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 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.

United States

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.

Germany

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.

Switzerland

João Barata

Meijian Li

China

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

Taking into account the Green-Schwarz anomaly counterterm in R-symmetry gauged $\textit{N}$ = (1$\textit{,}$ 0) supergravity in six dimensions, and the associated modification in the Maxwell kinetic term and potential, the theory admits half-supersymmetric Mink × $\textit{S}$ and non-supersymmetric dS × $\textit{S}$ solutions with or without a monopole on $\textit{S}$ . The monopole charge and the anomaly coefficients play key roles in the vacuum structure and a diagonal gauging in which an admixture of an external $\textit{U}$(1) with the R-symmetry $\textit{U}$(1) is needed for the de Sitter solutions to exist. We determine the full Kaluza-Klein spectrum for both vacua. The spectrum is unitary in the Minkowski case but in the case of de Sitter vacuum, the dilaton and the breathing mode are tachyonic. We show that turning on small perturbations of the tachyonic modes around dS × $\textit{S}$ with a monopole on $\textit{S}$ triggers a flow evolving towards Mink × $\textit{S}$ with the minimal potential energy. The diagonally gauged model also supports dS × $\textit{S}$ solution which avoids tachyons for certain values of the flux on dS . We also find nonsupersymmetric (A)dS × $\textit{S}$ solutions, when we turn on a flux associated with external $\textit{U}$(1) gauge field only, and show that they support the phenomenon of scale separation under certain conditions on anomaly coefficients.

Xu Guo

Yi Pang

Ergin Sezgin

4D de Sitter from 6D gauged supergravity with Green-Schwarz counterterm

Recent developments have yielded significant progress towards systematically understanding loop corrections to de Sitter (dS) correlators. In close analogy with physics in Anti-de Sitter (AdS), large logarithms can result from loops that can be interpreted as corrections to the dimensions of operators. In contrast with AdS, these dimensions are not manifestly real. This implies that the theoretical constraints on the associated correlators are less transparent, particularly in the presence of light scalars. In this paper, we revisit these issues by performing and comparing calculations using the spectral representation approach and the Soft de Sitter Effective Theory (SdSET). We review the general arguments that yield positivity constraints on dS correlators from both perspectives. Our particular focus will be on vertex operators for compact scalar fields, since this case introduces novel complications. We will explain how to resolve apparent disagreements between different techniques for calculating the anomalous dimensions for principal series fields coupled to these vertex operators. Along the way, we will offer new proofs of positivity of the anomalous dimensions, and explain why renormalization group flow associated with these anomalous dimensions in SdSET is the same as resumming bubble diagrams in the spectral representation.

Priyesh Chakraborty

Timothy Cohen

Daniel Green

Yiwen Huang

A compact story of positivity in de Sitter

We numerically solve the conjectured quantum spectral curve for strings on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>×</mo></mrow><msup><mrow><mi mathvariant="normal">S</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>×</mo><mtext> </mtext><msup><mrow><mi mathvariant="normal">T</mi></mrow><mrow><mn>4</mn></mrow></msup></mrow></math> with Ramond-Ramond charge from weak to strong coupling. At strong coupling, the spectrum organizes into flat-space string mass levels with universal square-root scaling in the string tension at leading order, and additional Kaluza-Klein fine-splitting at subleading order. At weak coupling, the energies are determined by a nearest-neighbor Bethe Ansatz, with universal subleading corrections that are suppressed at large volume.

Sweden

United Kingdom

Simon Ekhammar

Nikolay Gromov

Bogdan Stefański

Charles Thull

Short Strings in Three-Dimensional Anti–de Sitter Space: From Weak to Strong Coupling

We present remarkably simple covariant expressions for the graviton and ghost propagators in anti–de Sitter (AdS) spacetime valid in any spacetime dimension. In gravity there is a two-parameter family of covariant gauge-fixing conditions and the simplification occurs for a special choice of these parameters. In this gauge the graviton propagator satisfies <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mo>∇</mo></mrow><mrow><mi>μ</mi></mrow></msup><mi>μ</mi><msup><mrow><mo>∇</mo></mrow><mrow><mi>ν</mi></mrow></msup><mi>μ</mi><msub><mrow><mi>G</mi></mrow><mrow><mi>μ</mi><mi>ν</mi><mo>,</mo><msup><mrow><mi>α</mi></mrow><mrow><mo>′</mo></mrow></msup><msup><mrow><mi>β</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></msub><mo stretchy="false">(</mo><mi>μ</mi><mo stretchy="false">)</mo><mo>=</mo><mn>0</mn></mrow></math>, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi></math> is the geodesic distance between two points, and this condition implies an improved infrared behavior. This gauge choice is not possible in flat spacetime.

Radu N. Moga

Kostas Skenderis

Remarkably simple covariant graviton propagator in anti–de Sitter spacetime

Alexander Kamenshchik

Polina Petriakova

Erratum: IR finite correlation functions in de Sitter space, a smooth massless limit, and an autonomous equation