 34, 17, 0], [0, 0, 39, 0], [-80, 0, 0, 0], [0, 0, 108, 0], [0, -14, -7, 0], [0, 0, 0, -12], [0, 0, 36, 0], [44, 0, 0, 0], [0, 0, 0, -2], [-136, 0, 0, 0], [0, -40, -20, 0], [0, -34, -17, 0], [0, 0, 207, 0], [0, 0, -116, 0], [0, 0, 0, -4], [82, 0, 0, 0], [0, 0, 0, -72], [0, 40, 20, 0], [0, 0, -136, 0], [312, 0, 0, 0], [-12, 0, 0, 0], [0, 14, 7, 0], [0, 0, 113, 0], [-82, 0, 0, 0], [0, 0, -136, 0], [0, 0, 0, -112], [304, 0, 0, 0], [0, 0, 0, -84], [0, 0, -276, 0], [0, 0, 209, 0], [0, 0, 0, 18], [-40, 0, 0, 0], [0, -152, -76, 0], [0, 0, 0, -126], [0, 110, 55, 0], [0, 0, 60, 0], [0, -126, -63, 0], [0, 0, 0, -24], [0, 64, 32, 0], [0, 0, -368, 0], [292, 0, 0, 0], [0, -112, -56, 0], [0, 0, -279, 0], [-254, 0, 0, 0], [0, 0, -244, 0], [0, 0, 0, 96], [0, 142, 71, 0], [0, 216, 108, 0], [-572, 0, 0, 0], [0, 0, -137, 0], [0, 0, 0, -94], [0, -176, -88, 0], [0, 0, 0, 16], [640, 0, 0, 0], [0, 0, 0, -140], [656, 0, 0, 0], [0, 0, 0, 88], [0, -56, -28, 0], [-432, 0, 0, 0], [0, 0, -87, 0], [0, 0, 0, 210], [0, -160, -80, 0], [0, 0, 0, 0], [0, -210, -105, 0], [0, 0, 543, 0], [0, 0, 0, -136], [0, -222, -111, 0], [0, 0, 0, -84], [-660, 0, 0, 0], [0, 0, -129, 0], [0, 0, 0, 96], [0, 0, 0, -32], [0, 50, 25, 0], [-418, 0, 0, 0], [0, 98, 49, 0], [0, 0, 300, 0], [0, 0, 575, 0], [0, 0, 0, -110], [220, 0, 0, 0], [0, -16, -8, 0], [0, 0, -39, 0], [0, 0, -276, 0], [0, 0, 0, -24], [-880, 0, 0, 0], [0, 146, 73, 0], [0, -208, -104, 0], [0, 0, 80, 0], [52, 0, 0, 0], [544, 0, 0, 0], [0, 0, 0, 206], [0, -126, -63, 0], [0, 0, -687, 0], [0, 0, 248, 0], [0, 0, 0, 140], [-80, 0, 0, 0], [0, 168, 84, 0], [0, 0, 136, 0], [0, 0, -167, 0], [-548, 0, 0, 0], [0, 0, 0, -14], [-1230, 0, 0, 0], [0, 0, 0, 152], [0, -126, -63, 0], [0, -344, -172, 0], [-340, 0, 0, 0], [0, 0, 879, 0], [520, 0, 0, 0], [0, 280, 140, 0], [0, 0, 0, -96], [-306, 0, 0, 0], [0, 0, 216, 0], [0, 194, 97, 0], [0, 0, -752, 0], [0, 0, 0, 192], [436, 0, 0, 0], [0, 0, 0, 194], [0, 450, 225, 0], [0, 0, -697, 0], [1488, 0, 0, 0], [0, 0, 0, 112], [0, 112, 56, 0], [0, 0, 204, 0], [796, 0, 0, 0], [0, 0, -249, 0], [0, -232, -116, 0], [0, 0, 0, 126], [0, -546, -273, 0], [0, 0, -543, 0], [0, -114, -57, 0], [0, 0, 0, 168], [912, 0, 0, 0], [0, 0, 0, -306], [0, 280, 140, 0], [0, 0, 0, 256], [0, 0, 81, 0], [0, 0, -172, 0], [0, -322, -161, 0], [0, 0, 0, 324], [0, 0, -216, 0], [0, 0, -785, 0], [-640, 0, 0, 0], [0, -96, -48, 0]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_960_c_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_960_3_c_e();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
function MakeNewformModFrm_960_3_c_e(:prec:=4)
    chi := MakeCharacter_960_c();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 3));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(997) - 1;
    while true do
        trunc_vec := Vector(Kf, [0] cat [f_vec[i]: i in [1..prec]]);
        B := Basis(S, prec + 1);
        S_basismat := Matrix([AbsEltseq(g): g in B]);
        if Rank(S_basismat) eq Min(NumberOfRows(S_basismat), NumberOfColumns(S_basismat)) then
            S_basismat := ChangeRing(S_basismat,Kf);
            f_lincom := Solution(S_basismat,trunc_vec);
            f := &+[f_lincom[i]*Basis(S)[i] : i in [1..#Basis(S)]];
            return f;
        end if;
        error if prec eq maxprec, "Unable to distinguish newform within newspace";
        prec := Min(Ceiling(1.25 * prec), maxprec);
    end while;
end function;


// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_960_3_c_e();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function MakeNewformModSym_960_3_c_e( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_960_c();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,3,sign)));
    Vf := Kernel([<7,R![34, 0, 1]>,<17,R![-128, 0, 1]>,<19,R![-12, 1]>],Snew);
    return Vf;
end function;