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arxiv: 2508.11600 · v2 · pith:2E2B2KEYnew · submitted 2025-08-15 · 🧮 math.MG · math.AP· math.DG· math.FA

Explicit solutions to Christoffel-Minkowski problems and Hessian equations under rotational symmetries

Pith reviewed 2026-05-21 22:22 UTC · model grok-4.3

classification 🧮 math.MG math.APmath.DGmath.FA
keywords Christoffel-Minkowski problemconvex bodiesrotational symmetryMonge-Ampère equationsHessian equationssupport functionarea measures
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The pith

The Christoffel-Minkowski problem for convex bodies of revolution admits an explicit solution via a formula for the support function based on first moments of the measure.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

This paper solves the Christoffel-Minkowski problem explicitly when the convex body and the data are rotationally symmetric. The symmetry reduces the governing mixed Monge-Ampère equation to an integrable ordinary differential equation. As a result, the support function of the convex body is recovered by a direct formula involving integrals of the prescribed measure over spherical caps. The same reduction provides explicit convex solutions for mixed area measures and for the Dirichlet problem of k-Hessian equations under radial symmetry.

Core claim

Under the assumption of rotational symmetry, an explicit representation formula is derived for the support function of a convex body of revolution that solves the Christoffel-Minkowski problem for a given measure. The conditions required on the measure are formulated in terms of its first moments computed over spherical caps. The method extends to constructing explicit convex solutions of mixed Monge-Ampère equations on Euclidean space when restricted to radial symmetry, with data specified on open balls, and includes the Dirichlet problem for k-Hessian equations as a special case.

What carries the argument

Reduction of mixed Monge-Ampère equations to radially symmetric form allowing explicit integration of the support function from the measure data.

If this is right

  • The explicit formula directly yields the convex body from any measure satisfying the first-moment conditions on caps.
  • Existence for mixed area measures follows from the same radial integration procedure.
  • The k-Hessian Dirichlet problem on R^n possesses explicit radial solutions when symmetry is imposed.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • These formulas could benchmark general numerical solvers for the non-symmetric problem.
  • The radial reduction technique may apply to other fully nonlinear equations with symmetry assumptions.
  • One could test whether small perturbations from rotational symmetry preserve approximate explicit solutions.

Load-bearing premise

Both the convex body and the measure must be rotationally symmetric about the same axis for the reduction to ordinary differential equations to hold.

What would settle it

Construct a rotationally symmetric measure meeting the moment conditions and check whether the body defined by the explicit support function has the original measure as its mixed area measure.

read the original abstract

An explicit solution to the Christoffel-Minkowski problem for convex bodies of revolution is presented. The conditions on the prescribed measure involve only first moments over spherical caps, and the support function of the resulting convex body is given by an explicit representation formula in terms of the measure. More generally, existence problems for mixed area measures are addressed. The approach relies on constructing explicit convex solutions to mixed Monge-Amp\`ere equations on $\mathbb{R}^n$ under the assumption of radial symmetry, with the conditions on the measure being expressed through its values on open balls. As a special case, the Dirichlet problem for $k$-Hessian equations on $\mathbb{R}^n$ is treated.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 2 minor

Summary. The manuscript presents explicit solutions to the Christoffel-Minkowski problem for convex bodies of revolution. Under the assumption of rotational symmetry, the mixed Monge-Ampère equations reduce to a one-dimensional radial setting, yielding an explicit integral representation for the support function expressed solely in terms of first-moment conditions on the prescribed measure over spherical caps (equivalently, values on open balls for the radial measure). The paper extends the method to existence questions for mixed area measures and treats the Dirichlet problem for k-Hessian equations on R^n as a special case.

