arXiv subjects

Alan S. Cornell

Publications and source records attributed to Alan S. Cornell.

At least 19 recordsLinked to original sources

arXiv2026

The Force Concept Inventory Across Continents: Testing Q-Matrix Transferability and Cross-Cultural Differences in Mechanics Reasoning

The Force Concept Inventory (FCI) is one of the most widely used research-based assessments in physics education, yet the assumption that its underlying cognitive structure is transferable across educational contexts remains largely untested. This study investigates the transferability of FCI Q-matrices using the Generalized Deterministic Inputs, Noisy "And" Gate (G-DINA) cognitive diagnostic applied to two large cohorts: students from the Learning About STEM Student Outcomes (LASSO) online system database in the United States (N = 4,750) and introductory physics students at the University of Johannesburg, South Africa (N = 1,016). Rather than treating the analysis as a local model calibration exercise, we frame the problem as one of cross-context cognitive invariance. Differential Item Functioning (DIF) analyses revealed substantial cross-cultural differences, with 14 of 30 items exhibiting high DIF after controlling for latent skill mastery. These differences were concentrated in force dynamics and contact-force reasoning and remained invariant under alternative Q-matrix specifications. The findings suggest that observed differences reflect genuine variations in students' conceptual reasoning rather than psychometric artifacts, highlighting the importance of validating Q-matrix structures before deploying cognitive diagnostic and adaptive assessments across diverse non-local educational settings.

physics.ed-ph↗

arXiv2026

Composite dark matter at the LHC

We investigate a composite-inspired model in which a scalar dark matter candidate couples to third-generation quarks through a non-minimal set of coloured vector-like fermions, as motivated by partial compositeness. The simultaneous presence of several mediator states leads to a richer phenomenology than conventional single-mediator descriptions, and we confront the framework with the observed relic abundance, direct-detection and indirect-detection constraints, as well as data from the Large Hadron Collider. At colliders, we compare the sensitivity of dedicated new-physics searches with that of unfolded measurements of Standard Model processes, and we assess the impact of higher-order corrections on the different production mechanisms. We find that dedicated searches generally provide the strongest collider exclusions, while unfolded measurements offer complementary sensitivity. Direct detection becomes increasingly powerful as the interaction strength grows and can become the dominant constraint. This broader complementarity arises because collider data directly test the production and decay of the coloured mediators, whereas cosmological and astroparticle observables constrain the interactions governing dark-matter abundance, scattering and annihilation. Although present constraints significantly restrict the model, viable regions compatible with the observed dark-matter abundance remain.

hep-ph↗

arXiv2026

Gravitationally-decoupled hairy black holes: probing geometric, optical, and quasinormal mode signatures

Gravitational-decoupling provides a systematic framework for constructing black hole geometries from known (seed) solutions (such as the Schwarzschild), whose exterior properties closely resemble those of the seed solution while still retaining potentially distinguishable features. Using this approach, we study a class of static, spherically symmetric hairy black holes and examine how such deformations affect their horizon structure, photon spheres, shadow scales, and scalar quasinormal modes (QNMs). We first determine the physically controlled regions of the parameter space by imposing the relevant horizon and energy condition requirements, while retaining configurations outside these domains only for exploratory comparison. To isolate geometric effects, we compare solutions at a common horizon radius, while accounting explicitly for the distinction between the mass parameter entering the seed geometry and the ADM mass measured asymptotically. The resulting ADM normalized shadow scales are used for an illustrative comparison with the characteristic angular scales of M87* and Sgr A*. We also compute massless scalar QNMs using the sixth-order Wentzel-Kramers-Brillouin approximation and the improved Asymptotic Iteration Method, finding close agreement over the modes considered. Our results show that fixing the horizon radius does not uniquely determine either the optical or perturbative properties of the spacetime, and that mass normalization can significantly alter the interpretation of geometric trends. Horizon structure, null geodesic observables, and scalar QNMs therefore provide complementary probes of gravitationally-decoupled black hole geometries.

gr-qc↗

arXiv2026

Two-loop renormalisation and Higgs phenomenology in the five-dimensional MSSM

The five-dimensional Minimal Supersymmetric Standard Model (5D MSSM) provides an attractive framework in which power-law renormalisation group evolution naturally generates a sizeable trilinear stop coupling, allowing the observed Higgs boson mass to be reproduced without requiring too heavy a supersymmetric spectra. In this work we present a comprehensive two-loop analysis of the 5D MSSM, deriving the complete renormalisation group equations governing the gauge, Yukawa and soft supersymmetry-breaking sectors and examining the perturbative consistency of the theory. Particular attention is given to the ultraviolet behaviour of the model, where we demonstrate that the potentially dangerous leading two-loop contributions cancel as a consequence of the underlying $\mathcal{N}=2$ supersymmetry, leaving a well-behaved perturbative expansion. Building upon this framework, we compute the radiatively corrected Higgs effective potential including the complete Kaluza-Klein (KK) contributions through KK resummation, and investigate the resulting implications for the Higgs sector. The phenomenological viability of the model is subsequently explored through detailed numerical studies of the Higgs boson mass, electroweak precision observables, Higgs coupling modifiers and signal strengths, allowing constraints on the compactification scale and supersymmetric parameter space to be established. We find that the inclusion of the two-loop corrections preserves the characteristic power-law behaviour of the five-dimensional theory while yielding a phenomenologically viable parameter space consistent with current collider and precision measurements.

