In this work, a charged fluid system is studied by employing the complexity factor formalism for a static spherical spacetime. We proceed by calculating two distinct mass functions and obtaining the Einstein field equations for the anisotropic fluid. Following Herrera’s methodology, we designate $${Y}_{TF}$$ as the complexity factor as it integrates the two fundamental dynamic components like the density inhomogeneity and pressure anisotropy. Additionally, the field equations are addressed by applying a few constraints, with the first being the condition of zero complexity. By implementing two distinct forms for the radial metric potential, we derive two independent solutions. The unknowns involved in these models are then found using the junction conditions by taking into account the Reissner–Nordström exterior metric. Subsequently, observed data from multiple stars is used to generate a visual depiction of the obtained solutions. Our analysis demonstrates that both proposed models maintain physically stable and viable profiles, highlighting the critical role of the vanishing complexity condition in constructing anisotropic fluid solutions under the presence of an electric charge.

Pakistan

Azerbaijan

Tayyab Naseer

M. Sharif

Javeria Javid

Saudi Arabia

Jordan

Kottakkaran Nisar

Mohammed Zakarya

Orthogonal splitting of the Riemann curvature tensor and implications of resulting scalar(s) on compact stellar evolution

A model-agnostic search for Beyond the Standard Model physics is presented, targeting final states with at least four light leptons (electrons or muons). The search regions are separated by event topology and unsupervised machine learning is used to identify anomalous events in the full 140 fb $$^{-1}$$ of proton–proton collision data collected with the ATLAS detector during Run 2. No significant excess above the Standard Model background expectation is observed. Model-agnostic limits are presented in each topology, along with limits on several benchmark models including vector-like leptons, wino-like charginos and neutralinos, or smuons. Limits are set on the flavourful vector-like lepton model for the first time.

France

G. Aad

Norway

E. Aakvaag

United States

B. Abbott

United Arab Emirates

S. Abdelhameed

Germany

K. Abeling

N. Abicht

S. Abidi

M. Aboelela

Morocco

A. Aboulhorma

Israel

H. Abramowicz

Y. Abulaiti

Italy

United Kingdom

B. Acharya

A. Ackermann

C. Adam Bourdarios

Poland

L. Adamczyk

S. Addepalli

M. Addison

J. Adelman

Türkiye

A. Adiguzel

T. Adye

A. Affolder

Y. Afik

Spain

M. Agaras

A. Aggarwal

Romania

C. Agheorghiesei

F. Ahmadov

S. Ahuja

China

X. Ai

G. Aielli

A. Aikot

M. Ait Tamlihat

B. Aitbenchikh

M. Akbiyik

Sweden

T. Åkesson

A. Akimov

Japan

D. Akiyama

N. Akolkar

S. Aktas

G. Alberghi

Canada

J. Albert

Switzerland

U. Alberti

P. Albicocco

G. Albouy

S. Alderweireldt

Z. Alegria

M. Aleksa

I. Aleksandrov

C. Alexa

Greece

T. Alexopoulos

F. Alfonsi

M. Algren

M. Alhroob

Czechia

B. Ali

H. Ali

S. Ali

S. Alibocus

South Africa

M. Aliev

G. Alimonti

W. Alkakhi

C. Allaire

B. Allbrooke

D. Allen

J. Allen

P. Allport

A. Aloisio

Argentina

F. Alonso

C. Alpigiani

Z. Alsolami

A. Alvarez Fernandez

M. Alves Cardoso

M. Alviggi

M. Aly

Brazil

Y. Amaral Coutinho

A. Ambler

C. Amelung

M. Amerl

C. Ames

T. Amezza

D. Amidei

B. Amini

K. Amirie

A. Amirkhanov

Portugal

S. Amor Dos Santos

K. Amos

D. Amperiadou

S. An

C. Anastopoulos

T. Andeen

J. Anders

A. Anderson

A. Andreazza

S. Angelidakis

A. Angerami

A. Anisenkov

A. Annovi

C. Antel

E. Antipov

M. Antonelli

Search for Beyond the Standard Model physics with anomaly detection in multilepton final states in $\textit{pp}$ collisions at $$\sqrt{s}=13~\textrm{TeV}$$ with the ATLAS detector