Significance. If the explicit constructions hold, the work supplies concrete, closed-form solutions in a setting where general existence theorems exist but explicit formulas are uncommon. The symmetry reduction converts the mixed Hessian operator into an integrable radial form whose output is determined directly by the moment data, providing a parameter-free derivation that could serve as a benchmark for numerical methods and further analysis of Hessian-type equations in convex geometry.

major comments (1)
  1. The central claim that the constructed support function satisfies the prescribed mixed area measure rests on the radial integration step; a direct verification that the resulting function is convex and reproduces the given first moments (without additional regularity assumptions on the measure) would strengthen the argument. This appears in the derivation following the symmetry reduction but is not fully detailed in the provided outline.
minor comments (2)
  1. Clarify the precise relation between the spherical-cap moments and the open-ball values of the radial measure in the statement of the main theorem to avoid ambiguity for readers.
  2. The abstract mentions 'more generally, existence problems for mixed area measures'; a brief comparison with existing non-explicit existence results would help situate the contribution.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the careful reading and constructive suggestion. We address the major comment below and will revise the manuscript to incorporate a more detailed verification.

read point-by-point responses
  1. Referee: The central claim that the constructed support function satisfies the prescribed mixed area measure rests on the radial integration step; a direct verification that the resulting function is convex and reproduces the given first moments (without additional regularity assumptions on the measure) would strengthen the argument. This appears in the derivation following the symmetry reduction but is not fully detailed in the provided outline.

    Authors: We agree that expanding the verification would improve clarity. In the manuscript the support function is obtained from the explicit integral formula arising from the radial reduction; convexity follows because the integrand consists of support functions of convex sets (spherical caps) and the integral preserves convexity. Reproduction of the first moments holds by direct application of Fubini’s theorem to the radial integrals, which is valid for arbitrary positive Radon measures on the sphere without extra regularity. In the revision we will add a dedicated paragraph immediately after the symmetry reduction that carries out this verification step by step, including the passage to general measures via weak approximation. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper reduces the Christoffel-Minkowski problem and mixed Monge-Ampère equations to a radially symmetric one-dimensional setting under the assumption of rotational symmetry for convex bodies of revolution. This permits explicit integration yielding a support function expressed directly in terms of first-moment conditions on spherical caps (or values on open balls for the radial measure). The derivation chain consists of standard symmetry reductions and direct integration steps that follow from the form of the radial mixed Hessian operator; no step equates a claimed prediction or result to its own inputs by construction, and no load-bearing self-citation or uniqueness theorem imported from prior author work is invoked. The explicit representation formula is obtained from the symmetry assumptions without circular dependencies, rendering the central claims self-contained against the stated hypotheses.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The central claim rests on the domain assumption of rotational symmetry together with standard convexity and measure-theoretic background; no free parameters or new entities are introduced in the abstract.

axioms (2)
  • domain assumption Convex bodies and measures are rotationally symmetric (of revolution).
    This symmetry is invoked to reduce the mixed Monge-Ampère equations to a radially symmetric setting that permits explicit integration.
  • domain assumption The prescribed measure satisfies first-moment conditions over spherical caps.
    These integral conditions replace pointwise requirements and are stated as sufficient for the explicit formula to work.

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Reference graph

Works this paper leans on

39 extracted references · 39 canonical work pages

  1. [1]

    A. D. A LEKSANDROV , Dirichlet’s problem for the equation Det∥zi j∥ = ϕ(z1, . . .,zn,z,x1, . . .,xn). I (Russian). Vestnik Leningrad. Univ. Ser. Mat. Meh. Astr. 13 (1958), 5–24. English translation in: A. D. Aleksandrov, Selected Works Part I: Selected Scientific Papers, Classic of Soviet Mathematics, 4, Gordon and Branch Pub- lishers, Amsterdam, 1996. ↑ 6

  2. [2]

    I. J. B AKELMAN , Convex Analysis and Nonlinear Geometric Elliptic Equations . Springer-Verlag, Berlin,

  3. [3]

    B ERG, Corps convexes et potentiels sph´eriques

    C. B ERG, Corps convexes et potentiels sph´eriques. Mat.-Fys. Medd. Danske Vid. Selsk. 37 (1969), 64pp. ↑ 1

  4. [4]

    K. J. B ¨OR ¨OCZKY , A. F IGALLI , AND J. P. RAMOS , The Isoperimetric Inequality, the Brunn–Minkowski The- ory and Minkowski Type Monge–Amp `ere Equations on the Sphere . European Mathematical Society (EMS), Z¨urich, to appear. ↑ 2

  5. [5]

    B RAUNER , G

    L. B RAUNER , G. C. H OFST ¨ATTER , AND O. O RTEGA -MORENO , Lefschetz operators on convex valuations. Preprint, arXiv:2402.14731 (2024). ↑ 3

