We study classical background electric fields and the Schwinger effect in de Sitter space. We show that 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 that 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 $\textit{finite and positive}$ 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 for the Schwinger current of a non-minimally coupled scalar, including the conformally coupled case, which we find exhibits behaviour very similar to that of the fermion current. Our results may have physical implications for both magnetogenesis and inflationary dark matter production.

Spain

Mar Bastero-Gil

Portugal

Paulo B. Ferraz

António Torres Manso

Slovenia

Italy

Lorenzo Ubaldi

Roberto Vega-Morales

Schwinger current in de Sitter space * This work has been partially supported by Junta de Andalucía Projects P21-00199 and A-FQM-472-UGR20 (FEDER funds); SRA (10.13039/501100011033) and ERDF (PID2022-139466NB-C21) (R.V.M.); PID2022-140831NB-I00, funded by MICIU/AEI/10.13039/501100011033 and FEDER, UE (M.B.G., A.T.M.); by FCT CERN (10.54499/2024.00252.CERN) (M.B.G., A.T.M., P.F.); FCT Grant No. SFRH/BD/151475/2021 and 10.54499/SFRH/BD/151475/2021 (P.F.). LU is supported by the Slovenian Research Agency under research core funding No. P1-0035 and by research grants J1-60026 and J1-4389. This article is based upon work from COST Action COSMIC WISPers CA21106, supported by COST (European Cooperation in Science and Technology). R.V.M. thanks the Mainz Institute for Theoretical Physics (MITP) of the Cluster of Excellence PRISMA$^{+}$ (Project ID 390831469) for its hospitality and partial support during the completion of this work

We explore the microscopic origin of de Sitter entropy using a Lorentzian path-integral approach. We construct a Hilbert space whose states are associated with configurations of thin shells or end-of-the-world branes, with state overlaps defined by the gravitational path integral. By considering states which are indistinguishable to an observer, we find that the variance of microstate overlaps is dominated by Lorentzian wormhole topologies with conical singularities. Evaluating these overlaps, we recover the expected area law for the entropy, relating the dimension of the de Sitter Hilbert space to the area of the cosmological horizon. Extending this analysis to Schwarzschild-de Sitter spacetime, we show that both the cosmological and black hole horizons contribute to the total entropy. Along the way, we present an explicit construction of the shell and brane configurations and examine their compatibility with relevant consistency conditions, including the null energy condition.

Netherlands

Jan Boer

Switzerland

Diego Liska

Kamran Vaziri

Microstate counting from defects in de Sitter

We develop an analytic semiclassical effective model of Reissner-Nordström-de Sitter (RN-dS) discharge and evaporation by combining a spherically reduced two-dimensional description of the classical geometry with the pure Polyakov conformal sector for the radial energy flux. The framework captures the causal and thermodynamic structure of the static patch and yields closed adiabatic evolution equations for the mass and charge. With positive $$ \mathcal{F} $$ the outward Killing-energy flux from the black-hole horizon to the cosmological horizon, the chosen Unruh-de Sitter state gives $$ \mathcal{F} $$ = ($\textit{N}$ /48$\textit{π}$)( $$ {\kappa}_b^2-{\kappa}_c^2 $$ ), while the full mass evolution is $\textit{Ṁ}$ = $\textit{−}$ $$ \mathcal{F} $$ + $$ {\Phi}_b\dot{Q} $$ , with Φ = $\textit{Q}$/$\textit{r}$ . Along the sub-Nariai neutral Schwarzschild-de Sitter branch the ordering $\textit{κ}$ > $\textit{κ}$ implies monotonic mass loss. Standard Schwinger pair production provides the discharge channel. In the rapid-discharge regime, charged trajectories become effectively neutral on a timescale short compared with the Polyakov-driven mass-loss time and then follow the neutral SdS channel toward empty de Sitter space. The classical lukewarm locus $\textit{T}$ = $\textit{T}$ is only the nullcline of the Polyakov heat flux. Once discharge is included, the electromagnetic work term tilts the coupled effective vector field away from this curve. Thus the lukewarm locus is not an invariant trajectory of the coupled ($\textit{M}$, $\textit{Q}$) flow. When light charged species provide a rapid-discharge channel, the distinguished classical loci — cold/extremal, charged Nariai, ultracold, and lukewarm — are not attractors for controlled nondegenerate trajectories within this effective Polyakov-Schwinger model. These results give an adiabatically backreacted description of RN-dS evaporation in the specified two-dimensional regime and provide the semiclassical background for generalized-second-law monotonicity and conservative island/QES estimates.

