arXiv subjects

F. Javier Marañón-González

Publications and source records attributed to F. Javier Marañón-González.

5 recordsLinked to original sources

arXiv2026

Black-hole evaporation from the semiclassical Einstein equations in 3+1 dimensions

We solve the semiclassical Einstein equations for an evaporating Schwarzschild black hole in closed form, obtaining its backreacted geometry in 3+1 dimensions. This is achieved by a reformulation of the Hadamard renormalization prescription, which admits explicit stress-energy tensors for scalar quantum fields in 3+1-dimensional curved spacetimes without the standard mode-sum construction. The Unruh-like states we construct reproduce the Hawking flux at future null infinity and the associated ingoing negative-energy flux at the horizon, yielding the first analytical quasi-stationary solution describing black-hole evaporation in four-dimensional semiclassical gravity. The resulting geometry exhibits a timelike apparent horizon, providing a new analytical setting to study the causal structure of black-hole evaporation and its connection with the information-loss issue. Our results open a new route to semiclassical backreaction in four dimensions, extending the level of analytical control previously available only in two-dimensional effective models.

gr-qc↗

arXiv2026

Singularity resolution and unitarity in two-dimensional dilaton black holes with negative central charge

We study a one-loop corrected extension of the classical Callan-Giddings-Harvey-Strominger (CGHS) model of two-dimensional dilaton gravity. The effective action combines the non-local Polyakov action for matter fluctuations, a Polyakov-type term built from an auxiliary flat metric that implements Strominger's mechanism for the Faddeev-Popov reparametrization ghosts, and a local counterterm that simultaneously preserves the flatness of the auxiliary metric, ensures exact solvability, and keeps two-dimensional Minkowski spacetime as an exact solution of the backreacted equations. In the regime of negative total central charge, the classical curvature singularity is resolved and gives way to asymptotically flat regions inside the horizon. The exterior Hawking flux is preserved and turns out to be correlated with an internal radiation flux supported on null surfaces that approach null infinity from beyond the horizon; this internal flux, in particular, presents a short interval of negative values. These correlations point to the preservation of unitarity, provided the relevant null surfaces remain at a finite affine distance from the collapsing matter trajectory. Within the present formulation, however, a fully consistent energy balance cannot yet be established. We discuss possible strategies to overcome this issue.

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arXiv2025

Singularity resolution in spherically reduced 2D semiclassical gravity with negative central charge

We analyze the semiclassical Schwarzschild geometry in the Boulware quantum state in the framework of two-dimensional (2D) dilaton gravity. The classical model is defined by the spherical reduction of Einstein's gravity sourced with conformal scalar fields. The expectation value of the stress-energy tensor in the Boulware state is singular at the classical horizon of the Schwarzschild spacetime, but when backreaction effects are considered, previous results have shown that the 2D geometry is horizonless and described by a non-symmetric wormhole with a curvature singularity on the other side of the throat. In this work we show that reversing the sign of the central charge of the conformal matter removes the curvature singularity of the 2D backreacted geometry, which happens to be horizonless and asymptotically flat. This result is consistent with a similar analysis recently performed for the CGHS model. We also argue the physical significance of negative central charges in conformal anomalies from a four-dimensional perspective.

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arXiv2024

Adiabatic regularization for massive and massless spin-$1$ fields

The adiabatic regularization method is likely the most direct and intuitive renormalization scheme for FLRW cosmologies. The method requires one to start with a nonvanishing mass, but massless theories can be studied by taking the massless limit at the end of the calculations. For spin-$1$, however, this limit changes the number of degrees of freedom, so it cannot be performed directly. In this work, we show a direct approach that begins with the canonical quantization of the physical degrees of freedom of a massive Proca field. We give the details of the construction and show that, in the massless limit, the renormalized stress-energy tensor of the Proca field is closely related to that of a minimally coupled scalar field. For completeness and pedagogical purposes, we also include a brief orientation to the adiabatic method for scalar fields. The construction of the adiabatic subtractions in momentum space is compared with that of the BPHZ method for renormalizing Feynman loop integrals.

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arXiv2023

Adiabatic regularization for spin-$1$ fields

We analyze the adiabatic regularization scheme to renormalize Proca fields in a four-dimensional Friedmann-Lemaître-Robertson-Walker spacetime. The adiabatic method is well established for scalar and spin-$1/2$ fields, but is not yet fully understood for spin-$1$ fields. We give the details of the construction and show that, in the massless limit, the renormalized stress-energy tensor of the Proca field is closely related to that of a minimally coupled scalar field. Our result is in full agreement with other approaches, based on the effective action, which also show a discontinuity in the massless limit. The scalar field can be naturally regarded as a Stüeckelberg-type field. We also test the consistency of our results in de Sitter space.

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