arXiv subjects

Mathew Thomas Arun

Publications and source records attributed to Mathew Thomas Arun.

At least 19 recordsLinked to original sources

arXiv2026

Status of light inflaton: from inflation to laboratory

We investigate the viability of the light inflaton scenario in light of the latest inflationary constraints from the Atacama Cosmology Telescope (ACT), together with bounds from collider and intensity-frontier experiments searching for a feebly coupled light scalar with a sub-GeV mass. Assuming a quartic inflaton potential, we identify the region of parameter space consistent with the ACT observations and derive constraints on the inflaton mass and inflaton-Higgs mixing using results from NA62, KOTO, BaBar, Belle, LHCb, MATHUSLA, FASER2, SHiP, and neutral meson oscillations. We also explore the prospects for dark matter production during reheating within this framework, while remaining consistent with the inflationary observables.

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arXiv2026

Learning holographic QCD with unflavored meson spectra

We develop a data-driven neural network framework to reconstruct the five-dimensional background geometry, the dilaton potential, and the chiral-symmetry-breaking scalar potential of holographic QCD from hadron mass spectra. Framed as an inverse problem, the model is trained using a discretized form of the Schrödinger-like equation, which resembles a linear moose in ``deconstructed" 5 dimensions with Dirichlet boundary conditions, in contrast to the AdS/DL with ``emergent" space-time. Using the masses of the unflavored mesons $ρ$, $a_1$, $a_2$, and $f_0$ and their excitations as training data, the model learns confining effective potentials and computes a dilaton profile that satisfies the null energy condition. The network predicts that the dilaton's IR behavior will be much steeper than its quadratic form. Moreover, the symmetry-breaking bulk potential of the scalar field, $V(X) \sim k_1 X^3+k_2 X^4$, was computed, and the parameters $k_1$ and $k_2$ predicted to be $\sim -4$ and $\sim 9$ respectively. The deep-learned parameters, metric, and the dilaton profile were then used to predict the pion mass and its spectrum with good accuracy. A Python code, along with the trained models, is provided to facilitate further studies\footnote{Available at Github, https://github.com/rp-winter/NN-AdS-QCD

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arXiv2026

From WIMP to FIMP during reheating: collider vs non-collider probes for p-wave annihilation

By examining the transition from freeze-out to freeze-in dark matter (DM) production within the framework of perturbative reheating, where DM interacts with the visible sector through effective operators of dimension six, we have investigated how a broad range of new physics probes can reveal the nature of the pre-BBN Universe. Incorporating constraints from direct and indirect DM searches, invisible decay measurements, collider experiments, and gravitational wave observations, our analysis demonstrates that both current and forthcoming experimental sensitivities can serve as powerful tools for probing as well as constraining the post-inflationary era, together with new physics beyond the SM. Our analysis demonstrates that collider experiments at both the intensity and energy frontiers can impose strong bounds on derivative operators whose interactions are typically {\it p-wave suppressed}, and therefore only weakly constrained by astrophysical observations. In particular, these complementary searches can significantly restrict the allowed reheating temperature, DM mass and effective interaction scale required to reproduce the observed DM abundance for DM produced during the epoch of reheating.

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arXiv2025

RG evolution and effect of intermediate new-physics on $ΔB=1$ four-fermion operators

