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Riccardo Fantoni

Publications and source records attributed to Riccardo Fantoni.

At least 37 records · Page 2Linked to original sources
arXiv2024

Continuum limit of the Green function in scaled affine $φ^4_4$ quantum Euclidean covariant relativistic field theory

We prove through path integral Monte Carlo computer experiments that the affine quantization of the $φ_4^4$ scaled Euclidean covariant relativistic scalar field theory is a valid quantum field theory with a well defined continuum limit of the one- and two-point-function. Affine quantization leads to a completely satisfactory quantization of field theories using situations that involve scaled behavior leading to an unexpected, $\hbar^2/φ^2$ which arises only in the quantum aspects.

hep-th↗
arXiv2024

A Classical Luttinger liquid

We propose a binary nonadditive Asakura-Oosawa-like mixture as an example for the classical limit of a Luttinger liquid. We determine the equation of state and structure of this mixture and discuss the paradoxical situation that one faces when working with a quantum liquid without a ground state. We then propose a new class of one dimensional classical fluids.

cond-mat.stat-mech↗
arXiv2023

Monte Carlo simulation of Hard-, Square-Well, and Square-Shoulder Disks in narrow channels

We perform Monte Carlo simulation of the thermodynamic and structural properties of Hard-, Square-Well, and Square-Shoulder Disks in narrow channels. For the thermodynamics we study the internal energy per particle and the longitudinal and transverse compressibility factor. For the structure we study the Transverse Density and Density of Pairs Profiles, the Radial Distribution Function and Longitudinal Distribution Function, and the (static) Longitudinal Structure Factor. We compare our results with a recent exact semi-analytic solution found by Montero and Santos for the single file formation and first nearest neighbor fluid and explore how their solution performs when these conditions are not fulfilled making it just an approximation.

cond-mat.stat-mech↗
arXiv2023

Scaled Affine Quantization of $φ^{12}_3$ is Nontrivial

We prove through Monte Carlo analysis that the covariant euclidean scalar field theory, $φ^r_n$, where $r$ denotes the power of the interaction term and $n = s + 1$ where $s$ is the spatial dimension and $1$ adds imaginary time, such that $r = 12, n = 3$ can be acceptably quantized using scaled affine quantization and the resulting theory is nontrivial, unlike what happens using canonical quantization when the system is plagued by asymptotic freedom.

hep-lat↗
arXiv2023

A modest redirection of quantum field theory solves all current problems

Standard quantization using, for example, path integration of field theory models, includes paths of momentum and field reach infinity in the Hamiltonian density, while the Hamiltonian itself remains finite. That fact causes considerable difficulties. In this paper, we represent $π(x)$ by $k(x)/ϕ(x)$. To insure proper values for $π(x)$ it is necessary to restrict $0<|ϕ(x)|<\infty$ as well as $0\leq|k(x)|<\infty$. Indeed that leads to Hamiltonian densities in which $ϕ(x)^p$, where $p$ can be even integers between $4$ and $\infty$. This leads to a completely satisfactory quantization of field theories using situations that involve scaled behavior leading to an unexpected, $\hbar^2/\hatϕ(x)^2$ which arises only in the quantum aspects. Indeed, it is fair to claim that this symbol change leads to valid field theory quantizations.

physics.gen-ph↗
arXiv2023

One-component fermion plasma on a sphere at finite temperature. The anisotropy in the paths conformations

In our previous work [R. Fantoni, Int. J. Mod. Phys. C, {\bf 29}, 1850064 (2018)] we studied, through a computer experiment, a one-component fermion plasma on a sphere at finite, non-zero, temperature. We extracted thermodynamic properties like the kinetic and internal energy per particle and structural properties like the radial distribution function, and produced some snapshots of the paths to study their shapes. Here we revisit such a study giving some more theoretical details explaining the paths shape anisotropic conformation due to the inhomogeneity in the polar angle of the variance of the random walk diffusion from the kinetic action.

cond-mat.stat-mech↗
arXiv2023

The Magnificent Realm of Affine Quantization: valid results for particles, fields, and gravity

Affine quantization is a relatively new procedure, and it can solve many new problems. This essay reviews this new, and novel, procedure for particle problems, as well as those of fields and gravity. New quantization tools, which are extremely close to, and even constructed from, the tools of canonical quantization, are able to fully solve selected problems that using the standard canonical quantization would fail. In particular, improvements can even be found with an affine quantization of fields, as well as gravity.

physics.gen-ph↗
arXiv2022

Scaled Affine Quantization of Ultralocal $φ^4_2$ a comparative Path Integral Monte Carlo study with Canonical Quantization

After the success of affine quantization in proving through Monte Carlo analysis that the covariant euclidean scalar field theory, $φ^r_n$, where $r$ denotes the power of the interaction term and $n = s + 1$ with $s$ the spatial dimension and $1$ adds imaginary time, such that $r \geq 2n/(n-2)$ can be acceptably quantized and the resulting theory is nontrivial, unlike what happens using canonical quantization, we show here that the same has to be expected for $r>2$ and any $n$ even for the ultralocal field theory. In particular we consider the ultralocal $φ^4_2$ model and study its renormalized properties for both the scaled canonical quantization version and the scaled affine quantization version through path integral Monte Carlo.

hep-th↗
arXiv2022

Scaled Affine Quantization of $φ^4_4$ in the Low Temperature Limit

We prove through Monte Carlo analysis that the covariant euclidean scalar field theory, $φ^r_n$, where $r$ denotes the power of the interaction term and $n = s + 1$ where $s$ is the spatial dimension and $1$ adds imaginary time, such that $r = n = 4$ can be acceptably quantized using scaled affine quantization and the resulting theory is nontrivial and renormalizable even at low temperatures in the highly quantum regime.

