arXiv subjects

L. M. Nieto

Publications and source records attributed to L. M. Nieto.

At least 19 recordsLinked to original sources

arXiv2026

Constrained thermodynamics and geodesic observables of an effective non-commutative Kerr-like black hole

We investigate the horizon structure, constrained thermodynamics, and geodesic properties of an effective Kerr-like black hole in a non-commutative background. Deformation modifies the radial geometry through a mass-dependent charge-like contribution, while preserving the separability of the geodesic equations. We determine the conditions for horizon existence, identify the extremal zero-temperature configuration, and analyze the stationary-limit surfaces and the ergoregion. Special attention is paid to the thermodynamic interpretation of the model, where the geometric Hawking quantities are distinguished from the conjugate variables associated with the constrained state space at fixed non-commutative deformation parameter. The canonical and grand-canonical heat capacities are derived to characterize their ensemble-dependent local thermal behavior. We also obtain the spherical photon region, equatorial light rings, and shadow boundary, showing that the deformation shifts the characteristic photon orbits inwards and reduces the overall size of the shadow. Timelike circular motion is studied through the innermost stable circular orbit, where non-commutative correction produces an inward shift of both the prograde and retrograde branches. Finally, invariant photon frequency shifts are obtained by treating the emitter's orbital direction and the photon's tangential emission direction as independent physical choices.

gr-qc↗

arXiv2026

Analytical Solutions to Asymmetric Two-Photon Rabi Model

Within the Segal-Bargmann representation, a generalized Rabi model is considered that includes both two-photon and asymmetric terms. It is shown that, through a suitable transformation, nearly exact solutions can be obtained using the Bethe ansatz approach. Applying this approach to the meromorphic structure of the resulting differential equation, solutions in exact analytical form of the fourth-order problem are presented for both an arbitrary state and for the restriction between the parameters.

quant-ph↗

arXiv2025

Generalized Coulomb-type interaction embedded in a non-inertial cosmic string spacetime in a slow-rotation limit

Motivated by the great interest in studying quantum and gravitational phenomena in a unified way, scalar bosons are considered in a cosmic string spacetime and in a non-inertial frame, with a generalized Coulomb-type interaction containing both inverse quadratic and inverse cubic corrections. Solutions for this generalized interaction are shown for an arbitrary state in the slow rotation limit in a quasi-exact manner and a discussion is given of the structure of the problem, whose special case appears in the form of a doubly confluent Heun differential equation. The previously known solution for the simplest case of this problem, corresponding to the ordinary Coulomb interaction, is recovered.

gr-qc↗

arXiv2025

Planar Dirac equation with radial contact potentials

We investigate the planar Dirac equation with the most general time-independent contact (singular) potential supported on a circumference. Taking advantage of the radial symmetry, the problem is effectively reduced to a one-dimensional one (the radial), and the contact potential is addressed in a mathematically rigorous way using a distributional approach that was originally developed to treat point interactions in one dimension, providing a physical interpretation for the interaction parameters. The most general contact interaction for this system is obtained in terms of four physical parameters: the strengths of a scalar and the three components of a singular Lorentz vector potential supported on the circumference. We then investigate the bound and scattering solutions for several choices of the physical parameters, and analyze the confinement properties of the corresponding potentials.

math-ph↗

arXiv2025

Low-Energy DNA Bubble Dynamics via the Quantum Coulomb Potential

We developed a low-energy model that can be used at any time to describe the dynamics of DNA bubbles at temperatures below the melting point. The Schrödinger equation associated with this problem is solved in imaginary time with a quantum Coulomb potential, and we obtain an approximate expression for its more general physical solution as a linear combination of the states whose energies are close to the lower bound energy. We can then determine the probability density, the first-passage time density, and the correlation functions in terms of Bessel functions. Our findings are consistent with results obtained directly from the Fokker-Planck equation. Comparisons with the Gamma and Diffusion models are discussed.

physics.bio-ph↗

arXiv2025

Parity-deformed $sl(2,R)$, $su(2)$ and $so(3)$ Algebras: a Basis for Quantum Optics and Quantum Communications Applications

Having in mind the significance of parity (reflection) in various areas of physics, the single-mode and two-mode Wigner algebras are considered adding to them a reflection operator. The associated deformed $sl(2, R)$ algebra, $sl_ν(2,R)$ and the deformed $so(3)$ algebra, $so_ν(3)$, are constructed for the widely used Jordan-Schwinger and Holstein-Primakoff realizations, commenting on various aspects and ingredients of the formalism for both single-mode and two-mode cases. Finally, due to its potential application in the study of qubit and qutrit systems, the parity-deformed $so_ν(3)$ representation is analyzed based on the isomorphy of $so(3)$ and $su(2)$. Related applications are discussed as well.

math-ph↗

arXiv2025

Two types of $q$-Gaussian distributions used to study the diffusion in a finite region