Motivated by the stringent experimental bounds on proton lifetime and the need for precise low-energy predictions, there has been renewed interest in the renormalization group (RG) evolution of Wilson coefficients for baryon number violating (BNV) operators and their characteristic new-physics scales. In this work, we analyze the RG running of dimension-6 four-fermion operators in the $\overline{\text{MS}}$ scheme that mediate nucleon decay channels such as $p \to e^+ π^0$, while systematically accounting for the impact of baryon number conserving (BNC) new-physics that can enter the theory at an intermediate scale as higher-dimensional effective field theory operator. These BNC operators mix with BNV ones at 1-loop and alter the RG flow. The running is performed from the electroweak scale up to representative intermediate scales of $10^4~\text{GeV}$, $10^6~\text{GeV}$, and $10^9~\text{GeV}$, corresponding to possible thresholds for new BNC degrees of freedom. Comparing the RG evolved coefficients with current experimental bounds on nucleon decay lifetimes, we find that the inclusion of BNC-BNV mixing, dominated by top quark loops, can significantly lower the effective proton decay scale to $\sim 10^7$ GeV, thus mitigating the need of a large desert. A Python package is provided to facilitate the RG evolution of nucleon-decay Wilson coefficients, allowing for the inclusion of generic BNC effects.

hep-ph↗

arXiv2025

RG evolution and effect of intermediate new physics on $ΔB=2$ six-quark operators

The recent identification of possible 11 neutron-antineutron ($n$-$\bar{n}$) oscillation candidate events at Super-Kamiokande has renewed the interest in $ΔB = 2$ transitions. In this work, we analyze the Renormalization Group (RG) running of mass dimension-9 six-quark operators, in $\bar{MS}$ scheme, that generate processes like $nn\to π^0π^0$, deuteron decay, $n$-$\bar{n}$ oscillations etc, evolving them from the electroweak scale to baryon number violating scale ($\mathcal{O}(10^3~\text{TeV})$). Our goal is to systematically account for the influence of potential new physics at intermediate energies ($\gtrsim \mathcal{O}(10~ \text{TeV})$), especially given the fact that {\it Large Hadron Collider} has not ruled out new physics beyond $\sim 10~\text{TeV}$. To comprehensively investigate their influence, we consider two scenarios: (i) a minimal setup with only Standard Model degrees of freedom up to the high scale at $\mathcal{O}(10^3~\text{TeV})$, and (ii) an extended framework involving scalar and vector bosons above $\sim 10~\text{TeV}$ up till BNV scale. To facilitate further studies, we also provide a Python script that performs RG evolution of the BNV Wilson coefficients in the presence of generic bosonic new physics at any intermediate energy scale. It can be modified easily to meet the needs of the user to investigate the running of the BNV Wilson coefficients. We then compare the result with the experimental bound from the neutron-antineutron oscillation process and constrain the scale of baryon number violating new physics.

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arXiv2025

On the role of cosmological constant in modeling hadrons

Einsteins gravity with a cosmological constant $Λ$ in four dimensions can be reformulated as a $λϕ^4$ theory characterized solely by the dimensionless coupling $λ\propto G_N Λ$ ($G_N$ being Newton's constant). The quantum triviality of this theory drives $λ\to 0$, and a deviation from this behavior could be generated by matter couplings. Here, we study the significance of this conformal symmetry and its breaking in modeling non-perturbative QCD. The hadron spectra and correlation functions are studied holographically in an $AdS_5$ geometry with induced cosmological constants on four-dimensional hypersurface. Our analysis shows that the experimentally measured spectra of the $ρ$ and $a_1$ mesons, including their excitations and decay constants, favour a non-vanishing induced cosmological constant in both hard-wall and soft-wall models. Although this behavior is not as sharp in the soft-wall model as in the hard-wall model, it remains consistent. Furthermore, we show that the correction to the Gell-Mann-Oakes-Renner relation has an inverse dependence on the induced cosmological constant, underscoring its significance in holographic descriptions of low-energy QCD.

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arXiv2025

Constraining anti-baryonic dark matter through correlated nucleon decay signatures

Baryon number violation in the visible sector induced by anti-baryonic dark matter provides a viable mechanism for low-scale baryogenesis. Two of the most sensitive probes of this scenario are neutron decay processes such as $n \to \barν + \text{invisible}$ and $n \to π^0 + \text{invisible}$. In this work, we discuss the possible spontaneous breaking of baryon symmetry in the dark sector and the generation of di-nucleon decay processes such as $nn \to \barν\barν$ and $nn \to π^0π^0$ at one-loop, arising from the operators responsible for induced nucleon decays. While the induced nucleon decay rates in this model depend on the dark matter density, di-nucleon decay processes do not, providing a complementary probe of the new physics. We thus use nucleon and di-nucleon decay bounds to constrain the local density and mass of the anti-baryonic dark matter.

