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Walking on the Fiber: A Simple Geometric Approximation for Bayesian Neural Networks
KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL.ORCID iD: 0000-0001-8938-9363
KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Collaborative Autonomous Systems.ORCID iD: 0000-0002-5761-4105
KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL. KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Collaborative Autonomous Systems.ORCID iD: 0000-0003-2965-2953
2025 (English)In: Transactions on Machine Learning Research, E-ISSN 2835-8856, Vol. 2025-JulyArticle in journal (Refereed) Published
Abstract [en]

Bayesian Neural Networks provide a principled framework for uncertainty quantification by modeling the posterior distribution of network parameters. However, exact posterior inference is computationally intractable, and widely used approximations like the Laplace method struggle with scalability and posterior accuracy in modern deep networks. In this work, we revisit sampling techniques for posterior exploration, proposing a simple variation tailored to efficiently sample from the posterior in over-parameterized networks by leveraging the low-dimensional structure of loss minima. Building on this, we introduce a model that learns a deformation of the parameter space, enabling rapid posterior sampling without requiring iterative methods. Empirical results demonstrate that our approach achieves competitive posterior approximations with improved scalability compared to recent refinement techniques. These contributions provide a practical alternative for Bayesian inference in deep learning.

Place, publisher, year, edition, pages
Transactions on Machine Learning Research , 2025. Vol. 2025-July
National Category
Computer Sciences Control Engineering Bioinformatics (Computational Biology)
Identifiers
URN: urn:nbn:se:kth:diva-369023Scopus ID: 2-s2.0-105011329903OAI: oai:DiVA.org:kth-369023DiVA, id: diva2:1995902
Note

QC 20250908

Available from: 2025-09-08 Created: 2025-09-08 Last updated: 2026-02-16Bibliographically approved
In thesis
1. Interactive Representation Learning: Symmetries, Metric Spaces and Uncertainty
Open this publication in new window or tab >>Interactive Representation Learning: Symmetries, Metric Spaces and Uncertainty
2026 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis investigates how interaction can be used as self-supervision to learn structured state representations that simplify downstream tasks. We formalize two inductive biases naturally present in the trajectories generated by agents that interact with their environment: geometry and temporal consistency of the underlying state space. We show that injecting these biases into representation learning yields additional, taskrelevant properties. First, we focus on geometric bias: we learn translationally equivariant latent spaces from images in which agent actions correspond to vector additions. We show how these representations can be used to estimate a recovery policy that mitigates the compounding of error in data-driven sequential decision-making policies. We further extend equivariant representations to scenes with external objects. Under an interaction-by-contact model, we prove that aligning the object’s and the agent’s latent embeddings yields an isometric, disentangled representation of both. Second, we relax the geometry assumption and explore the milder temporal consistency bias. This allows us to construct representations where the temporal order between states is preserved, a property we refer to as distance monotonicity. In the reinforcement learning setting, we show that, under suitable conditions, this property is enough to recover an approximation of the value function and provably estimate an optimal policy. In a multiple-sensor framework, these representations can be used to construct a Bayesian filtering state estimate robust under unknown noise. Lastly, we extend the concept of interactions from physical systems to the parametric space of a learner. We show how distance monotonic representations of the parameters of a model can be used to approximate the posterior distribution of a Bayesian neural network. Finally,in a meta-learning setting, we explore implicit representations of the learner to reduce the variance of a fast-adaptation model. Collectively, these results demonstrate that interaction-driven biases produce structured representations that simplify or enhance the learning process.

Abstract [sv]

Denna avhandling undersöker hur interaktion kan användas som självövervakning för att lära strukturerade tillståndsrepresentationer som förenklar nedströmsuppgifter. Vi formaliserar två induktiva bias som naturligt uppstår i trajektorier genererade av agenter som interagerar med sin omgivning: geometri samt temporal konsistens i det underliggande tillståndsrummet. Vi visar att införandet av dessa bias i representationsinlärning ger ytterligare, uppgiftsrelevanta egenskaper. Först fokuserar vi på geometrisk bias: vi lär translationsekvivarianta latenta rum från bilder där agentens handlingar motsvarar vektoradditioner. Vi visar hur sådana representationer kan användas för att estimera en återhämtningsstrategi som dämpar felackumulering i datadrivna, sekventiella beslutspolicys. Vi utvidgar därefter ekvivarianta representationer till scener med externa objekt. Under en kontaktbaserad interaktionsmodell bevisar vi att en inriktning (alignment) av objektets och agentens latenta inbäddningar ger en isometrisk och separerad (disentangled) representation av båda. Därefter lättar vi på geometriantagandet och studerar den mildare biasen temporal konsistens. Detta möjliggör konstruktion av representationer där den temporala ordningen mellan tillstånd bevaras—en egenskap vi benämner distansmonotonicitet. I en förstärkningsinlärningsmiljö visar vi att denna egenskap, under lämpliga villkor, räcker för att återvinna en approximation av värdefunktionen och bevisligen skatta en optimal policy. I ett flersensorramverk kan dessa representationer dessutom användas för att konstruera en Bayesiansk filtreringsbaserad tillståndsskattning som är robust mot okänt brus. Slutligen utvidgar vi interaktionsbegreppet från fysikaliska system till en lärares parametriska rum. Vi visar hur distansmonotona representationer av modellparametrar kan utnyttjas för att approximera posteriordistributionen i en Bayesiansk neuronnätmodell. I en meta-inlärningssättning undersöker vi även implicita representationer av läraren för att minska variansen hos en modell för snabb anpassning. Sammantaget demonstrerar resultaten att interaktionsdrivna bias leder till strukturerade representationer som förenklar eller förbättrar inlärningsprocessen.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2026. p. xv, 57
Series
TRITA-EECS-AVL ; 2026:18
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Computer Science
Identifiers
urn:nbn:se:kth:diva-376773 (URN)978-91-8106-539-8 (ISBN)
Public defence
2026-03-16, https://kth-se.zoom.us/w/63788305553, F3, Lindstedtsvägen 26, Stockholm, 09:00 (English)
Opponent
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Note

QC 20260216

Available from: 2026-02-16 Created: 2026-02-16 Last updated: 2026-02-23Bibliographically approved

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Reichlin, AlfredoVasco, MiguelKragic Jensfelt, Danica

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