Properties

Label 21.4.c.a
Level $21$
Weight $4$
Character orbit 21.c
Analytic conductor $1.239$
Analytic rank $0$
Dimension $2$
CM discriminant -3
Inner twists $4$

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Newspace parameters

Copy content comment:Compute space of new eigenforms
 
Copy content gp:[N,k,chi] = [21,4,Mod(20,21)] mf = mfinit([N,k,chi],0) lf = mfeigenbasis(mf)
 
Copy content magma://Please install CHIMP (https://github.com/edgarcosta/CHIMP) if you want to run this code chi := DirichletCharacter("21.20"); S:= CuspForms(chi, 4); N := Newforms(S);
 
Copy content sage:from sage.modular.dirichlet import DirichletCharacter H = DirichletGroup(21, base_ring=CyclotomicField(2)) chi = DirichletCharacter(H, H._module([1, 1])) N = Newforms(chi, 4, names="a")
 
Level: \( N \) \(=\) \( 21 = 3 \cdot 7 \)
Weight: \( k \) \(=\) \( 4 \)
Character orbit: \([\chi]\) \(=\) 21.c (of order \(2\), degree \(1\), minimal)

Newform invariants

Copy content comment:select newform
 
Copy content sage:traces = [2] f = next(g for g in N if [g.coefficient(i+1).trace() for i in range(1)] == traces)
 
Copy content gp:f = lf[1] \\ Warning: the index may be different
 
Self dual: no
Analytic conductor: \(1.23904011012\)
Analytic rank: \(0\)
Dimension: \(2\)
Coefficient field: \(\Q(\sqrt{-3}) \)
Copy content comment:defining polynomial
 
Copy content gp:f.mod \\ as an extension of the character field
 
Defining polynomial: \( x^{2} - x + 1 \) Copy content Toggle raw display
Coefficient ring: \(\Z[a_1, a_2, a_3]\)
Coefficient ring index: \( 2\cdot 3 \)
Twist minimal: yes
Sato-Tate group: $\mathrm{U}(1)[D_{2}]$

$q$-expansion

Copy content comment:q-expansion
 
Copy content sage:f.q_expansion() # note that sage often uses an isomorphic number field
 
Copy content gp:mfcoefs(f, 20)
 

Coefficients of the \(q\)-expansion are expressed in terms of \(\beta = 3\sqrt{-3}\). We also show the integral \(q\)-expansion of the trace form.

\(f(q)\) \(=\) \( q - \beta q^{3} + 8 q^{4} + (3 \beta - 10) q^{7} - 27 q^{9} - 8 \beta q^{12} + 12 \beta q^{13} + 64 q^{16} - 30 \beta q^{19} + (10 \beta + 81) q^{21} - 125 q^{25} + 27 \beta q^{27} + (24 \beta - 80) q^{28} + \cdots + 264 \beta q^{97} +O(q^{100}) \) Copy content Toggle raw display
\(\operatorname{Tr}(f)(q)\) \(=\) \( 2 q + 16 q^{4} - 20 q^{7} - 54 q^{9} + 128 q^{16} + 162 q^{21} - 250 q^{25} - 160 q^{28} - 432 q^{36} - 220 q^{37} + 648 q^{39} + 1040 q^{43} - 286 q^{49} - 1620 q^{57} + 540 q^{63} + 1024 q^{64} - 1760 q^{67}+ \cdots - 1620 q^{93}+O(q^{100}) \) Copy content Toggle raw display

Character values

We give the values of \(\chi\) on generators for \(\left(\mathbb{Z}/21\mathbb{Z}\right)^\times\).

\(n\) \(8\) \(10\)
\(\chi(n)\) \(-1\) \(-1\)

Embeddings

For each embedding \(\iota_m\) of the coefficient field, the values \(\iota_m(a_n)\) are shown below.

For more information on an embedded modular form you can click on its label.