hep-ph↗

arXiv2026

Scalar quasinormal modes of Schwarzschild--anti-de Sitter black holes: spectral analysis and generalized boundary conditions

We study quasinormal modes (QNMs) of a minimally coupled massless scalar field on four-dimensional Schwarzschild--anti-de Sitter black holes using a Chebyshev spectral method. After compactifying the exterior domain, the radial problem is formulated as a quadratic matrix pencil in the dimensionless frequency. For the standard Dirichlet, or vanishing-field, boundary condition at the conformal AdS boundary, we reproduce the known scalar spectra across small, intermediate, and large black holes, including long overtone sequences and the expected approach to pure-AdS normal modes in the small black hole limit. We then deform the AdS boundary condition by imposing a generalized relation between the two independent asymptotic coefficients of the massless scalar. This deformation is treated as a generalized coefficient boundary condition for the massless scalar, and not as the usual alternative quantization for scalars in the Breitenlohner-Freedman window. The Dirichlet endpoint recovers the stable standard spectrum. For every non-Dirichlet value examined, and for representative small, intermediate, and large black holes, we find an additional mode with positive imaginary part, signaling a boundary-condition-induced instability. A near-Dirichlet refinement finds no finite critical angle down to the smallest deformation probed.

gr-qc↗

arXiv2025

Gravitational waves from flavoured SU(2) early-universe phase transitions

Flavourful extensions of the Standard Model aimed at explaining its fermionic mass structure typically rely on symmetries, broken at high-energy scales far beyond the reach of foreseeable direct collider searches. We illustrate, using a $SU(2)$ flavour gauge group, that the breaking of these symmetries up to scales as high as $10^7$ GeV could generate a gravitational-wave signal potentially observable by future observatories. We use dimensional reduction techniques to obtain the finite-temperature effective potential and study the possible first-order phase transitions. We match these transitions to steady-state hydrodynamical solutions in order to determine the corresponding gravitational-wave spectra. We observe that order-one gauge couplings are always required for a first-order phase transition to occur. On the other hand, adding leptoquarks (as an example of particles that are typically present in a complete flavour theory) significantly extends the testable parameter space. We find excellent prospects at the Einstein Telescope for future gravitational-wave detection of flavoured $SU(2)$ early-universe phase transitions.

hep-ph↗

arXiv2025

t-channel dark matter at the LHC -- a whitepaper

This report, summarising work achieved in the context of the LHC Dark Matter Working Group, investigates the phenomenology of $t$-channel dark matter models, spanning minimal setups with a single dark matter candidate and mediator to more complex constructions closer to UV-complete models. For each considered class of models, we examine collider, cosmological and astrophysical implications. In addition, we explore scenarios with either promptly decaying or long-lived particles, as well as featuring diverse dark matter production mechanisms in the early universe. By providing a unified analysis framework, numerical tools and guidelines, this work aims to support future experimental and theoretical efforts in exploring $t$-channel dark matter models at colliders and in cosmology.

hep-ph↗

arXiv2025

Analyzing the effect of higher dimensions on the black hole silhouette, deflection angles, and PINN approximated quasinormal modes

This study investigates the effects of higher dimensions on the observable properties of Schwarzschild-Tangherlini black holes, focusing on the photonsphere, shadow radius, deflection angles, and quasinormal modes (QNMs). By extending classical methods with Physics-Informed Neural Networks (PINNs), the research examines how increasing dimensionality alters these properties, causing shadow size reduction, weaker deflection angles, and shifts in QNM frequencies. The findings suggest that as black holes increase in dimensionality, their gravitational influence diminishes, particularly affecting light deflection and the stability of photon orbits. Through both weak and strong deflection analyses, this study indicates the need for ultrasensitive technology to detect these higher-dimensional signatures. Remarks on the observational data constraints currently favor four-dimensional spacetime; however, the exploration of additional dimensions remains vital in advancing models of quantum gravity. This work provides a theoretical framework for understanding black hole behavior in higher dimensions, potentially informing future astrophysical observations.

gr-qc↗

arXiv2025

Dominant misconceptions and alluvial flows between Engineering and Physical Science students

