arXiv subjects

Pedro Bargueño

Publications and source records attributed to Pedro Bargueño.

At least 19 recordsLinked to original sources

arXiv2026

Homogeneous and Isotropic Linearized Gravity as a Caldeira--Leggett System

We show that the homogeneous and isotropic sector of linearized gravity coupled to arbitrary additional degrees of freedom takes the Caldeira-Leggett form, provided their action contains no metric time derivatives at second order in perturbations. These additional degrees of freedom constitute the model's harmonic reservoir. Eliminating them yields a generalized Langevin equation for the metric perturbation, with their influence condensed in the reservoir's spectral density. This equivalence also yields a natural setting for reduced quantization of the perturbation and stochastic gravitational dynamics. We analyze the resulting dynamics with Laplace methods, extending results presented in other open-system settings.

gr-qc↗

arXiv2026

Logarithmic corrections to black hole entropy from minimum-assumptions discretization

We introduce here a general model, under agnostic and minimum assumptions, to uniquely find the entropy area law with a corresponding fixed logarithmic correction term. In this approach, the horizon is discretized into generic Planck-scale cells representing coarse-grained indistinguishable geometric structures, and it is just the statistical combinatorial counting that determines the form of the entropy terms. We highlight the role of the assumptions and their comparison with known models providing fixed logarithmic contributions to the entropy.

gr-qc↗

arXiv2026

Evading Cauchy horizon excision in scalarized regular black holes

Spontaneous scalarization provides a dynamical mechanism to evade the no-hair paradigm, but it has been argued to generically eliminate the Cauchy horizon in charged black holes. We show that this obstruction is not universal, but instead follows from the sign-definite structure of the Einstein-Maxwell source term. Within the $P$-dual formulation of nonlinear electrodynamics, we derive a general condition under which the effective scalar source changes sign between the horizons, allowing the integral constraint to be satisfied without destroying the Cauchy horizon. This establishes that the fate of the Cauchy horizon depends on the electromagnetic coupling and identifies candidate theories where scalarized horizons may persist. The resulting framework opens the possibility of studying scalarization in the interhorizon region and its interplay with mass inflation.

gr-qc↗

arXiv2026

Horizon Microstructure Thermodynamics in AdS Black Holes: Smarr-Consistent Excitation Enthalpy

In this work we formulate a horizon-microstructure description of four-dimensional AdS black holes in which a horizon of area $A$ is resolved into $\mathcal{N}=A/a_p$ microscopic sites and $N$ occupied horizon sites. The central result is that the combinatorics of this partially occupied horizon sector yields the entropy directly: in the finite-filling regime the leading term is proportional to the area, and the maximal-entropy filling reproduces the Bekenstein--Hawking law with $a_p=4\ln 2\ \ell_{p}^{2}$. Subleading corrections include a subtractive logarithmic term and an inverse-area expansion. We then show that this partially occupied regime admits a thermodynamic justification from an extended first law with chemical potential $μ$, a Smarr-consistent excitation enthalpy $δM(A,P,N)$, and an AdS control parameter $u=PS$. In this interpretation, the combinatorics provides the dominant horizon entropy, while the thermodynamic sector supplies a dressing that selects the equilibrium filling and assigns a finite excitation cost to departures from a reference partially occupied configuration.

hep-th↗

arXiv2026

Ultracold Amplification Proposal for Parity Violation in Chiral Molecules

We propose a theoretical mechanism to indirectly detect the small parity-violating energy difference (PVED) between chiral enantiomers through a macroscopic enantiomeric excess observed in an ultracold gas. We consider that chiral molecules are formed resonantly via ultracold collisions of achiral diatomic molecules, with PVED inducing a slight asymmetry in the resonance energies of right- and left-handed configurations. After formation, chiral molecules evolve within a Bose-Einstein condensate (BEC), incorporating nonlinear interactions, tunneling between enantiomeric states, intrinsic PVED, and thermal conversion rates. These collective dynamics enable amplification of the microscopic bias into a global population imbalance. Using coupled rate equations, we show that, under realistic regimes, a complete enantiomeric excess can be achieved even for extremely small intrinsic asymmetries. We illustrate the model with concrete examples (HSOH, H$_2$Se$_2$, H$_2$Te$_2$), predicting observable enantiomeric excesses under plausible experimental conditions. We also consider non-PVED effects that could be amplified under the proposed mechanism, including electric and magnetic fields as well as thermal fluctuations, the latter being illustrated through the aforementioned molecular examples. Overall, our results suggest that ultracold physics could provide a new pathway to probe molecular parity violation, a fundamental weak effect that remains experimentally undetected.

