arXiv subjects

S. D. Campos

Publications and source records attributed to S. D. Campos.

At least 19 recordsLinked to original sources

arXiv2026

Enthalpy-Based Thermal Response and Its Exact Relation to the Speed of Sound in Finite-Temperature QCD

A precise characterization of the QCD phase transition remains a fundamental open problem, primarily due to the intrinsically non-perturbative nature of the dynamics that govern the breakdown of We quantify the logarithmic thermal variation of the normalized enthalpy density in finite-temperature Quantum Chromodynamics using a dimensionless response thermal function, $\mathcal{H}(T)$. We establish an exact identity that links $\mathcal{H}(T)$ to the speed of sound, $c_s^2(T)$. Using continuum-extrapolated lattice Quantum Chromodynamics, Monte Carlo uncertainty propagation, and cubic spline interpolation, we extract a stable peak at $T_{\text{peak}} \approx 153.6\text{ MeV}$ ($\mathcal{H}_{\text{peak}} \approx 6.24$), which remains robust under changes in the smoothing parameter $s$. By contrast, $\mathcal{H}(T) = 0$ for the MIT Bag Model despite its non-vanishing trace anomaly. We highlight $\mathcal{H}(T)$ as an effective diagnostic of the QCD crossover and discuss its limitations for universal critical scaling at zero chemical potential.

hep-lat↗

arXiv2026

Dissipative Multi-Field Dynamics from Non-Hermitian Inflationary Potentials

In this work, we develop a perturbative framework for inflation driven by a complex inflaton with non-minimal gravitational coupling and a non-Hermitian potential. During the observable cosmic microwave background radiation era, the dynamics reduce to an effectively conservative two-field model, preserving the predictions of the $α$-attractor class and satisfying Planck 2018 and BICEP/Keck constraints on $n_s$, $r$, and $f_{\mathrm{NL}}$. Near the end of inflation, trajectory bending activates the non-Hermitian sector, triggering geometric reheating. The resulting non-unitary evolution modifies the curvature spectrum and stochastic gravitational-wave background through a calculable damping factor determined by the complex mass eigenvalues. While cosmic microwave background-scale observables remain essentially unchanged, a distinctive suppression emerges in the high-frequency gravitational-wave spectrum ($f > 10^2$ Hz), potentially testable by future detectors such as the Einstein Telescope and the Big Bang Observer.

gr-qc↗

arXiv2026

Beyond Plane Waves: Coherent Network Response to Collimated Gravitational-Wave Wavepackets

We present a paraxial wavepacket model for structured, collimated gravitational-wave bursts and derive the coherent response of detector networks to these signals. For current terrestrial baselines such as LIGO-Virgo, analytic mismatch estimates confirm that the paraxial wavepacket model waveforms are effectively indistinguishable from standard sine-Gaussian bursts, validating the robustness of the plane-wave approximation in this regime. However, we identify a physical scaling regime relevant to third-generation networks and galactic-scale Pulsar Timing Arrays in which finite transverse structure-motivated by wave-optics lensing or ultra-relativistic beaming induces non-negligible geometric phase shifts. A toy event-level Monte Carlo study compares a standard burst-search ranking with a paraxial wavepacket model-constrained statistic that penalizes geometric inconsistencies across detectors. In this controlled setup, the model prior yields an illustrative factor of $\sim 3$-$4$ gain in detection efficiency at a fixed false-alarm rate, while maintaining performance on plane-wave-like signals. These results suggest that paraxial corrections may provide a necessary metrological framework for signal discrimination and unbiased parameter estimation in future cosmic-scale observations.

gr-qc↗

arXiv2026

Low-Order Bessel-Type PID Dynamics in Lithium-Based Tritium Breeding and Heat-Removal Systems

Lithium plays a dual role in deuterium-tritium fusion systems by enabling tritium breeding in blankets and providing an efficient heat-removal medium in liquid-metal components. However, most existing investigations treat neutronic behavior, jet thermohydraulics, and feedback control as largely decoupled layers, and there is currently no compact analytical framework that simultaneously links lithium-based tritium breeding, jet thermal response, and controller dynamics. In this work, we integrate nuclear cross-section data for deuterium-tritium and lithium reactions with a reduced thermohydraulic model of a liquid-lithium jet and an operator-theoretic formulation of feedback control. The resulting blanket/jet configuration should be interpreted as a conceptual, reduced-order demonstration of how two Li-based subsystems can be coupled in a unified analytical framework, rather than as a fully realistic reactor design in which an IFMIF-type neutron source is directly attached to a self-sufficient power blanket. We derive a low-order model describing jet thermal expansion under deuteron-beam loading and demonstrate that a continuous-time proportional-integral-derivative controller, expressed in operator form, can be locally embedded within a family of Bessel-type differential operators acting on the tritium-inventory tracking error. The results suggest that lithium-based breeding and heat-removal systems admit low-order, proportional-integral-derivative controllable dynamics that can be interpreted in terms of localized Bessel modes, providing a compact analytical framework for guiding future controller design and blanket/jet optimization.

