In this work, we explore the feasibility of realizing the Dark Dimension Scenario through T-fold compactifications on $\textit{T}$ × $\textit{S}$ , where the base of the internal space $\textit{S}$ naturally acts as the requisite mesoscopic extra dimension. Utilizing Scherk-Schwarz reduction from 5D to 4D, and applying duality twists from both elliptic and parabolic conjugacy classes of subgroups of the T-duality group associated with $\textit{T}$ , we stabilize the volume of $\textit{T}$ and several other moduli. This approach generates a potential characterized by two runaway directions, one aligned with the Scherk-Schwarz radion. Further stabilization efforts yield a decreasing potential trajectory demanded by the Dark Dimension Scenario.

Netherlands

Guo-En Nian

Stefan Vandoren

Towards a string realization of the Dark Dimension via T-folds

This study explores the structure of compact stars using an extended theory of gravity known as <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi><mo stretchy='false'>)</mo></math> gravity, where <math altimg='si3.svg'><mi mathvariant='script'>R</mi></math>, is the Ricci scalar, <math altimg='si4.svg'><mi mathvariant='script'>G</mi></math>, the Gauss-Bonnet invariant, and <math altimg='si5.svg'><mi mathvariant='script'>T</mi></math> the trace of the energy-momentum tensor. Focusing on massive radio pulsars, specifically neutron stars with masses greater than 1.8 solar masses, utilize these extreme astrophysical environments to test gravity in regimes unreachable by Earth-based experiments. We adopt a linear form of the theory, <math altimg='si18.svg'><mi>f</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mi mathvariant='script'>R</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>&#945;</mi><mi mathvariant='script'>G</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>&#946;</mi><mi mathvariant='script'>T</mi></math>, with <italic>&#945;</italic>, <cross-ref refid='fn0010' id='crf0390'>1</cross-ref> and <italic>&#946;</italic> are dimensional constants, and derive an exact analytical solution for anisotropic perfect fluid spheres in hydrostatic equilibrium. This model incorporates the compactness factor <math altimg='si7.svg'><mi>C</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mn>2</mn><mi>G</mi><mi>M</mi></mrow><mrow><mi>R</mi><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac></math>, to describe all physical properties within the stellar interior. To constrain the model, we employ observational data from the pulsar <italic>U</italic>1724, using its mass and radius to fix the parameters at their upper bounds: <math altimg='si8.svg'><msub><mrow><mi>&#945;</mi></mrow><mrow><mn>1</mn></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi>&#945;</mi></mrow><mrow><msup><mrow><mi>R</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo>&#177;</mo><mn>0.023</mn></math> and <math altimg='si9.svg'><msub><mrow><mi>&#946;</mi></mrow><mrow><mn>1</mn></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mfrac><mrow><mi>&#946;</mi></mrow><mrow><msup><mrow><mi>&#954;</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></mfrac><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo>&#177;</mo><mn>0.001</mn></math>. The resulting model is consistent with physical viability and observational constraints. Notably, the squared sound speed in this framework remains below the theoretical limit ( <math altimg='si10.svg'><mmultiscripts><mrow><mtext mathvariant='normal'>c</mtext></mrow><mrow><mi>s</mi></mrow><none /><none /><mrow><mn>2</mn></mrow></mmultiscripts><mo linebreak='goodbreak' linebreakstyle='after'>&lt;</mo><msup><mrow><mi>c</mi></mrow><mrow><mn>2</mn></mrow></msup><mo stretchy='false'>/</mo><mn>3</mn></math>), contrasting with general relativity results. Without assuming a specific equation of state, the model exhibits linear behavior and predicts a core density several times higher than nuclear saturation density ( <math altimg='si11.svg'><msub><mrow><mi>&#961;</mi></mrow><mrow><mtext>nuc</mtext></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>2.6</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>14</mn></mrow></msup></math> g/cm 3), with surface density <math altimg='si12.svg'><msub><mrow><mi>&#961;</mi></mrow><mrow><mi>s</mi></mrow></msub></math>, also exceeding this threshold. Additionally, the derived mass-radius relation agrees well with existing astrophysical observations.

