Tootfinder

Asymptotically exact solution of the non-Hermitian disordered interacting Hatano-Nelson chain
Val\'eria M. Mattiello, Victor L. Quito, Eduardo Miranda
https://arxiv.org/abs/2509.16309

Asymptotically exact solution of the non-Hermitian disordered interacting Hatano-Nelson chain
We present an asymptotically exact solution of a paradigmatic non-Hermitian model: the disordered interacting fermionic Hatano-Nelson model, or equivalently, the non-Hermitian spin-1/2 XXZ model. We use a renormalization group method suited for disordered systems and show that non-Hermitian couplings are relevant perturbations to the Hermitian model, which ultimately leads to a quantum-to-classical crossover. The ground state of the model consists of a collection of strongly coupled pairs of sp…

Optimal Subspace Embeddings: Resolving Nelson-Nguyen Conjecture Up to Sub-Polylogarithmic Factors
Shabarish Chenakkod, Micha{\l} Derezi\'nski, Xiaoyu Dong
https://arxiv.org/abs/2508.14234

Optimal Subspace Embeddings: Resolving Nelson-Nguyen Conjecture Up to Sub-Polylogarithmic Factors
We give a proof of the conjecture of Nelson and Nguyen [FOCS 2013] on the optimal dimension and sparsity of oblivious subspace embeddings, up to sub-polylogarithmic factors: For any $n\geq d$ and $ε\geq d^{-O(1)}$, there is a random $\tilde O(d/ε^2)\times n$ matrix $Π$ with $\tilde O(\log(d)/ε)$ non-zeros per column such that for any $A\in\mathbb{R}^{n\times d}$, with high probability, $(1-ε)\|Ax\|\leq\|ΠAx\|\leq(1+ε)\|Ax\|$ for all $x\in\mathbb{R}^d$, where…

Punctuation and Predicates in Language Models
Sonakshi Chauhan, Maheep Chaudhary, Koby Choy, Samuel Nellessen, Nandi Schoots
https://arxiv.org/abs/2508.14067 https://

Punctuation and Predicates in Language Models
In this paper we explore where information is collected and how it is propagated throughout layers in large language models (LLMs). We begin by examining the surprising computational importance of punctuation tokens which previous work has identified as attention sinks and memory aids. Using intervention-based techniques, we evaluate the necessity and sufficiency (for preserving model performance) of punctuation tokens across layers in GPT-2, DeepSeek, and Gemma. Our results show stark model-sp…

Evidence for a gap in the envelope mass fraction of sub-Saturns
Luis Thomas, Louise D. Nielsen, Lorena Acu\~na-Aguirre, Alex Cridland
https://arxiv.org/abs/2509.12120 https://…

Evidence for a gap in the envelope mass fraction of sub-Saturns
Under the core-accretion model, gas giants form via runaway accretion. This process starts when the mass of the accreted envelope becomes equal to the mass of the core. Here, we model a population of warm sub-Saturns to search for imprints of their formation history in their internal structure. Using the GAS gianT modeL for Interiors (GASTLI), we calculate a grid of interior structure models on which we perform retrievals for our sample of 28 sub-Saturns to derive their envelope mass fractions …

BART gave me a nice welcome back at SFO with only half of the new fare gate opening while I have a suitcase.

The Curious Case of V CVn
Michael T. Power, Hilding R. Neilson, Galina Sherren
https://arxiv.org/abs/2509.11672 https://arxiv.org/pdf/2509.11672

The Curious Case of V CVn
Decades of observations on the star V Canum Venaticorum (V CVn) have revealed an unusual inverse relationship between its linear polarization and light curves (sometimes with a lead/lag time between them) and an almost constant polarization position angle. One theory proposed to explain this behaviour is the existence of a bow shock driven by a spherically symmetric time-varying dusty wind from the star, which is assumed to vary due to radial pulsations. To test this hypothesis, this study uses…

Technical Aspects of Plasma Operational Simulation (POPSIM): A Framework for Data-Driven Simulation and Control
Allen M. Wang, Zander Keith, Mark Dan Boyer, Andrew Oakleigh Nelson, Alex Saperstein, Alessandro Pau, Cristina Rea
https://arxiv.org/abs/2509.10244

Technical Aspects of Plasma Operational Simulation (POPSIM): A Framework for Data-Driven Simulation and Control
This paper reports on technical aspects of Plasma Operational Simulation (POPSIM), a research framework for data-driven simulation and control built in the machine learning framework JAX. The objective of the project is to address the extremely challenging simulation and modeling requirements of tokamak operations and control by combining simple principles-based models with data-driven models, spanning everything from power laws to new neural network architectures. This paper reports on key sof…

Generalized Jeffreys's approximate objective Bayes factor: Model-selection consistency, finite-sample accuracy, and statistical evidence in 71,126 clinical trial findings
Puneet Velidi, Zhengxiao Wei, Shreena Nisha Kalaria, Yimeng Liu, C\'eline M. Laumont, Brad H. Nelson, Farouk S. Nathoo
https://arxiv.org/abs/2510.10358

Generalized Jeffreys's approximate objective Bayes factor: Model-selection consistency, finite-sample accuracy, and statistical evidence in 71,126 clinical trial findings
Concerns about the misuse and misinterpretation of p-values and statistical significance have motivated alternatives for quantifying evidence. We define a generalized form of Jeffreys's approximate objective Bayes factor (eJAB), a one-line calculation that is a function of the p-value, sample size, and parameter dimension. We establish conditions under which eJAB is model-selection consistent and verify them for ten statistical tests. We assess finite-sample accuracy by comparing eJAB with Mark…

Identification and Properties of Topological States in the Bulk of Quasicrystals
Frode Balling-Ans{\o}, Jeppe Lykke Krogh, Ella Elisabeth Lassen, Anne E. B. Nielsen
https://arxiv.org/abs/2507.20722

Identification and Properties of Topological States in the Bulk of Quasicrystals
In contrast to the usual bulk-boundary correspondence, topological states localized within the bulk of the system have been numerically identified in quasicrystalline structures, termed bulk localized transport (BLT) states. These states exhibit properties different from edge states, one example being that the number of BLT states scales with system size, while the number of edge states scales with system perimeter. Here, we define an algorithm to identify BLT states, which is based on the phys…

Products of strictly hyperbolic conjugacy classes in symplectic groups
Klaus Nielsen
https://arxiv.org/abs/2509.26237 https://arxiv.org/pdf/2509.26237

Products of strictly hyperbolic conjugacy classes in symplectic groups
We call a conjugacy class of the symplectic group Sp$(2n, K)$ over a field $K$ strictly hyperbolic if its minimal polynomial is of the form $q(x) q^*(x)$, where the polynomial $q(x)$ is prime to its reciprocal $q^*(x) := x^n q(x^{-1})$. It is shown that the product of 2 cyclic, strictly hyperbolic conjugacy classes of Sp$(2n, K)$ contains all nonscalar elements of Sp$(2n, K)$. It follows that the projective symplectic group has a conjugacy class of covering number 2, i.e. PSp$(2n,K) = Ω^2$ for…