In this work, we explore both the ordinary $q$-Gaussian distribution and a new one defined here, determining both their mean and variance, and we use them to construct solutions of the $q$-deformed diffusion differential equation. This approach allows us to realize that the standard deviation of the distribution must be a function of time. In one case, we derive a linear Fokker-Planck equation within a finite region, revealing a new form of both the position- and time-dependent diffusion coefficient and the corresponding continuity equation. It is noteworthy that, in both cases, the conventional result is obtained when $q$ tends to zero. Furthermore, we derive the deformed diffusion-decay equation in a finite region, also determining the position- and time-dependent decay coefficient. A discrete version of this diffusion-decay equation is addressed, in which the discrete times have a uniform interval, while for the discrete positions the interval is not uniform.

cond-mat.stat-mech↗

arXiv2025

Hidden $sl(2)-$Symmetry of the Generalized Landau-Zener Vibronic Model

The one-dimensional harmonic vibronic model, which is a generalization of the so-called linear Landau-Zener model and appears in the form of coupled Schrödinger equations, is revisited. After decoupling the components, the resulting fourth-order equation is shown to have a hidden $sl(2)$ algebra. The so-called exceptional part of the spectrum is then expressed in a rather simple way. For completeness, the eigenfunctions are obtained via the Bethe ansatz approach directly in position space.

quant-ph↗

arXiv2025

Dirac Equation with Space Contributions Embedded in a Quantum-Corrected Gravitational Field

The Dirac equation is considered with the recently proposed generalized gravitational interaction (Kepler or Coulomb), which includes post-Newtonian (relativistic) and quantum corrections to the classical potential. The general idea in choosing the metric is that the spacetime contributions are contained in an external potential or in an electromagnetic potential which can be considered as a good basis for future studies of quantum physics in space. The forms considered for the scalar potential and the so-called vector (magnetic) potential, can be viewed as the multipole expansion of these terms and therefore the approach includes a simultaneous study of multipole expansions to both fields. We also discuss several known generalizations of the Coulomb potential within this formulation in terms of certain Heun functions. The impossibility of solving our equation for the quantum-corrected Coulomb terms using known exact or quasi-exact nonperturbative analytical techniques is discussed, and finally the Bethe-ansatz approach is proposed to overcome this challenging problem.

quant-ph↗

arXiv2025

The spin-one Duffin-Kemmer-Petiau equation revisited: analytical study of its structure and a careful choice of interaction

The Duffin-Kemmer-Petiau equation is investigated for spin one bosons with the so-called natural (normal) and unnatural (abnormal) parity states for non-minimal vector interactions. To illustrate the current state of knowledge about the equation, a thorough but concise discussion is made on what can be achieved analytically within this framework for well-known phenomenological interactions, including Coulomb, soft-core, Cornell, Kratzer, and exponential type interactions. In the non-exponential cases, the equation, depending on the chosen interaction, is studied in relation to the confluent, doubly-confluent, and biconfluent Heun functions. Furthermore, to show the need for careful treatment of various parity states, a Kratzer-type potential, such as a generalized Coulomb interaction, is discussed in depth using the Lie algebraic approach, showing the need for careful analysis of abnormal parity states in a fairly explicit way. The energies obtained are discussed using some figures to explicitly show the different regimes, as well as the absence of the Klein paradox. Finally, some directions for future work that would undoubtedly need to be explored in this field are discussed.

quant-ph↗

arXiv2025

The one-dimensional Coulomb Hamiltonian: Properties of its Birman-Schwinger operator

We study the Birman-Schwinger operator for a self-adjoint realisation of the one-dimensional Hamiltonian with the Coulomb potential. We study both the case in which this Hamiltonian is defined on the whole real line and when it is only defined on the positive semiaxis. In both cases, the Birman-Schwinger operator is Hilbert-Schmidt, even though it is not trace class. Then, we have considered some approximations to the Hamiltonian depending on a positive parameter, under given conditions, and proved the convergence of the Birman-Schwinger operators of these approximations to the original Hamiltonian as the parameter goes to zero. Further comments and results have been included.

math-ph↗

arXiv2025

Exact Floquet solutions in a Parity-Time-Symmetric Rabi Model

It is shown that a semiclassical Rabi model with parity-time (PT) symmetry has a hidden $sl(2)$ symmetry and hence possesses quasi-exact solutions. These are located precisely at the exceptional points of the spectrum, the boundaries of the PT-symmetric phase. The corresponding constraints on the model parameters can be interpreted as a resonance relationship between the constant and periodic driving terms.

