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Siamak Ravanbakhsh

37 accepted papers

2026

Inverting Data Transformations via Diffusion Sampling

ICML 2026poster

We study the problem of transformation inversion on general Lie groups: a datum is transformed by an unknown group element, and the goal is to recover an inverse transformation that maps it back to the original data distribution. We take a probabilistic view and model the posterior over transformati…

Cited by 0SourceScholar
2026

Long-Horizon Model-Based Offline Reinforcement Learning Without Conservatism

ICML 2026poster

Popular offline reinforcement learning (RL) methods rely on conservatism, penalizing out-of-dataset actions or restricting rollout horizons. We question the universality of this principle and revisit a complementary Bayesian perspective. By modeling a posterior over plausible world models and traini…

Cited by 0SourceScholar
2026

The Expressive Limits of Diagonal SSMs for State-Tracking

ICLR 2026poster

State-Space Models (SSMs) have recently been shown to achieve strong empirical performance on a variety of long-range sequence modeling tasks while remaining efficient and highly-parallelizable. However, the theoretical understanding of their expressive power remains limited. In this work, we study…

Cited by 0SourceScholar
2025

Beyond Scalar Rewards: An Axiomatic Framework for Lexicographic MDPs

NeurIPS 2025spotlight

Recent work has formalized the reward hypothesis through the lens of expected utility theory, by interpreting reward as utility. Hausner's foundational work showed that dropping the continuity axiom leads to a generalization of expected utility theory where utilities are lexicographically ordered ve…

Cited by 0SourceScholar
2025

Diffusion Tree Sampling: Scalable inference‑time alignment of diffusion models

NeurIPS 2025poster

Adapting a pretrained diffusion model to new objectives at inference time remains an open problem in generative modeling. Existing steering methods suffer from inaccurate value estimation, especially at high noise levels, which biases guidance. Moreover, information from past runs is not reused to i…

Cited by 32SourceScholar
2025

Progressive Inference-Time Annealing of Diffusion Models for Sampling from Boltzmann Densities

NeurIPS 2025spotlight

Sampling efficiently from a target unnormalized probability density remains a core challenge, with relevance across countless high-impact scientific applications. A promising approach towards this challenge is the design of amortized samplers that borrow key ideas, such as probability path design, f…

Cited by 0SourceScholar
2025

SymmCD: Symmetry-Preserving Crystal Generation with Diffusion Models

ICLR 2025poster

Generating novel crystalline materials has potential to lead to advancements in fields such as electronics, energy storage, and catalysis. The defining characteristic of crystals is their symmetry, which plays a central role in determining their physical properties. However, existing crystal generat…

2024

E(3)-Equivariant Mesh Neural Networks

AISTATS 2024poster

Triangular meshes are widely used to represent three-dimensional objects. As a result, many recent works have addressed the need for geometric deep learning on 3D meshes. However, we observe that the complexities in many of these architectures do not translate to practical performance, and simple de…

2024

Efficient Dynamics Modeling in Interactive Environments with Koopman Theory

ICLR 2024poster

The accurate modeling of dynamics in interactive environments is critical for successful long-range prediction. Such a capability could advance Reinforcement Learning (RL) and Planning algorithms, but achieving it is challenging. Inaccuracies in model estimates can compound, resulting in increased e…

Cited by 3SourcePDFScholar
2024

Iterated Denoising Energy Matching for Sampling from Boltzmann Densities

ICML 2024poster

Efficiently generating statistically independent samples from an unnormalized probability distribution, such as equilibrium samples of many-body systems, is a foundational problem in science. In this paper, we propose Iterated Denoising Energy Matching (iDEM), an iterative algorithm that uses a nove…

2024

On Diffusion Modeling for Anomaly Detection

ICLR 2024spotlight

Known for their impressive performance in generative modeling, diffusion models are attractive candidates for density-based anomaly detection. This paper investigates different variations of diffusion modeling for unsupervised and semi-supervised anomaly detection. In particular, we find that Denois…

2024

Weight-Sharing Regularization

AISTATS 2024poster

Weight-sharing is ubiquitous in deep learning. Motivated by this, we propose a “weight-sharing regularization” penalty on the weights $w \in \mathbb{R}^d$ of a neural network, defined as $\mathcal{R}(w) = \frac{1}{d - 1}\sum_{i > j}^d |w_i - w_j|$. We study the proximal mapping of $\mathcal{R}$ and…