United States

Damien Easson

The fate of Reissner-Nordström-de Sitter black holes: nonequilibrium discharge and evaporation

We study QED in de Sitter space as a minimal interacting gauge theory in which cosmological expansion directly competes with quantum dynamics. In cosmic time, the hopping redshifts as 1/$\textit{a}$($\textit{t}$) while the electric term grows as $\textit{g}$ $\textit{a}$($\textit{t}$), sweeping the spectrum through a moving narrow-gap region in the ($\textit{τ}$, $\textit{m}$) plane. Exact diagonalization shows that this defines a pseudo-critical line governing the loss of adiabaticity, excitation growth, and redshifted response. Using matrix-product states at a fixed mass, we separate the fixed-cutoff thermodynamic limit from the continuum extrapolation. The late-time dip survives in the infinite physical box size limit, and shifts to later $\textit{τ}$ as the lattice spacing goes to zero, with current data favoring $\textit{τ}$ ≈ 3.1, while the dip depth remains less controlled. For Gibbs initial states, the same mechanism produces an irreversibility front in the relative entropy that tracks the pseudo-critical line and is detectable via LOCC-accessible observables. These results identify de Sitter QED as a controlled setting for linking curved-space gauge dynamics, near-critical spectral structure, and operational irreversibility.

Kazuki Ikeda

Israel

Yaron Oz

Quantum information dynamics of QED2 in expanding de Sitter universe

For light and massless scalar fields, cosmological correlation functions suffer from infrared divergences and secular logarithms. Soft de Sitter Effective Theory (SdSET) has been proposed by Cohen and Green as the effective description of the non-trivial dynamics of long-wavelength modes $\textit{k}$ < $\textit{H}$ in de Sitter space, which is responsible for the infrared and late-time logarithms, and as a systematic extension of the stochastic approach. In this article, we construct SdSET in dimensional regularisation, including an initial-condition functional. We demonstrate by examples that renormalisation and matching works as for flat-space effective field theories. Adopting massless $\textit{κϕ}$ theory as the UV theory, we match the tree-level trispectrum and six-point function, and the one-loop power spectrum to SdSET, verifying explicitly that SdSET is the appropriate effective field theory for the quantum dynamics of superhorizon modes.

Germany

Martin Beneke

Patrick Hager

Andrea Sanfilippo

Renormalisation and matching of massless scalar correlation functions in Soft de Sitter Effective Theory

We investigate the dynamics of quantum-state texture (QST) for Dirac fields in Schwarzschild-de Sitter spacetime. As a quantum resource sensitive to phase cancellations, QST offers a unique perspective on how spacetime curvature reshapes interference patterns, distinct from entanglement or coherence. We find that the gravitational effects from both the black hole and cosmological horizons lead to a complex redistribution of texture. Specifically, QST between physically accessible modes decreases monotonically with increasing black hole mass, while correlations involving inaccessible modes exhibit non-monotonic behaviors due to competing horizon temperatures. Furthermore, we demonstrate that QST does not satisfy a simple conservation law; instead, it obeys a nonlinear constraint relation that evolves dynamically with the spacetime parameters. These findings establish QST as a sensitive diagnostic tool for probing the interface of quantum mechanics and gravity in multi-horizon environments.

