🧭 New here?
Take a guided tour of the site.
← Back to Families
This function is certified starlike - the sharp, proven-exact coefficient bounds for the starlike class apply to it. See the certified proofs →
Canonical Key
3*z**3+z
Closed Form
f(z) = z + 3*z**3

Image domain \(f(\mathbb{D})\)

The image of the unit disk under \(f\): concentric circles \(|z|=r\) and radial spokes mapped through \(f(z)=z+a_2z^2+\dots\); the bold curve is the boundary \(f(e^{i\theta})\). Rendered in your browser from the certified Taylor coefficients - nothing is computed server-side.

Taylor series
r* ≈ 0.999
Radius of starlikeness r* ≈ 0.9990
proven f is starlike on |z| < r*; the colored disk shows the certified region.

Unit disk explorer - hover to evaluate

Hover over the disk

Related

Univalence Criteria

Schwarzian norm ||S(f)||
3.355
✗ exceeds Nehari bound 2
Pre-Schwarzian norm ||T(f)||
2.715
✗ exceeds Becker bound 1

Facts (5)

Property Kind Params Holds Value / r Status Confidence
B membership {} 2.7149 ✗ disproven rigorous_verified
N membership {} 3.3551 ✗ disproven rigorous_verified
||T(f)|| bound {} 2.7149 ✓ proven rigorous_verified
||S(f)|| bound {} 3.3551 ✓ proven rigorous_verified
S* membership {} r ≤ 0.999 ✓ proven rigorous_verified

Transitively Implied Properties

Because starlikeness is proven, these properties follow by classical implications (unconditional edges in the lattice):

S C

Verification Runs (5)

Verifier Property Direction Outcome Domain r Witness Engine
boundary_scan_closed_form_v31 starlike proves pass 0.999 - boundary_v3.1
pointwise_nehari_univalent_iv nehari_univalent disproves pass 0.334 [2.0474242074820665e-17, 0.33436974789915963] gft-0.1.0-reaudit-20260610
pointwise_becker_univalent_iv becker_univalent disproves pass 0.334 [2.0474242074820665e-17, 0.33436974789915963] gft-0.1.0-reaudit-20260610
boundary_scan_centered_v31 starlike disproves pass 0.000 - boundary_v3.1
boundary_scan_closed_form starlike proves pass 0.999 - boundary_v3.0

Instances (1)

{}
↑↓ navigate openesc close
✦ You're explorer #5,461 to wander the registry - thanks for stopping by. Tell us what you'd like to see →
💬 Feedback