We introduce the Higgs mechanism for the self-dual spin connection (also known as the Ashtekar connection), using the Plebański formulation of gravity. We develop our formalism within the framework of the chiral action and derive the equations of motion of the theory. One particular test model is explored: since anisotropy is an intrinsic property of the theory, a modified version of the spatially flat Bianchi I model with two different scale factors is considered. We apply our formalism and derive the Friedmann equations which regulate the scale factors and the Higgs field. We also present a Proca-like term for the connection, which when reduced to minisuperspace with a positive $$\Lambda $$ yields a De Sitter universe with an effective cosmological constant that depends on the mass of the gauge fields. We finally investigate the effect of these mass terms on gravitational waves and find that the wave equation remains unchanged relatively to GR; however the Weyl tensor is scaled by a constant which depends on the mass of the connection components.

United Kingdom

Bruno Alexandre

Higgs mechanism for the Ashtekar self-dual connection

The manifest disparity in Hawking radiation temperatures between black hole and cosmological horizons in de Sitter (dS) spacetime reveals a non-equilibrium thermal configuration, inherently violating thermodynamic stability criteria. This asymmetry poses significant challenges to the systematic analysis of dS thermodynamics. In this study, we construct a thermodynamic framework for dS spacetime under the condition that the system’s thermodynamic quantities adhere to the first law of thermodynamics, while enforcing thermal equilibrium between horizons through radiation temperature-equivalent conditions. Our ansatz postulates that spacetime entropy constitutes both horizon entropy contributions with a supplementary correction term. Through variational analysis constrained by equilibrium thermodynamics, we derive and solve thermodynamic constraints to obtain corrected entropy relations that explicitly resolve the two-horizon entropy puzzle for $\textit{n}$-dimensional charged dilaton-dS black holes. Utilizing these corrected entropy relations, we renormalize associated thermodynamic quantities, thereby establishing self-consistent extended thermodynamics. Numerical solutions of the Gibbs criteria reveal parameter-dependent critical points, where heat capacity is diverging signal possible second-order phase transitions. The system manifests phase transition phenomena, structurally homologous to liquid–gas transition in conventional thermodynamic systems. We proved that the system satisfies the conditions for equilibrium stability, allowing equilibrium phase transitions to occur near critical points.

China

Hui-Hua Zhao

Yun-Zhi Du

Yu-Bo Ma

Entropy correction and phase transition of $\textit{n}$-dimensional charged dilaton dS black holes

We construct new families of supersymmetric AdS solutions in both massive and massless Type IIA supergravity via deformations to known backgrounds preserving $$ \mathcal{N} $$ = (4, 0) and $$ \mathcal{N} $$ = (6, 0) supersymmetry. These deformations are performed along internal isometries and lead to backgrounds with fully preserved or reduced supersymmetry. Using the formalism of $\textit{G}$-structures, we systematically characterise the resulting geometries and track the evolution of their supersymmetric properties under the deformation. In particular, we identify transitions among SU(3), SU(2), and identity structures, and demonstrate the preservation of Killing spinors through explicit spinor bilinear constructions. Additionally, we investigate D-brane embeddings in the deformed geometries, uncovering stable and supersymmetric configurations supported by the new backgrounds. Our results offer new insights into the classification of AdS flux vacua and provide a concrete framework for understanding their potential holographic duals.

Belgium

Anayeli Ramírez

Czechia

Salomón Zacarías

On deformations of AdS

We present an analytic reconstruction of one-loop amplitudes for the process $$ 0\to \overline{q} qt\overline{t}H $$ . Our calculation is a novel use of analytic reconstruction, retaining explicit covariance in the massive spin states through the massive spinor-helicity formalism. The analytic reconstruction relies on embedding the massive five-point kinematics in a fully massless eight-point phase space while still building a minimal ansatz directly in the five-point phase space. In order to obtain compact analytic expressions it is necessary to identify suitable partial fraction decompositions and extract common numerator factors, which we achieve through careful inspection of limits in which pairs of denominators vanish. We find that the resulting amplitudes are more numerically efficient than ones computed using automatic methods but that the gains are not as significant as in the massless case, at least at present. The method opens the door to applications at two-loop order, where numerical efficiency and improvements in the reconstruction methodology are more crucial, especially with regards to the number of free parameters in the ansatz.

United States

John Campbell

Giuseppe Laurentis

R. Ellis

Analytic reconstruction with massive particles: one-loop amplitudes for $$ 0\to \overline{q} qt\overline{t}H $$

We present an analytic calculation of the integrated double-emission eikonal function of a massive and a massless emitter whose momenta are at an arbitrary angle to each other. This quantity provides one of the required ingredients for extending the nested soft-collinear subtraction scheme to processes with massive final-state particles. To calculate it, we use the standard methodology involving reverse unitarity and its extension to cases with Heaviside functions, integration-by-parts technology and reduction to master integrals, and differential equations. In addition, we also describe a semi-numerical method based on the subtraction of infra-red and collinear singularities from the eikonal function, allowing us to extract divergences of the integrated eikonal function analytically, and to derive a simple integral representation for the finite remainder.

Germany

Dennis Horstmann

Kirill Melnikov

Ming-Ming Long

Andrey Pikelner

Integral of the double-emission eikonal function for a massive and a massless emitter at an arbitrary angle

We present analytic results for electroweak precision observables (EWPO) at next-to-leading order (NLO) in dimension-six SMEFT, with no assumptions on the flavour structure of SMEFT Wilson coefficients. The results are given in five different electroweak input schemes, thus offering a simple means, along with scale variations, of estimating theory uncertainties related to higher-order terms in the SMEFT expansion. Our results will be useful to assess the constraining power of existing and future lepton colliders for new physics scenarios.

