Parametrizing Convex Sets Using Sublinear Neural Networks
Pith reviewed 2026-05-07 15:28 UTC · model grok-4.3
The pith
Sublinear neural networks parametrize arbitrary convex sets by learning their support and gauge functions.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
We propose a neural parameterization of convex sets by learning sublinear functions. Our networks implicitly represent both the support and gauge functions of a convex body. We prove a universal approximation theorem for convex sets under this parametrization. Empirically, we demonstrate the method on shape optimization and inverse design tasks, achieving accurate reconstruction of target shapes.
What carries the argument
Sublinear neural networks that are positively homogeneous and convex, representing the support and gauge functions of convex bodies.
If this is right
- Shape optimization can proceed by directly optimizing the weights of the sublinear network instead of explicit geometric variables.
- Inverse design tasks gain the ability to reconstruct target convex shapes from partial observations or objectives.
- Convex constraints become differentiable components that can be embedded inside larger end-to-end neural pipelines.
- The universal approximation result removes the need to hand-craft different representations for different families of convex sets.
Where Pith is reading between the lines
- The same homogeneity property might extend the technique to parametrizing convex functions rather than just sets.
- Hybrid models could combine these networks with standard architectures to enforce convexity in high-dimensional learning problems.
- Training dynamics in high dimensions or with noisy data remain open questions that would affect practical deployment beyond the reported tasks.
Load-bearing premise
Sublinear neural networks can be trained to represent the support and gauge functions of any convex set to arbitrary accuracy without restrictions on the class of convex bodies.
What would settle it
A specific convex body whose support function cannot be approximated below a fixed positive error by any sublinear network, regardless of size or training.
Figures
read the original abstract
We propose a neural parameterization of convex sets by learning sublinear (positively homogeneous and convex) functions. Our networks implicitly represent both the support and gauge functions of a convex body. We prove a universal approximation theorem for convex sets under this parametrization. Empirically, we demonstrate the method on shape optimization and inverse design tasks, achieving accurate reconstruction of target shapes.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript proposes a neural parameterization of convex sets by learning sublinear functions (positively homogeneous and convex) that implicitly represent both the support and gauge functions of a convex body. It establishes a universal approximation theorem for convex sets under this parametrization and demonstrates the approach empirically on shape optimization and inverse design tasks, reporting accurate reconstruction of target shapes.
Significance. If the universal approximation result holds, the work provides a theoretically grounded neural representation of convex bodies that exactly preserves convexity and positive homogeneity, enabling differentiable parametrizations suitable for optimization. The empirical demonstrations on shape optimization and inverse design illustrate practical utility, and the explicit proof of density among support functions (via finite maxima of linear forms) strengthens the contribution relative to heuristic convex representations.
minor comments (2)
- The abstract and introduction would benefit from a brief statement of the precise function space (e.g., continuous support functions on the unit sphere) and the norm in which approximation is proved, to make the theorem statement immediately self-contained.
- In the empirical section, explicit reporting of the number of training samples, the precise loss formulation (e.g., Hausdorff distance or integrated support-function error), and any regularization used to enforce sublinearity would improve reproducibility.
Simulated Author's Rebuttal
We thank the referee for their positive evaluation of the manuscript, including recognition of the universal approximation theorem for sublinear neural networks and the empirical results on shape optimization and inverse design. We appreciate the recommendation to accept.
Circularity Check
No significant circularity; universal approximation theorem is independent
full rationale
The paper establishes a parametrization of convex sets via sublinear neural networks that preserve positive homogeneity and convexity, thereby representing support and gauge functions. The central load-bearing step is the universal approximation theorem, which is stated as proven from first principles using the fact that sublinear networks are closed under the required operations and that finite maxima of linear forms are dense in the uniform norm on the unit sphere (equivalent to Hausdorff distance on compact convex sets). This density argument is a standard result in convex analysis and does not reduce to any fitted parameter, self-citation chain, or redefinition within the paper. Empirical tasks on shape optimization are presented separately as validation and do not feed back into the theorem. No self-definitional, fitted-input, or ansatz-smuggling patterns appear in the derivation chain.
Axiom & Free-Parameter Ledger
axioms (1)
- standard math Sublinear functions are positively homogeneous and convex.
