We investigate the quasinormal modes (QNMs) and greybody factors of dilaton–Euler–Heisenberg (dEH) de Sitter (dS) black holes in string-inspired Euler–Heisenberg gravity. Since the axial gravitational and electromagnetic perturbations decouple, we analyze them independently. By applying the asymptotic iteration method (AIM) together with a sixth-order WKB approximation, we compute the quasinormal frequencies and find excellent agreement between the two methods. We also find that the QNM spectra depend sensitively on the magnetic charge $Q_{\text{m}}$ , cosmological constant Λ, and nonlinear coupling $\epsilon$ , with a notable topological anomaly appearing in the electromagnetic frequency trajectories. Additionally, larger values of $Q_{\text{m}}$ or the multipole number $\textit{l}$ generally suppress wave transmission, while the electromagnetic sector with $\epsilon=1$ exhibits an anomalous response.

Ming Zhang

Guo-Xin Chen

China

Xufen Zhang

Cheng-Fu Feng

Sheng-Yuan Li

Rui-Hong Yue

De-Cheng Zou

Quasinormal frequencies and greybody factors for axial perturbations of dilaton–Euler–Heisenberg de Sitter black holes * This research was supported by the National Natural Science Foundation of China (NNSFC) (12365009), the Natural Science Basic Research Program of Shaanxi Province (2026JC-YBMS-0083), and the Jiangxi Provincial Natural Science Foundation (20262BAC240347)

We employ machine learning techniques to estimate the amount of information contained in three Krylov-space observables: the spread complexity <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo></mrow></math>, the discrete Wigner negativity <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo></math>, and the normalized negativity <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo><mo>=</mo><mi>N</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo><mo>/</mo><mo stretchy="false">|</mo><mi>S</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo><mo stretchy="false">|</mo></math>, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo></math> is the survival amplitude. We study thermofield-double evolutions on Gaussian unitary ensemble (GUE), Gaussian orthogonal ensemble (GOE), and Poisson spectra, and on the integrable <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>L</mi><mo stretchy="false">(</mo><mn>2</mn><mo>,</mo><mi>R</mi><mo stretchy="false">)</mo></math> Krylov chain of a two-dimensional conformal field theory (CFT) primary with Lanczos coefficients <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>n</mi></msub><mo>=</mo><mi>α</mi><msqrt><mrow><mi>n</mi><mo stretchy="false">(</mo><mi>n</mi><mo>+</mo><mn>2</mn><mi>h</mi><mo>−</mo><mn>1</mn><mo stretchy="false">)</mo></mrow></msqrt></math>. To introduce chaos we add a GUE random matrix to the integrable chain, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>H</mi><mo stretchy="false">(</mo><mi>ϵ</mi><mo stretchy="false">)</mo><mo>=</mo><msub><mrow><mi>H</mi></mrow><mrow><mi>S</mi><mi>L</mi><mo stretchy="false">(</mo><mn>2</mn><mo>,</mo><mi>R</mi><mo stretchy="false">)</mo></mrow></msub><mo>+</mo><mi>ϵ</mi><msub><mrow><mi>R</mi></mrow><mrow><mn>0</mn></mrow></msub><msub><mrow><mi>W</mi></mrow><mrow><mi>GUE</mi></mrow></msub></mrow></math>, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mn>0</mn></msub></math> is its spectral half-width. Either <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo></math> or <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo></math> alone determines the thermofield temperature, with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>R</mi><mn>2</mn></msup><mo>≃</mo><mn>0.999</mn></math>. However, neither can reconstruct the fine structure of the spectral form factor. In the integrable sector all three observables carry the same information. When we turn on chaos an asymmetry appears: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi></math> predicts <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi></math> better than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi></math> predicts <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi></math>. This gap grows from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>+</mo><mn>0.33</mn></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>+</mo><mn>0.77</mn></math>, while the same gap for the raw negativity decays to zero. Thus we conclude the extra information comes from the survival amplitude and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo></math> carries it while <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo></math> can still be recovered from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi><mo stretchy="false">(</mo><mi>t</mi><mo stretchy="false">)</mo></math>. We derive a lower bound on this gap, set by the fraction of the variance of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>χ</mi></math> that comes from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>.