2023

Equivariance with Learned Canonicalization Functions

ICML 2023poster

Symmetry-based neural networks often constrain the architecture in order to achieve invariance or equivariance to a group of transformations. In this paper, we propose an alternative that avoids this architectural constraint by learning to produce canonical representations of the data. These canonic…

Cited by 84SourcePDFScholar
2023

Equivariant Adaptation of Large Pretrained Models

NeurIPS 2023poster

Equivariant networks are specifically designed to ensure consistent behavior with respect to a set of input transformations, leading to higher sample efficiency and more accurate and robust predictions. However, redesigning each component of prevalent deep neural network architectures to achieve cho…

Cited by 24SourcePDFScholar
2023

Lie Point Symmetry and Physics-Informed Networks

NeurIPS 2023poster

Symmetries have been leveraged to improve the generalization of neural networks through different mechanisms from data augmentation to equivariant architectures. However, despite their potential, their integration into neural solvers for partial differential equations (PDEs) remains largely unexplor…

Cited by 17SourcePDFScholar
2022

EqR: Equivariant Representations for Data-Efficient Reinforcement Learning

ICML 2022spotlight

We study a variety of notions of equivariance as an inductive bias in Reinforcement Learning (RL). In particular, we propose new mechanisms for learning representations that are equivariant to both the agent’s action, as well as symmetry transformations of the state-action pairs. Whereas prior work…

2022

SpeqNets: Sparsity-aware permutation-equivariant graph networks

ICML 2022spotlight

While message-passing graph neural networks have clear limitations in approximating permutation-equivariant functions over graphs or general relational data, more expressive, higher-order graph neural networks do not scale to large graphs. They either operate on $k$-order tensors or consider all $k$…

2022

Structuring Representations Using Group Invariants

NeurIPS 2022accept

A finite set of invariants can identify many interesting transformation groups. For example, distances, inner products and angles are preserved by Euclidean, Orthogonal and Conformal transformations, respectively. In an equivariant representation, the group invariants should remain constant on the e…

Cited by 20SourcePDFScholar
2018

Deep Models of Interactions Across Sets

ICML 2018oral

We use deep learning to model interactions across two or more sets of objects, such as user{–}movie ratings or protein{–}drug bindings. The canonical representation of such interactions is a matrix (or tensor) with an exchangeability property: the encoding’s meaning is not changed by permuting rows…

2017

Deep Sets

NeurIPS 2017oral

We study the problem of designing models for machine learning tasks defined on sets. In contrast to the traditional approach of operating on fixed dimensional vectors, we consider objective functions defined on sets and are invariant to permutations. Such problems are widespread, ranging from the es…

2016

Boolean Matrix Factorization and Noisy Completion via Message Passing

ICML 2016poster

Boolean matrix factorization and Boolean matrix completion from noisy observations are desirable unsupervised data-analysis methods due to their interpretability, but hard to perform due to their NP-hardness. We treat these problems as maximum a posteriori inference problems in a graphical model and…

2016

Estimating Cosmological Parameters from the Dark Matter Distribution

ICML 2016poster

A grand challenge of the 21st century cosmology is to accurately estimate the cosmological parameters of our Universe. A major approach in estimating the cosmological parameters is to use the large scale matter distribution of the Universe. Galaxy surveys provide the means to map out cosmic large-sc…

Cited by 98SourcePDFScholar
2016

Stochastic Neural Networks with Monotonic Activation Functions

AISTATS 2016poster

We propose a Laplace approximation that creates a stochastic unit from any smooth monotonic activation function, using only Gaussian noise. This paper investigates the application of this stochastic approximation in training a family of Restricted Boltzmann Machines (RBM) that are closely linked to…

Cited by 30SourcePDFScholar
2016

Survey Propagation beyond Constraint Satisfaction Problems

AISTATS 2016poster

Survey propagation (SP) is a message passing procedure that attempts to model all the fixed points of Belief Propagation (BP), thereby improving BP’s approximation in loopy graphs where BP’s assumptions do not hold. For this, SP messages represent distributions over BP messages. Unfortunately this r…

Cited by 10SourcePDFScholar
2015

Embedding Inference for Structured Multilabel Prediction

NeurIPS 2015poster

A key bottleneck in structured output prediction is the need for inference during training and testing, usually requiring some form of dynamic programming. Rather than using approximate inference or tailoring a specialized inference method for a particular structure---standard responses to the scal…

Cited by 23SourcePDFScholar