Reference graph
Works this paper leans on
-
[1]
Shape optimization problems over classes of convex domains.Journal of Convex Analysis, 4:343–352, 1997
Giuseppe Buttazzo and Paolo Guasoni. Shape optimization problems over classes of convex domains.Journal of Convex Analysis, 4:343–352, 1997. 9
1997
-
[2]
Numerical minimization of eigenmodes of a membrane with respect to the domain.ESAIM Control Optim
Édouard Oudet. Numerical minimization of eigenmodes of a membrane with respect to the domain.ESAIM Control Optim. Calc. Var., 10(3):315–330, 2004
2004
-
[3]
Minimizing within Convex Bodies Using a Convex Hull Method.SIAM J
Thomas Lachand-Robert and Édouard Oudet. Minimizing within Convex Bodies Using a Convex Hull Method.SIAM J. Optim., 2006
2006
-
[4]
Shape Optimization Under Width Constraint.Discrete Comput
Édouard Oudet. Shape Optimization Under Width Constraint.Discrete Comput. Geom., 49(2): 411–428, 2013
2013
-
[5]
Pedro R. S. Antunes and Beniamin Bogosel. Parametric shape optimization using the support function.Comput. Optim. Appl., 82(1):107–138, 2022
2022
-
[6]
Semidefinite programming for optimizing convex bodies under width constraints.Optim
Térence Bayen and Didier Henrion. Semidefinite programming for optimizing convex bodies under width constraints.Optim. Methods Softw., 2012
2012
-
[7]
Numerical Shape Optimization Among Convex Sets.Appl
Beniamin Bogosel. Numerical Shape Optimization Among Convex Sets.Appl. Math. Optim., 87(1):1, 2023
2023
-
[8]
Optimization of Neumann Eigenvalues Under Convexity and Geometric Constraints.SIAM J
Beniamin Bogosel, Antoine Henrot, and Marco Michetti. Optimization of Neumann Eigenvalues Under Convexity and Geometric Constraints.SIAM J. Math. Anal., November 2024
2024
-
[9]
Improved Description of Blaschke–Santaló Diagrams via Numerical Shape Opti- mization.Appl
Ilias Ftouhi. Improved Description of Blaschke–Santaló Diagrams via Numerical Shape Opti- mization.Appl. Math. Optim., 91(3):55, 2025
2025
-
[10]
Numerical solution of the minkowski problem.Journal of computational and applied mathematics, 137(2):213–227, 2001
L Lamberg and M Kaasalainen. Numerical solution of the minkowski problem.Journal of computational and applied mathematics, 137(2):213–227, 2001
2001
-
[11]
Numerical Approximation of Optimal Convex Shapes
Sören Bartels and Gerd Wachsmuth. Numerical Approximation of Optimal Convex Shapes. SIAM J. Sci. Comput., April 2020
2020
-
[12]
An improved numerical approach for solving shape optimization problems on convex domains.Numerical Algorithms, 96(2): 621–663, 2024
Abdelkrim Chakib, Ibrahim Khalil, and Azeddine Sadik. An improved numerical approach for solving shape optimization problems on convex domains.Numerical Algorithms, 96(2): 621–663, 2024
2024
-
[13]
Topology optimization via machine learning and deep learning: a review.Journal of Computational Design and Engineering, 10(4): 1736–1766, 2023
Seungyeon Shin, Dongju Shin, and Namwoo Kang. Topology optimization via machine learning and deep learning: a review.Journal of Computational Design and Engineering, 10(4): 1736–1766, 2023
2023
-
[14]
V olume-preserving geometric shape optimization of the Dirichlet energy using variational neural networks.Neural Networks, 184:106957, 2025
Amaury Bélières Frendo, Emmanuel Franck, Victor Michel-Dansac, and Yannick Privat. V olume-preserving geometric shape optimization of the Dirichlet energy using variational neural networks.Neural Networks, 184:106957, 2025
2025
-
[15]
Meshless Shape Optimization Using Neural Networks and Partial Differential Equations on Graphs
Eloi Martinet and Leon Bungert. Meshless Shape Optimization Using Neural Networks and Partial Differential Equations on Graphs. InScale Space and Variational Methods in Computer Vision, pages 285–297. 2025
2025
-
[16]
Zico Kolter
Brandon Amos, Lei Xu, and J. Zico Kolter. Input convex neural networks. InInternational Conference on Machine Learning (ICML), 2017
2017
-
[17]
Convex shape prior for deep convolution neural network-based image segmentation.Journal of Mathematical Imaging and Vision, 67(6):61, 2025
Jun Liu, Kehui Zhang, Xue-Cheng Tai, and Shousheng Luo. Convex shape prior for deep convolution neural network-based image segmentation.Journal of Mathematical Imaging and Vision, 67(6):61, 2025
