// Make newform 4928.2.a.bm in Magma, downloaded from the LMFDB on 28 March 2024. // To make the character of type GrpDrchElt, type "MakeCharacter_4928_a();" // To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();" // To make the newform (type ModFrm), type "MakeNewformModFrm_4928_2_a_bm();". // 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_4928_2_a_bm();". // 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 := [-1, -1, 1]; Kf := NumberField(Polynomial([elt : elt in poly])); AssignNames(~Kf, ["nu"]); end if; Rf_num := [[1, 0], [-1, 2]]; 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_4928_a();" function MakeCharacter_4928_a() N := 4928; order := 1; char_gens := [4159, 1541, 2817, 3137]; v := [1, 1, 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; function MakeCharacter_4928_a_Hecke(Kf) return MakeCharacter_4928_a(); 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 := 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 := 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 := 2; raw_aps := [[0, 0], [-1, -1], [2, 0], [1, 0], [1, 0], [-1, 1], [-1, 1], [-2, 2], [-2, -2], [-4, 2], [-5, -1], [4, -2], [-9, 1], [-8, 0], [5, 1], [-4, -2], [-1, -1], [5, -1], [-10, 2], [-6, 2], [-3, -1], [0, 4], [-2, -6], [2, 0], [4, -6], [7, 1], [1, -3], [4, 0], [0, -2], [2, 0], [12, 4], [-4, 8], [12, -2], [6, 2], [-14, 0], [0, -4], [-2, 4], [-10, -6], [-4, -4], [15, 1], [0, -4], [12, -6], [-12, -4], [-6, -8], [2, 0], [9, 5], [-4, -8], [1, 5], [12, 8], [0, -2], [-4, -6], [8, 8], [7, 9], [-11, -3], [-6, 0], [0, 0], [0, 6], [-6, 2], [2, -8], [-8, -2], [-12, 8], [5, -9], [0, -4], [-15, -3], [6, -4], [-14, 0], [-4, -8], [-16, -2], [-12, 4], [5, -1], [2, -8], [-16, 4], [-3, 9], [-6, 0], [-6, 14], [11, 7], [2, 8], [18, -8], [14, -4], [-11, -9], [-9, 7], [0, 10], [12, 0], [-4, 2], [6, -2], [16, -4], [-24, 2], [-2, 12], [1, -5], [-10, -2], [5, 13], [18, 2], [-14, 10], [0, 0], [-6, -2], [10, -6], [-36, 2], [8, -10], [-44, 0], [6, 12], [-28, 0], [30, -4], [-26, -6], [12, 2], [24, 4], [-24, -2], [-7, 9], [-39, 3], [-10, 6], [-17, 9], [4, -4], [16, 14], [20, 6], [9, 9], [-24, 0], [-20, -2], [9, 9], [7, -13], [-34, -4], [0, -8], [14, -12], [-8, 6], [3, -3], [-12, -8], [15, 15], [20, 2], [6, -4], [-9, 19], [-13, -17], [-11, -1], [-16, 4], [-16, -8], [34, 2], [2, 8], [-7, 11], [25, 3], [16, -10], [30, -6], [6, -4], [30, 4], [8, -12], [-18, 12], [-32, -8], [4, -4], [-10, 12], [15, -13], [15, -7], [13, -1], [-7, -15], [-12, -4], [-28, -6], [16, 6], [0, -4], [18, 10], [-18, 2], [38, -2], [24, -8], [-12, 18], [5, 7], [17, 11], [32, 12], [14, -4], [4, 8], [9, 9], [14, -4], [33, 5], [14, -18], [-17, -7], [-30, 8], [-20, 2], [-4, 16], [10, 8], [0, -4], [-52, 2], [-3, 1], [36, -6], [4, -4], [-12, -18], [-2, 6], [15, 1], [-28, -4], [-2, -14], [-30, 8], [-13, -3], [4, 4], [16, -2], [-14, -16], [-39, -7], [-8, 6], [-12, 4], [40, 6], [4, 0], [-42, 2], [-18, 12], [32, 8], [34, 0], [12, 2], [36, -10], [-7, -13], [-30, -14], [-38, 0], [-32, -16], [-24, -18], [25, -13], [41, 1], [2, -16], [1, 13], [16, 12], [10, -16], [-1, -17], [-32, -2], [4, -6], [24, 0], [-1, -1], [2, 18], [18, 8], [-4, -8], [-19, 7], [-22, 10], [-10, 4], [-12, 