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Lucio Marassi

Publications and source records attributed to Lucio Marassi.

3 recordsLinked to original sources

Irreversibility from Self-Reference: Gradient Flow and an H-Theorem for a Self-Referential Statistical Operator Framework

This paper is a direct companion to arXiv:2605.06705, where the self-referential operator Omega was introduced and the Tsallis index q = alpha + beta was derived as a fixed-point condition within the local kernel approximation (LKA). Here we address four aspects deferred from the previous work. First, we carry out the first-order perturbative expansion of Omega beyond the LKA and demonstrate structural stability of q = alpha + beta at leading order in (xi/L)^2. Second, we define the iterative dynamical scheme Psi_(n+1) = Omega[Psi_n] and analyze convergence via Frechet spectral radius. Third, and centrally, we establish an H-theorem rigorously within the LKA for both the discrete iteration and the continuous gradient flow: we compute dF/dtau explicitly along the flow, identify the negative semi-definite dissipation term, establish the result rigorously in the LKA using strict convexity of F proved in the companion paper, and provide numerical evidence showing monotone decrease of F[Psi_n] across 53 iterations on an N = 80 discrete system. Fourth, we characterize the non-perturbative role of the self-coupling parameter kappa, identifying a re-entrant disordered phase at kappa > kappa* approximately 0.50 +/- 0.05. The paper is explicit about what is proved, what is established numerically, and what open problems remain for a complete analytical proof beyond the LKA.

cond-mat.stat-mech

Emergence of Tsallis Statistics from a Self-Referential Nonlinear Operator: A Variational Framework

We develop a variational thermodynamic framework for statistical systems governed by a self-referential nonlinear operator Omega characterized by structural exponents alpha > 0, beta >= 0, a symmetric kernel K, and a self-coupling constant kappa >= 0. The central object is the self-consistency entropy S[Psi] = -D_KL(Psi || Omega Psi), which vanishes at the fixed points of Omega and serves as a natural Lyapunov functional. Within the local kernel (mean-field) approximation, minimization of the free energy F = U - T S admits the Tsallis q-exponential distribution as an equilibrium state, with the entropic index q = alpha + beta emerging directly from the fixed-point structure of the operator rather than being postulated. The framework yields a consistent thermodynamic description, including a generalized equation of state PV = (2 - q) T, response functions, and a critical temperature associated with spontaneous symmetry breaking. The relation q = alpha + beta connects independently measurable structural exponents of the feedback mechanism to the observed tail index, providing a parameter-free criterion that distinguishes this approach from superstatistics, constrained entropy maximization, and q-deformed formalisms. This work establishes an operator-theoretic foundation for nonextensive statistical mechanics in which nonlinear self-referential feedback naturally generates Tsallis statistics in the mean-field limit.

cond-mat.stat-mech

Formation of Dark Matter Haloes in a Homogeneous Dark Energy Universe

Several independent cosmological tests have shown evidences that the energy density of the Universe is dominated by a dark energy component, which cause the present accelerated expansion. The large scale structure formation can be used to probe dark energy models, and the mass function of dark matter haloes is one of the best statistical tools to perform this study. We present here a statistical analysis of mass functions of galaxies under a homogeneous dark energy model, proposed in the work of Percival (2005), using an observational flux-limited X-ray cluster survey, and CMB data from WMAP. We compare, in our analysis, the standard Press-Schechter (PS) approach (where a Gaussian distribution is used to describe the primordial density fluctuation field of the mass function), and the PL (Power Law) mass function (where we apply a nonextensive q-statistical distribution to the primordial density field). We conclude that the PS mass function cannot explain at the same time the X-ray and the CMB data (even at 99% confidence level), and the PS best fit dark energy equation of state parameter is $ω=-0.58$, which is distant from the cosmological constant case. The PL mass function provides better fits to the HIFLUGCS X-ray galaxy data and the CMB data; we also note that the $ω$ parameter is very sensible to modifications in the PL free parameter, $q$, suggesting that the PL mass function could be a powerful tool to constrain dark energy models.

astro-ph.CO