arXiv subjects

Waqas Ahmed

Publications and source records attributed to Waqas Ahmed.

At least 19 recordsLinked to original sources

arXiv2026

Entanglement, Discord, and Residual Coherence in Scalar-Induced Gravitational Waves

Scalar-induced gravitational waves (SIGWs) are usually characterized by their power spectrum, although their quadratic scalar source also carries higher-order correlation information. We investigate whether phase-sensitive correlations of a primordial Gaussian scalar state can survive decoherence and be transferred to the induced tensor sector. The scalar state is described in a fixed oscillator basis by the occupation $N_k^ζ$ and anomalous moment $M_k^ζ$, while the transfer is formulated through the unequal-time scalar Wightman function. The late-time tensor moments $d_k$ and $γ_k$ define an effective Gaussian reference state and its discord, whereas the exact SIGW state is generally non-Gaussian and contains an additional connected fourth-order cumulant. We therefore introduce the baseline-subtracted observable $Δκ_{\rm coh}=κ_N[G^>_{\rm coh}]-κ_N[G^>_{\rm ref}]$. For phase damping with $M_k^ζ\propto e^{-D_k}$, the Gaussian-reference contribution conditionally scales as $|γ_k|\propto e^{-2D_k}$ and $κ_N^{\rm G}\propto e^{-4D_k}$. This provides a framework in which the SIGW spectrum fixes the signal band, while higher-order statistics probe residual coherence beyond the power spectrum.

gr-qc↗

arXiv2026

Probing Massive Invisible Dark Photons in Higgs Decays via Gluon--Gluon Fusion at ATLAS Run 3

The ATLAS Collaboration has searched for Higgs-boson decays into a photon and missing transverse momentum using $135~\mathrm{fb}^{-1}$ of Run~3 proton--proton collision data at $\sqrt{s}=13.6~\mathrm{TeV}$. For the benchmark decay $H\toγ\gD$ with a massless invisible dark photon, ATLAS reports observed (expected) 95\% confidence-level limits of $1.4\%$ ($1.2\%$) on the branching fraction. We reinterpret this search for a massive detector-invisible dark photon with $0\leq m_{\gD}\leq70~\gev$, focusing on Higgs production through gluon--gluon fusion. \audit{The relative signal acceptance, normalized to the massless benchmark, remains nearly unchanged up to $m_{\gD}\simeq40~\gev$, but decreases to $0.888$, $0.736$, and $0.524$ at $50$, $60$, and $70~\gev$, respectively, as the photon-$p_T$ and transverse-mass spectra move toward the analysis thresholds.} Using the published massless gluon--gluon-fusion yield for normalization, we obtain simplified expected (observed) 95\% confidence-level limits on $\BR(H\toγ\gD)$ from $1.64\%$ ($1.76\%$) at $m_{\gD}=30~\gev$ to $3.50\%$ ($3.75\%$) at $70~\gev$. These results extend the ATLAS interpretation to massive invisible dark photons and quantify the resulting loss of sensitivity at large dark-photon mass.

hep-ph↗

arXiv2026

Kaluza--Klein Dark-Photon Mediation of Inelastic Dark Matter at LUX-ZEPLIN

We study a five-dimensional realization of endothermic dark matter motivated by the recent high-recoil LUX-ZEPLIN event. A pseudo-Dirac Standard-Model singlet fermion is localized in the extra dimension and couples to a bulk $U(1)_D$ gauge field. The same localization that suppresses a distant-brane Majorana operator and generates the inelastic splitting also controls the couplings to the Kaluza--Klein (KK) dark-photon tower, producing a localization-filtered mediator propagator. We organize the phenomenology around two representative mass--splitting points: an LZ benchmark, $m_χ=1.10~\TeV$ and $δ=365~\keV$, and an IceCube-motivated comparison point, $m_χ=1.08~\TeV$ and $δ=566~\keV$. The latter is used only to compare terrestrial and solar kinematics; the published IceCube bound is Higgsino-specific and is not directly imposed on our singlet KK model. At the LZ benchmark with $R^{-1}=0.30~\GeV$ and $m_0=0.10~\GeV$, the KK tower enhances the high-recoil xenon rate by a factor of about four relative to a single dark photon at fixed microscopic coupling. The LZ point lies just below the terrestrial halo speed ceiling, whereas the $566~\keV$ comparison point is inaccessible to ordinary xenon scattering and instead lies in a kinematic regime accessible to solar capture; any neutrino constraint on the present singlet model remains dependent on its capture and annihilation dynamics. The characteristic prediction of the extra-dimensional construction is therefore a correlated interplay of localization, KK spectral distortion, and inelastic kinematics.