cond-mat.quant-gas↗

arXiv2026

Penrose-Rindler equation and horizon thermodynamics of stationary black holes

Black holes are the natural arena for exploring the interplay between gravity and thermodynamics. Although the association between black hole mechanics and black hole thermodynamics is well established, the comprehensive geometric formulation of thermodynamic variables deserves further investigation. In this work, both Newman-Penrose (NP) and Geroch-Held-Penrose (GHP) formalisms are considered within the framework of horizon thermodynamics. We show that the NP formalism reformulates the horizon condition as the Penrose-Rindler equation. In this context, a Smarr-like formula for stationary black holes is recovered from the Penrose-Rindler equation reinterpreted as a horizon equilibrium of pressures, which includes a pressure associated with the horizon rotation. A complete geometric reformulation of this reinterpretation of the Penrose-Rindler equation evaluated at the horizon is developed within the GHP formalism. The GHP approach further inspires the introduction of the horizon-averaged matter pressure and its conjugate volume, thereby enabling a quasilocal realization of the Smarr-like formula for stationary black holes. This geometric formulation clarifies the connection between horizon dynamics and thermodynamics and offers a unified setting for extending black hole thermodynamics beyond spherical symmetry.

gr-qc↗

arXiv2025

Traversable ghost wormholes

Ghost stars are compact configurations characterized by an arbitrarily small total mass. Such objects require regions of negative energy density -a condition typically regarded as unphysical within the context of conventional stellar models. Nevertheless, negative energy densities arise naturally in traversable wormhole geometries, where the violation of the null energy condition is essential to sustain the flaring-out behavior at the throat. This connection suggests that ghost-like configurations may find a natural realization within wormhole physics. In this work, we investigate the existence of ghost configurations by analyzing their associated Hawking mass. Although in spherical symmetry the Misner and Hawking masses are known to coincide, we show that when the ghost condition is extended beyond spherical symmetry and applied to the Hawking mass, it faces topological obstructions that hinder its straightforward realization. As a concrete example, we demonstrate that a Casimir-like traversable wormhole can be naturally constructed within this framework. Finally, to illustrate the properties of the resulting geometry, we analyze its Penrose-Carter diagram.

gr-qc↗

arXiv2025

The Universe in four letters: a bedtime history

One evening, a father tells his three daughters, Lucía, Inés, and Ana, a bedtime story unlike any other. It is a tale of four silent architects ($c$, $\hbar$, $G$, and $Λ$) whose presence or absence shapes the very fabric of reality. By imagining worlds where each constant is removed, they explore realms from the quantum gravity of the Planck scale to the stretching cosmos of de Sitter space, from the mass of the observable Universe to the surprising link with the proton's whisper. Woven with the insights of great scientists, this narrative reveals how these fundamental constants write the story of everything, from the smallest particle to the vast cosmic horizon, suggesting a beautiful and hidden unity in the architecture of our world.

physics.pop-ph↗

arXiv2025

General Framework for the Spontaneous Scalarization of Regular Black Holes

We investigate the spontaneous scalarization of generic, static, and spherically symmetric regular black holes supported by nonlinear electrodynamics. Starting from an arbitrary seed metric, we employ the P-dual formalism to reconstruct the electromagnetic sector and subsequently couple a real scalar field nonminimally. As a worked example, we apply the framework to the regular Balart-Vagenas black hole, showing that scalarized and scalar-free branches can coexist in a region where the scalarized configurations are entropically preferred. We further assess possible observational imprints, finding percent-level deviations in both the shadow size and the fundamental scalar quasi-normal modes ($< 10\%$ for small charge-to-mass ratios), indicating that current electromagnetic and gravitational-wave observations do not rule out these solutions. Our construction thus provides a general route to explore scalarization on top of nonlinear-electrodynamics-supported spacetimes, extending beyond specific Reissner-Nordström-like cases.