We probe potential variations of the proton-to-electron mass ratio ( $$\mu $$ ) using high-resolution H $$_2$$ Lyman transitions in the white dwarf GD 133, observed with the $\textit{Hubble Space Telescope Cosmic Origins Spectrograph}$ (HST/COS). White dwarf atmospheres provide a powerful laboratory for testing fundamental physics in strong gravitational fields. Applying a self-consistent spectral analysis, we obtain a tight constraint of $$\Delta \mu /\mu = (0.02 \pm 0.09)$$ in a gravitational potential approximately $$10^{4}$$ times stronger than that of Earth. The measured uncertainty implies that any variation of $$\mu $$ is tightly bounded in this strong-field fields, placing meaningful limits on models predicting couplings between fundamental constants and gravity.

Vietnam

T. Le

Probing proton–electron mass ratio variations using high-precision $$H_2$$ Lyman lines

In this work, we construct novel traversable wormhole solutions supported by gravitational particle creation mechanism and study their physical viability through energy conditions, throat dynamics and asymptotic behavior. We further study their geometry through the lens of embedding diagrams. Subsequently, we explore their observational signatures, focusing on the shadow structure, quasinormal spectra, and greybody factors obtained via the WKB approximation. In doing so, we aim to provide a comprehensive framework where particle creation naturally sustains traversable wormholes and simultaneously enriches their phenomenology in a testable manner.

India

Madhukrishna Chakraborty

Thailand

Malaysia

Subenoy Chakraborty

Traversable wormholes induced by particle creation mechanism: from geometry to observations

We construct a class of wormhole geometries supported by the non-local gravitational self-energy that regularizes the particle and black-hole sectors of spacetime. Using this framework, inspired by T-duality, we show that two entangled particles (or particle–black-hole pairs) naturally source an Einstein-Rosen–type geometry in which the required violation of the strong energy condition arises from intrinsic quantum-gravity effects rather than from ad hoc exotic matter, which is matter that violates the null energy condition. We classify the resulting wormholes, analyze their horizons, throat structure and embedding properties, and we identify the exotic energy needed at the minimal surface. Imposing the $$\textrm{ER}=\textrm{EPR}$$ requirement of non-traversability and the absence of a macroscopic throat, we find that only the zero-throat geometry is compatible with an entanglement-induced Einstein–Rosen bridge, providing a concrete realization of $$\textrm{ER}=\textrm{EPR}$$ within a fully regular spacetime. Finally, we briefly discuss possible implications for microscopic ER networks from vacuum fluctuations, replica-wormhole interpretations of Hawking radiation, and possible links to entanglement-driven dark-energy scenarios.

North Macedonia

Kimet Jusufi

Francisco Lobo

Chile

Emmanuel Saridakis

Douglas Singleton

Emergence of $$\textrm{ER}=\textrm{EPR}$$ from non-local gravitational energy

Open quantum systems are powerful effective descriptions of quantum systems interacting with their environments. Studying changes of Fock state probabilities can be intricate in this context since the prevailing description of open quantum dynamics is by master equations of the systems’ reduced density matrices, which usually requires finding solutions for a set of complicated coupled differential equations. In this article, we show that such problems can be circumvented by employing a recently developed path integral-based method for directly computing reduced density matrices in scalar quantum field theory. For this purpose, we consider a real scalar field $$\phi $$ as an open system interacting via a $$\lambda \chi ^2\phi ^2$$ -term with an environment comprising another real scalar field $$\chi $$ that has a finite temperature. In particular, we investigate how the probabilities for observing the vacuum or two-particle states change over time if there were initial correlations of these Fock states. Subsequently, we apply our resulting expressions to a neutrino toy model. We show that, within our model, lighter neutrino masses would lead to a stronger distortion of the observable number of particles due to the interaction with the environment after the initial production process.

