Author

N. Chepiga

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Preprint Oct 2026

Quantum Ising transition on the Cayley tree: boundary criticality, universality, and an effective Bethe line

We investigate quantum criticality in the transverse-field Ising model on finite Cayley trees and demonstrate that their extensive boundary fundamentally changes the nature of the quantum phase transition compared with the infinite, boundary-free Bethe lattice. Using tree tensor-network simulations for systems with up...

Pietro Richelli, N. Chepiga · 0 citations

Preprint Sep 2026

Criticality enabled long-range order in a U(1)-symmetric spin-1 Heisenberg chain with biquadratic interactions

In a recent paper Nahum argued on the basis of a renormalization-group analysis that, contrary to standard lore, ground states of 1D spin chains with short-range interactions can spontaneously break U(1) ``easy-plane''spin rotation symmetry. True long-range order of $(S^x,S^y)$ arises at the phase transition between tw...

N. Chepiga, F. Essler · 2 citations