hep-ph↗

arXiv2026

Xenon Isotope Filtering at the Kinematic Edge of Inelastic Dark Matter

Motivated by high-energy xenon recoil searches, we study isotope-dependent endothermic dark-matter scattering near the upper speed boundary of a truncated Galactic halo. Small differences among xenon nuclear masses shift the minimum incident speed and can be strongly amplified when the required velocity approaches the end of the halo distribution. We formulate the isotope-resolved coherent-contact rate and separate this kinematic filtering from high-momentum nuclear suppression. For $m_χ=1.1~\TeV$, $δ=365~\keV$, and $E_R=248~\keV$, the kinematic-only benchmark gives $f_{136}^{\rm kin}\simeq0.289$, while after Helm weighting the largest contribution is $f_{132}\simeq0.346$ and the $^{136}$Xe fraction falls to $\simeq0.094$. For idealized pure-isotope targets at fixed detector mass, microscopic coupling, and halo, the integrated $225$--$271~\keV$ responses relative to natural xenon are approximately $0.404$, $1.235$, and $1.693$ for $^{129}$Xe, $^{132}$Xe, and $^{136}$Xe, respectively. A single effective-xenon nucleus also fails to reproduce the full isotope sum accurately near the edge, changing the benchmark window rate by about $8\%$ and producing larger spectral distortions. These quantitative results depend on the high-speed halo and on the assumed nuclear response; the isotope-dependent kinematic support does not. The calculation is a theory-level diagnostic rather than an LZ likelihood fit or event-by-event isotope identification.

hep-ph↗

arXiv2026

F-Term Hybrid Inflation with T-Model Kähler Geometry and Beyond

We analyze F-term hybrid inflation (FHI) within various grand unified theories (GUTs) in the presence of a Kähler potential for the inflaton field which parameterizes the Kähler manifolds $SU(1,1)/U(1)$ or $SU(2)/U(1)$. We take into account supergravity, radiative, and soft supersymmetry-breaking corrections to the tree-level potential and find that viable FHI can be realized without extrema along the inflationary trajectory for a broad region of the parameter space. For selected superpotential parameters the models' predictions are largely influenced by the curvature of the internal space and the magnitude of the tadpole parameter which are constrained so as to achieve compatibility with the current ACT and SPT data. We also discuss the formation of cosmic strings and their associated gravitational wave signals, potentially detectable by current and upcoming experiments.

hep-ph↗

arXiv2026

A Dark-Dimension Origin of Geometric Inelastic Dark Matter: The LUX-ZEPLIN High-Recoil Event and Multi-Target Tests

The extended nuclear-recoil analysis of LUX-ZEPLIN (LZ) has reported one event compatible with a recoil energy near $248$ keV, motivating endothermic dark-matter scenarios with support at large recoil energy. We study a pseudo-Dirac electroweak-doublet dark-matter model embedded in a five-dimensional Dark-Dimension framework. The Standard Model and the vectorlike electroweak doublets are localized on the visible brane, while dark-number violation is communicated through a neutral bulk state. The resulting mass splitting is exponentially suppressed, $δ=δ_{\rm UV}e^{-2πMR}$, providing a geometric origin for the few-hundred-keV scale relevant to inelastic scattering. The neutral weak current is dominantly off diagonal, fixing the neutron-scale normalization at $σ_{χn}^{Z}\simeq1.86\times10^{-39}\,\mathrm{cm^2}$. Using a two-bin Poisson diagnostic of the extended LZ recoil window, we find a shallow minimum near $(m_χ,δ)\simeq(1.35~\TeV,366~\keV)$, while the thermally motivated point $(1.1~\TeV,360~\keV)$ lies only $Δχ^2\simeq0.21$ higher. The same benchmark is kinematically inaccessible to light targets but remains open for xenon and tungsten, providing a characteristic multi-target test of the model. For CaWO$_4$ we obtain an integrated tungsten rate of $3.15\times10^{-2}$ events kg$^{-1}$ yr$^{-1}$ in the $95$--$150$ keV interval. These results connect the geometric origin of the pseudo-Dirac splitting with high-recoil direct-detection phenomenology.

