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Lemniscatic Torus


The name lemniscatic torus is used for several objects involving a lemniscate. In geometric modeling it denotes a surface of revolution generated from a lemniscate in a plane offset from the axis (Iglesias et al. 2013). In elliptic function theory it denotes the square complex torus (Cecotti and Vafa 2013, Eremenko 2023). A limiting solid of revolution whose meridian is a lemniscate also occurs in gravitational modeling (Zavizion 2006).

LemniscaticTorus

For the geometric construction, let A>0 and B>0, and define

f(v)=(Acosv)/(1+sin^2v)
(1)
g(v)=(Acosvsinv)/(1+sin^2v).
(2)

The plane curve (f(v),g(v)) satisfies the Bernoulli lemniscate equation

 (f^2+g^2)^2=A^2(f^2-g^2),
(3)

where A is the half-width and the distance from the center to either focus is A/sqrt(2). Rotating the curve (B,f(v),g(v)) about the z-axis gives

x(u,v)=Bcosu-f(v)sinu
(4)
y(u,v)=Bsinu+f(v)cosu
(5)
z(u,v)=g(v).
(6)

One lobe, with -pi/2<=v<=pi/2 and its endpoints identified, generates the entire surface as 0<=u<2pi. Using 0<=v<2pi covers the surface twice. The formulas above correct the inconsistent half-width normalization and the first coordinate of the printed rotation formula in Flores-Córdova et al. (2026, p. 118).

Eliminating the parameters gives the quartic surface

 (x^2+y^2+z^2-B^2)^2=A^2(x^2+y^2-z^2-B^2).
(7)

In cylindrical coordinates, with rho=sqrt(x^2+y^2), a meridian is parametrized by

 (rho,z)=(sqrt(B^2+f(v)^2),g(v)),
(8)

and the bounds are B<=rho<=sqrt(A^2+B^2) and |z|<=A/(2sqrt(2)). This meridian is generally not a Bernoulli lemniscate. The generating lemniscate lies in the offset plane x=B, which does not contain the axis of revolution.

LemniscaticTorusMeridians

For B=A/(2sqrt(2)), the surface becomes an ordinary ring torus with major radius c=A/sqrt(2) and tube radius a=A/(2sqrt(2)), so c=2a (Iglesias et al. 2013). Its equation can be written

 (x^2+y^2+z^2+3A^2/8)^2=2A^2(x^2+y^2).
(9)
LemniscaticTorusCurve

Curves on the geometric surface have been used to choose vertices for polyhedra (Velezmoro-León et al. 2021, 2022) and, after orthogonal projection onto a plane, control points for a wire antenna (Flores-Córdova et al. 2026). Writing the parametric equations above as T(u,v), one useful family is

 C_(p,q)(t)=T(pt,qt),
(10)

where p and q are positive integers and 0<=t<=2pi. Its orthogonal projection onto the xy-plane has the complex number representation

 w_(p,q)(t)=e^(ipt)[B+if(qt)],
(11)

and satisfies

 w_(p,q)(t+2pi/q)=e^(2piip/q)w_(p,q)(t).
(12)

Thus relatively prime p and q give q-fold rotational symmetry. If d>1 is a common integer factor, write p=dp^' and q=dq^'. Then C_(p,q)(t)=C_(p^',q^')(dt), so the common factor repeats the parametrization. Flores-Córdova et al. (2026) use p=3, q=7, A=1, and B=1/4. Their actual antenna is a polygonal wire constructed from sampled points of the projected curve, rather than the smooth projected curve itself.

LemniscaticTorusSquareLattice

In the complex torus usage, the defining lattice is square,

 Lambda=omega(Z+iZ),
(13)

where omega!=0 is a complex number, and the quotient space C/Lambda has half-period ratio tau=i. Its Weierstrass elliptic function has invariants g_3=0 and g_2!=0, giving the lemniscate case. The normalized Klein's absolute invariant is J(i)=1, whereas the usual j-function has j(i)=1728. An equivalent elliptic curve, completed by its point at infinity, is

 y^2=x^3-x.
(14)

This usage specifies a complex structure and does not select an embedding as a particular surface of revolution in three-dimensional space (Cecotti and Vafa 2013, Appendix B.3; Eremenko 2023).

LemniscaticTorusAxialLimit

Zavizion (2006) uses the name for a homogeneous solid of revolution bounded by rotating a Bernoulli lemniscate about its symmetry axis in a study of gravitational fields. Its meridian is a lemniscate, and its boundary is the B=0 limit of the geometric family above,

 (rho^2+z^2)^2=A^2(rho^2-z^2).
(15)

It has a singular point at the origin. The B>0 family has an open central hole.


See also

Complex Torus, Lemniscate, Lemniscate Case, Ring Torus, Surface of Revolution, Torus

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References

Cecotti, S. and Vafa, C. "Classification of Complete N=2 Supersymmetric Theories in 4 Dimensions." Surveys in Differential Geometry 18, 19-101, 2013. https://doi.org/10.4310/SDG.2013.v18.n1.a2.Eremenko, A. "A Famous Torus." Jul. 3, 2023. https://www.math.purdue.edu/~eremenko/Pdf/torus1.pdf.Flores-Córdova, D. A.; Arellano-Ramírez, C. E.; Velezmoro-León, R.; and Ipanaqué-Chero, R. "Design and Simulation of a Wideband Wire Antenna Generated from Control Points of a Curve Projected from a Lemniscatic Torus for 5G Applications." In Proceedings of the 1st Workshop on Systems, Applications, Artificial Intelligence and Innovation 2026 (Ed. O. Peña-Cáceres and H. Silva-Marchan). Bonn, Germany: CEUR-WS Team, pp. 116-133, 2026. https://ceur-ws.org/Vol-4264/iwsai_10.pdf.Iglesias, A.; Velezmoro, R.; and Ipanaqué, R. "Parameterization of Some Surfaces of Revolution Through Curvature-Varying Curves: A Computational Analysis." International Journal of Hybrid Information Technology 6, 71-82, 2013. https://gvpress.com/journals/IJHIT/vol6_no4/7.pdf.Velezmoro-León, R.; Ipanaqué-Chero, R.; Velásquez Fernández, M.; and Jimenez Gomez, J. "Construction of Polyhedra Whose Vertices Are Points on Curve Which Lying on Lemniscatic Torus with Mathematica." In Computational Science and Its Applications--ICCSA 2021, Part II (Ed. O. Gervasi, B. Murgante, S. Misra, C. Garau, I. Blečić, D. Taniar, B. O. Apduhan, A. M. A. C. Rocha, E. Tarantino, and C. M. Torre). Cham, Switzerland: Springer, pp. 3-17, 2021. https://doi.org/10.1007/978-3-030-86960-1_1.Velezmoro-León, R.; Ipanaqué-Chero, R.; Velásquez-Fernández, F. M.; and Jimenez Gomez, J. "Construction of a Convex Polyhedron from a Lemniscatic Torus." In Congress on Intelligent Systems: Proceedings of CIS 2021, Volume 1 (Ed. M. Saraswat, H. Sharma, K. Balachandran, J. H. Kim, and J. C. Bansal). Singapore: Springer, pp. 895-909, 2022. https://doi.org/10.1007/978-981-16-9416-5_65.Zavizion, O. V. "Using of Equigravitating Figures for Description of Gravitational Field of Celestial Bodies." Candidate of Physical and Mathematical Sciences dissertation. Kyiv, Ukraine: Main Astronomical Observatory, National Academy of Sciences of Ukraine, 2006.

Cite this as:

Weisstein, Eric W. "Lemniscatic Torus." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/LemniscaticTorus.html

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