Stefano Ruffo
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View article: Lagrangian Homotopy Analysis Method using the Least Action Principle
Lagrangian Homotopy Analysis Method using the Least Action Principle Open
The Homotopy Analysis Method (HAM) is a powerful technique which allows to derive approximate solutions of both ordinary and partial differential equations. We propose to use a variational approach based on the Least Action Principle (LAP)…
View article: Energy cascade and Burgers turbulence in the Fermi-Pasta-Ulam-Tsingou chain
Energy cascade and Burgers turbulence in the Fermi-Pasta-Ulam-Tsingou chain Open
The dynamics of initial long-wavelength excitations of the Fermi-Pasta-Ulam-Tsingou chain has been the subject of intense investigations since the pioneering work of Fermi and collaborators. We have recently found a regime where the spectr…
View article: Ensemble Inequivalence in Long-Range Quantum Systems
Ensemble Inequivalence in Long-Range Quantum Systems Open
Ensemble inequivalence, i.e., the possibility of observing different thermodynamic properties depending on the statistical ensemble which describes the system, is one of the hallmarks of long-range physics, which has been demonstrated in n…
View article: Energy cascade and Burgers turbulence in the Fermi-Pasta-Ulam-Tsingou chain
Energy cascade and Burgers turbulence in the Fermi-Pasta-Ulam-Tsingou chain Open
The dynamics of initial long-wavelength excitations of the Fermi-Pasta-Ulam-Tsingou chain has been the subject of intense investigations since the pioneering work of Fermi and collaborators. We have recently found a new regime where the sp…
View article: Ensemble Inequivalence in Ising Chains with Competing Interactions
Ensemble Inequivalence in Ising Chains with Competing Interactions Open
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 nearest-neighbor and next-nearest-neighbor couplings which can be…
View article: Stabilization of discrete time-crystalline response on a superconducting quantum computer by increasing the interaction range
Stabilization of discrete time-crystalline response on a superconducting quantum computer by increasing the interaction range Open
The simulation of complex quantum many-body systems is a promising short-term goal of noisy intermediate-scale quantum (NISQ) devices. However, the limited connectivity of native qubits hinders the implementation of quantum algorithms that…
View article: Stabilization of discrete time-crystalline response on a superconducting quantum computer by increasing the interaction range
Stabilization of discrete time-crystalline response on a superconducting quantum computer by increasing the interaction range Open
The simulation of complex quantum many-body systems is a promising short-term goal of noisy intermediate-scale quantum (NISQ) devices. However, the limited connectivity of native qubits hinders the implementation of quantum algorithms that…
View article: 1953: Fermi's "little discovery" and the birth of the numerical experiment
1953: Fermi's "little discovery" and the birth of the numerical experiment Open
The year 1953 is pivotal for computational physics: the first application of the Monte-Carlo method is published and calculations of the so-called Fermi-Pasta-Ulam-Tsingou experiment are started. It is the beginning of the massive use in t…
View article: Long-range interacting quantum systems
Long-range interacting quantum systems Open
The presence of non-local and long-range interactions in quantum systems\ninduces several peculiar features in their equilibrium and out-of-equilibrium\nbehavior. In current experimental platforms control parameters such as\ninteraction ra…
View article: Transition to anomalous dynamics in a simple random map
Transition to anomalous dynamics in a simple random map Open
The famous Bernoulli shift (or dyadic transformation) is perhaps the simplest deterministic dynamical system exhibiting chaotic dynamics. It is a piecewise linear time-discrete map on the unit interval with a uniform slope larger than one,…
View article: Nonequilibrium steady states of long-range coupled harmonic chains
Nonequilibrium steady states of long-range coupled harmonic chains Open
Understanding the organization of matter under the long-range electrostatic\nforce is a fundamental problem in multiple fields. In this work, based on the\nelectrically charged tethered membrane model, we reveal regular structures\nunderly…
View article: Lifetime of locally stable states near a phase transition in the Thirring model
Lifetime of locally stable states near a phase transition in the Thirring model Open
We study the lifetime of locally stable states in the Thirring model, which describes a system of particles whose interactions are long-range. The model exhibits first-order phase transitions in the canonical ensemble and, therefore, a fre…
View article: Non-equilibrium steady states of long-range coupled harmonic chains
Non-equilibrium steady states of long-range coupled harmonic chains Open
We perform a numerical study of transport properties of a one-dimensional chain with couplings decaying as an inverse power $r^{-(1+σ)}$ of the intersite distance $r$ and open boundary conditions, interacting with two heat reservoirs. Desp…
View article: Quantization of Integrable and Chaotic Three-Particle Fermi–Pasta–Ulam–Tsingou Models