hep-ph↗

arXiv2026

MultiShadow: Multi-Object Shadow Generation for Image Compositing via Diffusion Model

Realistic shadow generation is crucial for achieving seamless image compositing, yet existing methods primarily focus on single-object insertion and often fail to generalize when multiple foreground objects are composited into a background scene. In practice, however, modern compositing pipelines and real-world applications often insert multiple objects simultaneously, necessitating shadows that are jointly consistent in terms of geometry, attachment, and location. In this paper, we address the under-explored problem of multi-object shadow generation, aiming to synthesize physically plausible shadows for multiple inserted objects. Our approach exploits the multimodal capabilities of a pre-trained text-to-image diffusion model. An image pathway injects dense, multi-scale features to provide fine-grained spatial guidance, while a text-based pathway encodes per-object shadow bounding boxes as learned positional tokens and fuses them via cross-attention. An attention-alignment loss further grounds these tokens to their corresponding shadow regions. To support this task, we augment the DESOBAv2 dataset by constructing composite scenes with multiple inserted objects and automatically derive prompts combining object category and shadow positioning information. Experimental results demonstrate that our method achieves state-of-the-art performance in both single and multi-object shadow generation settings.

cs.CV↗

arXiv2026

Decoherence Effects on Primordial Black Holes and Scalar-Induced Gravitational Waves

Primordial black holes (PBHs) form when large primordial curvature perturbations re-enter the Hubble radius and exceed the classical collapse threshold. These perturbations originate as quantum fluctuations of the inflationary vacuum, motivating a quantum-information description of the PBH-producing scalar sector. We develop a conservative extension of the standard PBH and scalar-induced gravitational-wave (SIGW) framework in which Gaussian quantum discord is used as a diagnostic of residual quantum correlations, not as a new PBH-formation criterion. We describe each $(\bm k,-\bm k)$ pair as a two-mode Gaussian state and show that, in the pure squeezed limit, discord grows rapidly with the squeezing parameter, so low discord thresholds are automatically satisfied for strongly squeezed modes. The nontrivial regime is the mixed state produced by decoherence. Using a Lindblad open-system description, we motivate a Gaussian loss channel for the scalar covariance matrix and distinguish the discord from a covariance-survival factor $Q_{\rm dec}(k)$. If the decoherence channel suppresses the scalar two-point covariance, PBH abundance can be affected through the classical collapse variance, while the SIGW spectrum is modified more directly by the factors $Q_{\rm dec}(ku)Q_{\rm dec}(kv)$ inside the radiation-era convolution. For a narrow scalar peak and slowly varying $Q_{\rm dec}$, this gives the benchmark scaling $Ω_{\rm GW}^{\rm eff}\simeq Q_{\rm dec}^2Ω_{\rm GW}^{\rm class}$. Thus quantum discord and decoherence provide a controlled way to characterize the quantum-to-classical transition of PBH-producing perturbations, with the clearest imprint appearing in scalar-induced gravitational waves.

gr-qc↗

arXiv2026

Probing Two Dark Dimensions through Primordial Black Holes, Gravitational Waves, and Colliders