  6. [6]

    B RAUNER , G

    L. B RAUNER , G. C. H OFST ¨ATTER , AND O. O RTEGA -M ORENO , The Klain approach to zonal valuations . Preprint, arXiv:2410.18651 (2024). ↑ 22

  7. [7]

    B RAUNER , G

    L. B RAUNER , G. C. H OFST ¨ATTER , AND O. O RTEGA -M ORENO , Mixed Christoffel-Minkowski problems for bodies of revolution. Preprint, arXiv:2508.09794 (2025). ↑ 1, 2, 3, 16, 20, 21, 22

  8. [8]

    B RAUNER , G

    L. B RAUNER , G. C. H OFST ¨ATTER , AND O. O RTEGA -MORENO , The Christoffel problem for the disk area measure. Preprint, arXiv:2508.09800 (2025). ↑ 21

  9. [9]

    B RYAN, M

    P. B RYAN, M. N. I VAKI, AND J. SCHEUER , Christoffel-Minkowski flows. Trans. Amer. Math. Soc.376 (2023), 2373–2393. ↑ 1

  10. [10]

    C AFFARELLI , L

    L. C AFFARELLI , L. N IRENBERG , AND J. S PRUCK , The Dirichlet problem for nonlinear second-order elliptic equations. III. Functions of the eigenvalues of the Hessian. Acta Math. 155 (1985), 261–301. ↑ 4

  11. [11]

    C HOU AND X.-J

    K.-S. C HOU AND X.-J. W ANG, Minkowski problems for complete noncompact convex hypersurfaces. Topol. Methods Nonlinear Anal. 6 (1995), 151–162. ↑ 5

  12. [12]

    E. B. C HRISTOFFEL , Ueber die Bestimmung der Gestalt einer krummen Oberfl ¨ache durch lokale Messungen auf derselben. J. Reine Angew. Math. 64 (1865), 193–209. ↑ 1

  13. [13]

    C OLESANTI AND D

    A. C OLESANTI AND D. H UG, Hessian measures of convex functions and applications to area measures . J. Lond. Math. Soc. (2) 71 (2005), 221–235. ↑ 6

  14. [14]

    C OLESANTI , M

    A. C OLESANTI , M. L UDWIG , AND F. M USSNIG , Hessian valuations . Indiana Univ. Math. J. 69 (2020), 1275–1215. ↑ 6, 7, 9

  15. [15]

    C OLESANTI , M

    A. C OLESANTI , M. L UDWIG , AND F. M USSNIG , The Hadwiger theorem on convex functions, III: Steiner formulas and mixed Monge-Amp `ere measures. Calc. Var. Partial Differential Equations 61 (2022), Art. 181. ↑ 7

  16. [16]

    C OLESANTI AND P

    A. C OLESANTI AND P. SALANI , Hessian equations in non-smooth domains. Nonlinear Anal. 38 (1999), 803–

  17. [17]

    F IGALLI , The Monge-Amp `ere Equation and Its Applications

    A. F IGALLI , The Monge-Amp `ere Equation and Its Applications . European Mathematical Society (EMS), Z¨urich, 2017. ↑ 5, 6, 12

  18. [18]

    W. J. F IREY , Christoffel’s problem for general convex bodies. Mathematika 15 (1968), 7–21. ↑ 1

  19. [19]

    W. J. F IREY , Intermediate Christoffel-Minkowski problems for figures of revolution. Israel J. Math. 8 (1970), 384–390. ↑ 1, 9, 22

  20. [20]

    G UAN, C

    P. G UAN, C. L IN, AND X.-N. M A, The Christoffel-Minkowski problem. II. Weingarten curvature equations. Chinese Ann. Math. Ser. B 27 (2006), 595–614. ↑ 1 23

  21. [21]

    G UAN AND X.-N

    P. G UAN AND X.-N. M A, The Christoffel-Minkowski problem. I. Convexity of solutions of a Hessian equation. Invent. Math. 151 (2003), 553–577. ↑ 1

  22. [22]

    G UAN, X.-N

    P. G UAN, X.-N. M A, AND F. Z HOU, The Christofel-Minkowski problem. III. Existence and convexity of admissible solutions. Comm. Pure Appl. Math. 59 (2006), 1352–1376. ↑ 1