China

Zhiming Huang

Quantum-state texture in Schwarzschild-de Sitter spacetime

We consider a de Sitter observer in his rest frame at late times who observes a particle slightly displaced from unstable equilibrium. Initially, the observer notices an axisymmetric and parity-violating deformation along the trajectory of the displaced particle of his cosmological horizon. On a time scale of order $\textit{ℓ}$, the de Sitter radius, the particle is nearly absorbed by the cosmological horizon and has been accelerated to an ultra-relativistic speed and thus is well approximated as a shock wave. In the shock wave limit, the observer sees an axisymmetric deformation of his horizon with parity restored, which we interpret as arising due to a particle from the complementary static patch. We comment on the holographic implications of this result and note that there is no need to extend the holographic screen of de Sitter spacetime beyond the empty static patch to account for this signal.

Willy Fischler

Hare Krishna

Sarah Racz

Seeing double: shock waves and the de Sitter horizon

We combine spectral- and split representations to factorize multi-loop momentum space diagrams, in the Schwinger-Keldysh formulation for cosmological correlators, with massive scalars in the loop. This allows us to extend the resummation of loop contributions from flat to de Sitter space. Furthermore, in our split representation the signal part of the correlators can be identified directly on the integrand level from the spectral function. We apply this to describe the non-perturbative flow of the EFT background and the cosmological collider signals in a large-$\textit{N}$ model.

Jonathan Gräfe

Ivo Sachs

Split representations and bubble resummation for massive de Sitter correlators

Hard scattering events in high-energy collisions produce highly virtual partons that subsequently fragment into collimated hadronic cascades. When such partonic showers evolve in a QCD medium, as in deep-inelastic scattering or heavy-ion collisions, the resulting multi-particle distributions encode information about the surrounding matter. Decades of theoretical developments have led to a consistent and order-by-order improvable perturbative description of the shower. This description needs, however, the non-perturbative input that encodes the structure of the hadronic matter. The determination of such input remains challenging within conventional computational approaches, thereby limiting the applicability of the approach. In this work, we develop a framework that employs quantum simulation techniques to compute multi-particle processes in such environments by mapping partonic cross-sections to quantum circuits. As benchmarks, we analyze dipole formation and the QCD antenna radiation pattern at leading order in the strong coupling constant, comparing the results with analytic estimates in simplified limits. The quantum circuit formulation here introduced naturally extends to higher perturbative orders and enables amplitude-level computations in complex matter backgrounds. This provides a systematic foundation for applying quantum information science methods to study multi-particle dynamics in QCD media.

João Barata

Meijian Li

Wenyang Qian

Carlos Salgado

João Silva

Quantum simulating multi-particle processes in high energy nuclear physics: dijet production and color (de)coherence

This article presents a detailed study of an Ayón–Beato–García–de Sitter black hole surrounded by a quintessential field and cloud of strings. We begin by observing the metric and examining how different parameter choices impact the spacetime structure. Specifically, we study scenarios with positive (1/2) $$\Lambda $$ and changing other parameters. We then study particle geodesic motion, examining the effect of the modified spacetime on neighboring massive and massless particles, where we also discuss the stability for timelike geodesics. We then calculate the expression for the energy corresponding to circular orbits, examine the Lyapunov exponent and geodesic precession frequency for various values, and demonstrate how different parameters impact the evolution. Lastly, we utilize the null geodesics of photons to investigate the gravitational lensing properties of a black hole enveloped by quintessence and a cloud of strings by employing finite-distance formalism. The overall effort will allow us to understand the dynamical and stability properties of spacetime with small perturbations. In conclusion, a comprehensive study of the impacts of de-Sitter black holes on particle dynamics and motion in curved geometry has been provided in this article by considering additional fields.

Saudi Arabia

I. Shakir

Pakistan

Z. Yousaf

A. Farhat

Türkiye

I. Siddique

Azerbaijan

M. Bhatti

Geodesic dynamics of an Ayón–Beato–García–de Sitter black hole in the presence of quintessence and a cloud of strings