arXiv subjects

António Torres Manso

Publications and source records attributed to António Torres Manso.

9 recordsLinked to original sources

arXiv2026

The Lanczos potential in the Plebanski paradigm of gravity

We present a new Plebanski formulation of General Relativity. The key difference is that we work with a gauge vector field derived from the Lanczos potential of the Weyl tensor. We show that, on shell, the gauge vector field encodes all nontrivial gravitational degrees of freedom and, in a suitable Lorentz gauge, Bianchi identities ensure that this gauge vector field satisfies a source-free wave equation for Ricci-flat spacetimes. This description suggests new ways of interpreting the true geometrical degrees of freedom with applications in both classical and quantum gravity.

gr-qc↗

arXiv2026

Lukewarm inflation, primordial black holes and gravitational waves

We show that a secondary period of warm inflation, at temperatures parametrically below the GUT scale, may not only dilute any unwanted thermal relics formed after reheating but also significantly enhance the power spectrum of primordial curvature perturbations on small scales. The latter is nearly scale-invariant over an exponentially large range of comoving scales, resulting in a stochastic gravitational wave background with a nearly constant energy density over a broad range of frequencies and an associated population of sub-solar mass primordial black holes (PBHs). This scenario could, in particular, explain the NANOGrav signal if it persists at much higher frequencies with a comparable magnitude, up to a sharp cut-off, $f_{max}$. The associated PBH mass distribution may exhibit either a peak at a mass $M_*\propto f_{max}^{-2}$ or a broad plateaux above this mass threshold, depending on the spectral tilt. Moreover, in this scenario the NANOGrav signal is compatible with a significant fraction of dark matter in PBHs in the asteroid- and planetary-mass ranges.

hep-ph↗

arXiv2026

Lukewarm inflation and the QCD axion

We show that a late period of warm inflation, at temperatures just above the QCD scale, can dilute the abundance of the QCD axion produced by the misalignment mechanism, thus avoiding the need to fine-tune the initial misalignment angle in scenarios with an axion decay constant close to the GUT scale. We develop a concrete realization of this lukewarm inflation stage involving right-handed neutrinos in 0.1 - 1 GeV mass range and an associated scalar sector, showing that coherent axion oscillations are damped during this period. In this scenario, a previously generated large baryon asymmetry may also be diluted to yield the observed value, and lukewarm inflation is followed by an early-matter era dominated by the lightest right-handed neutrino, before it decays into Standard Model states. This model can be tested via changes to the number of relativistic species and the induced small-scale enhancements of the primordial curvature power spectrum, leading to primordial black holes and scalar-induced gravitational waves.

hep-ph↗

arXiv2026

Not So Minimal Warm Inflation

An axion-like inflaton coupled to non-Abelian gauge bosons provides a compelling microphysical framework for warm inflation. Starting even from cold initial conditions, in these systems, sphaleron heating may generate thermal friction sufficient to sustain finite temperatures throughout the inflationary epoch. Insisting on shift-symmetric potentials, in this work we revisit the viability of these scenarios under the designation of Minimal Warm Inflation. We examine both observational constraints and model-building limitations on models with a hierarchy between the decay constants appearing in the friction rate and in the inflaton potential. We conclude that the popular clockwork mechanism cannot generate the required hierarchy; however, partial-wave unitarity bounds admit effective descriptions that remain consistent with observations.

hep-ph↗

arXiv2026

Schwinger Current in de Sitter Space

We study classical background electric fields and the Schwinger effect in de Sitter space. We show that having a constant electric field in de Sitter requires the photon to have a tachyonic mass proportional to the Hubble scale. This has physical implications for the induced Schwinger current which affect its IR behaviour. To study this we recompute the Schwinger current in de Sitter space for charged fermions and minimally coupled scalars imposing a physically consistent renormalization condition. We find a finite and positive Schwinger current even in the massless limit. This is in contrast to previous calculations in the literature which found a negative IR divergence. We also obtain the first result of the Schwinger current for a non-minimally coupled scalar, including for a conformally coupled scalar which we find has very similar behaviour to the fermion current. Our results may have physical implications for both magnetogenesis and inflationary dark matter production.

