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Jon Spalding

Publications and source records attributed to Jon Spalding.

3 recordsLinked to original sources

Survey-Based Calibration of the One-Community and Two-Community Social Network Models Used for Testing Singapore's Resilience to Pandemic Lockdown

A resilient society is one capable of withstanding and thereafter recovering quickly from large shocks. Brought to the fore by the COVID-19 pandemic of 2020--2022, this social resilience is nevertheless difficult to quantify. In this paper, we measured how quickly the Singapore society recovered from the pandemic, by first modeling it as a dynamic social network governed by three processes: (1) random link addition between strangers; (2) social link addition between individuals with a friend in common; and (3) random link deletion . To calibrate this model, we carried out a survey of a representative sample of $N = 2,057$ residents and non-residents in Singapore between Jul and Sep 2022 to measure the numbers of random and social contacts gained over a fixed duration, as well as the number of contacts lost over the same duration, using phone contacts as proxy for social contacts. Lockdown simulations using the model that fits the survey results best suggest that Singapore would recover from such a disruption after 1--2 months.

physics.soc-ph

Corrections to Conformal Charge at BKT Transitions

The conformal anomaly is key to describing the physics of interacting field theories in two dimensions, and has been shown to obtain finite-size corrections that are useful to numerical and experimental studies. At Berezinskii-Kosterlitz-Thouless transitions, the corrections are logarithmic with previously unknown universal coefficients. In this paper, I reveal the universal, $1^{st}$-order correction to the conformal anomaly for finite-sized systems at BKT transitions. This term results solely from topological defects that are irrelevant in the infrared limit. I compare the result with careful observations of entanglement for the quantum Heisenberg model with periodic boundary conditions in one spatial dimension.

cond-mat.str-el

Critical Entanglement for the Half-Filled Extended Hubbard Model

We study the ground state of the one-dimensional extended Hubbard model at half-filling using the entanglement entropy calculated by Density Matrix Renormalization Group (DMRG) techniques. We apply a novel curve fitting and scaling method to accurately identify a $2^{nd}$ order critical point as well as a Berezinskii-Kosterlitz-Thouless (BKT) critical point. Using open boundary conditions and medium-sized lattices with very small truncation errors, we are able to achieve similar accuracy to previous authors. We also report observations of finite-size and boundary effects that can be remedied with careful pinning.

cond-mat.str-el