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arXiv2025

Axi-Higgs portal Dark Matter via Wess-Zumino mechanism

We study the axion portal between the visible and the dark sector, where the dark matter is charged under an abelian extension of the Standard Model. In general, such models are anomalous and are rendered gauge invariant by a St{ü}ckelberg axion through Wess-Zumino/Green-Schwarz mechanism. Scenarios such as this naturally exist in TeV scale string theory completions of Standard Model. This axion mixes with other Goldstone bosons in the model to give a physical axi-Higgs which becomes massive upon breaking the anomalous gauge group. Such axi-Higgs fields charged under the anomalous symmetry act as mediators for the dark matter annihilation to Standard Model particles and can lead to an efficient freeze-out mechanism. Here, we show that the St{ü}ckelberg axion, and the resultant axi-Higgs, with its appropriate shift symmetry cancels the quantum anomalies and also generates the observed relic density for the dark matter. Moreover, we show that the relevant parameter space in our model, where photon production dominates, is safe from {\it Fermi}LAT, Cherenkov Telescope Array, and H.E.S.S. indirect detection experiments.

hep-ph↗

arXiv2024

Assisted baryon number violation from $4k+2$ dimensions

Proton decay in six dimensions orbifolded on square $T^2/Z_2$ is highly suppressed at tree-level. This is because baryon number violating (BNV) operators containing only the zero mode of bulk fermions must satisfy the selection rule $\frac{3}{2} ΔB \pm \frac{1}{2}ΔL = 0 \ mod \ 4$. In this article, we show that the above relation does not prohibit mass dimension-6 BNV operators containing Kaluza Klein (KK) partners of the bulk fermions. Together with `spinless' adjoint scalar partner of hypercharge gauge boson (the Dark Matter candidate), these novel operators generate Dark Matter assisted proton decay at mass dimension-8. Here, with explicit examples of scalar and vector baryon number violating interactions, we discuss the importance of such $ΔB=1 =ΔL$ and $ΔB=2=ΔL$ operators and derive the limit on New Physics.

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arXiv2024

Constraint on cosmological constant in generalized Skryme-teleparallel system

The Einstein-Skyrme system is understood to defy the "no hair" conjecture by possessing black-hole solutions with fractional baryon number outside the event horizon. In this article, we extend the study of the Skyrme system to teleparallel gravity framework. We consider two scenarios, the Teleparallel Equivalent of General Relativity (TEGR) and generalized teleparallel gravity $f(T)$. In our analysis, we compute the fractional baryon number beyond the black-hole horizon and its correlation with the cosmological constant ($Λ$). In the TEGR context, where $f(T) = -T - 2Λ$, the results match with the Einstein-Skyrme model, assuming a positive $Λ$. More interestingly, in generalized teleparallel gravity scenario, defined by $f(T) = -T - τT^2 - 2Λ$, we show that the existence of a solution demands that not only must $Λ$ be positive but has to lie in a range, $Λ_{min} < Λ< Λ_{max}$. While the upper bound depends inversely on $τ$, the lower bound is a linear function of it. Hence, in the limiting case with generalized teleparallel gravity converging towards TEGR ($τ\rightarrow 0$), the constraints on the cosmological constant relax to the Einstein Skryme system ($Λ_{min}$ approaches zero and $Λ_{max}$ becomes unbounded). On the other hand, in f(T) gravity, vanishing cosmological constant solution is found only if the lower bound on the energy of the soliton is very large.