physics.plasm-ph↗

arXiv2026

Complex Inflaton Potentials with Nonminimal Coupling: Robust Inflation and Geometric Reheating

We investigate an inflationary scenario driven by a complex scalar field nonminimally coupled to gravity and subject to a non-symmetric complex potential. The real part of the potential controls the cosmological background and realizes a plateau-type inflation compatible with $α$-attractor $\mathrm{T}$-models, while the imaginary part acts as an effective non-Hermitian deformation encoding dissipative effects. Working in the Jordan frame and imposing ghost-free conditions on the effective Planck mass, we derive the background equations and define a complex equation-of-state parameter whose real part governs the expansion and whose imaginary part quantifies departures from conservative dynamics. Numerical integration shows that the duration of inflation is primarily controlled by the nonminimal coupling $ζ$, whereas the complex asymmetry parameter $Δ\varepsilon$ has a negligible impact on the real background: the real energy density and pressure vary by less than $10^{-5}$ as $Δ\varepsilon$ is scanned over its allowed range. Mapping the two-field dynamics to an effective single-field description in the Einstein frame, we obtain a spectral index $n_s\simeq 0.968-0.971$ and a tensor-to-scalar ratio $r<10^{-3}$, fully consistent with Planck 2018 bounds. We introduce a relevance parameter and show that non-Hermitian effects remain strongly suppressed during slow roll but grow to $\mathcal{O}(1)$ near the end of inflation, triggering an efficient reheating phase without additional fields or {\it ad hoc} friction terms. In this sense, the imaginary sector behaves as an effective $\mathcal{PT}$-symmetric channel for energy transfer, providing a geometrical mechanism for inflation and its exit within a non-Hermitian scalar-tensor framework.

gr-qc↗

arXiv2025

Low-Mass Neutron Stars and Effective Phase Transitions from a Hybrid Van der Waals-Polytropic Equation of State

We study phase-transition-like behavior in neutron stars using a simplified, piecewise equation of state that couples a modified van der Waals-type core to a polytropic crust. The model remains analytically tractable while allowing for nonlinear density dependence. We impose thermodynamic and causal consistency conditions and determine the critical densities at which the curvature of the pressure-energy density relation changes. In the non-relativistic limit, the generalized Lane-Emden equations describe a smooth core-crust transition layer. We integrate the Tolman-Oppenheimer-Volkoff equations across different $(τ_1,σ_1)$ regimes, where these parameters encode thermal and interaction effects in the core. The resulting mass-radius sequences yield low neutron star masses $(0.99-2.05)M_{\odot}$, and the chemical potential exhibits the characteristic signatures of phase-transition behavior at densities well above the matching point. Our results show that analytic EOS models can reproduce the key phenomenology of phase transitions and provide a controlled framework for exploring low-mass neutron star configurations.

astro-ph.HE↗

arXiv2024

Gravitational Surface Tension as the Origin for the Black Hole Entropy

In this work, we explore the thermodynamics of black holes using the Gouy-Stodola theorem, traditionally applied to mechanical systems relating entropy production to the difference between reversible and irreversible work. We model black holes as gravitational bubbles with surface tension defined at the event horizon, deriving the Bekenstein-Hawking entropy relation for non-rotating black holes. One extends this approach to rotating black holes, incorporating the effects of angular momentum, demonstrating that the Gouy-Stodola theorem can similarly derive the entropy-area law in this case. Additionally, we analyze the merging of two black holes, showing that the resultant total entropy exceeds the sum of the individual entropies, thereby adhering to the second law of thermodynamics. Our results suggest that gravitational surface tension is a key factor in black hole thermodynamics, providing a novel and coherent framework for understanding the entropy production in these extreme astrophysical objects.