Anke Biekötter

Benjamin Pecjak

Analytic results for electroweak precision observables at NLO in SMEFT

We use holography to study correlation functions of local operators in maximally supersymmetric Yang-Mills theories arising on the world-volume of D$\textit{p}$-branes in the large-$\textit{N}$ and strong-coupling limit. The relevant supergravity backgrounds obtained from the near-horizon limit of the D$\textit{p}$-branes enjoy a scaling similarity, which leads to an auxiliary AdS space of fractional dimension. This suggests that holographic correlation functions in this setup can be computed by integrating standard CFT correlators over the auxiliary extra dimensions. We apply this prescription to analytically compute two- and three-point correlators of scalar operators. The resulting two-point functions take a familiar CFT form but with shifted conformal dimensions, while the three-point correlators have a much more involved position dependence which we calculate explicitly in terms of a sum of Appell functions.

Nikolay Bobev

Guillermo Mera Álvarez

Hynek Paul

Correlation functions for non-conformal D$\textit{p}$-brane holography

We describe the most general local, Lorentz-invariant, effective field theory of scalars, fermions and gauge bosons up to mass dimension 6. We first obtain both a Green and a physical basis for such an effective theory, together with the on-shell reduction of the former to the latter. We then proceed to compute the renormalization group equations for the bosonic operators of this general effective theory at one-loop order.

Spain

Renato Fonseca

Italy

Pablo Olgoso

José Santiago

Renormalization of general Effective Field Theories: formalism and renormalization of bosonic operators

The observation of a resonance structure in the opening angle of the electron-positron pairs in the $$^{7}$$ Li(p,e $$^+$$ e $$^-$$ ) $$^{8}$$ Be reaction was claimed and interpreted as the production and subsequent decay of a hypothetical particle (X17). Similar excesses, consistent with this particle, were later observed in processes involving $$^{4}$$ He and $$^{12}$$ C nuclei with the same experimental technique. The MEG II apparatus at PSI, designed to search for the $$\mu ^+ \rightarrow \textrm{e}^+ \gamma $$ decay, can be exploited to investigate the existence of this particle and study its nature. Protons from a Cockroft–Walton accelerator, with an energy up to 1.1 MeV, were delivered on a dedicated Li-based target. The $$\gamma $$ and the e $$^{+}$$ e $$^{-}$$ pair emerging from the $$^8\textrm{Be}^*$$ transitions were studied with calorimeters and a spectrometer, featuring a broader angular acceptance than previous experiments. We present in this paper the analysis of a four-week data-taking in 2023 with a beam energy of 1080 keV, resulting in the excitation of two different resonances with Q-value 17.6 and 18.1 MeV. No significant signal was found, and limits at 90% C.L. on the branching ratios (relative to the $$\gamma $$ emission) of the two resonances to X17 were set, $$R_{17.6} <{1.8}\,\times \,10^{-6}$$ and $$R_{18.1} < {1.2}\,\times \,10^{-5}$$ in the mass range between $${16.5}\hbox { MeV}/\hbox {c}^{2}$$ and $${17.1}\hbox { MeV}/\hbox {c}^{2}$$ .

Russia

K. Afanaciev

A. Baldini

Japan

S. Ban

H. Benmansour

G. Boca

P. Cattaneo

G. Cavoto

F. Cei

M. Chiappini

A. Corvaglia

Switzerland

G. Maso

A. Bari

M. Gerone

L. Barusso

M. Francesconi

L. Galli

G. Gallucci

F. Gatti

L. Gerritzen

F. Grancagnolo

E. Grandoni

M. Grassi

D. Grigoriev

M. Hildebrandt

F. Ignatov

F. Ikeda

T. Iwamoto

S. Karpov

P. Kettle

N. Khomutov

A. Kolesnikov

N. Kravchuk

V. Krylov

N. Kuchinskiy

F. Leonetti

W. Li

V. Malyshev

A. Matsushita

M. Meucci

S. Mihara

W. Molzon

T. Mori

D. Nicolò

H. Nishiguchi

A. Ochi

W. Ootani

A. Oya

D. Palo

M. Panareo

A. Papa

V. Pettinacci

A. Popov

F. Renga

S. Ritt

M. Rossella

A. Rozhdestvensky

S. Scarpellini

P. Schwendimann

G. Signorelli

M. Takahashi

Y. Uchiyama

A. Venturini

B. Vitali

C. Voena

K. Yamamoto

R. Yokota

T. Yonemoto

Search for the X17 particle in $$^{7}\textrm{Li}(\textrm{p},\textrm{e}^+ \textrm{e}^{-}) ^{8}\textrm{Be}$$ processes with the MEG II detector

I investigate the higher dimensional black holes of quartic quasitopological-scalar gravity within the scope of extended quasitopological electromagnetism. It is demonstrated that only positive values of the quartic quasitopological parameter can result in physically acceptable solutions. In accordance with the values of the mass, conformal coupling constants, and quasitopological electromagnetic charges, the derived solution characterizes the dyonic hairy black holes with a single horizon, two horizons, and naked singularity. I also demonstrate that this solution has an essential curvature singularity at the centre $$r=0.$$ Additionally, the thermodynamic and conserved quantities for the resultant solution are worked out and the extended first law satisfied by these quantities is established. Ultimately, I address the consequences of a scalar field and electromagnetic charges on the local thermodynamic stability of dyonic hairy black holes.

Pakistan

Askar Ali

Black holes of quartic quasitopological gravity, conformal scalar field and extended quasitopological electromagnetism