We study primordial-black-hole (PBH) dark matter in the two-dark-dimensions (2DD) framework, a six-dimensional brane-world scenario with two compact extra dimensions and a fundamental gravity scale of order $10\,\mathrm{TeV}$. We calculate the evolution of higher-dimensional PBHs including the recently proposed quantum-gravitational memory-burden effect. For a memory exponent $p=2$, the evaporation rate is strongly suppressed, allowing PBHs with initial masses as small as $\sim10^{-3}\,\mathrm{g}$ to survive until the present epoch. Consequently, PBHs can account for the observed dark matter over a mass range extending from $10^{-3}\,\mathrm{g}$ to $10^{21}\,\mathrm{g}$. We further compute the stochastic gravitational-wave background generated at second order by the primordial curvature perturbations responsible for PBH formation. We show that the conventional four-dimensional formalism for scalar-induced gravitational waves remains applicable throughout the mass range accessible to current and future gravitational wave experiments. The resulting signals can be probed by LISA, DECIGO, and pulsar timing arrays. Using Fisher forecasts, we find that these observations can constrain the PBH mass, dark-matter fraction, and width of the primordial curvature spectrum with high precision. The low fundamental gravity scale of the 2DD framework also permits the production of microscopic black holes at future high-energy colliders. Their decay signatures, together with gravitational-wave measurements, provide complementary tests of higher-dimensional gravity, the memory-burden mechanism, and primordial-black-hole dark matter.

gr-qc↗

arXiv2026

Quantum Memory in Scalar-Induced Gravitational Waves

Scalar-induced gravitational waves are usually treated as a classical stochastic background sourced by phase-random curvature perturbations. We show that this description can miss residual quantum information. Starting from a decohered two-mode Gaussian scalar state, we derive explicit transfer relations between the scalar anomalous coherence and the covariance matrix of induced tensor modes. For a localized scalar power spectrum, the ordinary tensor power is sourced by scalar power contractions, whereas the opposite-mode tensor coherence is sourced by scalar anomalous-coherence contractions. This coherence can generate nonzero tensor discord and a connected tensor-power covariance even after scalar entanglement has vanished. We identify the connected covariance and phase-sensitive strain correlations as probes of primordial quantum coherence in secondary gravitational-wave backgrounds, and discuss their possible relevance for future space-based interferometers and pulsar timing arrays.

gr-qc↗

arXiv2026

GUT-Scale Smooth Hybrid Inflation with a Stabilized Modulus in Light of ACT and SPT Data

We analyze a generalized framework of smooth F-term hybrid inflation (smFHI) consistent with gauge coupling unification within the Minimal Supersymmetric Standard Model (MSSM). The embedding of the model in two specific Supergravity settings addresses at the same time the $η$ problem and the compatibility with the recent ACT or SPT data. The one relies on the choice of a shift-symmetric Kähler potential for the inflaton which revitalizes the SUSY predictions of smFHI, whereas the other employs a Kähler potential associated with an hyperbolic Kähler manifold. An essential role in both our constructions is played by a decoupled superheavy field without superpotential and Kaehler potential inspired by string- and D-brane--based models. Our proposal can be realized for a variety of representations for the Higgs fields involved in smFHI and assures monotonic inflationary potential.

hep-ph↗

arXiv2026

Secondary Gravitational Wave Signatures from 5D Rotating Primordial Black Holes in the Dark Dimension

We investigate five-dimensional rotating primordial black holes (PBHs) as dark matter candidates within the Dark Dimension (DD) scenario motivated by the Swampland Program. In this framework, a micron-scale extra dimension suppresses Hawking evaporation, allowing PBHs with initial masses $M \gtrsim 10^{10}\,\mathrm{g}$ to survive to the present epoch. Moreover, the memory burden effect, a quantum-gravitational suppression of the evaporation rate by $S^{-p}$, significantly prolongs PBH lifetimes and enlarges the allowed parameter space. We compute the evaporation dynamics for rotating 5D PBHs, derive the enhanced lifetime for $p=2$, and establish the dark matter window $10^{10}\,\mathrm{g} \lesssim M \lesssim 10^{21}\,\mathrm{g}$. The curvature perturbations responsible for PBH formation also generate a stochastic gravitational wave background through second-order scalar-induced effects. Assuming a log-normal primordial power spectrum with $σ=1$ and $f_{\mathrm{PBH}}=1$, we calculate the present-day energy density $Ω_{\mathrm{GW}}h^2$ across the Dark Dimension window. The predicted signals peak at frequencies from nHz to Hz, within the sensitivity ranges of LISA and DECIGO/BBO, while remaining consistent with current CMB spectral distortion bounds. Fisher forecasts show that future observatories can constrain the PBH mass, dark matter fraction, spectral width, and memory burden exponent with percent-level precision. A detection of the predicted gravitational wave background would provide simultaneous evidence for a micron-sized extra dimension, PBH dark matter, and the memory burden effect, offering a decisive test of quantum gravity and extra-dimensional physics.

