Ramanujan's $1/π$ series and conformal field theories

Fuente: arXiv
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Autores principales: Bhat, Faizan, Sinha, Aninda
Formato: Preprint
Publicado: 2025
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author Bhat, Faizan
Sinha, Aninda
author_facet Bhat, Faizan
Sinha, Aninda
contents In 1914, Ramanujan unveiled 17 extraordinary infinite series for $1/π$. In this work, we uncover their physics origin by relating them to 2D logarithmic conformal field theories (LCFTs), which emerge in diverse settings such as the fractional quantum Hall effect, percolation, polymers, and even holography. Through this LCFT connection, we reinterpret such infinite series in terms of fundamental CFT data -- the operator spectrum and OPE coefficients. This perspective leads to novel physics-inspired approximations for $1/π$. Drawing lessons from Ramanujan's formulae, we construct a new family of bases for expanding LCFT correlators that converge far more rapidly than the standard conformal block decomposition. This is achieved using recently developed stringy/parametric crossing-symmetric dispersion relations. Remarkably, when working with these new expansions, the action of a certain differential operator (which arises naturally from the Ramanujan connection) dramatically enhances convergence, with the entire contribution collapsing to that of the logarithmic identity operator. This striking simplification hints at a universal property of LCFTs. Finally, we discuss a new holographic interpretation of this unexpected mathematics-physics connection.
format Preprint
id arxiv_https___arxiv_org_abs_2503_21656
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Ramanujan's $1/π$ series and conformal field theories
Bhat, Faizan
Sinha, Aninda
High Energy Physics - Theory
Mathematical Physics
In 1914, Ramanujan unveiled 17 extraordinary infinite series for $1/π$. In this work, we uncover their physics origin by relating them to 2D logarithmic conformal field theories (LCFTs), which emerge in diverse settings such as the fractional quantum Hall effect, percolation, polymers, and even holography. Through this LCFT connection, we reinterpret such infinite series in terms of fundamental CFT data -- the operator spectrum and OPE coefficients. This perspective leads to novel physics-inspired approximations for $1/π$. Drawing lessons from Ramanujan's formulae, we construct a new family of bases for expanding LCFT correlators that converge far more rapidly than the standard conformal block decomposition. This is achieved using recently developed stringy/parametric crossing-symmetric dispersion relations. Remarkably, when working with these new expansions, the action of a certain differential operator (which arises naturally from the Ramanujan connection) dramatically enhances convergence, with the entire contribution collapsing to that of the logarithmic identity operator. This striking simplification hints at a universal property of LCFTs. Finally, we discuss a new holographic interpretation of this unexpected mathematics-physics connection.
title Ramanujan's $1/π$ series and conformal field theories
topic High Energy Physics - Theory
Mathematical Physics
url https://arxiv.org/abs/2503.21656