In this article we assess the comprehension of physics concepts by Physical Science and Engineering students enrolled in their first semester at the University of Johannesburg (UJ), South Africa ($2022$). We employ different graphical measures to explore similarities and differences using the results of both pre- and post-test data from the Force Concept Inventory assessment tool, from which we calculate dominant misconceptions (DMs) and gains. We also use alluvial diagrams to track the choices made by these two groups of students from pre- to post-test stages. In our analysis, we find that DM results indicate that participating Engineering students outperformed Physical Science students on average, however, the same types of normalised DMs persist at the post-test level. We call these DMs "persistent misconceptions." This is very useful when tracking persistent misconceptions, where when using repeated measures and alluvial diagrams with smaller groups of students, we find that Physical Science students tend to make more chaotic choices.

physics.ed-ph↗

arXiv2025

Solving the Regge-Wheeler and Teukolsky equations: supervised versus unsupervised physics-informed neural networks

To expand on the burgeoning research on physics-informed neural networks (PINNs) and their ability to solve the eigenvalue problems in black hole (BH) perturbation theory, we implement a supervised learning approach to solve the Regge-Wheeler and Teukolsky equations, the equations of gravitational perturbations of Schwarzschild and Kerr BHs, respectively. To date, applications of PINNs using the data-free (unsupervised) learning approach have proven their ability to compute quasinormal mode frequencies of BHs, quantities with physical significance in gravitational wave astronomy. To investigate the potential use of PINNs to compute quasinormal mode overtones higher than the low-lying $n=0$ and $n=1$ modes (with $n$ indexing overtones), the present work has instead applied the supervised approach to simplify computations. Consistent with the universal approximation theory of neural networks, it is found that the PINN algorithm has the intrinsic ability to recover the complex frequencies for various spin sequences (i.e. $s=-2$, $a \in \{0.1, 0.2, 0.3, 0.4\}$, $\ell = 2$, $m \in \{0, 1, 2\}$, $n \in \{0, 1, 2, 3, 4\}$), with approximation errors increasing with the rotation parameter $a$ and overtone number $n$ as a result of the residuals from the training data.

gr-qc↗

arXiv2025

Quasinormal frequencies in Reissner-Nordström de Sitter black holes: constraints from space-time and scalar field parameters

We examine the quasinormal modes exhibited by a massive scalar test field carrying an electric charge, oscillating in the outer region of a Reissner-Nordström de Sitter black hole. We examine the quasinormal mode effective potential throughout the black hole mass-charge phase space, finding a single-peaked barrier potential on $r_+ < r < r_c$ for all non-extremised black hole solutions for $\ell \geq 1$. Unlike in the Schwarzschild background, increasing scalar field mass heightens the peak of this barrier potential, while increasing the scalar field charge suppresses it. We compute the corresponding quasinormal frequency spectrum using a WKB-based semi-classical method, where, like the Schwarzschild case, we observe anomalous QNM damping behaviour for small scalar field mass below some critical mass $μ_{crit}$, which is $\ell$-independent for $q=0$.

gr-qc↗

arXiv2025

A note on Strong Cosmic Censorship and its violation in Reissner-Nordström de Sitter black hole space-times

Penrose's Strong Cosmic Censorship conjecture safeguards determinism in General Relativity. Within the initial value approach to General Relativity, proof of Strong Cosmic Censorship preservation is predicated on the unique evolution of the metric. For the Kerr-Newman family of black hole solutions, this requires the inextendability of the metric past the Cauchy horizon, due to the development of a "blue-shift" instability. Attempts to provide a rigorous mathematical proof of Strong Cosmic Censorship has led to the formulation of several Strong Cosmic Censorship conjectures of varying strengths, which seem to be discussed rarely outside of the mathematical relativity literature. In this note, we review some of the arguments for and against Strong Cosmic Censorship preservation, with a focus on the Reissner-Nordström de Sitter context, where the positive cosmological constant invites a "red-shift" effect that competes against the "blue-shift". We study the consequent role of quasinormal mode behaviour and illustrate the parameter space for which we consistently observe violations of the Strong Cosmic Censorship conjecture within Reissner-Nordström de Sitter black holes.

gr-qc↗

arXiv2025

Are there minimal exceptional aGUTs from stable 5D orbifolds?