gr-qc↗

arXiv2023

Tri-bimaximal-Cabibbo Mixing: Flavour violations in the charged lepton sector

The well understood structure of $U_{pmns}$ matrix mandates a Cabibbo mixing matrix in the first two generations of the charged lepton sector if we assume Tri-bimaximal mixing in the neutrino sector. This ansatz, called Tri-bimaximal-Cabibbo mixing, is ruled out immediately by the experiments searching for charged lepton flavour violating currents. In this article, we aim to show that the resurrection of the theoretically well motivated Tri-bimaximal mixing scenario comes naturally within Minimal Flavour Violation hypothesis in the lepton sector. We analyse the flavour violating currents $μ\rightarrow e e e$, $μTi \to e Ti$, $μ\rightarrow e γ$, $π^0\rightarrow e^+ μ^{-}$ and $K_L \rightarrow μ^+ e^-$ in this scenario and show that the New Physics that generates mixing among the charged lepton could lie within the reach of hadron colliders. In the minimal field content scenario, though the most stringent constrain on New Physics is $\gtrsim \mathcal{O}(10$ TeV) for maximal coupling, considering more natural couplings relaxes it to $\gtrsim \mathcal{O}(4$ TeV). On the other hand, New Physics with the extended field content is even more strongly constrained to $\gtrsim \mathcal{O}(75$ TeV) for maximal coupling, while it gets relaxed to $\gtrsim \mathcal{O}(31$ TeV) for natural scenario.

hep-ph↗

arXiv2023

Constraining SMEFT BSM scenarios with EWPO and $Δ_{CKM}$

Precision observables are well known for constraining most of the Beyond Standard Model (BSM) scenarios tightly. We present here a simple and comprehensive fitting framework for various BSM scenarios to these observables. We start with the fit of $S$, $T$ and $V$ parameter and their correlations using the Electroweak Precision Observables (EWPO) including the recent $m_W$ measurement from CDF-II. Utilizing these observables, we also fit various New Physics (NP) scenarios consisting of different subsets of dimension-6 Standard Model Effective Field Theory (SMEFT) operators in the Warsaw basis out of a total of 10 appearing at tree level in EWPO. To further constrain these scenarios, we augment these observables with $Δ_{CKM}$ measurement using 1-loop matching of the Low Energy Effective Field Theory (LEFT) to SMEFT operators at the Z-pole. We show that the inclusion of $Δ_{CKM}$ constraint indeed results in stronger bounds on the SMEFT Wilson Coefficients. We also constrain the UV parameters of BSM extensions like Vectorlike leptons (VLL) and find out that such a minimal extension is in tension with the forward-backward asymmetry in $b$-sector ($A_b^{FB}$) and the recent measurement of $M_W$. In order to lift the two blind directions, which one encounters while fitting all the 10 SMEFT WCs at tree-level, we also include the LEP-II observables pertaining to the $WW$ production and present the results for the fits with and without $Δ_{CKM}$ constraint.

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arXiv2023

Baryon number violation from confining New Physics

The detection of neutron-antineutron oscillation will be a discovery of fundamental importance in particle physics and cosmology. In models discussed widely in literature, the process is generated through heavy New Physics with weak, perturbative, coupling at the scale of the experiment. Acknowledging the fact that Nature has been quite evasive regarding the strength and scale of New Physics, we discuss a new mechanism, generated by confining New Physics, at $\sim 2$ GeV, resulting in low-energy baryon number violating effects. The mechanism predicts baryon number violating processes like neutron disappearance, neutron-neutron annihilation and neutron-anti neutron oscillation generated through the condensation of the linear moose.

hep-ph↗

arXiv2023

Search for the $Z^\prime$ boson decaying to a right-handed neutrino pair in leptophobic $\mathrm{U(1)}$ models