hep-lat↗
arXiv2022

Kinetic Factors in Affine Quantization and Their Role in Field Theory Monte Carlo

Affine quantization, which is a parallel procedure with canonical quantization, needs to use its principal quantum operators, most simply $D=(PQ+QP)/2$ and $Q\neq0$, to represent appropriate kinetic factors, normally $P^2$, which involve only one canonical quantum operator. The need for this requirement stems from the quantization of selected problems that require affine quantization to achieve valid Monte Carlo results. This task is resolved for introductory examples as well as examples that involve scalar quantum field theories.

hep-lat↗
arXiv2021

Jellium at finite temperature

We adopt the fixed node restricted path integral Monte Carlo method within the "Worm algorithm" to simulate Wigner's Jellium model at finite, non zero, temperatures using free-particle nodes of the density matrix. The new element is that we incorporate the Worm algorithm paradigm of Prokof'ev and Svistunov in the grand canonical ensemble in order to more efficiently handle the fermionic exchanges. We present results for the structure and thermodynamic properties of the ideal Fermi gas and three points for the interacting electron gas. We treat explicitly the case of the partially polarized electron gas.

cond-mat.str-el↗
arXiv2021

Monte Carlo evaluation of the continuum limit of the two-point function of the Euclidean free real scalar field subject to affine quantization

We study canonical and affine versions of the quantized covariant Euclidean free real scalar field-theory on four dimensional lattices through the Monte Carlo method. We calculate the two-point function at small values of the bare coupling constant and near the continuum limit at finite volume. Our investigation shows that affine quantization is able to give meaningful results for the two-point function for which is not available an exact analytic result and therefore numerical methods are necessary.

hep-lat↗
arXiv2021

Jellium at finite temperature using the restricted worm algorithm

We study the Jellium model of Wigner at finite, non-zero, temperature through a computer simulation using the canonical path integral worm algorithm where we successfully implemented the fixed-nodes free particles restriction necessary to circumvent the fermion sign problem. Our results show good agreement with the recent simulation data of Brown et al. and of other similar computer experiments on the Jellium model at high density and low temperature. Our algorithm can be used to treat any quantum fluid model of fermions at finite, non zero, temperature and has never been used before in literature.

cond-mat.str-el↗
arXiv2020

How should we choose the boundary conditions in a simulation which could detect anyons in one and two dimensions?

We discuss the problem of anyonic statistics in one and two spatial dimensions from the point of view of statistical physics. In particular we want to understand how the choice of the Bornvon Karman or the twisted periodic boundary conditions necessary in a Monte Carlo simulation to mimic the thermodynamic limit of the many body system influences the statistical nature of the particles. The particles can either be just bosons, when the configuration space is simply connected as for example for particles on a line. They can be bosons and fermions, when the configuration space is doubly connected as for example for particles in the tridimensional space or in a Riemannian surface of genus greater or equal to one (on the torus, etc . . . ). They can be scalar anyons with arbitrary statistics, when the configuration space is infinitely connected as for particles on the plane or in the circle. They can be scalar anyons with fractional statistics, when the configuration space is the one of particles on a sphere. One can further have multi components anyons with fractional statistics when the configuration space is doubly connected as for particles on a Riemannian surface of genus greater or equal to one. We determine an expression for the canonical partition function of hard core particles (including anyons) on various geometries. We then show how the choice of boundary condition (periodic or open) in one and two dimensions determine which particles can exist on the considered surface. In the conclusion, we mention the Laughlin wavefunction and give a few comments about experiments.

cond-mat.stat-mech↗
arXiv2019

Form invariance of the moment sum-rules for jellium with the addition of short-range terms in the pair-potential

We find the first three (even) structure factor moments for a (non-quantum) one-component Jellium made of particles living in three dimensions and interacting with a Coulomb pair-potential plus a short-range term with either a finite range or decaying exponentially fast at large distances. Starting from the hierarchical Born-Green-Yvon equations we show that they are all form invariant respect to the addition of the short-range term. We discuss the relevance of the present study to interpret the failure of the moment sum-rules of ionic-liquids at criticality.

cond-mat.stat-mech↗
arXiv2019

Plasma living in a curved surface at some special temperature

The simplest statistical mechanics model of a Coulomb plasma in two spatial dimensions admits an exact analytic solution at some special temperature in several (curved) surfaces. We present in a unifying perspective these solutions for the (non-quantum) plasma, made of point particles carrying an absolute charge $e$, in thermal equilibrium at a temperature $T=e^2/2k_B$, with $k_B$ Boltzmann's constant, discussing the importance of having an exact solution, the role of the curvature of the surface, and the densities of the plasma.

cond-mat.stat-mech↗
arXiv2018

From the Liouville to the Smoluchowski equation for a colloidal solute particle in a solvent

We show how the Smoluchowski dynamics of a colloidal Brownian particle suspended in a molecular solvent can be reached starting from the microscopic Liouvillian evolution of the full classical model in the high friction limit. The integration of the solvent degrees of freedom goes through a multiple time scale perturbation expansion which removes the secular divergences. A simple dynamical Monte Carlo scheme is then proposed to solve the resulting evolution equation for the colloid solute particle. In particular we study the approach to the equilibrium Boltzmann distribution at late times and its resilience behavior at shorter times as influenced by the steepness of the external potential and the friction coefficient around their respective minima. This is very important to understand the fate of the Brownian particle's random walk and its evolution history.

cond-mat.soft↗