hep-ph↗

arXiv2026

ReproScore: Separating Readiness from Outcome in Research Software Reproducibility Assessment

Digital libraries curate millions of research software artefacts yet lack scalable infrastructure for assessing whether those artefacts remain executable. Existing automated assessment tools treat static repository completeness -- what a repository contains -- as a proxy for execution success -- whether it runs. We term this the readiness-outcome conflation and present ReproScore, a two-tier framework that explicitly separates reproducibility readiness (RRS) from reproducibility outcome (ROS), combining them into a coverage-adaptive Composite Score (RCS). RRS comprises 26 sub-metrics across five categories; ROS provides execution-based probes when sandbox infrastructure is available; a community rubric externalises weighting priorities as versioned YAML profiles. Evaluated on 423 GitHub repositories from a large-scale ground-truth corpus spanning five failure modes, two complementary findings emerge: the environment category strongly discriminates failure mode, confirming static signals capture meaningful structural differences; yet RRS exhibits near-zero binary success correlation, empirically quantifying the readiness-outcome gap at repository scale. Together, these findings validate the architectural separation as both necessary and non-trivial, positioning ReproScore as scalable infrastructure for reproducibility-aware curation in digital library workflows.

cs.SE↗

arXiv2026

Radiatively Corrected Hybrid Inflation: Parameter Scans and Machine Learning with ACT and Future CMB Experiments

We investigate a realistic non-supersymmetric hybrid inflation model incorporating right-handed neutrinos and assess its viability in light of recent cosmological observations. At tree level, the inflaton potential yields a blue-tilted scalar spectrum, which is disfavored by current data from Planck and ACT that instead support a red tilt. We show that including one-loop quantum corrections, arising from generic couplings required for reheating, significantly modifies the potential, flattening it at large field values. This leads to a red-tilted spectral index ($n_s < 1$) and a suppressed tensor-to-scalar ratio $r$, both consistent with observational constraints. To ensure theoretical control, we focus on sub-Planckian field values, where the effective field theory description remains valid. The coupling of the inflaton to right-handed neutrinos naturally facilitates efficient reheating and enables the generation of the baryon asymmetry via non-thermal leptogenesis. We further explore the model's parameter space using a multi-output random forest classifier, achieving prediction accuracies in the range of $87.5\%$ to $98.9\%$. Our analysis shows that approximately $15\%$ of the parameter space satisfies at least one current experimental constraint, underscoring the essential role of quantum corrections in reconciling particle physics models with precision cosmology, and highlighting the effectiveness of machine learning techniques in probing complex theoretical frameworks.

hep-ph↗

arXiv2026

Revisiting Polynomial Hybrid Inflation: Planck and ACT Compatibility via Radiative Corrections

We investigate the impact of one-loop radiative corrections in a non-supersymmetric model of hybrid inflation with a chaotic (polynomial-like) potential,$V(ϕ) = V_0 + λ_p ϕ^p$, in the light of the latest constraints from \textit{Planck} and \textit{Atacama Cosmology Telescope} (ACT) observations. Here, $V_0$ denotes the energy scale of inflation, and $λ_p$ is a coupling associated with the polynomial term of power $p$. These corrections can naturally arise from couplings of the inflaton to other matter fields, which also facilitate the reheating process. At the tree level, the predictions of such models for the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$ typically lie outside the current observational bounds. However, incorporating one-loop radiative corrections modifies the potential to, \[ V(ϕ) = V_0 + λ_p ϕ^p + A ϕ^4 \ln (ϕ/ μ), \] where $A$ characterizes the strength of the inflaton's coupling to other fields, and $μ$ is an appropriate renormalization scale. This radiatively corrected potential can reconcile the model with the combined \textit{Planck}+ACT data over a suitable range of parameter space explored in this work. In particular, radiative corrections from fermionic loops ($A < 0$) suppress the tensor-to-scalar ratio $r$, while simultaneously yielding a red-tilted spectrum with $n_s < 1$, even for sub-Planckian field excursions. This brings the prediction in line with current observations, while still allowing for potentially detectable signatures of primordial gravitational waves. Furthermore, the inflaton's couplings enable successful reheating and naturally accommodate non-thermal leptogenesis, providing a unified framework for inflation and baryogenesis.

