arXiv subjects

Mansoor Ur Rehman

Publications and source records attributed to Mansoor Ur Rehman.

At least 19 recordsLinked to original sources

arXiv2026

Sneutrino Tribrid Inflation in Flipped $\mathbf{SU(5)}$: Confronting ACT DR6 and Planck Observations

We construct a realization of sneutrino tribrid inflation within the $R$-symmetric flipped $SU(5)$ grand unified theory. A vector-like pair of matter multiplets, $10_V+\overline{10}_V$, provides a $D$-flat inflaton direction along the right-handed sneutrino component, with an additional $Z_2$ symmetry forbidding a direct inflaton mass term so that the leading inflationary interaction is a non-renormalizable Kähler-driven operator. Unlike previous studies, we treat the superpotential cutoff scale $M_s$ as independent of the reduced Planck mass, $m_P$, substantially enlarging the viable parameter space. Confronting the model with the ACT DR6/Planck determination $n_s=0.9734\pm0.0034$ and the $2σ$ bound on the running of the spectral index, we identify broad regions of viable parameter space in which the flipped $SU(5)$ symmetry-breaking scale can approach the conventional GUT scale, $M\simeq M_{\rm GUT}$, and the tensor-to-scalar ratio can reach observable values, $r\gtrsim10^{-3}$, within reach of forthcoming CMB $B$-mode experiment such as LiteBIRD. We further study the post-inflationary dynamics, identifying the inflaton with the lightest right-handed sneutrino in a conventional type-I seesaw sector, whose out-of-equilibrium decay generates a lepton asymmetry that is converted into the observed baryon asymmetry via non-thermal leptogenesis and electroweak sphalerons, for a reheating temperature consistent with both successful leptogenesis and the gravitino constraint.

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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.

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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.

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arXiv2026

Shifted Hybrid Realization of Non-Minimal Higgs Inflation in Light of ACT DR6 and Planck Data

We investigate non-minimal Higgs inflation in a no-scale-inspired supergravity framework and confront its predictions with the latest CMB constraints from ACT DR6 and \emph{Planck}. Working within a shifted hybrid inflation scenario, we construct an effective single-field description in which the GUT Higgs direction serves as the inflaton after stabilization of the orthogonal scalar fields. We show that the inclusion of the leading nonrenormalizable operator in the superpotential induces a controlled deformation of the Starobinsky attractor, allowing the scalar spectral index to be shifted into the range favored by recent ACT and related CMB datasets while maintaining a small tensor-to-scalar ratio, $r \sim 10^{-3}-10^{-2}$. The resulting inflationary dynamics remain theoretically consistent, with controlled supergravity corrections and sub-Planckian inflaton field values. We perform a detailed numerical analysis of the model parameter space, including reheating and nonthermal leptogenesis, and identify regions that simultaneously satisfy current observational constraints and yield a viable post-inflationary cosmological history.

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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.

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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.

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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.

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arXiv2025

Supersymmetric hybrid inflation and current-carrying metastable cosmic strings in $SU(4)_c \times SU(2)_L \times U(1)_R$

We construct a realistic supersymmetric model for superheavy metastable cosmic strings (CSs) that can be investigated in the current pulsar timing array (PTA) experiments. It is based on shifted $μ$-hybrid inflation in which the symmetry breaking $SU(4)_c \times SU(2)_L \times U(1)_R\rightarrow SU(3)_c\times SU(2)_L \times U(1)_{B-L}\times U(1)_R$ proceeds along an inflationary trajectory such that the topologically unstable primordial monopoles are inflated away. {{The breaking of $U(1)_{B-L} \times U(1)_R \rightarrow U(1)_Y$ after inflation ends yields the superheavy metastable CSs carrying the right handed neutrino zero modes that generate the stochastic gravitational wave background (SGWB), which we show is consistent with the current PTA data set and the LIGO O3 run}}. The scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$ are compatible with the Planck 2018 and Atacama Cosmology Telescope measurements. Both reheating and leptogenesis are briefly discussed.