gr-qc↗

arXiv2024

Mimicking Negative Mass Properties

In the present work, one analyzes two systems trying to obtain physical conditions where some properties attributed to negative mass can be mimicked by positive mass particles. The first one is the well-known 1/2-spin system described by the Dirac equation in the presence of an external electromagnetic field. Assuming some physical restrictions, one obtains that the use of $e\rightarrow-e$ can lead to the same results as using $m\rightarrow-m$. In particular, for a null dielectric function, it is possible to obtain a negative mass behavior from a positive mass system composed of negatively charged particles. The second system is based on the de Broglie matter wave. The dispersion relation of such a wave can be negative (real or imaginary valued) if one assumes an imaginary wavenumber. The consequence is the emergence of a negative refractive index for positive mass particles. However, this behavior is generally attributed to a negative mass system.

quant-ph↗

arXiv2023

On Negative Mass, Partition Function and Entropy

This work examines some aspects related to the existence of negative mass. The requirement for the partition function to converge leads to two distinct approaches. Initially, convergence is achieved by assuming a negative absolute temperature, which results in an imaginary partition function and complex entropy. Subsequently, convergence is maintained by keeping the absolute temperature positive while introducing an imaginary velocity. This modification leads to a positive partition function and real entropy. It seems the utilization of imaginary velocity may yield more plausible physical results compared to the use of negative temperature, at least for the partition function and entropy.

cond-mat.stat-mech↗

arXiv2022

Optical Theorem, Crossing Property and Derivative Dispersion Relations: Implications on the Asymptotic Behavior of $σ_{tot}(s)$ and $ρ(s)$

In this paper, one presents some results concerning the behavior of the total cross section and $ρ$-parameter at asymptotic energies in proton-proton ($pp$) and antiproton-proton ($\bar{p}p$) collisions. For this intent, we consider three of the main theoretical results in high energy physics: the crossing property, the derivative dispersion relation, and the optical theorem. The use of such machinery allows the analytic formulas for wide set of the measured global scattering parameters and some important relations between them. The suggested parameterizations approximate simultaneously the energy dependence for total cross section and $ρ$-parameter for $pp$ and $\bar{p}p$ with statistically acceptable quality in multi-TeV region. Also the qualitative description is obtained for important interrelations, namely difference, sum and ratio of the antiparticle-particle and particle-particle total cross sections. Despite the reduced number of experimental data for the total cross section and $ρ$-parameter in TeV-scale, which turns any prediction for the beginning of the asymptotic domain a hard task, the fitting procedures indicates that asymptotia lies in the energy range 25.5-130 TeV. Moreover, in the asymptotic regime, one obtains $α_{\mathbb{P}}=1$. Detailed quantitative study of energy behavior of measured scattering parameters and their combinations in ultra-high energy domain indicates that the scenario with the generalized formulation of the Pomeranchuk theorem is more favorable with respect to the original formulation of this theorem.

hep-ph↗

arXiv2022

Evaluating the Gouy-Stodola Theorem in Classical Mechanic Systems: A Study of Entropy Generation

We propose to apply the entropy generation $(\dot S_{gen}$) concept to a mechanical system: the well-known simple pendulum. When considering the ideal case, where only conservative forces act on the system, one has $\dot S_{gen}=0$, and the entropy variation is null. However, as shall be seen, the time entropy variation is not null all the time. Considering a non-conservative force proportional to the pendulum velocity, the amplitude of oscillations decreases to zero as $t$ grows. In this case, $\dot S_{gen}>0$ indicates that it is related to energy dissipation, as stated by the Gouy-Stodola theorem. Hence, as shall be seen, the greater the strength of the non-conservative force, the greater are both the energy dissipation and the time rate of entropy variation.

cond-mat.stat-mech↗

arXiv2022

Entropy Production in the Inflationary Epoch Using the Gouy-Stodola Theorem

In this work, we use the Gouy-Stodola theorem to calculate the entropy production rate in the inflationary epoch of the universe. This theorem allows us the simple calculation of entropy and entropy production rate occasioned by the decaying of the inflaton scalar field. Both the entropy and entropy production rate achieve large values, agreeing with the expected values present in the literature.

gr-qc↗

arXiv2021

Chiral Symmetry Restoration using the Running Coupling Constant from the Light-Front Approach to QCD

