arXiv subjects

Estevão F. Borel

Publications and source records attributed to Estevão F. Borel.

2 recordsLinked to original sources

arXiv2026

The BEG model at the FAD triple point on the square lattice

In this note, we prove that the two-dimensional Blume-Emery-Griffiths model at the triple point Ferromagnetic-Antiquadrupolar-Disordered (FAD) has a unique Gibbs measure at any temperature, thereby establishing the absence of phase transitions. The FAD point lies at the intersection of lines separating three regions of the phase diagram, and it is a singular point where the model exhibits infinitely many ground states. Our proof is based on a random-cluster type representation with configuration-dependent cluster weights and a coupling with Bernoulli site percolation with parameter $1/2$.

math-ph↗

arXiv2024

Anisotropic Ising model in d+s dimensions

In this note, we consider the asymmetric nearest neighbor ferromagnetic Ising model on the $(d+s)$-dimensional unit cubic lattice $\Z^{d+s}$, at inverse temperature $β=1$ and with coupling constants $J_s>0$ and $J_d>0$ for edges of $\Z^s$ and $\Z^d$, respectively. We obtain a lower bound for the critical curve in the phase diagram of $(J_s,J_d)$. In particular, as $J_d$ approaches its critical value from below, our result is directly related to the so-called dimensional crossover phenomenon.

math-ph↗