India

Ritam Basu

Information content of Krylov observables: A machine learning approach

High-energy <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi></math> collisions, realizable as an operational mode of future lepton linear colliders such as the ILC and CLIC, provide a promising environment to probe extended Higgs sectors. We investigate the sensitivity of such colliders to doubly charged Higgs bosons within the 2-Higgs doublet model with type-II seesaw (2HDMcT). Focusing on the three-body production channels <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi><mo stretchy="false">→</mo><msup><mi>H</mi><mrow><mo>±</mo><mo>±</mo></mrow></msup><msubsup><mi>H</mi><mn>1</mn><mo>∓</mo></msubsup><msubsup><mi>H</mi><mn>1</mn><mo>∓</mo></msubsup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi><mo stretchy="false">→</mo><msup><mi>H</mi><mrow><mo>±</mo><mo>±</mo></mrow></msup><msubsup><mi>H</mi><mn>1</mn><mo>∓</mo></msubsup><msup><mi>W</mi><mo>∓</mo></msup></math>, we perform a parameter space scan consistent with theoretical constraints as well as current collider, flavor, and electroweak precision observables (EWPOs). We show that <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi></math> collisions can rival the discovery potential of the conventional <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></math> mode for probing doubly charged Higgs bosons through a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>4</mn><mo>ℓ</mo><mo>+</mo><msub><menclose notation="updiagonalstrike"><mi>E</mi></menclose><mi>T</mi></msub></math> signature (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>ℓ</mo><mo>=</mo><mi>e</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>μ</mi></mrow></math>). Despite the reduced effective luminosity resulting from the photon spectrum, the significantly enhanced production cross sections, exceeding those in electron-positron collisions by more than one order of magnitude, compensate for this limitation. By performing a detailed signal-to-background analysis at center-of-mass energies of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>830</mn></math> and 1245 GeV, we demonstrate that a discovery significance at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>5</mn><mi>σ</mi></math> level can be achieved for viable benchmark points (BPs).

France

Abdesslam Arhrib

Morocco

Rachid Benbrik

Poland

Mohammed Boukidi

Mohamed Chabab

Khalid Goure

United Kingdom

Stefano Moretti

Can <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi></math> collisions rival <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>−</mo></msup><msup><mi>e</mi><mo>+</mo></msup></math> in probing doubly charged Higgs bosons?

We present a combined analytical and numerical study of the effective action of field theory cosmic strings in the Abelian-Higgs model in flat space. Starting directly from the underlying solitonic field theory description, we provide a systematic derivation of the low energy effective action and present evidence for the absence of nontrivial curvature correction terms when only the translational Goldstone modes are retained. Using this framework, we extend the effective theory to include higher energy fluctuations of the soliton profile, which map to massive degrees of freedom propagating on the worldsheet. We show that the leading curvature contribution enters only through the coupling between these massive modes and the worldsheet Ricci scalar. We validate the resulting effective theory via lattice simulations of the full field theory equations of motion in flat space, implemented with adaptive mesh refinement to capture the string dynamics across different scales. The numerical simulations confirm the dynamics obtained using the effective action in its validity range. Furthermore, they also demonstrate the existence of the predicted parametric instability of excited strings that drives the transfer of energy from massive excitations to the Goldstone sector.