In this work, the distance between a quark-antiquark pair is analyzed through both the confinement potential as well as the hadronic total cross section. Using the Helmholtz free energy, entropy is calculated near the minimum of the total cross section through the confinement potential. A fitting procedure for the proton-proton total cross section is performed, defining the fitting parameters. Therefore, the only free parameter remaining in the model is the mass scale $κ$ used to define the running coupling constant of the light-front approach to QCD. The mass scale controls the distance $r$ between the quark-antiquark pair and, under some conditions, it allows the occurrence of free quarks even in the confinement regime of QCD.

hep-ph↗

arXiv2021

Chiral Symmetry in the Confinement Phase of QCD

Based on the Pomeranchuk theorem, one constructs the $δ(s)$ parameter to measure the difference between experimental data for the particle-particle and particle-antiparticle total cross section at the same energy. The experimental data for the proton-proton and proton-antiproton total cross section were used to show that, at the same energy, this parameter tends to zero as the collision energy grows. Furthermore, one assumes a classical description of the total cross section, dividing it into a finite number of non-interacting disjoint cells, each one containing a quark-antiquark pair subject to the confinement potential. Near the minimum of the total cross section, one associates $δ(s)$ with the entropy generated by these cells, analogous to the XY model. Using both the Quigg-Rosner and Cornell confinement potentials and neglecting other energy contributions, one can calculate the internal energy of the hadron. One obtains that both the entropy and internal energy possess the same logarithmic dependence on the spatial separation between the pairs in the cell. The Helmholtz free energy is used to estimate the transition temperature, which is far from the temperature widely related to the Quark-Gluon Plasma.

hep-ph↗

arXiv2021

The Debye Length and the Running Coupling of QCD: a Potential and Phenomenological Approach

In this paper, one uses a damped potential to present a description of the running coupling constant of QCD in the confinement phase. Based on a phenomenological perspective for the Debye screening length, one compares the running coupling obtained here with both the Brodsky-de Téramond-Deur and the Richardson approaches. The results seem to indicate the model introduced here corroborate the Richardson approach. Moreover, the Debye screening mass in the confinement phase depends on a small parameter, which tends to vanish in the non-confinement phase of QCD.

hep-ph↗

arXiv2020

Hollowness effect and entropy in high energy elastic scattering

This paper presents a qualitative explanation for the hollowness effect based on the inelastic overlap function, claiming this result is a consequence of fundamental thermodynamic processes. Using the Tsallis entropy, one identifies the entropic index $w$ with the ratio of the collision energy to critical one in the total cross-section. The integrated probability density function is replaced by the inelastic overlap function, which represents the probability of occurrence of an inelastic event depending on both the collision energy and impact parameter. The Coulomb potential, as well as the confinement potential, are used as naive approaches to describe the (internal) energy of the colliding hadrons. The Coulomb potential in the impact parameter picture is not able to furnish any reliable physical result near the forward direction. However, the confinement potential in the impact parameter space results in the hollowness effect shown by the inelastic overlap function near the forward direction.

hep-ph↗

arXiv2020

The Effects of the Tsallis Entropy in the Proton Internal Pressure

In this paper, one discusses the effects of the Tsallis entropy on the radial pressure distribution in the proton. Using a damped confinement potential the pressure distribution is obtained from the Tsallis entropy approach, being the entropic-index $ω$ connected with the proton temperature concerning some transition temperature. Then, the approach allows the study of the proton thermal evolution up to the Quark-Gluon Plasma regime. The von Laue stability condition, arising from the pressure distribution results in positive and negative energy regions. An analogy between the results for the radial pressure distribution and the proton-proton and the antiproton-proton total cross section is performed. The negative energy region is identified with the odderon exchange while the positive represents the pomeron exchange dominance above some transition energy $\sqrt{s_c}$. The hollowness effect is also discussed in terms of the results obtained and the proposed analogy.

hep-ph↗

arXiv2020

Logarithmic Regge Pole

This work presents the subtraction procedure and the Regge cut in the logarithmic Regge pole approach. The subtraction mechanism leads to the same asymptotic behavior as previously obtained in the non-subtraction case. The Regge cut, on the other hand, introduces a clear role to the non-leading contributions for the asymptotic behavior of the total cross section. From these results, one introduces some simple parameterization to fit the experimental data for the proton-proton and antiproton-proton total cross section above some minimum value up to the cosmic-ray. The fit parameters obtained are used to present predictions for the $ρ(s)$-parameter as well as to the elastic slope $B(s)$ at high energies.

hep-ph↗