  23. [23]

    H UANG , D

    Y. H UANG , D. YANG , AND G. Z HANG , Minkowski problems for geometric measures. Bull. Amer. Math. Soc. (N.S.) 62 (2025), 359–425. ↑ 2

  24. [24]

    D. H UG, F. M USSNIG , AND J. U LIVELLI , Kubota-type formulas and supports of mixed measures . Preprint, arXiv:2401.16371 (2024). ↑ 7, 8, 9, 14

  25. [25]

    D. H UG, F. MUSSNIG , AND J. U LIVELLI , Additive kinematic formulas for convex functions. Canad. J. Math., to appear. ↑ 7, 11, 22

  26. [26]

    K NOERR AND J

    J. K NOERR AND J. U LIVELLI , From valuations on convex bodies to convex functions. Math. Ann. 390 (2024), 5987–6011. ↑ 14

  27. [27]

    L IU, X.-N

    P. L IU, X.-N. M A, AND L. X U, A Brunn-Minkowski inequality for the Hessian eigenvalue in three- dimensional convex domain. Adv. Math. 225 (2010), 1616–1633. ↑ 4

  28. [28]

    M A AND L

    X.-N. M A AND L. X U, The convexity of solution of a class Hessian equation in bounded convex domain in R3. J. Funct. Anal. 255 (2008), 1713–1723. ↑ 4

  29. [29]

    M. A. M OUAMINE AND F. M USSNIG , The vectorial Hadwiger theorem on convex functions . Preprint, arXiv:2504.04952 (2025). ↑ 7

  30. [30]

    R. T. R OCKAFELLAR , Convex Analysis. Princeton Landmarks in Mathematics, Princeton University Press, Princeton, NJ, 1997. ↑ 5, 6, 10, 11

  31. [31]

    S ALANI , Boundary blow-up problems for Hessian equations

    P. S ALANI , Boundary blow-up problems for Hessian equations. Manuscripta Math.96 (1998), 281–294. ↑ 4, 9

  32. [32]

    S ALANI , Convexity of solutions and Brunn-Minkowski inequalities for Hessian equations inR3

    P. S ALANI , Convexity of solutions and Brunn-Minkowski inequalities for Hessian equations inR3. Adv. Math. 229 (2012), 1924–1948. ↑ 4

  33. [33]

    S CHNEIDER , Convex Bodies: The Brunn–Minkowski Theory

    R. S CHNEIDER , Convex Bodies: The Brunn–Minkowski Theory. Second expanded ed., Encyclopedia of Math- ematics and its Applications, vol. 151, Cambridge University Press, Cambridge, 2014. ↑ 1, 2, 5, 16, 22

  34. [34]

    N. S. T RUDINGER , On the Dirichlet problem for Hessian equations. Acta Math. 175 (1995), 151–164. ↑ 4, 6

  35. [35]

    N. S. T RUDINGER , Weak solutions of Hessian equations . Comm. Partial Differential Equations 22 (1997), 1251–1261. ↑ 4

  36. [36]

    N. S. T RUDINGER AND X.-J. W ANG, Hessian measures. I. Topol. Methods Nonlinear Anal. 10 (1997), 225–

  37. [37]

    N. S. T RUDINGER AND X.-J. W ANG, Hessian measures. II. Ann. of Math. (2) 150 (1999), 579–604. ↑ 4, 6

  38. [38]

    N. S. T RUDINGER AND X.-J. W ANG, Hessian measures. III. J. Funct. Anal. 193 (2002), 1–23. ↑ 4, 7

  39. [39]

    U LIVELLI , Entire Monge–Amp`ere equations and weighted Minkowski problems

    J. U LIVELLI , Entire Monge–Amp`ere equations and weighted Minkowski problems. Commun. Contemp. Math., to appear. ↑ 5 Fabian Mussnig Institut f¨ur Diskrete Mathematik und Geometrie TU Wien Wiedner Hauptstraße 8-10/1046 1040 Wien, Austria e-mail: fabian.mussnig@tuwien.ac.at Jacopo Ulivelli Institut f¨ur Diskrete Mathematik und Geometrie TU Wien Wiedner Hau...