# On the Stability of Spherical Hellinger-Kantorovich Flows and Their Implications for Differential Privacy

arXiv: https://arxiv.org/abs/2605.23879 · HTML: https://mlsanity.com/paper/2605.23879/

## Key facts

- No citing papers in the map yet (data through 14 Oct 2026).
- Builds on 12 of its 31 references that are in the map.
- First posted on arXiv 22 May 2026.

## Builds on (most cited first, 12 of 12)

- [Deep Learning with Differential Privacy](https://mlsanity.com/paper/1607.00133/) (2016)
- [Exploiting Unintended Feature Leakage in Collaborative Learning](https://mlsanity.com/paper/1805.04049/) (2018)
- [Privacy Amplification by Subsampling: Tight Analyses via Couplings and Divergences](https://mlsanity.com/paper/1807.01647/) (2018)
- [Optimal Entropy-Transport problems and a new Hellinger-Kantorovich distance between positive measures](https://mlsanity.com/paper/1508.07941/) (2015)
- [Differential Privacy Dynamics of Langevin Diffusion and Noisy Gradient Descent](https://mlsanity.com/paper/2102.05855/) (2021)
- [Privacy of Noisy Stochastic Gradient Descent: More Iterations without More Privacy Loss](https://mlsanity.com/paper/2205.13710/) (2022)
- [Accelerating Langevin Sampling with Birth-death](https://mlsanity.com/paper/1905.09863/) (2019)
- [Faster Differentially Private Samplers via R'enyi Divergence Analysis of Discretized Langevin MCMC](https://mlsanity.com/paper/2010.14658/) (2020)
- [Optimal Membership Inference Bounds for Adaptive Composition of Sampled Gaussian Mechanisms](https://mlsanity.com/paper/2204.06106/) (2022)
- [Accelerate Langevin Sampling with Birth-Death Process and Exploration Component](https://mlsanity.com/paper/2305.05529/) (2023)
- [Differentially Private Sampling from Rashomon Sets, and the Universality of Langevin Diffusion for Convex Optimization](https://mlsanity.com/paper/2204.01585/) (2022)
- [Privacy Risk for anisotropic Langevin dynamics using relative entropy bounds](https://mlsanity.com/paper/2302.00766/) (2023)

## Abstract (arXiv)

Gradient-flow sampling interprets a Gibbs distribution as the minimizer of an energy functional over probability measures and generates dynamics converging to this target. Under spherical Hellinger-Kantorovich (SHK) geometry, the flow couples transport and reaction and coincides with birth-death Langevin dynamics. In this work, we develop a perturbation theory for SHK gradient flows. For two potentials V and Vprime, we compare the associated flows from a common initialization and quantify how potential discrepancies propagate over time. A uniform perturbation bound yields dimension-free, pointwise control of the log-likelihood ratio and R'enyi divergence, while additional structure allows us to derive bounds for the KL divergence as well. We apply these results to approximate sampling for the exponential mechanism in differential privacy. The likelihood-ratio control provides explicit time-dependent Pure-DP guarantees for SHK-based samplers, while the KL bound yields Approximate-DP certificates via hockey-stick divergence. We also derive a utility bound separating intrinsic exponential-mechanism suboptimality from finite-time sampling error.