Egypt

South Africa

G.G.L. Nashed

Constraining linear form of <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mrow><mi mathvariant='script'>R</mi><mo>,</mo><mi mathvariant='script'>G</mi><mo>,</mo><mi mathvariant='script'>T</mi></mrow><mo stretchy='false'>)</mo></math> gravity from astrophysical observations of the Pulsar U1724

The arrival time of electromagnetic signals traveling in chiral cosmic media is investigated in the context of Maxwell-Carroll-Field-Jackiw electrodynamics. Considering the interstellar medium (ISM) as a cold, ionized, chiral plasma, we derive the time delay between two traveling signals, expressed in terms of a modified dispersion measure (DM) which receives additional contribution from the chiral parameters. Faraday rotation angle is also addressed in this chiral plasma scenario, yielding modified rotation measures (RM). Using DMs data from five pulsars, we establish constraints on the chiral parameter magnitude at the order of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>23</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>22</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>. On the other hand, the Faraday rotation retrieved from RM measurements implied upper constraints as tight as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>36</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>.

Brazil

Filipe S. Ribeiro

Pedro D.S. Silva

Manoel M. Ferreira

Constraining <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi><mi>T</mi></mrow></math>-odd electromagnetic chiral parameters with pulsar timing

In this paper, we investigate regular black hole solutions in the (2+1)-dimensional versions of general relativity and $\textit{f}$($\textit{R}$, $\textit{T}$) gravity, both coupled to nonlinear electrodynamics. By admitting that the matter content that generates such geometries satisfies the Maxwell limit condition, we obtain a class of regular black holes that give rise to new solutions and successfully reproduce particular cases found in earlier studies of (2+1)-dimensional general relativity. Moreover, we discover the first regular black hole solutions in (2+1)-dimensional $\textit{f}$($\textit{R}$, $\textit{T}$) gravity and explore both qualitatively and quantitatively the non-conservation of the energy–momentum tensor present in those solutions.

Portugal

Miguel Pinto

Roberto Maluf

Spain

Gonzalo Olmo

Regular black hole solutions in $$(2 + 1)$$ -dimensional $\textit{f}$($\textit{R}$, $\textit{T}$) gravity coupled to nonlinear electrodynamics

We consider the effects of a local axion dark matter background on $\textit{g}$ − 2 of the electron. We calculate loop corrections to the photon-electron vertex and determine analytical formulas for the spin and cyclotron frequencies when the electron is in an external magnetic field. By comparing with current measurements of these observables, we are able to place the strongest constraint on the axion-elecron coupling for axion masses below 3 × 10 eV.

China

Ariel Arza

Jason Evans

Electron $\textit{g −}$ 2 corrections from axion dark matter

We explore dark matter phenomenology in Myrzakulov <math altimg='si1.svg'><mi>F</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo stretchy='false'>)</mo></math> gravity, formulated via the vielbein approach in Weitzenb&#246;ck spacetime. In this torsion-based extension of gravity, dark matter emerges as a geometric effect rather than a particle species, with curvature and torsion contributing dynamically to the field equations.

United States

Davood Momeni

Kazakhstan

Ratbay Myrzakulov

Dark matter constraints in Myrzakulov <italic>F</italic>( <italic>R</italic>, <italic>T</italic>) gravity: A vielbein approach in Weitzenb&#246;ck spacetime with observational data

The ALPHA-g experiment at CERN aims to precisely measure the terrestrial gravitational acceleration of antihydrogen atoms. A radial Time Projection Chamber (rTPC), that surrounds the ALPHA-g magnetic trap, is employed to determine the annihilation location, called the vertex. The standard approach requires identifying the trajectories of the ionizing particles in the rTPC from the location of their interaction in the gas (spacepoints), and inferring the vertex positions by finding the point where those trajectories (helices) pass closest to one another. In this work, we present a novel approach to vertex reconstruction using an ensemble of models based on the PointNet deep learning architecture. The newly developed model, PointNet Ensemble for Annihilation Reconstruction (PEAR), directly learns the relation between the location of the vertices and the rTPC spacepoints, thus eliminating the need to identify and fit the particle tracks. PEAR shows strong performance in reconstructing vertical vertex positions from simulated data, that is superior to the standard approach for all metrics considered. Furthermore, the deep learning approach can reconstruct the vertical vertex position when the standard approach fails.