Copy content comment:embeddings in the coefficient field
 
Copy content gp:mfembed(f)
 
Label   \(\iota_m(\nu)\) \( a_{2} \) \( a_{3} \) \( a_{4} \) \( a_{5} \) \( a_{6} \) \( a_{7} \) \( a_{8} \) \( a_{9} \) \( a_{10} \)
20.1
0.500000 + 0.866025i
0.500000 0.866025i
0 5.19615i 8.00000 0 0 −10.0000 + 15.5885i 0 −27.0000 0
20.2 0 5.19615i 8.00000 0 0 −10.0000 15.5885i 0 −27.0000 0
\(n\): e.g. 2-40 or 990-1000
Significant digits:
Format:

Inner twists

Char Parity Ord Mult Type
1.a even 1 1 trivial
3.b odd 2 1 CM by \(\Q(\sqrt{-3}) \)
7.b odd 2 1 inner
21.c even 2 1 inner

Twists

       By twisting character orbit
Char Parity Ord Mult Type Twist Min Dim
1.a even 1 1 trivial 21.4.c.a 2
3.b odd 2 1 CM 21.4.c.a 2
4.b odd 2 1 336.4.k.a 2
7.b odd 2 1 inner 21.4.c.a 2
7.c even 3 1 147.4.g.a 2
7.c even 3 1 147.4.g.b 2
7.d odd 6 1 147.4.g.a 2
7.d odd 6 1 147.4.g.b 2
12.b even 2 1 336.4.k.a 2
21.c even 2 1 inner 21.4.c.a 2
21.g even 6 1 147.4.g.a 2
21.g even 6 1 147.4.g.b 2
21.h odd 6 1 147.4.g.a 2
21.h odd 6 1 147.4.g.b 2
28.d even 2 1 336.4.k.a 2
84.h odd 2 1 336.4.k.a 2
    
        By twisted newform orbit
Twist Min Dim Char Parity Ord Mult Type
21.4.c.a 2 1.a even 1 1 trivial
21.4.c.a 2 3.b odd 2 1 CM
21.4.c.a 2 7.b odd 2 1 inner
21.4.c.a 2 21.c even 2 1 inner
147.4.g.a 2 7.c even 3 1
147.4.g.a 2 7.d odd 6 1
147.4.g.a 2 21.g even 6 1
147.4.g.a 2 21.h odd 6 1
147.4.g.b 2 7.c even 3 1
147.4.g.b 2 7.d odd 6 1
147.4.g.b 2 21.g even 6 1
147.4.g.b 2 21.h odd 6 1
336.4.k.a 2 4.b odd 2 1
336.4.k.a 2 12.b even 2 1
336.4.k.a 2 28.d even 2 1
336.4.k.a 2 84.h odd 2 1

Hecke kernels

This newform subspace can be constructed as the kernel of the linear operator \( T_{2} \) acting on \(S_{4}^{\mathrm{new}}(21, [\chi])\). Copy content Toggle raw display

Hecke characteristic polynomials

$p$ $F_p(T)$
$2$ \( T^{2} \) Copy content Toggle raw display
$3$ \( T^{2} + 27 \) Copy content Toggle raw display
$5$ \( T^{2} \) Copy content Toggle raw display
$7$ \( T^{2} + 20T + 343 \) Copy content Toggle raw display
$11$ \( T^{2} \) Copy content Toggle raw display
$13$ \( T^{2} + 3888 \) Copy content Toggle raw display
$17$ \( T^{2} \) Copy content Toggle raw display
$19$ \( T^{2} + 24300 \) Copy content Toggle raw display
$23$ \( T^{2} \) Copy content Toggle raw display
$29$ \( T^{2} \) Copy content Toggle raw display
$31$ \( T^{2} + 24300 \) Copy content Toggle raw display
$37$ \( (T + 110)^{2} \) Copy content Toggle raw display
$41$ \( T^{2} \) Copy content Toggle raw display
$43$ \( (T - 520)^{2} \) Copy content Toggle raw display
$47$ \( T^{2} \) Copy content Toggle raw display
$53$ \( T^{2} \) Copy content Toggle raw display
$59$ \( T^{2} \) Copy content Toggle raw display
$61$ \( T^{2} + 874800 \) Copy content Toggle raw display
$67$ \( (T + 880)^{2} \) Copy content Toggle raw display
$71$ \( T^{2} \) Copy content Toggle raw display
$73$ \( T^{2} + 139968 \) Copy content Toggle raw display
$79$ \( (T - 884)^{2} \) Copy content Toggle raw display
$83$ \( T^{2} \) Copy content Toggle raw display
$89$ \( T^{2} \) Copy content Toggle raw display
$97$ \( T^{2} + 1881792 \) Copy content Toggle raw display
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