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arXiv2025

Supersymmetric Hybrid Inflation with Kähler-Induced $\mathbf{R}$-Symmetry Breaking

We explore the role of explicit nonrenormalizable $R$-symmetry breaking interactions in the context of supersymmetric hybrid inflation. In particular, we focus on scenarios where such breaking arises predominantly from the Kähler potential, while the renormalizable terms in both the superpotential and Kähler potential preserve $R$-symmetry. Incorporating radiative corrections, soft SUSY-breaking contributions, and supergravity effects, we construct a consistent and predictive inflationary framework. Notably, the presence of $R$-symmetry violating terms at the nonrenormalizable level helps resolve the common issue of light waterfall fields in grand unified theories, rendering them sufficiently heavy without disturbing gauge coupling unification. Our numerical analysis demonstrates that these $R$-symmetry breaking contributions play a crucial role in bringing the scalar spectral index $n_s$ into excellent agreement with the recent cosmological observations, particularly the Data Release 6 of the Atacama Cosmology Telescope. The tensor-to-scalar ratio remains suppressed, with $r < 10^{-5}$, below the reach of current and near-future experiments. However, observable gravitational waves with $r \lesssim 0.03$ can be achieved by allowing moderate deviations in the parameter space associated with a non-minimal Kähler potential.

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arXiv2025

Tribrid Inflation, Type II Leptogenesis, and Observable Gravitational Waves in $SU(3)_c \times SU(2)_L \times SU(2)_R \times U(1)_{B-L}$

We present a concrete realization of tribrid inflation within the framework of the gauge group $SU(3)_c \times SU(2)_L \times SU(2)_R \times U(1)_{B-L}$. In this model, inflation is driven by the neutral components of left-handed Higgs triplets, which also play a central role in generating the observed baryon asymmetry of the universe via non-thermal leptogenesis. Tiny neutrino masses arise naturally through a type-II seesaw mechanism, facilitated by right-handed triplet fields. Supergravity corrections, stemming from the leading-order terms in a non-minimal Kähler potential, are essential in bringing the predictions of the scalar spectral index $n_s$ into agreement with the latest cosmological data, including the Atacama Cosmology Telescope Data Release 6, Planck 2018, and LB-BK18. A key feature of this model is the existence of a viable parameter space that predicts potentially observable primordial gravitational waves, with a tensor-to-scalar ratio $r \lesssim 0.005$, placing it within reach of upcoming experiments.

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arXiv2025

Radiatively Corrected Starobinsky Inflation and Primordial Gravitational Waves in Light of ACT Observations

Nonminimal coupling between the inflaton and the Ricci scalar plays a crucial role in shaping the predictions of single-field inflationary models. While a quartic potential with such coupling represents one of the simplest realizations compatible with cosmological observations, it generically receives important radiative corrections when the inflaton interacts with other fields, particularly those involved in the reheating process. In this work, we focus on radiative corrections arising from bosonic scalar couplings and study their impact on inflationary dynamics within the nonminimally coupled quartic potential framework. We demonstrate that bosonic corrections, unlike fermionic ones, yield predictions more compatible with the latest constraints from the Atacama Cosmology Telescope (ACT) Data Release 6, especially when combined with Planck and BICEP/Keck data. We begin with a general model involving a gauge-singlet real scalar inflaton coupled to a complex scalar field, which could be the Standard Model Higgs or a GUT Higgs. As a concrete realization, we also investigate the case where the inflaton serves as a dark matter candidate through a Higgs portal interaction while highlighting its potential to generate observable levels of primordial gravitational waves. Notably, the nonminimally coupled inflation model studied here is field-theoretically equivalent to the Starobinsky model, and the inclusion of quantum corrections from scalar fields leads to characteristic imprints in the $(n_s, r)$ plane, allowing for refined constraints on scalar couplings from current and future observations.

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arXiv2025

Supersymmetric Hybrid Inflation in light of Atacama Cosmology Telescope Data Release 6, Planck 2018 and LB-BK18

