964 citations · 2.1k across the 42 of their papers we have counts for
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Restoration of Ensemble Equivalence by Quantum Fluctuations
Alessandro Campa, Andrea Trombettoni
We study the thermodynamic phase diagram of a one-dimensional quantum spin chain subjected to both mean-field and nearest-neighbor interactions, and to a transverse magnetic field…
Phase diagram of the one-dimensional three-state Potts model with an additional mean-field interaction
Alessandro Campa, Vahan Hovhannisyan, Stefano Ruffo +1
We derive the phase diagram of the one-dimensional three-state Potts model with an additional mean-field interaction in the canonical ensemble. The free energy is obtained by mappi…
Ensemble Inequivalence in Ising Chains with Competing Interactions
Alessandro Campa, Vahan Hovhannisyan, Stefano Ruffo +1
We study the effect of competing interactions on ensemble inequivalence. We consider a one-dimensional Ising model with ferromagnetic mean-field interactions and short-range neares…
Synchronization in a System of Kuramoto Oscillators with Distributed Gaussian Noise
Alessandro Campa, Shamik Gupta
We consider a system of globally-coupled phase-only oscillators with distributed intrinsic frequencies and evolving in presence of distributed Gaussian, white noise, namely, a Gaus…
Relaxation dynamics in a long-range system with mixed Hamiltonian and non-Hamiltonian interactions
Alessandro Campa, Shamik Gupta
Sometimes the dynamics of a physical system is described by non-Hamiltonian equations of motion, and additionally, the system is characterized by long-range interactions. A concret…
The study of the dynamics of the order parameter of coupled oscillators in the Ott-Antonsen scheme for generic frequency distributions
Alessandro Campa
The Ott-Antonsen ansatz shows that, for certain classes of distribution of the natural frequencies in systems of globally coupled Kuramoto oscillators, the dynamics of the orde…
Modified Thirring model beyond the excluded-volume approximation
Alessandro Campa, Lapo Casetti, Pierfrancesco Di Cintio +3
Long-range interacting systems may exhibit ensemble inequivalence and can possibly attain equilibrium states under completely open conditions, for which energy, volume and number o…
Computation of microcanonical entropy at fixed magnetization without direct counting
Alessandro Campa, Giacomo Gori, Vahan Hovhannisyan +2
We discuss a method to compute the microcanonical entropy at fixed magnetization without direct counting. Our approach is based on the evaluation of a saddle-point leading to an op…
Monte Carlo simulations in the unconstrained ensemble
Ivan Latella, Alessandro Campa, Lapo Casetti +3
The unconstrained ensemble describes completely open systems whose control parameters are chemical potential, pressure, and temperature. For macroscopic systems with short-range in…
Phase diagram of noisy systems of coupled oscillators with a bimodal frequency distribution
Alessandro Campa
We study the properties of large systems of globally coupled oscillators in the presence of noise. When the distribution of the natural frequencies of the oscillators is bimodal an…
Phase transitions in the unconstrained ensemble
Alessandro Campa, Lapo Casetti, Ivan Latella +1
The unconstrained ensemble describes completely open systems in which energy, volume and number of particles fluctuate. Here we show that not only equilibrium states can exist in t…
Ensemble inequivalence in the Blume-Emery-Griffiths model near a fourth order critical point
V. V. Prasad, Alessandro Campa, David Mukamel +1
The canonical phase diagram of the Blume-Emery-Griffiths (BEG) model with infinite-range interactions is known to exhibit a fourth order critical point at some negative value of th…
Ising chains with competing interactions in presence of long-range couplings
Alessandro Campa, Giacomo Gori, Vahan Hovhannisyan +2
In this paper we study an Ising spin chain with short-range competing interactions in presence of long-range ferromagnetic interactions in the canonical ensemble. The simultaneous…
Concavity, Response Functions and Replica Energy
Alessandro Campa, Lapo Casetti, Ivan Latella +2
In nonadditive systems, like small systems or like long-range interacting systems even in the thermodynamic limit, ensemble inequivalence can be related to the occurrence of negati…
Complete analysis of ensemble inequivalence in the Blume-Emery-Griffiths model
V. V. Hovhannisyan, N. S. Ananikian, A. Campa +1
We study inequivalence of canonical and microcanonical ensembles in the mean-field Blume-Emery-Griffiths model. This generalizes previous results obtained for the Blume-Capel model…
Long-range interacting systems in the unconstrained ensemble
Ivan Latella, Agustín Pérez-Madrid, Alessandro Campa +2
Completely open systems can exchange heat, work, and matter with the environment. While energy, volume, and number of particles fluctuate under completely open conditions, the equi…
The quasilinear theory in the approach of long-range systems to quasi-stationary states
Alessandro Campa, Pierre-Henri Chavanis
We develop a quasilinear theory of the Vlasov equation in order to describe the approach of systems with long-range interactions to quasi-stationary states. We derive a diffusion e…
Phase transitions in Thirring's model
Alessandro Campa, Lapo Casetti, Ivan Latella +2
In his pioneering work on negative specific heat, Walter Thirring in\-tro\-duced a model that is solvable in the microcanonical ensemble. Here, we give a complete description of th…
Thermodynamics of nonadditive systems
Ivan Latella, Agustín Pérez-Madrid, Alessandro Campa +2
The usual formulation of thermodynamics is based on the additivity of macroscopic systems. However, there are numerous examples of macroscopic systems that are not additive, due to…
Nonequilibrium inhomogeneous steady state distribution in disordered, mean-field rotator systems
Alessandro Campa, Shamik Gupta, Stefano Ruffo
We present a novel method to compute the phase space distribution in the nonequilibrium stationary state of a wide class of mean-field systems involving rotators subject to quenche…
Kuramoto model of synchronization: Equilibrium and nonequilibrium aspects
Shamik Gupta, Alessandro Campa, Stefano Ruffo
Recently, there has been considerable interest in the study of spontaneous synchronization, particularly within the framework of the Kuramoto model. The model comprises oscillators…
Nonequilibrium first-order transition in coupled oscillator systems with inertia and noise
Shamik Gupta, Alessandro Campa, Stefano Ruffo
We study the dynamics of a system of coupled oscillators of distributed natural frequencies, by including the features of both thermal noise, parametrized by a temperature, and ine…
Caloric curves fitted by polytropic distributions in the HMF model
A. Campa, P. H. Chavanis
We perform direct numerical simulations of the HMF model starting from non-magnetized initial conditions with a velocity distribution that is (i) gaussian, (ii) semi-elliptical, an…
Overdamped dynamics of long-range systems on a one-dimensional lattice: Dominance of the mean-field mode and phase transition
Shamik Gupta, Alessandro Campa, Stefano Ruffo
We consider the overdamped dynamics of a paradigmatic long-range system of particles residing on the sites of a one-dimensional lattice, in the presence of thermal noise. The inter…