arXiv subjects

L. Tinti

Publications and source records attributed to L. Tinti.

7 recordsLinked to original sources

arXiv2023

Spatial correlations of charm and anticharm quarks at hadronisation

Heavy-ion collisions are a unique tool for studying properties of strong interactions at high energy densities. In particular, the momentum correlations of charm and bottom hadrons have been considered for testing heavy quark thermalisation in the dense matter produced by the collisions. In this respect, two effects have been considered: the decrease of the initial back-to-back correlations and the increase of correlations due to heavy-quark interactions with the collectively flowing medium. Here, we show that information on the spatial correlations of the charm-anticharm quarks at the hadronisation can be extracted by measuring the momentum correlation of charm and anticharm hadrons produced in central collisions of two heavy nuclei. This, however, requires collisions with a single charm-anticharm quark pair created - the condition likely to be fulfilled in central Pb+Pb collisions at the CERN SPS energies. We introduce a method to correct the measured joint distribution function for the smearing of the charm and anticharm hadron momenta caused by hadronisation. Then the results are directly sensitive to the spatial correlations at the hadronisation. Using an example of central Pb+Pb collisions at the CERN SPS energies, we demonstrate that even a limited statistics of charm-anticharm hadron pairs can distinguish between different spatial correlation functions of charm-anticharm quarks at hadronisation. The results on spatial charm-anticharm quark correlations will provide a unique test of different assumptions on heavy quark creation in space-time and transport in dense, strongly interacting matter. We show that the existing detector technology and beam intensities at the CERN SPS should allow us to conduct the needed experiments soon.

hep-ph↗

arXiv2021

Relativistic quantum fluid with boost invariance

We study a relativistic fluid with longitudinal boost invariance in a quantum-statistical framework as an example of a solvable non-equilibrium problem. For the free quantum field, we calculate the exact form of the expectation values of the stress-energy tensor and the entropy current. For the stress-energy tensor, we find that a finite value can be obtained only by subtracting the vacuum of the density operator at some fixed proper time τ_0. As a consequence, the stress-energy tensor acquires non-trivial quantum corrections to the classical free-streaming form.

hep-th↗

arXiv2018

Resummed hydrodynamic expansion for a plasma of particles interacting with fields

A novel description of kinetic theory dynamics is proposed in terms of resummed moments that embed information of both hydrodynamic and non-hydrodynamic modes. The resulting expansion can be used to extend hydrodynamics to higher orders in a consistent and numerically efficient way; at lowest order it reduces to an Israel-Stewart-like theory. This formalism is especially suited to investigate the general problem of particles interacting with fields. We tested the accuracy of this approach against the exact solution of the coupled Boltzmann-Vlasov-Maxwell equations for a plasma in an electromagnetic field undergoing Bjorken-like expansion, including extreme cases characterized by large deviations from local equilibrium and large electric fields. We show that this new resummed method maintains the fast convergence of the traditional method of moments. We also find a new condition, unrelated to Knudsen numbers and pressure corrections, that justifies the truncation of the series even in situations far from local thermal equilibrium.

nucl-th↗

arXiv2015

Local thermodynamical equilibrium and the beta frame for a quantum relativistic fluid

We discuss the concept of local thermodynamical equilibrium in relativistic hydrodynamics in flat spacetime in a quantum statistical framework without an underlying kinetic description, suitable for strongly interacting fluids. We show that the appropriate definition of local equilibrium naturally leads to the introduction of a relativistic hydrodynamical frame in which the four-velocity vector is the one of a relativistic thermometer at equilibrium with the fluid, parallel to the inverse temperature four-vector β, which then becomes a primary quantity. We show that this frame is the most appropriate for the expansion of stress-energy tensor from local thermodynamical equilibrium and that therein the local laws of thermodynamics take on their simplest form. We discuss the difference between the βframe and Landau frame and present an instance where they differ.

hep-th↗

arXiv2013

Nonequilibrium Thermodynamical Inequivalence of Quantum Stress-energy and Spin Tensors

It is shown that different pairs of stress-energy and spin tensors of quantum relativistic fields related by a pseudo-gauge transformation, i.e. differing by a divergence, imply different mean values of physical quantities in thermodynamical nonequilibrium situations. Most notably, transport coefficients and the total entropy production rate are affected by the choice of the spin tensor of the relativistic quantum field theory under consideration. Therefore, at least in principle, it should be possible to disprove a fundamental stress-energy tensor and/or to show that a fundamental spin tensor exists by means of a dissipative thermodynamical experiment.

hep-th↗

arXiv2011

Thermodynamical inequivalence of quantum stress-energy and spin tensors

It is shown that different couples of stress-energy and spin tensors of quantum relativistic fields, which would be otherwise equivalent, are in fact inequivalent if the second law of thermodynamics is taken into account. The proof of the inequivalence is based on the analysis of a macroscopic system at full thermodynamical equilibrium with a macroscopic total angular momentum and a specific instance is given for the free Dirac field, for which we show that the canonical and Belinfante stress-energy tensors are not equivalent. For this particular case, we show that the difference between the predicted angular momentum densities for a rotating system at full thermodynamical equilibrium is a quantum effect, persisting in the non-relativistic limit, corresponding to a polarization of particles of the order of \hbar ω/KT (ωbeing the angular velocity) and could in principle be measured experimentally. This result implies that specific stress-energy and spin tensors are physically meaningful even in the absence of gravitational coupling and raises the issue of finding the thermodynamically right (or the right class of) tensors. We argue that the maximization of the thermodynamic potential theoretically allows to discriminate between two different couples, yet for the present we are unable to provide a theoretical method to single out the "best" couple of tensors in a given quantum field theory. The existence of a non-vanishing spin tensor would have major consequences in hydrodynamics, gravity and cosmology.

hep-th↗

arXiv2010

The ideal relativistic rotating gas as a perfect fluid with spin

We show that the ideal relativistic spinning gas at complete thermodynamical equilibrium is a fluid with a non-vanishing spin density tensor σ_μν. After having obtained the expression of the local spin-dependent phase space density f(x,p)_(στ) in the Boltzmann approximation, we derive the spin density tensor and show that it is proportional to the acceleration tensor Omega_μνconstructed with the Frenet-Serret tetrad. We recover the proper generalization of the fundamental thermodynamical relation, involving an additional term -(1/2) Ω_μνσ^μν. We also show that the spin density tensor has a non-vanishing projection onto the four-velocity field, i.e. t^μ= sigma_μνu^ν\ne 0, in contrast to the common assumption t^μ= 0, known as Frenkel condition, in the thus-far proposed theories of relativistic fluids with spin. We briefly address the viewpoint of the accelerated observer and inertial spin effects.

gr-qc↗