Supersymmetry-based hybrid inflation models (referred to as `spontaneously broken supersymmetry' by the Planck collaboration) are attractive for several reasons, including the appealing feature that inflation is associated with local gauge symmetry breaking in the early universe. Following the Planck collaboration's notation, the inflationary potential with sub-Planckian inflaton field values is given by: $V = Λ^4 [1 + α_h \log(ϕ/ M_{Pl})] - m_{3/2} Λ^2 ϕ+ Λ^4 O((ϕ/ M_{Pl})^4)$. Here, $Λ= \sqrtκ M$ denotes the energy scale of inflation, $M$ is the gauge symmetry breaking scale, $κ$ is a dimensionless parameter that sets the inflaton mass ($\sqrt{2} κM$), and $α_h$ is determined from quantum corrections in terms of $κ$ and the underlying gauge group. A soft supersymmetry-breaking term proportional to the gravitino mass $m_{3/2}$ (~10 TeV) and linear in the inflaton field $ϕ$ is also present during inflation. The final term in $V$ represents the leading-order supergravity correction. (Note that the last two terms were not taken into account in the Planck analysis.) We provide estimates for the parameters $κ$ (and $α_h$) that yield a scalar spectral index $n_s$ in the range 0.96 to 0.98, which is fully consistent with recent P-ACT-LB measurements presented by the Atacama Cosmology Telescope, as well as earlier measurements by Planck. We recall that in the absence of the soft SUSY-breaking term proportional to $m_{3/2}$ in $V$, the spectral index $n_s = 1 - 1/N = 0.98$, where $N = 50$ denotes the number of e-foldings. The tensor-to-scalar ratio $r$ in this minimal model is tiny, but it can reach potentially observable values ($r \lesssim 0.01$) in non-minimal models.

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arXiv2025

$\mathbfμ$-Hybrid Inflation and Metastable Cosmic Strings in $\mathbf{SU(3)_c\times SU(2)_L\times SU(2)_R \times U(1)_{B-L}}$

We develop a scenario based on $μ$-hybrid inflation within the framework of a left-right symmetric model defined by the gauge symmetry group $G_{3221} = SU(3)_c \times SU(2)_L \times SU(2)_R \times U(1)_{B-L}$. This model features a two-stage symmetry breaking to the Standard Model, with inflation occurring between the two stages, resulting in the dilution of primordial monopoles produced during the symmetry breaking of $SU(2)_R$ to $U(1)_R$. The second symmetry breaking gives rise to a network of metastable cosmic strings, which produces gravitational waves that can be observed by current and future experiments. A crucial aspect of this model is the inclusion of $R$-symmetry breaking terms in the superpotential, which helps explain the origin of the first symmetry breaking scale and ensures experimentally viable inflation with a minimal (canonical) Kähler potential. We show that the model successfully implements consistent inflation, leptogenesis, metastable cosmic strings, and gravitino dark matter, all in agreement with the observational data and constraints on reheating temperature from leptogenesis and gravitino overproduction bounds. We explore the potential embedding of $G_{3221}$ within the gauge symmetry $G_{422} = SU(4)_c \times SU(2)_L \times SU(2)_R$, and provide a brief discussion on the proton decay predictions, which can be tested by the upcoming experiments.

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arXiv2025

Exploring primordial black holes and gravitational waves with R-symmetric GUT Higgs inflation

This study investigates the realization of R-symmetric Higgs inflation within the framework of no-scale-like supergravity, aiming to elucidate the formation of primordial black holes and observable gravitational waves within a class of GUT models. We explore the possibility of an ultra-slow-roll phase in a hybrid inflation framework, where the GUT Higgs field primarily takes on the role of the inflaton. The amplification of the scalar power spectrum gives rise to scalar-induced gravitational waves and the generation of primordial black holes. The predicted stochastic gravitational wave background falls within the sensitivity range of existing and upcoming gravitational wave detectors, while primordial black holes hold the potential to explain the abundance of dark matter. Furthermore, we highlight the significance of the leading-order nonrenormalizable term in the superpotential of achieving inflationary observables consistent with the latest experimental data. Additionally, the predicted range of the tensor-to-scalar ratio, a key measure of primordial gravitational waves, lies within the observational window of future experiments searching for B-mode polarization patterns in cosmic microwave background data.

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arXiv2024

The Stochastic Gravitational-Wave Background from Primordial Black Holes in R-Symmetric $SU(5)$ Inflation

This study explores the realization of nonminimally coupled Higgs inflation in the context of no-scale supergravity, investigates the formation of primordial black holes, and examines the potential for observable proton decay within the framework of the R-symmetric $SU(5)$ model. For inflation, both single and multifield scenarios are investigated. The prediction of the single-field model for the tensor-to-scalar ratio, $r$, is approximately $10^{-3}$, and the scalar spectral index falls within Plank's 1$σ$ range. The running of the scalar spectral index, $-{dn_{s}}/{d\ln{k}}$, is approximately $10^{-4}$. A realistic scenario of reheating and non-thermal leptogenesis is employed with reheat temperature $T_r\sim10^9$ GeV. In the multifield case, we mainly focus on Primordial Black Holes (PBHs) and Gravitational Waves (GWs). In this inflationary framework, we demonstrate how a suitable choice of parameters can result in an enhanced scalar power spectrum, leading to the production of primordial black holes (PBHs) capable of fully accounting for dark matter. We also show that this scenario leads to Scalar Induced Gravitational Waves (SIGW) which can be detected in current and future GW detectors. We explore different proton decay channels to look for observable predictions for the next-generation proton decay experiments Hyper-K and DUNE consistent with gauge coupling unification and cosmological bounds.

