
// Make newform 684.5.h.b in Magma, downloaded from the LMFDB on 24 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_684_h();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_684_h_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_684_5_h_b();".
// 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_684_5_h_b();".
// 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 := [-14, -1, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0], [-2, 3]];
    Rf_basisdens := [1, 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_684_h();"
function MakeCharacter_684_h()
    N := 684;
    order := 2;
    char_gens := [343, 533, 325];
    v := [2, 2, 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_684_h_Hecke();"
function MakeCharacter_684_h_Hecke(Kf)
    N := 684;
    order := 2;
    char_gens := [343, 533, 325];
    char_values := [[1, 0], [1, 0], [-1, 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 := 5;
    raw_aps := [[0, 0], [0, 0], [17, 3], [39, 5], [-119, -5], [0, 0], [-159, 35], [361, 0], [158, 0], [0, 0], [0, 0], [0, 0], [0, 0], [-1721, 85], [441, -325], [0, 0], [0, 0], [-1841, -515], [0, 0], [0, 0], [4879, -275], [0, 0], [5678, 0], [0, 0], [0, 0], [9998, 0], [0, 0], [0, 0], [0, 0], [0, 0], [0, 0], [4281, -2485], [14721, 1955], [-1561, -2955], [-8159, -3245], [0, 0], [-49198, 0], [9362, 0], [0, 0], [0, 0], [0, 0], [0, 0], [-30839, 2635], [0, 0], [69518, 0], [10999, -5675], [0, 0], [0, 0], [0, 0], [51999, -595], [53281, -1085], [42841, -5285], [0, 0], [-62119, 1035], [0, 0], [18041, 10395], [0, 0], [-126718, 0], [-63441, 5885], [0, 0], [8199, 12245], [0, 0], [0, 0], [88601, 7035], [152162, 0], [0, 0], [0, 0], [0, 0], [103241, -8325], [-7841, 18445], [-10882, 0], [-93079, 12555], [-266878, 0], [0, 0], [0, 0], [0, 0], [-144079, -8925], [-112081, 15645], [0, 0], [0, 0], [-229522, 0], [0, 0], [0, 0], [0, 0], [0, 0], [-196759, -3045], [0, 0], [-2401, -31875], [-126399, -27565], [-86121, -30955], [207081, 13115], [-428482, 0], [0, 0], [-360562, 0], [95239, -33995], [-358882, 0], [0, 0], [0, 0], [0, 0], [171119, -34275], [0, 0], [297841, 17155], [0, 0], [0, 0], [-442318, 0], [-328881, -12595], [302681, 28875], [702398, 0], [0, 0], [0, 0], [0, 0], [345679, 26845], [161041, -50765], [-328078, 0], [-168041, -57035], [0, 0], [-235481, -54635], [55081, -62645], [-338159, 35875], [0, 0], [0, 0], [0, 0], [0, 0], [0, 0], [473399, 16485], [-222802, 0], [731762, 0], [-92599, -78645], [520199, -9435], [538322, 0], [367799, -57435], [0, 0], [0, 0], [226079, -77715], [564161, 27555], [-18801, -90355], [0, 0], [0, 0], [0, 0], [631601, 34515], [0, 0], [-44639, -103085], [-577801, -61035], [0, 0], [0, 0], [0, 0], [-394318, 0], [0, 0], [-328121, 97045], [0, 0], [0, 0], [-597519, 68915], [480759, 99365], [0, 0], [0, 0], [0, 0], [1415522, 0], [1313918, 0], [798239, -47235], [0, 0], [-1555282, 0], [0, 0], [1333922, 0], [0, 0], [0, 0], [0, 0], [0, 0], [-977041, -41475]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_684_h_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_684_5_h_b();".
// 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_684_5_h_b(:prec:=2)
    chi := MakeCharacter_684_h();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 5));
    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_684_5_h_b();".
// 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_684_5_h_b( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_684_h();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,5,sign)));
    Vf := Kernel([<5,R![-914, -31, 1]>],Snew);
    return Vf;
end function;