In analysing five dimensional orbifolds with exceptional gauge groups, we seek to find stable vacua configurations which satisfy the minimal requirements for asymptotic grand unified models. In this respect we show that no minimal asymptotic grand unified theory can be built. Our results point towards non-minimal models based on $E_6$: one featuring supersymmetry, and the other needing a modification of the Coleman-Weinberg potential to stabilise the breaking of $E_6$ to the standard model gauge group.

hep-ph↗

arXiv2024

Improving smuon searches with Neural Networks

We demonstrate that neural networks can be used to improve search strategies, over existing strategies, in LHC searches for light electroweak-charged scalars that decay to a muon and a heavy invisible fermion. We propose a new search involving a neural network discriminator as a final cut and show that different signal regions can be defined using networks trained on different subsets of signal samples (distinguishing low-mass and high-mass regions). We also present a workflow using publicly-available analysis tools, that can lead, from background and signal simulation, to network training, through to finding projections for limits using an analysis and ${\tt ONNX}$ libraries to interface network and recasting tools. We provide an estimate of the sensitivity of our search from Run 2 LHC data, and projections for higher luminosities, showing a clear advantage over previous methods.

hep-ph↗

arXiv2024

General vacuum stability of orbifold gauge breaking and application to asymptotic grand unification

We examine the vacuum stability of gauge symmetry breaking in five dimensions, compactified on the $S_1/(\mathbb{Z}_2 \times \mathbb{Z}'_2)$ orbifold. We consider $SU(N)$, $Sp(N)$, $SO(2N)$ and $SO(2N+1)$ theories in the bulk, and provide an exhaustive classification of possible parity assignments that lead to stable orbifolds and of the corresponding symmetry breaking patterns. We use these results in the search for viable asymptotic grand unification theories (aGUT), testing the stability criteria on models based on $SU(6)$ and $SU(8)$. As a result, we identify two viable aGUTs: a unique $SU(6)$ pathway down to the Standard Model, and one $SU(8)$ model leading to an intermediate Pati-Salam partial unification.

hep-ph↗

arXiv2024

A semi-analytic treatment of quasinormal excitation factors in the eikonal regime

In this paper, we present an enhanced semi-analytic method for calculating quasinormal excitation factors in the eikonal regime, specifically for Schwarzschild black holes. To achieve improved accuracy in our quasinormal mode computations, we extend the Dolan and Ottewill inverse multipolar expansion technique and incorporate higher-order corrections from the WKB method of Iyer and Will. Our approach is carried out to a higher order than previous methods, thereby reducing the relative error, particularly for lower multipolar numbers. We validate our results by comparing them with those obtained using the Mano, Suzuki, and Takasugi method, demonstrating excellent agreement. A key advantage of our method is its ability to extract quasinormal excitation factors, which are crucial for accurately modeling gravitational wave signals from binary black hole mergers. This advancement provides a useful tool for future gravitational wave studies, enabling better quantification of quasinormal mode excitations and more precise identification of individual modes during black hole ringdowns.

gr-qc↗

arXiv2023

A three-year comparative study of dominant misconceptions among first-year physics students at a South African university

This article discusses a three-year study (2020 - 2022) of dominant misconceptions (DMs) for a large cohort of first-year physics course students at the University of Johannesburg (UJ), South Africa. Our study considered pre-test scores on the Force Concept Inventory using a graphical method, where we found statistical differences between the mean DM scores for the 2020 cohort, as compared to the 2021 and 2022 cohort; possibly due to the onset of COVID lockdowns. We also compared our data from South Africa with cohorts based in Spain and the Kingdom of Saudi Arabia, where the method of DMs was also applied. From this comparison, we found some differences in the preconception knowledge of the cohorts. Furthermore, we included an analysis of DMs through the `gender lens' for the South African cohort, finding no statistically significant difference between the means for DM scores of students who identify as male or female. Finally, given the diverse language backgrounds and levels of matriculation preparation for university level physics courses, we have also shown how quickly responding to student misconceptions can be efficiently addressed using the method of DMs.

physics.ed-ph↗

arXiv2023

Reissner-Nordström black holes in de Sitter space-time: bounds with quasinormal frequencies

Rich physics can be divined from charged black holes subjected to extremal conditions. When applied in conjunction with principles like Weak Cosmic Censorship, this naturally leads to constraints on the mass and charge of the black hole. However, more nuanced principles such as the Weak Gravity Conjecture (WGC) and the recently proposed Festina-Lente (FL) bound can provide, respectively, upper and lower bounds on elementary charged particles. In this study, we examine the quasinormal modes (QNMs) exhibited by a massive scalar test field carrying an electric charge, oscillating in the outer region of the black hole. These modes are subjected to the constraints imposed by the FL and WGC bounds. Our analysis provides insight into the behaviour of QNMs, particularly in regions that approach the extremal conditions of the black hole. Notably, in these regimes, the stability of the modes becomes precarious, particularly in the presence of a positive cosmological constant. The implications of our findings are far-reaching and significant. They extend from safeguarding the principles of cosmic censorship to addressing the structural stability of the black hole's interior. Our semi-classical analysis presents compelling evidence suggesting that Strong Cosmic Censorship may be violated for black holes that are in close proximity to extremality within the context of Reissner-Nordström-de Sitter (RNdS) geometries.

gr-qc↗