2025
-
[18]
B. Deng, K. Genova, S. Yazdani, S. Bouaziz, G. Hinton, and A. Tagliasacchi. Cvxnet: Learnable convex decomposition. InProceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition (CVPR), 2020
2020
-
[19]
On convex decision regions in deep network representations.Nature Communications, 16(1):5419, 2025
Lenka Tˇetková, Thea Brüsch, Teresa Dorszewski, Fabian Martin Mager, Rasmus Ørtoft Aagaard, Jonathan Foldager, Tommy Sonne Alstrøm, and Lars Kai Hansen. On convex decision regions in deep network representations.Nature Communications, 16(1):5419, 2025
2025
-
[20]
Schneider.Convex Bodies: The Brunn-Minkowski Theory
R. Schneider.Convex Bodies: The Brunn-Minkowski Theory. Cambridge University Press, 2nd expanded edition edition, 2013. 10
2013
-
[21]
Maxout networks
Ian Goodfellow, David Warde-Farley, Mehdi Mirza, Aaron Courville, and Yoshua Bengio. Maxout networks. InInternational conference on machine learning, pages 1319–1327. PMLR, 2013
2013
-
[22]
Frame averaging for invariant and equivariant network design.arXiv preprint arXiv:2110.03336,
Omri Puny, Matan Atzmon, Heli Ben-Hamu, Ishan Misra, Aditya Grover, Edward J Smith, and Yaron Lipman. Frame averaging for invariant and equivariant network design.arXiv preprint arXiv:2110.03336, 2021
-
[23]
Eloi Martinet and Ilias Ftouhi. Numerical exploration of the range of shape functionals using neural networks.arXiv preprint arXiv:2602.14881, 2026
work page internal anchor Pith review arXiv 2026
-
[24]
Lawrence C Evans.Measure theory and fine properties of functions. 2025
2025
-
[25]
Pytorch: An imperative style, high-performance deep learning library.Advances in neural information processing systems, 32, 2019
Adam Paszke, Sam Gross, Francisco Massa, Adam Lerer, James Bradbury, Gregory Chanan, Trevor Killeen, Zeming Lin, Natalia Gimelshein, Luca Antiga, et al. Pytorch: An imperative style, high-performance deep learning library.Advances in neural information processing systems, 32, 2019
2019
-
[26]
Measurement of Areas on a Sphere Using Fibonacci and Latitude–Longitude Lattices.Math
Álvaro González. Measurement of Areas on a Sphere Using Fibonacci and Latitude–Longitude Lattices.Math. Geosci., 42(1):49–64, 2010
2010
-
[27]
Lawrence C Evans.Partial differential equations, volume 19. 2022
2022
-
[28]
Meshless galerkin methods using radial basis functions.Mathematics of Computation, 68(228):1521–1531, 1999
Holger Wendland. Meshless galerkin methods using radial basis functions.Mathematics of Computation, 68(228):1521–1531, 1999
1999
-
[29]
World Scientific Publishing Company, 2007
Gregory E Fasshauer.Meshfree approximation methods with Matlab (With Cd-rom), volume 6. World Scientific Publishing Company, 2007
2007
-
[30]
Neural-network-based approximations for solving partial differential equations.communications in Numerical Methods in Engineering, 10(3):195–201, 1994
MWM Gamini Dissanayake and Nhan Phan-Thien. Neural-network-based approximations for solving partial differential equations.communications in Numerical Methods in Engineering, 10(3):195–201, 1994
1994
-
[31]
Can physics-informed neural networks beat the finite element method?IMA Journal of Applied Mathematics, 89(1):143–174, 2024
Tamara G Grossmann, Urszula Julia Komorowska, Jonas Latz, and Carola-Bibiane Schönlieb. Can physics-informed neural networks beat the finite element method?IMA Journal of Applied Mathematics, 89(1):143–174, 2024
2024
-
[32]
Weak baselines and reporting biases lead to overoptimism in machine learning for fluid-related partial differential equations.Nature machine intelligence, 6(10):1256–1269, 2024
Nick McGreivy and Ammar Hakim. Weak baselines and reporting biases lead to overoptimism in machine learning for fluid-related partial differential equations.Nature machine intelligence, 6(10):1256–1269, 2024
2024
-
[33]
Krzysztof Burdzy, Ilias Ftouhi, and Phanuel Mariano. Geometric properties of optimizers for the maximum gradient of the torsion function.arXiv preprint arXiv:2512.09400, 2025
-
[34]
Minkowski problems for geometric measures