Clare Burrage

Austria

Christian Käding

Fock state probability changes in open quantum systems

Howard Haber

P. Ferreira

Erratum: RG-stable parameter relations of a scalar field theory in absence of a symmetry

In this work, we revisit several thin-crust approximations presented in the literature and compare them with the exact solutions of the Tolman–Oppenheimer–Volkoff (TOV) equations. In addition, we employ three different equations of state (EoSs) and one with pasta phase, each based on a distinct framework: the variational method, relativistic Brueckner–Hartree–Fock, and relativistic mean-field theory. We emphasize that these approximations require only the TOV solutions for the core and the EoS properties at the core–crust interface, in our approach only the energy density. Finally, the relativistic approximation, as well as the Newtonian approximation with corrections, show good agreement with the exact solutions. This means that a simple treatment of the crust would suffice for structural purposes, independently of the possible uncertainties in the sub-nuclear equation of state which are not very large. The unified EOS SINPA (relativistic mean-field theory) including the pasta phase was used to study the thin-crust approximation, while degeneracy in the $$M$$ - $$R$$ relation is demonstrated through: (i) anisotropic pressure in the modified TOV equation, (ii) $$f(R,L_m,T)$$ gravity model, and (iii) dark matter admixture. As demonstrated, modifications to the description of gravitation introduce degeneracies in the mass–radius relation that are challenging to disentangle or quantify precisely.

F. Köpp

J. Horvath

C. Vasconcellos

The crusts of neutron stars revisited: approximations within a polytropic equation of state approach

The aim of this paper is to investigate the stability and existence of the closed Einstein Universe (EU) under linear homogeneous perturbations within the framework of $$ f(\mathcal {R}, \phi , \chi ) $$ gravity. For this, we consider a closed Friedmann–Roberson–Walker universe filled with isotropic matter. Perturbations are imposed on the matter parameters and on the scale factor. We systematically derive the static and perturbed field equations for scenarios with and without conservation of the energy–momentum tensor and examine the associated stability regions through selected models in $$f(\mathcal {R},\phi ,\chi )$$ gravity. The graphical analysis shows that for suitable choices of model parameters such as $$ \alpha $$ , $\textit{b}$ and scalar field $$\phi _o$$ , the stable regions of the Einstein universe can be obtained in this theory of gravity. Significant differences in stability regions are observed for scalar fields governed by standard kinetic energy and for those characterized by negative kinetic energy. The scalar field and coupling parameters play a key role in the existence of stable regions of the Einstein universe.

 Muhammad

M. Azam

A perturbative approach on the stability of the Einstein universe in $$f(\mathcal {R},\phi ,\chi )$$ gravity

We study the strong decay of $$D_{s0}^*(2317)^+$$ to $$D_s^+ \pi ^0$$ considering the coupled channels of $$D^0 K^+, D^+ K^0, D_s^+ \eta $$ and $$D_s^+ \pi ^0$$ within a picture for the interaction based on the local hidden gauge approach. We also address the problem of the radiative decay to $$D_s^{*+} \gamma $$ , using the same information obtained from the molecular picture. We obtain a strong width of the $$D_{s0}^*(2317)^+$$ of about $$77 \,\mathrm keV$$ from coupled channels interaction and a radiative decay of about $$1.7 \,\mathrm keV$$ . We also show that the extra consideration of $$\pi ^0-\eta $$ mixing can double the strong decay width to values around $$140 \,\mathrm keV$$ . The anomalous terms for the radiative decay are considered for the first time, but they are found negligible. We make a thorough discussion of this and other results to the light of the recent measurement of Belle for the ratio of these two decay modes, and make a call for the precise measurement of the two decay widths independently to clarify the present situation concerning the nature of the $$D_{s0}^*(2317)^+$$ state.

Pei-Sen Su

Wen-Tao Lyu

Wei-Hong Liang

Eulogio Oset

The $$D_{s0}^*(2317)^+$$ decay to $$D_s^+\pi ^0$$ and $$D_s^{*+}\gamma $$