Atlas › Modular forms › Weight 2 › Level 687 › 687.2.a › 687.2.a.a

Newform orbit 687.2.a.a

Trace form

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

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

Coefficient field

The coefficients $a_n$ generate $\mathbb{Q}(\sqrt{5})$ . It is generated by the eigenvalue $\alpha$ of $T = T_{2} + T_{5}$ , whose minimal polynomial is

$x^{2} + 3x - 9$

Atkin–Lehner signs

$p$	$w_p$
3	$+1$
229	$+1$

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	−1	4	−2	−9	6	3	−2	−7	−11	−18	−6	−13	15	−7	−5	15	−18	−24	17	−28	4	−5

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

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.225 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, 3, 229, 687]: [0, 1, 19, 78] (certified at ell = 2147478649)
T = [(2, 1), (5, 1)]; h of degree 39 = 1 x 39 (phi(ord eps) x dim S_k^new); 4 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(687, 2)[0]   # 687.2.a.a

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

cargo run --release -p sagebrush-web --example atlas -- 687:2 1000