quant-ph↗

arXiv2025

Black holes immersed in polytropic scalar field gas

By implementing the concept of polytropic structures as a scalar field gas with a dark energy-like behavior, we obtain a static spherically symmetric black hole solution in the framework of general relativity. In this paper, we study the quasinormal modes, the greybody bound process, the shadow behaviors, and the sparsity of black holes with a surrounding polytropic scalar field gas. Using the Wentzel-Kramers-Brillouin approach, we evaluate the impact of a particular set of polytropic parameters $(ξ, A)$ with a fixed setting of the polytropic index $n$ on the oscillation frequency and damping rate of gravitational waves. The results show that the effect of the parameter $ξ$ is much less significant than that of the parameter $A$ on the gravitational waves oscillation frequency and damping rate. Furthermore, the analysis of the greybody factor bounds reveals special insight into the effect of certain parameters where the multipole moments $l$ and the polytropic index $n$ have similar effects, in contrast to the pair of polytropic parameters ($ξ,A$). On the other hand, exploring the sparsity of Hawking radiation is another task that provides a better understanding of the behaviour of the black hole solution. In this respect, the results show that the black hole behaves like blackbody radiation for a sufficiently large entropy. And for $ξ=A=0$, the relevant sparsity acts exactly like the Schwarzschild sparsity. These results provide an insight into the dynamics of black holes with a surrounding polytropic scalar field gas from the analysis of their quasinormal modes, greybody factors, shadow behaviors, energy emission rate and sparsity process. Constraints on the associated BH parameters, derived from the Event Horizon Telescope observations of M87* and Sgr A*, indicate that this black hole model stands as a compelling candidate for representing astrophysical black holes.

gr-qc↗

arXiv2024

Influences of modified Chaplygin dark fluid around a black hole

In this work, we study a static, spherically charged AdS black hole within a modified cosmological Chaplygin gas (MCG), adhering to the calorific equation of state, as a unified dark fluid model of dark energy and dark matter. We explore the influence of model parameters on several characteristics of the MCG-motivated charged AdS black hole (MCG-AdSBH), including the geodesic structure and some astrophysical phenomena such as null trajectories, shadow silhouettes, light deflection angles, and the determination of greybody bounds. We then discuss how the model parameters affect the Hawking temperature, remnant radius, and evaporation process of the MCG-AdSBH. Quasinormal modes are also investigated using the eikonal approximation method. Constraints on the MCG-AdSBH parameters are derived from EHT observations of M87* and Sgr A*, suggesting that MCG-AdSBH could be strong candidates for astrophysical black hole.

astro-ph.HE↗

arXiv2024

Scattering between orthogonally wobbling kinks

The resonant energy transfer mechanism, responsible for the presence of fractal patterns in the velocity diagrams of kink-antikink scattering, is analyzed for a family of two-component scalar field theory models, in which the kink solutions have two shape modes (one longitudinal and one orthogonal to the kink orbit), in addition to the zero mode, and in which energy redistribution can occur among these three discrete modes. We investigate the scattering between wobbling kinks whose orthogonal shape mode is initially excited, examining how the final velocities, amplitudes, and frequencies depend on the initial excitation amplitude. The differences that this model presents with respect to the $ϕ^4$ model and its novel properties are highlighted. This analysis sheds light on the intricate dynamics that arise from the interplay between multiple degrees of freedom in kink scattering processes, offering insights distinct from those observed in simpler models.

hep-th↗

arXiv2024

Exploring Supersymmetry: Interchangeability Between Jaynes-Cummings and Anti-Jaynes-Cummings Models

The supersymmetric connection that exists between the Jaynes-Cummings (JC) and anti-Jaynes Cummings (AJC) models in quantum optics is unraveled entirely. A new method is proposed to obtain the temporal evolution of observables in the AJC model using supersymmetric techniques, providing an overview of its dynamics and extending the calculation to full photon counting statistics. The approach is general and can be applied to determine the high-order cumulants given an initial state. The analysis reveals that engineering the collapse-revival behavior and the quantum properties of the interacting field is possible by controlling the initial state of the atomic subsystem and the corresponding atomic frequency in the AJC model. The substantial potential for applications of supersymmetric techniques in the context of photonic quantum technologies is thus demonstrated.

quant-ph↗

arXiv2024

On Some Quantum Correction to the Coulomb Potential in Generalized Uncertainty Principle Approach

Taking into account the importance of the unified theory of quantum mechanics and gravity, and the existence of a minimal length of the order of the Planck scale, we consider a modified Schrödinger equation resulting from a generalized uncertainty principle, which finds applications from the realm of quantum information to large-scale physics, with a quantum mechanically corrected gravitational interaction proposed very recently. As the resulting equation cannot be solved by common exact approaches, we propose a Bethe ansatz approach, which will be applied and whose results we will discuss, commenting on the analogy of the present study with some other interesting physical problems.

quant-ph↗

arXiv2023

Wobbling kinks and shape mode interactions in a coupled two-component $ϕ^4$ theory

The dynamics of a wobbling kink in a two-component coupled $ϕ^4$ scalar field theory (with an excited orthogonal shape mode) is addressed. For this purpose, the vibration spectrum of the second order small kink fluctuation is studied in order to find the corresponding vibration modes associated to the first (longitudinal) and second (orthogonal) field components. By means of this analysis, it was found that the number of possible shape modes depends on the value of the coupling constant. It is notable that when one of the orthogonal field shape modes is initially triggered, the unique shape mode of the longitudinal field is also activated. This coupling causes the kink to emit radiation with twice the frequency of excited mode in the first field component. Meanwhile, in the orthogonal channel we find radiation with two different frequencies: one is three times the frequency of the orthogonal wobbling mode and another is the sum of the frequencies of the longitudinal shape mode and the triggered mode. All the analytical results obtained in this study have been successfully contrasted with those obtained through numerical simulations.

nlin.PS↗