hep-ph↗

arXiv2026

Classical constant electric fields and the Schwinger effect in de Sitter

We study constant classical electric fields and the Schwinger effect in de Sitter space, with potential implications for magnetogenesis and inflationary dark matter production. Treating the photon as a dynamical field, we show that sustaining a constant electric field in de Sitter requires a tachyonic photon mass of order the Hubble scale. This observation has physical implications, as it alters the infrared behaviour of the induced Schwinger current. Using an on-shell renormalization condition consistent with a tachyonic photon, we recompute the current for charged fermions and scalars, finding it to be finite and positive even in the massless limit of the charge carriers-contrary to earlier results predicting a puzzling negative IR divergence. For scalars, we include a non-minimal coupling to the Ricci curvature, enabling us to analyze the conformal limit, where the current closely matches that of charged fermions.

hep-ph↗

arXiv2025

Duality Symmetry and Anomaly for Gravitational Waves in Curved Spacetime

The vacuum Einstein equations admit a formulation closely analogous to the source-free Maxwell theory. In particular, the linearized equations exhibit an electric-magnetic duality symmetry. We develop a framework that makes this analogy manifest by explicitly identifying the electric and magnetic components of perturbative gravitational waves. Within this formulation, we show that duality rotations between these gravitoelectric and gravitomagnetic fields constitute a Noether symmetry of the linearized theory, and we derive the associated conserved current. The corresponding conserved charge encodes the difference in intensity between the right- and left-handed circularly polarized components of the gravitational wave - that is, between its self-dual and anti-self-dual parts. Remarkably, this conservation law remains valid even when the gravitational perturbations propagate on generic curved backgrounds. We then investigate whether this symmetry survives quantization. While the duality symmetry is preserved at the quantum level in flat spacetime, we find that it is anomalously broken in curved backgrounds. As a result, an imbalance between right- and left-handed gravitons could be excited from the vacuum. This effect represents a chiral anomaly for massless spin-two fields, generalizing known results for fermions and spin-one photon fields.

gr-qc↗

arXiv2023

Parity violating gravitational waves at the end of inflation

Inflaton-vector interactions of the type $ϕF\tilde{F}$ have provided interesting phenomenology to tackle some of current problems in cosmology, namely the vectors could constitute the dark matter component. It could also lead to possible signatures imprinted in a gravitational wave spectrum. Through this coupling, a rolling inflaton induces an exponential production of the transverse polarizations of the vector field, having a maximum at the end of inflation when the inflaton field velocity is at its maximum. These gauge particles, already parity asymmetric, will source the tensor components of the metric perturbations, leading to the production of parity violating gravitational waves. In this work we examine the vector particle production with an attempt to mimic its backreaction effects on the inflation evolution in the weak coupling regime. Furthermore, we fully integrate the gauge particle amplitudes spectrum during this production epoch, studying the behavior until the end of reheating. Finally, we calculate the gravitational wave spectrum solely relying on the vector mode WKB expansion in its regime of validity.

gr-qc↗

arXiv2021

Supersymmetric $ν$-Inflaton Dark Matter

We present the supersymmetric extension of the unified model for inflation and Dark Matter studied in Ref. arXiv:1811.02302. The scenario is based on the incomplete decay of the inflaton field into right-handed (s)neutrino pairs. By imposing a discrete interchange symmetry on the inflaton and the right-handed (s)neutrinos, one can ensure the stability of the inflaton field at the global minimum today, while still allowing it to partially decay and reheat the Universe after inflation. Compatibility of inflationary predictions, BBN bounds and obtaining the right DM abundance for the inflaton Dark Matter candidate typically requires large values of its coupling to the neutrino sector, and we use supersymmetry to protect the inflaton from potentially dangerous large radiative corrections which may spoil the required flatness of its potential. In addition, the inflaton will decay now predominatly into sneutrinos during reheating, which in turn give rise both to the thermal bath made of Standard Model particles, and inflaton particles. We have performed a through analyses of the reheating process following the evolution of all the partners involved, identifying the different regimes in the parameter space for the final Dark Matter candidate. This as usual can be a WIMP-like inflaton particle or an oscillating condensate, but we find a novel regime for a FIMP-like candidate.

hep-ph↗