Quantization of Integrable and Chaotic Three-Particle Fermi–Pasta–Ulam–Tsingou Models Open
We study the transition from integrability to chaos for the three-particle Fermi–Pasta–Ulam–Tsingou (FPUT) model. We can show that both the quartic β-FPUT model (α=0) and the cubic one (β=0) are integrable by introducing an appropriate Fou…
View article: Quantum heat engine with long-range advantages
Quantum heat engine with long-range advantages Open
Long-range interacting quantum devices provides a promising route for quantum technology applications. Here, the presence of long-range interactions is shown to enhance the performances of a quantum heat engine featuring a many-body workin…
View article: Villain model with long-range couplings
Villain model with long-range couplings Open
A bstract The nearest-neighbor Villain, or periodic Gaussian, model is a useful tool to understand the physics of the topological defects of the two-dimensional nearest-neighbor XY model, as the two models share the same symmetries and are…
View article: Logarithmic, Fractal and Volume-Law Entanglement in a Kitaev chain with long-range hopping and pairing
Logarithmic, Fractal and Volume-Law Entanglement in a Kitaev chain with long-range hopping and pairing Open
Thanks to their prominent collective character, long-range interactions promote information spreading and generate forms of entanglement scaling, which cannot be observed in traditional systems with local interactions. In this work, we stu…
View article: Modified Thirring model beyond the excluded-volume approximation
Modified Thirring model beyond the excluded-volume approximation Open
Long-range interacting systems may exhibit ensemble inequivalence and can possibly attain equilibrium states under completely open conditions, for which energy, volume and number of particles simultaneously fluctuate. Here we consider a mo…
View article: Villain model with long-range couplings
Villain model with long-range couplings Open
The nearest-neighbor Villain, or periodic Gaussian, model is a useful tool to understand the physics of the topological defects of the two-dimensional nearest-neighbor $XY$ model, as the two models share the same symmetries and are in the …
View article: Burgers Turbulence in the Fermi-Pasta-Ulam-Tsingou Chain
Burgers Turbulence in the Fermi-Pasta-Ulam-Tsingou Chain Open
We prove analytically and show numerically that the dynamics of the Fermi-Pasta-Ulam-Tsingou chain is characterized by a transient Burgers turbulence regime on a wide range of time and energy scales. This regime is present at long waveleng…
View article: Quantum heat engine with long-range advantages
Quantum heat engine with long-range advantages Open
The employment of long-range interactions in quantum devices provides a promising route towards enhancing their performance in quantum technology applications. Here, the presence of long-range interactions is shown to enhance the performan…
View article: Burgers turbulence in the Fermi-Pasta-Ulam-Tsingou chain
Burgers turbulence in the Fermi-Pasta-Ulam-Tsingou chain Open
We prove analytically and show numerically that the dynamics of the Fermi-Pasta-Ulam-Tsingou chain is characterised by a transient Burgers turbulence regime on a wide range of time and energy scales. This regime is present at long waveleng…
View article: Tricritical point in the quantum Hamiltonian mean-field model
Tricritical point in the quantum Hamiltonian mean-field model Open
Engineering long-range interactions in experimental platforms has been achieved with great success in a large variety of quantum systems in recent years. Inspired by this progress, we propose a generalization of the classical Hamiltonian m…
View article: Classical and quantum harmonic mean-field models coupled intensively and extensively with external baths
Classical and quantum harmonic mean-field models coupled intensively and extensively with external baths Open
We study the nonequilibrium steady-state of a fully-coupled network of N quantum harmonic oscillators, interacting with two thermal reservoirs. Given the long-range nature of the couplings, we consider two setups: one in which the number o…
View article: Classical and quantum harmonic mean-field models coupled intensively and extensively with external baths
Classical and quantum harmonic mean-field models coupled intensively and extensively with external baths Open
We study the nonequilibrium steady-state of a fully-coupled network of $N$ quantum harmonic oscillators, interacting with two thermal reservoirs. Given the long-range nature of the couplings, we consider two setups: one in which the number…
View article: Report on scipost_202201_00009v1
Report on scipost_202201_00009v1 Open
We study the nonequilibrium steady-state of a fully-coupled network of N harmonic oscillators, interacting with two thermal reservoirs.Given the long-range nature of the couplings, we consider two setups: one in which the number of particl…
View article: Hydrodynamics and transport in the long-range-interacting <i>φ</i> <sup>4</sup> chain
Hydrodynamics and transport in the long-range-interacting <i>φ</i> <sup>4</sup> chain Open
We present a simulation study of the one-dimensional φ 4 lattice theory with long-range interactions decaying as an inverse power r −(1+ σ ) of the intersite distance r , σ > 0. We consider the cases of single and double-well local potenti…