Atlas › Modular forms › Weight 2 › Level 172 › 172.2.a

Newspace 172.2.a: $S_{2}^{\mathrm{new}}(\Gamma_0(172))$

Newforms

Label	Dim	Coefficient field	Trace form	AL signs	Sign	CM	Elliptic curve
172.2.a.a	1	$\mathbb{Q}$	$q - 2q^{3} - 4q^{7} + O(q^{8})$	−			172a1 rank 1
172.2.a.b	2	$\mathbb{Q}(\sqrt{2})$	$2q + 4q^{3} + O(q^{8})$	+

Hecke characteristic polynomials

The eigenvalue of $T = T_{3} + 3T_{5}$ 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 $T$
172.2.a.a	$x + 2$
172.2.a.b	$x^{2} - 4x - 4$

Dimensions

Newforms $S_{2}^{\mathrm{new}}(\Gamma_0(172))$	3
Old forms	17
Cusp forms $S_{2}(\Gamma_0(172))$	20
Eisenstein series $E_{2}(\Gamma_0(172))$	5
Modular forms $M_{2}(\Gamma_0(172))$	25

Decomposition of the old subspace

$S_{2}^{\mathrm{old}}(\Gamma_0(172)) =$ $S_{2}^{\mathrm{new}}(\Gamma_0(43))^{\oplus 3}$ $\oplus$ $S_{2}^{\mathrm{new}}(\Gamma_0(86))^{\oplus 2}$

Provenance

Stored in the atlas: computed by Sagebrush's modular symbols engine in 0.203 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, 2, 4, 43, 86, 172]: [0, 1, 2, 4, 13, 25] (certified at ell = 2147483647)
T = [(3, 1), (5, 3)]; 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(172, 2)

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

cargo run --release -p sagebrush-web --example atlas -- 172:2 1000

← 171.2.a · 173.2.a →