arXiv subjects

Sergei Kuznetsov

Publications and source records attributed to Sergei Kuznetsov.

3 recordsLinked to original sources

arXiv2026

ContextRAG: Extraction-Free Hierarchical Graph Construction for Retrieval-Augmented Generation

Graph-structured retrieval-augmented generation (RAG) systems can improve answer quality on multi-hop questions, but many current systems rely on large language models (LLMs) to extract entities, relations, and summaries during indexing. These calls add token and wall-clock costs that grow with corpus size. We present ContextRAG, a graph RAG system whose graph topology is constructed without LLM-based entity or relation extraction. ContextRAG derives a fuzzy concept graph over chunk embeddings using residual-quantization k-means and Formal Concept Analysis with Lukasiewicz residuated logic. Bridge-like and meet-derived context nodes are induced by soft fuzzy join and meet operations, rather than by LLM-written graph edges. On a 130-task UltraDomain subset, ContextRAG builds its index with 30 LLM calls and 22,073 tokens. In contrast, a local HiRAG reproduction stress test required 870 indexing calls and 3.54M tokens on a 20-task subset before failing during graph construction; linear extrapolation to 130 tasks implies over 23M indexing tokens. ContextRAG obtains 33.6% F1 overall and 36.8% F1 on multi-hop tasks. An activation analysis shows that queries retrieving at least one lattice-derived node in the top five achieve +3.9 percentage points F1 over queries that do not; this association is diagnostic rather than causal.

cs.CL↗

arXiv2025

Wide-Angle Reflection Suppression of Dielectric Slabs Using Nonlocal Metasurface Coatings

Any discontinuity of constitutive parameters along a wave propagation path causes scattering. For a plane wave incident onto a flat dielectric slab, reflection becomes strongly dependent on the incident angle as the electrical thickness becomes large. This behavior limits the applicability of conventional single- and multilayer anti-reflective coatings. Recently, inspired by the generalized Huygens' condition, synthesized admittance sheets implemented as metasurfaces with local response have been shown to remove reflection from a dielectric slab in a wide range of incident angles, applicable, however, only in the case of small optical slab thickness. In this work, we study plane wave transmission through dielectric slabs with arbitrary thickness coated from both sides by identical metasurfaces with nonlocal response, whose grid impedance is angularly dependent (spatially dispersive). Nonlocality is shown to play a key role in obtaining wide-angle reflection suppression in the case of optically thick slabs. To validate our approach, we study a metasurface realization composed of Interconnected Split-Ring Resonators that approximates the predicted spatial dispersion law. As demonstrated numerically and experimentally, such properly devised nonlocal metasurface coatings indeed provide transmittance enhancement (and reflectance suppression) of thick dielectric slabs across a broad range of angles, paving the path to optically thin and easy-to-fabricate anti-reflective coatings efficiently operating in a wide angular range even for optically thick dielectric slabs.

physics.optics↗

arXiv2019

On Pattern Setups and Pattern Multistructures

Modern order and lattice theory provides convenient mathematical tools for pattern mining, in particular for condensed irredundant representations of pattern spaces and their efficient generation. Formal Concept Analysis (FCA) offers a generic framework , called pattern structures, to formalize many types of patterns, such as itemsets, intervals, graph and sequence sets. Moreover, FCA provides generic algorithms to generate irredundantly all closed patterns, the only condition being that the pattern space is a meet-semilattice. This does not always hold, e.g., for sequential and graph patterns. Here, we discuss pattern setups consisting of descriptions making just a partial order. Such a framework can be too broad, causing several problems, so we propose a new model, dubbed pattern multistructure, lying between pattern setups and pattern structures, which relies on multilattices. Finally, we consider some techniques , namely completions, transforming pattern setups to pattern structures using sets/antichains of patterns.

cs.DM↗