Atlas › Modular forms › Weight 2 › Level 387 › 387.2.a

Newspace 387.2.a: $S_{2}^{\mathrm{new}}(\Gamma_0(387))$

Newforms

Label	Dim	Coefficient field	Trace form	AL signs	Elliptic curve
387.2.a.a	1	$\mathbb{Q}$	$q - q^{2} - q^{4} - 2q^{5} + O(q^{8})$	+	387d1 rank 0
387.2.a.b	1	$\mathbb{Q}$	$q - q^{2} - q^{4} + q^{5} - 3q^{7} + O(q^{8})$	+	387c1 rank 1
387.2.a.c	1	$\mathbb{Q}$	$q - 2q^{4} + 2q^{5} - 2q^{7} + O(q^{8})$	+	387a1 rank 0
387.2.a.d	1	$\mathbb{Q}$	$q + q^{2} - q^{4} - q^{5} - 3q^{7} + O(q^{8})$	+	387b1 rank 1
387.2.a.e	1	$\mathbb{Q}$	$q + 2q^{2} + 2q^{4} + 4q^{5} + O(q^{8})$	+	387e1 rank 0
387.2.a.f	2	$\mathbb{Q}(\sqrt{2})$	$2q - 2q^{2} + 2q^{4} - 2q^{5} + 2q^{7} + O(q^{8})$	−
387.2.a.g	2	$\mathbb{Q}(\sqrt{3})$	$2q - 4q^{4} + 4q^{7} + O(q^{8})$	−
387.2.a.h	2	$\mathbb{Q}(\sqrt{2})$	$2q - 4q^{5} - 4q^{7} + O(q^{8})$	−
387.2.a.i	3	degree 3	$3q + 2q^{2} + 8q^{4} + 4q^{5} + 4q^{7} + O(q^{8})$	+
387.2.a.j	4	degree 4	$4q + 12q^{4} - 2q^{7} + O(q^{8})$	−

Hecke characteristic polynomials

The eigenvalue of $T = T_{2} + 3T_{5}$ generates each orbit's coefficient field; on the newspace its characteristic polynomial factors over $\mathbb{Q}$ as one irreducible factor per orbit:

Orbit	Characteristic polynomial of $T$
387.2.a.a	$x + 7$
387.2.a.b	$x - 2$
387.2.a.c	$x - 6$
387.2.a.d	$x + 2$
387.2.a.e	$x - 14$
387.2.a.f	$x^{2} + 8x + 8$
387.2.a.g	$x^{2} - 108$
387.2.a.h	$x^{2} + 12x + 28$
387.2.a.i	$x^{3} - 14x^{2} + 40x - 16$
387.2.a.j	$x^{4} - 121x^{2} + 4$

Dimensions

Newforms $S_{2}^{\mathrm{new}}(\Gamma_0(387))$	18
Old forms	23
Cusp forms $S_{2}(\Gamma_0(387))$	41
Eisenstein series $E_{2}(\Gamma_0(387))$	7
Modular forms $M_{2}(\Gamma_0(387))$	48

Decomposition of the old subspace

$S_{2}^{\mathrm{old}}(\Gamma_0(387)) =$ $S_{2}^{\mathrm{new}}(\Gamma_0(43))^{\oplus 3}$ $\oplus$ $S_{2}^{\mathrm{new}}(\Gamma_0(129))^{\oplus 2}$

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.2 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 engine's checks

dim M^+ at levels [1, 3, 9, 43, 129, 387]: [0, 1, 2, 4, 16, 46] (certified at ell = 2147483647)
T = [(2, 1), (5, 3)]; h of degree 18 = 1 x 18 (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(387, 2)

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

cargo run --release -p sagebrush-web --example atlas -- 387:2 1000

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