gr-qc↗

arXiv2025

Exact Classicalization of N-Level Quantum Systems Interacting with a Bath: Theory and Applications

In this manuscript, starting from a five-step algorithmic procedure for exactly classicalizing the dynamics of N-level quantum systems, we incorporate a classical bath of harmonic oscillators to model environmental interactions. Using the geometry of complex projective spaces CP(N-1) and a Langevin formalism, we obtain N-1 Hamilton's equations which encode both the quantum system and the bath degrees of freedom, representing a generalization of the Caldeira-Legget model in a complex projective space. We demonstrate the efficacy of the method by applying it to two paradigmatic systems: a two-qubit system in CP(3) under entangling interactions, reproducing quantum observables such as state populations, quaternionic population differences and concurrence, and the seven-state Fenna-Matthews-Olson (FMO) complex in CP(6), reproducing state populations in the picosecond timescale.

quant-ph↗

arXiv2025

Doubly regular black holes

In addition to curvature singularities, electrovacuum black holes in general relativity exhibit thermodynamic singularities. These so-called Davies' points occur at nonextremal values of charge and spin where the heat capacity diverges and may indicate a type of theoretical incompleteness. The thermodynamic regularity of several families of static, asymptotically flat spacetimes with bounded curvature invariants is examined using a theory-agnostic framework, showing that, while they may be regular in physical space, they are generally not in phase space. The inclusion of angular momentum, via the Newman-Janis algorithm, makes the set of such "doubly regular" objects especially restrictive. It is argued that, if thermodynamic regularity is to be considered a desirable property for an astrophysical black hole, these considerations could be used to narrow down the viable pool of regular extensions to the Kerr-Newman metric.

gr-qc↗

arXiv2025

Physical reinterpretation of heat capacity discontinuities for static black holes

A generic characteristic of self-gravitating systems is that they have a negative heat capacity. An important example of this behavior is given by the Schwarzschild black hole. The case of charged and rotating black holes is even more interesting since a change of sign of the specific heat takes place through an infinite discontinuity. This has been usually associated with a black hole thermodynamic phase transition appearing at the points where the heat capacity diverges, the so-called Davies points. This aspect of black hole thermodynamics has been addressed from different perspectives, motivating different interpretations since its discovery in the 1970s. In this paper, a physical reinterpretation of the heat capacity is provided for spherically symmetric and static black holes. Our analysis is partially based on a reformulation of the black hole heat capacity using the Newman-Penrose formalism. The application to the Reissner-Nordström-de Sitter black hole case reveals a clear physical interpretation of the Newman-Penrose scalars evaluated at the event horizon. This allows us to write the heat capacity as a balance of pressures defined at the horizon, in particular, a matter pressure (coming from the energy-momentum tensor) and a thermal pressure (coming from the holographic energy equipartition of the horizon). The Davies point is identified with the point where the Komar thermal energy density matches the matter pressure at the horizon. We also compare the black hole case with the case of self-gravitating objects and their corresponding thermal evolutions. We conclude that the heat capacity of black holes and self-gravitating systems can be understood qualitatively in similar terms.

gr-qc↗

arXiv2025

An Exact Five-Step Method for Classicalizing N-level Quantum Systems: Application to Quantum Entanglement Dynamics

In this manuscript, we present a general and exact method for classicalizing the dynamics of any $N$-level quantum system, transforming quantum evolution into a classical-like framework using the geometry of complex projective spaces $\mathbb{CP}^{N-1}$. The method can be expressed as five-step algorithmic procedure to derive a classical Hamiltonian and a symplectic structure for the Poisson brackets, yielding $N-1$ Hamilton's equations that precisely replicate the quantum dynamics, including complex phenomena like entanglement. We demonstrate the method's efficacy by classicalizing two interacting qubits in $\mathbb{CP}^3$, exactly reproducing quantum observables such as quantum probabilities, quaternionic population differences and the concurrence, capturing entanglement dynamics via a classical analog.

