News

Mrs. Tatiana Patera generously donated $30,000 to the CRM. This amount will be allocated to the Jiri Patera and Pavel Winternitz Fund, in memory of these two researchers who were members of the CRM throughout their careers at the Université de Montréal.

The purpose of this donation is to support the development of mathematical physics in Montreal. In particular, the money donated to this fund will be used to hold an annual event where a renowned researcher, working at the intersection of mathematics and physics, will present recent developments in mathematical physics and interact with senior and junior CRM researchers.

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Gilles Parez, Clement Berthiere, William Witczak-Krempa just published a preprint of their paper entitled “Separability and entanglement of resonating valence-bond states“.

Summary of the article

Determining whether a given quantum state is separable is extremely challenging. We achieve this formidable task for local Rokhsar-Kivelson (RK) states and resonating valence-bond (RVB) states. Ubiquitous in condensed matter physics these states can describe quantum critical phases of matter and quantum spin liquids. We proved the exact separability of the reduced density matrix of two disconnected subsystems for dimer RK states on arbitrary graphs. For more general RK states with local constraints we argue separability in the thermodynamic limit. For RVB states we show separability up to exponentially small terms in the distance between the two subsystems thus holding exactly in the scaling limit.

Figure

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Lena Engström, Chia-Chuan Liu, William Witczak-Krempa and T. Pereg-Barnea have just prepublished their paper entitled “Strain-induced superconductivity in Sr2IrO4“.

On the initiative of the CNRS, an international network in quantum sciences and technologies will be officially launched on January 1, 2023. It will bring together 16 French and Canadian universities, including the University of Montreal, which will be officially represented on the scientific committee of this network by William Witczak-Krempa.

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Clément Berthiere, Benoit Estienne, Jean-Marie Stéphan, William Witczak-Krempa have just pre-published their paper entitled “Full-counting statistics of charge fluctuations in quantum Hall states“.

Abstract

We study the cumulants of the charge distribution of a subregion for two-dimensional quantum Hall states of bosons and fermions at both integer and fractional fillings, focusing on subregions with corners.
The variance (second cumulant) is known to be superuniversal, i.e. it takes the same form for a large class of unrelated systems, independently of the observable. We show that superuniversality breaks down for cumulants higher than the variance. However, we have discovered that the shape dependence of the third cumulant shows nearly universal behavior for integer and fractional Laughlin Hall states in the lowest Landau level.

Dr. Shai M. Chester (Harvard University), who co-authored the paper “Evidence for 3d bosonization from monopole operators” with William Witczak-Krempa, recently presented their results at the international workshop “Bootstrapping Nature: Non-perturbative Approaches to Critical Phenomena” held from October 3 to November 4, 2022 at the Galileo Galilei Institute in Florence (Italy), and co-organized by William.

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Shai M. Chester, Éric Dupuis and William Witczak-Krempa recently published a preprint of their new paper “Evidence for 3d bosonization from monopole operators”. 

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Chia-Chuan Liu, Juliette Geoffrion and William Witczak-Krempa recently published a preprint of their new paper “Entanglement negativity versus mutual information in the quantum Hall effect and beyond”. They study the entanglement properties of quantum mixed states, with an emphasis on quantum Hall states, using the mutual information and the logarithmic negativity (LN). The LN of integer quantum Hall states is studied at zero and finite temperature in various tripartite geometries containing angles. At zero-temperature, they discover an angle-dependent geometric contribution to the LN. They find a rapid decrease of the LN as temperature increases.