// Make newform 945.2.a.k in Magma, downloaded from the LMFDB on 29 March 2024. // To make the character of type GrpDrchElt, type "MakeCharacter_945_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_945_2_a_k();". // 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_945_2_a_k();". // 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 := [-2, 0, 1]; Kf := NumberField(Polynomial([elt : elt in poly])); AssignNames(~Kf, ["nu"]); end if; Rfbasis := [Kf.1^i : i in [0..Degree(Kf)-1]]; 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_945_a();" function MakeCharacter_945_a() N := 945; order := 1; char_gens := [596, 757, 136]; v := [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_945_a_Hecke(Kf) return MakeCharacter_945_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 := [[1, 1], [0, 0], [1, 0], [-1, 0], [-1, 1], [1, 1], [2, 2], [3, -1], [2, -2], [-4, 0], [6, 0], [0, -6], [-5, -2], [-1, -4], [-1, 6], [-1, -7], [2, -6], [0, -6], [5, 2], [2, 0], [5, -5], [12, 2], [1, -6], [-3, -4], [0, 10], [-17, -2], [8, 2], [-2, -6], [-5, 6], [7, -3], [11, 4], [-2, 10], [-7, -1], [10, 8], [-2, 14], [-12, -8], [12, 2], [12, -4], [0, -8], [4, 8], [-1, -9], [0, 4], [-13, -5], [-14, 6], [3, 7], [-1, -1], [-6, 6], [0, -4], [1, 6], [12, -4], [1, -11], [2, 16], [4, -14], [-16, 10], [12, -4], [-2, 4], [-14, 0], [17, -3], [-10, 4], [22, 4], [-4, -6], [-10, -6], [-6, -6], [20, -4], [9, 13], [27, 1], [6, 0], [6, 16], [6, -2], [-6, -14], [12, 10], [-1, 21], [26, 0], [2, 12], [-6, 20], [16, -4], [-6, -8], [12, 2], [-14, 14], [8, -8], [-6, 2], [-7, 0], [-35, -1], [-3, -19], [15, -3], [24, -12], [-14, 2], [-16, -10], [9, -16], [17, 4], [-4, 4], [-12, -10], [19, 8], [10, -16], [20, -14], [-13, -16], [10, -4], [19, 6], [24, -2], [-5, -16], [-12, -20], [24, 14], [11, 12], [20, -8], [-24, -14], [-7, 9], [24, -8], [-24, 10], [15, -7], [2, 16], [32, 6], [4, 24], [-12, 26], [-5, -15], [24, -16], [8, -6], [-8, 26], [-31, 4], [-28, 14], [-18, 4], [-28, 14], [6, -2], [28, -10], [-24, 6], [13, 11], [34, -4], [-21, 16], [-16, -14], [0, 34], [-37, -3], [-38, 2], [6, 4], [-18, -2], [-30, -6], [-2, -16], [10, 26], [-30, -10], [-16, 14], [16, 0], [4, 34], [-1, -13], [26, -12], [1, 20], [28, 6], [-24, 2], [-6, -14], [4, -6], [6, 8], [-3, -25], [-34, -4], [-32, -2], [-10, -4], [8, -4], [19, -26], [-35, 6], [3, -31], [0, 26], [27, -12], [9, 7], [15, -8], [16, -18], [-32, -10], [11, 2], [-12, 18], [-11, -23], [-20, 12], [26, -2], [-40, 6]]; aps := ConvertToHeckeField(raw_aps); chi := MakeCharacter_945_a_Hecke(Universe(aps)); return ExtendMultiplicatively(weight, aps, chi); end function; // To make the newform (type ModFrm), type "MakeNewformModFrm_945_2_a_k();". // 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_945_2_a_k(:prec:=2) chi := MakeCharacter_945_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(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_945_2_a_k();". // 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_945_2_a_k( : sign := -1) R := PolynomialRing(Rationals()); chi := MakeCharacter_945_a(); // SetVerbose("ModularSymbols", true); Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign))); Vf := Kernel([<2,R![-1, -2, 1]>,<11,R![-1, 2, 1]>],Snew); return Vf; end function;