Atlas › Modular forms › Weight 2 › Level 642 › 642.2.a › 642.2.a.d

Newform orbit 642.2.a.d

Trace form

The 2 newforms in this orbit are conjugate over $\mathbb{Q}$ ; the sum of their $q$ -expansions is

$2q - 2q^{2} + 2q^{3} + 2q^{4} - q^{5} - 2q^{6} - 7q^{7} - 2q^{8} + 2q^{9} + q^{10} + q^{11} + 2q^{12} - 7q^{13} + 7q^{14} - q^{15} + 2q^{16} - q^{17} - 2q^{18} - 10q^{19} - q^{20} - 7q^{21} - q^{22} - 3q^{23} - 2q^{24} + O(q^{25})$

Coefficient field

The coefficients $a_n$ generate $\mathbb{Q}(\sqrt{5})$ . It is generated by the eigenvalue $\alpha$ of $T = T_{5} + 3T_{7}$ , whose minimal polynomial is

$x^{2} + 22x + 101$

Atkin–Lehner signs

$p$	$w_p$
2	$+1$
3	$-1$
107	$-1$

For $p \parallel N$ every form in the orbit has $a_p = -p^{k/2-1} w_p$ . The Fricke sign is $w_N = +1$ , so the sign of the functional equation is $(-1)^{k/2} w_N = -1$ : each L-function in the orbit has odd analytic rank.

Traces of Hecke eigenvalues

$p$	2	3	5	7	11	13	17	19	23	29	31	37	41	43	47	53	59	61	67	71	73	79	83	89	97
$\operatorname{tr} a_p$	−2	2	−1	−7	1	−7	−1	−10	−3	−2	−9	−3	10	−5	−3	4	10	3	−8	−4	−4	−6	−11	14	−10

$\operatorname{tr} a_n$ for every $n \le 1000$ is in the JSON.

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.473 s (one thread) and proven: the dimensions are certified, and the characteristic polynomial of $T$ over $\mathbb{Z}$ is reconstructed by CRT past a rigorous coefficient bound. The label, dimension and $\operatorname{tr} a_p$ for every $p < 1000$ equal LMFDB's.

The engine's checks

dim M^+ at levels [1, 2, 3, 6, 107, 214, 321, 642]: [0, 1, 1, 3, 10, 29, 38, 112] (certified at ell = 2147482621)
T = [(5, 1), (7, 3)]; h of degree 19 = 1 x 19 (phi(ord eps) x dim S_k^new); 3 primes, 0 rejected

Open in the notebook · JSON · stored data

Recompute it yourself

In Sage mode at sagebrush.space (or npx sagebrush --sage):

newform_orbits(642, 2)[3]   # 642.2.a.d

With the Rust engine (source), in engine/:

cargo run --release -p sagebrush-web --example atlas -- 642:2 1000