Atlas › Modular forms › Weight 2 › Level 105 › 105.2.a

Newspace 105.2.a: $S_{2}^{\mathrm{new}}(\Gamma_0(105))$

Newforms

Label	Dim	Coefficient field	Trace form	AL signs	Sign	CM	Elliptic curve
105.2.a.a	1	$\mathbb{Q}$	$q + q^{2} + q^{3} - q^{4} + q^{5} + q^{6} + q^{7} + O(q^{8})$	− − −	$+1$		105a1 rank 0
105.2.a.b	2	$\mathbb{Q}(\sqrt{5})$	$2q - 2q^{3} + 6q^{4} - 2q^{5} + 2q^{7} + O(q^{8})$	+ + −	$+1$

Hecke characteristic polynomials

The eigenvalue of $T = T_{2} + T_{11}$ 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 $T$
105.2.a.a	$x - 1$
105.2.a.b	$x^{2} - 4x - 1$

Dimensions

Newforms $S_{2}^{\mathrm{new}}(\Gamma_0(105))$	3
Old forms	10
Cusp forms $S_{2}(\Gamma_0(105))$	13
Eisenstein series $E_{2}(\Gamma_0(105))$	7
Modular forms $M_{2}(\Gamma_0(105))$	20

Decomposition of the old subspace

$S_{2}^{\mathrm{old}}(\Gamma_0(105)) =$ $S_{2}^{\mathrm{new}}(\Gamma_0(15))^{\oplus 2}$ $\oplus$ $S_{2}^{\mathrm{new}}(\Gamma_0(21))^{\oplus 2}$ $\oplus$ $S_{2}^{\mathrm{new}}(\Gamma_0(35))^{\oplus 2}$

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.094 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, 5, 7, 15, 21, 35, 105]: [0, 1, 1, 1, 4, 4, 6, 20] (certified at ell = 2147483629)
T = [(2, 1), (11, 1)]; h of degree 3 = 1 x 3 (phi(ord eps) x dim S_k^new); 1 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(105, 2)

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

cargo run --release -p sagebrush-web --example atlas -- 105:2 1000

← 104.2.a · 106.2.a →