Yong Huang, Deane Yang, and Gaoyong Zhang. Minkowski problems for geometric measures. Bulletin of the American Mathematical Society, 62(3):359–425, 2025
2025
-
[35]
Cambridge university press, 2004
Stephen P Boyd and Lieven Vandenberghe.Convex optimization. Cambridge university press, 2004
2004
-
[36]
Correction to: convex analysis and monotone operator theory in hilbert spaces
Heinz H Bauschke and Patrick L Combettes. Correction to: convex analysis and monotone operator theory in hilbert spaces. InConvex analysis and monotone operator theory in Hilbert spaces. Springer, 2020
2020
-
[37]
Stability and convergence of the method of fundamental solutions for helmholtz problems on analytic domains.Journal of Computational Physics, 227 (14):7003–7026, 2008
Alex H Barnett and Timo Betcke. Stability and convergence of the method of fundamental solutions for helmholtz problems on analytic domains.Journal of Computational Physics, 227 (14):7003–7026, 2008
2008
-
[38]
The method of fundamental solutions applied to boundary eigenvalue problems.J
Beniamin Bogosel. The method of fundamental solutions applied to boundary eigenvalue problems.J. Comput. Appl. Math., 306:265–285, 2016
2016
-
[39]
The method of fundamental solutions for the cauchy problem in two-dimensional linear elasticity.International journal of solids and structures, 41(13): 3425–3438, 2004
Liviu Marin and Daniel Lesnic. The method of fundamental solutions for the cauchy problem in two-dimensional linear elasticity.International journal of solids and structures, 41(13): 3425–3438, 2004. 11
2004
-
[40]
Fundamental solutions for the stokes equations: Numerical applications for 2d and 3d flows.Applied Numerical Mathematics, 170: 55–73, 2021
Carlos JS Alves, Rodrigo G Serrao, and Ana L Silvestre. Fundamental solutions for the stokes equations: Numerical applications for 2d and 3d flows.Applied Numerical Mathematics, 170: 55–73, 2021
2021
-
[41]
Spectral inequalities in quantitative form.arXiv preprint arXiv:1604.05072, 2016
Lorenzo Brasco and Guido De Philippis. Spectral inequalities in quantitative form.arXiv preprint arXiv:1604.05072, 2016
-
[42]
The deep ritz method: a deep learning-based numerical algorithm for solving variational problems.Communications in Mathematics and Statistics, 6(1):1–12, 2018
Bing Yu et al. The deep ritz method: a deep learning-based numerical algorithm for solving variational problems.Communications in Mathematics and Statistics, 6(1):1–12, 2018
2018
-
[43]
The sharp quantitative isoperimetric inequality.Annals of mathematics, pages 941–980, 2008
Nicola Fusco, Francesco Maggi, and Aldo Pratelli. The sharp quantitative isoperimetric inequality.Annals of mathematics, pages 941–980, 2008
2008
-
[44]
On the volume product of planar polar convex bodies—lower estimates with stability.Studia Scientiarum Mathematicarum Hungarica, 50(2):159–198, 2013
K Böröczky, E Makai, Mathieu Meyer, and Shlomo Reisner. On the volume product of planar polar convex bodies—lower estimates with stability.Studia Scientiarum Mathematicarum Hungarica, 50(2):159–198, 2013
2013
-
[45]
European Mathematical Society (EMS), Zürich, 2018
Antoine Henrot and Michel Pierre.Shape variation and optimization, volume 28 ofEMS Tracts in Mathematics. European Mathematical Society (EMS), Zürich, 2018
2018
-
[46]
Gmsh: A 3-d finite element mesh generator with built-in pre-and post-processing facilities.International journal for numerical methods in engineering, 79(11):1309–1331, 2009
Christophe Geuzaine and Jean-François Remacle. Gmsh: A 3-d finite element mesh generator with built-in pre-and post-processing facilities.International journal for numerical methods in engineering, 79(11):1309–1331, 2009
2009
-
[47]
scikit-fem: A python package for finite element assembly.Journal of Open Source Software, 5(52):2369, 2020
Tom Gustafsson and Geordie Drummond Mcbain. scikit-fem: A python package for finite element assembly.Journal of Open Source Software, 5(52):2369, 2020. A Reminder of convex analysis Here we give some useful results of convex analysis. We begin with the definition of the convex conjugate of a function, that can be found in [35]. Definition A.1(Convex conju...
2020
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.