10], [-46, 10], [36, -10], [24, -16], [-32, 4], [-36, 10], [-16, -10], [8, -16], [-22, -14], [28, 4], [12, 6], [-48, -12], [-44, -4], [-26, 12], [1, -7], [10, 10], [-4, -14], [14, -12], [2, -10], [-17, 19], [10, -2], [18, -2], [31, -5], [-32, 2], [-21, -19], [36, 4], [-1, 3], [-21, 11], [12, -8], [52, -4], [18, -16], [-3, -9], [42, -6], [-10, -12], [37, -1], [-56, -4], [4, -26], [-46, 6], [30, 4], [15, -7], [4, 16], [-32, -12], [21, 23], [-69, -3], [22, 12], [1, -7], [12, -26], [24, -18], [-32, -8], [36, 10], [-2, 20], [18, -26], [8, 6], [0, 16], [45, -9], [-7, 5], [12, 8], [-26, 4], [-10, -12], [46, -6], [8, 8], [38, 14], [18, -14], [11, 5], [26, -18], [46, 14], [20, 22], [38, 4], [-59, 1], [-13, 5], [24, -6], [1, -23], [-8, 30], [10, 6], [-34, 4], [-31, -21], [-1, -13], [-12, -14], [-6, -18], [-14, 14], [25, 27], [28, -22], [-52, -16], [2, -26], [-18, 2], [60, -2], [-40, 12], [-6, 24], [-4, -4], [6, 20], [52, 12], [26, -16], [-12, 10], [8, 28], [-4, 0], [-51, 15], [-35, 5], [4, 28], [32, 6], [-16, 6], [-20, 8], [-10, -4], [73, 3], [-12, -12], [2, 16], [10, 16], [18, 30], [-31, 17], [16, 20], [28, 18], [-42, 20], [-12, 30], [-72, -8], [6, -6], [12, 4], [-3, 21], [-12, 30], [-49, -15], [-22, 24], [-42, -2], [-54, 16], [12, -10], [-9, 1], [-72, 0], [-34, 12], [-24, 4], [-20, 2], [2, 14], [-28, 4], [-4, 2], [-6, -18], [40, -6], [58, -8], [14, -10], [2, 24], [7, -15], [-71, -3], [20, 0], [-26, 20], [12, -4], [-18, 4], [31, 25], [-28, 12], [12, 4], [-95, 1], [-4, 30], [63, 1], [-56, 8], [6, -28], [-14, -2], [27, 27], [4, 28], [-2, 44], [24, -32], [-16, -14], [9, 1], [76, 0], [71, 9], [23, -7], [15, -7], [10, 8], [-32, 2], [-60, -8], [-14, -8], [6, -38], [-11, 17], [56, 0], [42, -8], [36, 8], [61, 1], [20, -2], [-32, -2], [-26, 26], [-79, -7], [-12, 20], [-24, 14], [-78, -6], [-66, 12], [42, -10], [-4, -22], [53, -1], [42, 8], [0, 16], [86, 4], [39, 1], [-20, 28], [66, 0], [2, 16], [-41, -9], [-13, -13], [-31, -21], [40, -26], [-16, 12], [-16, 0], [-12, 18], [58, 0], [-56, -8], [-37, -17], [-30, 24], [-52, -12], [86, 4], [21, 23], [-18, -26], [20, -16], [18, 16], [-24, -18], [-10, 34], [20, 26], [63, -1], [30, -18]]; aps := ConvertToHeckeField(raw_aps); chi := MakeCharacter_4928_a_Hecke(Universe(aps)); return ExtendMultiplicatively(weight, aps, chi); end function; // To make the newform (type ModFrm), type "MakeNewformModFrm_4928_2_a_bm();". // 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_4928_2_a_bm(:prec:=2) chi := MakeCharacter_4928_a(); f_vec := qexpCoeffs(); Kf := Universe(f_vec); // SetVerbose("ModularForms", true); // SetVerbose("ModularSymbols", true); S := CuspidalSubspace(ModularForms(chi, 2)); S := BaseChange(S, Kf); maxprec := NextPrime(2999) - 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_4928_2_a_bm();". // 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_4928_2_a_bm( : sign := -1) R := PolynomialRing(Rationals()); chi := MakeCharacter_4928_a(); // SetVerbose("ModularSymbols", true); Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign))); Vf := Kernel([<3,R![-4, 2, 1]>,<5,R![-2, 1]>,<13,R![-4, 2, 1]>,<17,R![-4, 2, 1]>,<19,R![-16, 4, 1]>,<23,R![-16, 4, 1]>],Snew); return Vf; end function;