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arXiv2024

Magnetic Monopole Phenomenology at Future Hadron Colliders

In the grand tapestry of Physics, the magnetic monopole is a holy grail. Therefore, numerous efforts are underway in search of this hypothetical particle at CMS, ATLAS and MoEDAL experiments of LHC by employing different production mechanisms. The cornerstone of our comprehension of monopoles lies in Dirac's theory which outlines their characteristics and dynamics. Within this theoretical framework, an effective $U(1)$ gauge field theory, derived from conventional models, delineates the interaction between spin magnetically-charged fields and ordinary photons under electric-magnetic dualization. The focus of this paper is the production of magnetic monopoles from Drell-Yan and the Photon-Fusion mechanisms to produce velocity-dependent scalar, fermionic, and vector monopoles of spin angular momentum $0,\frac{1}{2},1$ respectively at LHC. A computational work is performed to compare the monopole pair-production cross-sections for both methods at different center-of-mass energies ($\sqrt{s}$) with various magnetic dipole moments. The comparison of kinematic distributions of monopoles at Parton and reconstructed level are demonstrated including both DY and PF mechanisms. Extracted results showcase how modern machine-learning techniques can be used to study the production of magnetic monopoles at the Future proton-proton Particle Colliders at 100 TeV. We demonstrate the observability of magnetic monopoles against the most relevant Standard Model background using multivariate methods such as Boosted Decision Trees (BDT), Likelihood, and Multilayer Perceptron (MLP). This study compares the performance of these classifiers with traditional cut-based and counting approaches, proving the superiority of our methods.

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arXiv2024

Inflation, Proton Decay and Gravitational Waves from Metastable Strings in $SU(4)_C \times SU(2)_L \times U(1)_R$ Model

We present a realistic supersymmetric $μ$-hybrid inflation model within the framework of $SU(4)_C \times SU(2)_L \times U(1)_R$ gauge symmetry, wherein the symmetry breaking $SU(4)_C \times SU(2)_L \times U(1)_R\rightarrow SU(3)_C\times SU(2)_L \times U(1)_{B-L}\times U(1)_R$ occurs before observable inflation, effectively eliminating topologically stable primordial monopoles. Subsequent breaking of $U(1)_{B-L} \times U(1)_R \rightarrow U(1)_Y$ after inflation leads to the formation of superheavy metastable cosmic strings (CSs), capable of producing a stochastic gravitational wave background (SGWB) consistent with the recent PTA data. Moreover, the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$ align with Planck 2018 observations. A consistent scenario for reheating and non-thermal leptogenesis is employed to explain the observed matter content of the universe. Finally, the embedding of $G_{421}$ into the Pati-Salam gauge symmetry $G_{422}$ is briefly discussed, predicting potentially observable proton decay rates detectable at facilities such as Hyper Kamiokande and DUNE.

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arXiv2023

Observable proton decay and gauge coupling unification in the improved missing doublet SU(5) model

We investigate the possibility of observable proton decay within the improved missing doublet model (IMDM75), which utilizes a Higgs in 75 representation for $SU(5)$ gauge symmetry breaking. The realization of observable proton decay in IMDM75 is made feasible primarily due to chirality nonflipping color-triplet mediation, while chirality flipping mediation is adequately suppressed. Our predictions suggest a range of proton lifetimes between $10^{34}-10^{36}$ yr, which can be observed in upcoming experiments such as Hyper-K and DUNE, for a corresponding range of color-triplet mass parameter $M_T$ in the order of $10^{11}-10^{14}$GeV. IMDM75 is shown to offer unique predictions for branching ratios when compared to other grand unified theory models. Finally, a realization of successful gauge coupling unification is achieved, even with the presence of particles at intermediate scales.

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