quant-ph↗

arXiv2025

Chiral environment effects on the dynamics of a central chiral molecule

In this work, we develop a system {\it plus} environment approach for interacting chiral molecules under a quantum-classical description of the spin-spin model using a Caldeira-Leggett-like coupling. After presenting the interacting model, we show that a long-ranged parity-nonconserving interaction, encoded within a non-linear Schrödinger equation, produces an energy difference between the two enantiomers of the central chiral molecule when it interacts with a chiral environment. Three examples of such interactions are considered, with particular focus on $Z^0$-photon vacuum polarization. Finally, we reveal a {\it chirality transmission effect} phenomenon, where the time-averaged population difference of the central molecule is amplified when the chiral asymmetry of the environment is considered.

quant-ph↗

arXiv2025

The Smarr formula within the Geroch-Held-Penrose formalism

The connection between classical thermodynamics and black hole horizons is a fundamental topic in gravitational physics, offering a potential pathway to understanding quantum aspects of gravity. However, while black hole mechanics exhibits well-known thermodynamic parallels, a rigorous geometric interpretation of thermodynamic variables directly from the field equations warrants further research. In this manuscript, we present a thermodynamic formulation of the field equations through the decomposition of the Riemann tensor, employing the Geroch-Held-Penrose (GHP) formalism, to clarify a strong correspondence between black hole thermodynamic variables and geometrical quantities derived from horizon geometry. Our analysis reveals an intrinsic connection between the Penrose and Rindler $K$-curvature and the Smarr relation, motivating a revised definition of both trapping gravity and black hole internal energy. Additionally, we derive through this GHP formalism the Smarr formula for the Reissner-Nördstrom black hole cointained in an AdS spacetime and we explore the implications of this relationship for black holes with exotic topologies and in the context of extended theories, exemplified by $f(R)$ gravity. These findings suggest a deeper geometrical basis for black hole thermodynamics, potentially advancing our understanding of gravitational energy, horizon entropy, and their significance within quantum gravity frameworks.

gr-qc↗

arXiv2025

On the role of true and false chirality in producing parity violating energy differences

In this work we tackle the problem of showing which type of influences can lift the degeneracy between truly and falsely chiral systems, showing that only when both systems and influences are both truly (falsely) chiral, a parity violating energy difference between left- and right-handed systems can be produced. In particular, after considering the enantiomers of a chiral molecule as paradigmatic truly chiral systems, we rigorously show, under a quantum field theoretically approach, that only a truly chiral influence such as the $Z^{0}$-mediated electroweak interaction can lift the degeneracy between enantiomers. On the contrary, we explicitly show that a falsely chiral influence, such as an axion-mediated interaction in chiral molecules, can not lift the aforementioned degeneracy. These results extend Barron's seminal ideas [L. D. Barron, True and false chirality and parity violation, Chem. Phys. Lett {\bf 123}, 423 (1986)] to a quantum field theory-based approach.

quant-ph↗

arXiv2025

Dissipative evolution of a two-level system through a geometry-based classical mapping

In this manuscript, we introduce a geometry-based formalism to obtain a Meyer-Miller-Stock-Thoss mapping in order to study the dynamics of both isolated and interacting two-level systems. After showing the description of the isolated case using canonically conjugate variables, we implement an interaction model by bilinearly coupling the corresponding population differences {\it à la} Caldeira-Leggett, showing that the dynamics behave as a Gross-Pitaevskii-like one. We also find a transition between oscillatory and tunneling-suppressed dynamics that can be observed by varying the coupling constant. After extending our model to the {\it system plus environment} case, where the environment is considered as a collection of two-level systems, we show tunneling-suppressed dynamics in the strong coupling limit and the usual damping effect similar to that of a harmonic oscillator bath in the weak coupling one. Finally, we observe that our interacting model turns an isolated symmetric two-level system into an environment-assisted asymmetric one.

quant-ph↗

arXiv2024

Static and spherically symmetric vacuum spacetimes with non-expanding principal null directions in $f(R)$ gravity

In this work we characterize all the static and spherically symmetric vacuum solutions in $f(R)$ gravity when the principal null directions of the Weyl tensor are non-expanding. In contrast to General Relativity, we show that the Nariai spacetime is not the only solution of this type when general $f(R)$ theories are considered. In particular, we find four different solutions for the non-constant Ricci scalar case, all of them corresponding to the same theory, given by $f(R) = r_0^{-1}\left\lvert R-3/r_0^2\right\rvert^{1/2}$, where $r_0$ is a non-null constant. Finally, we briefly present some geometric properties of these solutions.

gr-qc↗