Canada

A. Ferreira

M. Singh

Y. Saito

A. Capra

I. Carli

D. Duque Quiceno

W. Fedorko

M. Fujiwara

M. Li

L. Martin

G. Smith

A. Xu

Antimatter annihilation vertex reconstruction with deep learning for ALPHA-g radial Time Projection Chamber

In this paper, we analyze the potential variation of the gravitational constant <italic>G</italic> using data from strong gravitational lensing systems and Type Ia supernovae. Testing <math altimg='si1.svg'><mi>G</mi><mo stretchy='false'>(</mo><mi>z</mi><mo stretchy='false'>)</mo></math> parameterizations where <math altimg='si2.svg'><mi>G</mi><mo stretchy='false'>(</mo><mi>z</mi><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msub><mrow><mi>G</mi></mrow><mrow><mn>0</mn></mrow></msub><mo stretchy='false'>(</mo><mn>1</mn><mo linebreak='badbreak' linebreakstyle='after'>+</mo><msub><mrow><mi>G</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>z</mi><mo stretchy='false'>)</mo></math> and <math altimg='si3.svg'><mi>G</mi><mo stretchy='false'>(</mo><mi>z</mi><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msub><mrow><mi>G</mi></mrow><mrow><mn>0</mn></mrow></msub><msup><mrow><mo stretchy='false'>(</mo><mn>1</mn><mo linebreak='badbreak' linebreakstyle='after'>+</mo><mi>z</mi><mo stretchy='false'>)</mo></mrow><mrow><msub><mrow><mi>G</mi></mrow><mrow><mn>1</mn></mrow></msub></mrow></msup></math>, we also account for the influence of <italic>G</italic> on the luminosity of SNe Ia through the Chandrasekhar mass-luminosity relation. Only the flat universe hypothesis is considered. Constraints from 158 lensing systems and the Pantheon+ sample show no significant evidence of <italic>G</italic> variation. However, although the results are compatible with no variation, the errors are not yet sufficiently restrictive to rule out any variation of <italic>G</italic> with high statistical confidence. This study highlights the viability of using combined astrophysical data to probe variations in fundamental constants, suggesting that future surveys could refine these constraints.

R.F.L. Holanda

Marcelo Ferreira

Javier E. Gonzalez

An investigation of a varying G through Strong Lensing and SNe Ia observations

In this work we investigate the muon anomalous magnetic dipole moment <math altimg='si1.svg'><msub><mrow><mi>a</mi></mrow><mrow><mi>&#956;</mi></mrow></msub></math> in a model that extends the Standard Model with a scalar triplet and a lepton triplet. Different from previous studies, we find that there is still viable parameter space in this model to explain the discrepancy <math altimg='si2.svg'><mi mathvariant='normal'>&#916;</mi><msub><mrow><mi>a</mi></mrow><mrow><mi>&#956;</mi></mrow></msub><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msub><mrow><mi>a</mi></mrow><mrow><mi>&#956;</mi></mrow></msub><mo stretchy='false'>(</mo><mrow><mi mathvariant='normal'>Exp</mi></mrow><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>&#8722;</mo><msub><mrow><mi>a</mi></mrow><mrow><mi>&#956;</mi></mrow></msub><mo stretchy='false'>(</mo><mrow><mi mathvariant='normal'>SM</mi></mrow><mo stretchy='false'>)</mo></math>. While being consistent with the current data of neutrino mass, electroweak precision measurements and the perturbativity of couplings, our model can provide new physics contribution <math altimg='si128.svg'><msubsup><mrow><mi>a</mi></mrow><mrow><mi>&#956;</mi></mrow><mrow><mtext mathvariant='normal'>NP</mtext></mrow></msubsup></math> to cover the central region of <math altimg='si18.svg'><mi mathvariant='normal'>&#916;</mi><msub><mrow><mi>a</mi></mrow><mrow><mi>&#956;</mi></mrow></msub></math> with new scalar and lepton mass as low as around TeV. This mass scale is allowed by the current collider searches for doubly charged scalars and the lepton triplet, and they can be tested at future high energy and/or high luminosity colliders.

Lei Cai

South Korea

Chengcheng Han

Shi-Ping He

Peiwen Wu

Hybrid Type-II and Type-III seesaw model for the muon <italic>g</italic>&#8239;&#8722;&#8239;2 anomaly

The self-dual condition, which ensures invariance under electromagnetic duality, manifests as a partial differential equation in nonlinear electromagnetism theories. The general solution to this equation is expressed in terms of an auxiliary field, $\textit{τ}$, and Courant-Hilbert functions, $\textit{ℓ}$($\textit{τ}$), which depend on $\textit{τ}$. Recent studies have shown that duality-invariant nonlinear electromagnetic theories fulfill the principle of causality under the conditions $$ \frac{\partial \ell }{\partial \tau}\ge 1 $$ and $$ \frac{\partial^2\ell }{\partial {\tau}^2}\ge 0 $$ .

H. Babaei-Aghbolagh

Iran

Komeil Babaei Velni

Germany

Song He

Zahra Pezhman

Root- $$ T\overline{T} $$ deformations on causal self-dual electrodynamic theories