hep-ph↗

arXiv2026

SARS: A Novel Face and Body Shape and Appearance Aware 3D Reconstruction System extends Morphable Models

Morphable Models (3DMMs) are a type of morphable model that takes 2D images as inputs and recreates the structure and physical appearance of 3D objects, especially human faces and bodies. 3DMM combines identity and expression blendshapes with a basic face mesh to create a detailed 3D model. The variability in the 3D Morphable models can be controlled by tuning diverse parameters. They are high-level image descriptors, such as shape, texture, illumination, and camera parameters. Previous research in 3D human reconstruction concentrated solely on global face structure or geometry, ignoring face semantic features such as age, gender, and facial landmarks characterizing facial boundaries, curves, dips, and wrinkles. In order to accommodate changes in these high-level facial characteristics, this work introduces a shape and appearance-aware 3D reconstruction system (named SARS by us), a c modular pipeline that extracts body and face information from a single image to properly rebuild the 3D model of the human full body.

cs.CV↗

arXiv2026

Warm Hybrid Axion Inflation in $α$-Attractor Models Constrained by ACT and Future Plan experiments

We present a comprehensive study of warm hybrid inflation within the framework of $α$-attractor models, where an axionic inflaton is coupled to a waterfall field in the presence of thermal dissipation. The model is analyzed for both linear ($Υ\propto T$) and cubic ($Υ\propto T^{3}$) dissipation regimes. Confronting the theoretical predictions with the latest observational data from Planck+BICEP/Keck, P-ACT-LB-BK18 and SPT, and , we find that in the weak dissipative regime ($Q_{*} \lesssim 10^{-5}$), the scalar spectral index $n_{s} \simeq 0.965$ lies at the boundary of the combined P-ACT-LB-BK18 constraints, while the tensor-to-scalar ratio $r$ remains within observable ranges. For stronger dissipation ($Q_{*} \gtrsim 10^{-5}$), the model predicts values of $n_{s}$ well within the $1$--$2σ$ confidence region of all datasets, with tensor modes remaining fully observable in both dissipation scenarios. These results indicate that forthcoming CMB polarization experiments may be capable of detecting primordial gravitational waves, thereby providing a robust observational test of warm hybrid inflation across different dissipative regimes.

hep-ph↗

arXiv2026

Quantum AI for Cybersecurity: A hybrid Quantum-Classical models for attack path analysis

Modern cyberattacks are increasingly complex, posing significant challenges to classical machine learning methods, particularly when labeled data is limited and feature interactions are highly non-linear. In this study we investigates the potential of hybrid quantum-classical learning to enhance feature representations for intrusion detection and explore possible quantum advantages in cybersecurity analytics. Using the UNSW-NB15 dataset, network traffic is transformed into structured feature vectors through classical preprocessing and normalization. Classical models, including Logistic Regression and Support Vector Machines with linear and RBF kernels, are evaluated on the full dataset to establish baseline performance under large-sample conditions. Simultaneously, a quantum-enhanced pipeline maps classical features into variational quantum circuits via angle encoding and entangling layers, executed on a CPU-based quantum simulator, with resulting quantum embeddings classified using a classical SVM. Experiments show that while classical models achieve higher overall accuracy with large datasets, quantum-enhanced representations demonstrate superior attack recall and improved class separability when data is scarce, suggesting that quantum feature spaces capture complex correlations inaccessible to shallow classical models. These results highlight the potential of quantum embeddings to improve generalization and representation quality in cybersecurity tasks and provide a reproducible framework for evaluating quantum advantages as quantum hardware and simulators continue to advance.

cs.CR↗