United States

Josu C. Aurrekoetxea

Spain

Jose J. Blanco-Pillado

Alberto García Martín-Caro

J.M. Queiruga

Revisiting curvature corrections for field theory cosmic strings

We consider off-diagonal asymptotic series for integral kernels of functions of Laplace-type operators on curved backgrounds. These expansions are obtained by applying integral transforms to the DeWitt series for the heat kernel of the corresponding operator and thus represent a DeWitt-type series in the heat kernel coefficients and some hypergeometric-type functions of the Synge world function (which we call basis kernels). Basis kernels of certain class of operator functions were found previously in terms of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math>-fold Mellin-Barnes integrals. In this paper, we study series representations of the corresponding Mellin-Barnes integrals in both nonresonant and resonant cases and suggest a physical interpretation for the emerging series, which is related to the UV and IR properties of operator functions.

Russia

A.O. Barvinsky

A.E. Kalugin

W. Wachowski

Multiple Mellin-Barnes integrals in Schwinger-DeWitt technique

The two-loop renormalization constants <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mi>m</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mn>1</mn></msub><mo>=</mo><msub><mi>Z</mi><mn>2</mn></msub></math> of Feynman gauge quantum electrodynamics (QED) in the on-shell scheme are computed using dimensional regularization. Analytic results are obtained for these constants. In addition, analytic expressions are obtained for their expansion coefficients in the dimensional regularization parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ε</mi></math> from order <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1</mn><mo>/</mo><msup><mi>ε</mi><mn>2</mn></msup></math> through order <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ε</mi><mn>5</mn></msup></math>. The high-order expansion coefficients will be needed for future multiloop calculations in QED and will provide a useful check for multiloop calculations in QCD.

Gregory S. Adkins

Elias Mitchell

A. Volkan Turan

Analytic results for the two-loop renormalization constants of Feynman gauge QED

The standard type-I seesaw can also be regarded as a low-scale seesaw by using the freedom of the Casas-Ibarra parametrization. In this framework, radiative corrections to the neutrino mass matrix can dominate over the tree-level contribution, so that the tree-level Casas-Ibarra construction no longer solves the equation that determines the physical neutrino masses and mixings. We show how the Casas-Ibarra parametrization can be consistently extended to this loop-corrected equation, by reabsorbing the one-loop corrections into the right-handed neutrino mass matrix, so that the resulting light neutrino mass matrix is consistent with experimental values. On the other hand, we show that physical processes related to right-handed neutrino propagation, such as heavy neutral lepton searches, do not depend on the one-loop corrections. Moreover, we show that <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mtext>Br</mtext><mo stretchy="false">(</mo><mi>μ</mi><mo stretchy="false">→</mo><mi>e</mi><mi>γ</mi><mo stretchy="false">)</mo></math> provides competitive constraints on the parameter space of heavy neutral lepton search experiments for masses above 100 GeV.

Italy

Gennaro Miele

Stefano Morisi

Mexico

Eduardo Peinado

Kainat Qamar

Insights into one-loop corrections to the neutrino low-scale type-I seesaw mechanism

The cosmic dawn 21-cm signal is a highly sensitive probe of any process which injects energy into the intergalactic medium, enabling novel searches for anomalous energy injection through dark matter interactions. In addition to modifying the global 21-cm signal, these processes would leave distinct imprints on the frequency-resolved 21-cm power spectrum with a morphology jointly set by the time and spatial dependence of energy emission and absorption. In this work, we extend the DM21cm code package, which models the effects of spatially inhomogeneous energy emission and deposition on 21-cm cosmology, to study three well-motivated scenarios which 21-cm measurements are particularly well suited to probe dark matter annihilation through <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>p</mi></mrow></math>-wave processes, the Hawking radiation of light primordial black holes, and energetic emission from accreting solar-mass primordial black holes. We project sensitivities to each of these scenarios, demonstrating that leading or near-leading sensitivity to each can be achieved through 21-cm probes. We also make public our updates to the DM21cm code package that enable it to accommodate energy injection processes for general continuum spectra with arbitrary spatial and temporal dependence in an accompanying release.

Canada

Yitian Sun

Joshua W. Foster

Julian B. Muñoz

Constraining inhomogeneous energy injection from annihilating dark matter and primordial black holes with 21-cm cosmology

We study dark photon dark matter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math> associated with a dark <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>X</mi></msub></math> gauge symmetry. To evade laboratory and cosmological constraints on kinetic mixing with the Standard Model <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>Y</mi></msub></math>, we assign a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>Z</mi><mn>2</mn></msub></math>-odd dark parity to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math> that forbids such mixing. The leading interactions then arise from gauge-invariant dimension-6 Higgs-portal operators, including both parity-even and parity-odd terms. We assume that the dark matter mass is generated via the Stueckelberg mechanism. In the interacting Stueckelberg EFT, a gauge-invariant dimension-6 parent reduces in unitary gauge to the nominal dimension-4 Higgs-portal interaction <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><msup><mi>H</mi><mi>†</mi></msup><mi>H</mi><mo stretchy="false">)</mo><msub><mi>X</mi><mi>μ</mi></msub><msup><mi>X</mi><mi>μ</mi></msup></math>, with its coefficient correlated with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>m</mi><mi>X</mi><mn>2</mn></msubsup><mo>/</mo><msup><mi mathvariant="normal">Λ</mi><mn>2</mn></msup></math>, while additional derivative operators are organized by the same longitudinal-mode power counting. We investigate freeze-in production of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi></math> from Higgs-pair annihilations after reheating, incorporating both field-strength and Stueckelberg-allowed operators. First, we consider the case in which the Wilson coefficients of the gauge-invariant dimension-6 operators, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>C</mi><mo stretchy="false">˜</mo></mover></math>, are of order unity. Under a conservative single-cutoff power counting in which the strong-coupling scales of the longitudinal mode lie above the cutoff of the field-strength effective theory, we find that the Stueckelberg contributions remain subdominant in dark matter production. We emphasize that this ordering of scales is an explicit assumption rather than a universal consequence of perturbative unitarity. Next, we explore a more general situation in which <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>C</mi><mo stretchy="false">˜</mo></mover></math> are smaller than unity. In this second case, Stueckelberg-allowed operators can become comparable and generate contributions proportional to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>T</mi><mrow><mi>reh</mi></mrow><mn>3</mn></msubsup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>T</mi><mrow><mi>reh</mi></mrow><mn>5</mn></msubsup></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>T</mi><mrow><mi>reh</mi></mrow><mn>7</mn></msubsup></math>, including sign-dependent interference effects. For both cases, we show that there exists a wide parameter space consistent with the observed dark matter relic density.

Japan

Antonio De Felice

Takehiro Ogura

Shinji Tsujikawa

Kimiko Yamashita

Higgs-portal Stueckelberg dark matter

The nature of dark matter remains an outstanding problem in particle physics and cosmology. Hidden-sector extensions of the Standard Model predict a neutral partner of the neutron, whose weak mixing with ordinary neutrons induces oscillations between visible and dark baryonic states. We propose and analyze a macroscopic quantum interferometric strategy that could provide a direct and experimentally accessible probe of this phenomenon. In particular, a Mach-Zehnder interferometer with very cold neutrons converts neutron–hidden neutron oscillations into measurable phase-dependent intensity modulations. By combining controlled phase shifts with tunable magnetic fields and material potentials, the setup enables a resonant exploration of the hidden-sector parameter space. Under representative experimental conditions on neutron flux, magnetic-field homogeneity, vertical-aperture and beam-overlap control in the presence of gravity, and interferometric stability, the expected reach extends to mixing amplitudes down to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ε</mi><mrow><mi>n</mi><msup><mi>n</mi><mo>′</mo></msup></mrow></msub><mo>∼</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>14</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math> for mass splittings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>δ</mi><mi>m</mi><mo>∼</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>9</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math>, accessing a previously unexplored region of parameter space and relevant to baryonic dark matter scenarios. These results suggest that neutron interferometry may become a precision laboratory tool for testing hidden-sector physics.