The $U(1)$ extensions of the Standard Model contain a heavy neutral gauge boson $Z^\prime$. If leptophobic, the boson can evade the stringent bounds from the dilepton resonance searches. We consider two theoretically well-motivated examples of leptophobic $U(1)$ extensions in which the $Z'$ decays to right-handed neutrinos (RHNs) with substantial branchings. The coexistence of a leptophobic $Z^\prime$ and the RHNs opens up a new possibility of searching for these particles simultaneously through the production of a $Z^\prime$ at the LHC and its decay to a RHN pair. For this decay to occur, the RHNs need to be lighter than the $Z^\prime$. Hence, we study this process in an inverse seesaw setup where the RHNs can be in the TeV range. However, in this case, they have a pseudo-Dirac nature, i.e., a RHN pair would produce only opposite-sign lepton pairs, as opposed to the Majorana-type neutrinos, which can produce both same- and opposite-sign lepton pairs. Hence, the final state we study has a same-flavour opposite-sign lepton pair plus hadronically-decaying boosted $W$ bosons. Our analysis shows that the high luminosity LHC can discover a TeV-scale leptophobic $Z^\prime$ decaying via a RHN pair in a wide range of available parameters. Interestingly, large parameter regions beyond the reach of future dijet-resonance searches can be probed exclusively through our channel.

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arXiv2022

Flavour violating charged lepton decays in Little Randall-Sundrum Model

The Little Randall-Sundrum (Little RS) model receives significantly stronger constraints from the flavour observables in comparison to Randall-Sundrum (RS) model. In this paper, we analyse the effect of the electro-weak sector in Little RS on flavour changing decays of charged leptons. We compare the predictions of the model with the current limits on the flavour violating Branching Ratios of $μ\rightarrow e e e $, $τ\rightarrow e e e $, $τ\rightarrow μμμ$, $τ\rightarrow μe e $, $τ\rightarrow e μμ$ , $μ\rightarrow e γ$, and $μTi \rightarrow e Ti $. And we show that the dominant constraint arises from the $μTi \rightarrow e Ti$ process which strongly limits the KK-1 gauge boson mass ($M_{KK}$) to be $\gtrsim 30.7 TeV $. We then derive and show that generalising the electro-weak gauge sector to include the Brane Localised Kinetic Term (BLKT) relaxes this constraint to $\gtrsim 12 TeV$. Towards the conclusion, we comment on the possibility that the large flavour violating currents can be mitigated by relaxing the assumption regarding the unnatural thinness and rigidity of the UV-brane and discuss the possibility of suppression of these currents in presence of fat fluctuating branes.

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arXiv2022

Testing left-right symmetry with an inverse seesaw mechanism at the LHC

In the left-right symmetric models, a heavy charged gauge boson $W'$ can decay to a lepton and a right-handed neutrino (RHN). If the neutrino masses are generated through the standard type-I seesaw mechanism, the Yukawa couplings controlling two-body decays of the RHN become very small. As a result, the RHN decays to another lepton and a pair of jets via an off-shell $W'$. This is the basis of the Keung-Senjanović (KS) process, which was originally proposed as a probe of lepton number violation at the LHC. However, if a different mechanism like the inverse seesaw generates the neutrino masses, a TeV-scale RHN can have large Yukawa couplings and hence dominantly decay to a lepton and a $W$ boson, leading to a kinematically different process from the KS one. We investigate the prospect of this unexplored process as a probe of the inverse seesaw mechanism in the left-right symmetric models at the High Luminosity LHC (HL-LHC). Our signal arises from the Drell-Yan production of a $W'$ and leads to two high-$p_T$ same-flavour-opposite-sign leptons and a boosted $W$-like fatjet in the final state. We find that a sequential $W'$ with mass up to $\sim 6$~TeV along with a TeV-scale RHN can be discovered at the HL-LHC.

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arXiv2022

Neutron oscillation and Baryogenesis from six dimensions

Considering a six-dimensional geometry orbifolded on $S^1/Z_2\times S^1/Z_2$ with quarks and leptons localised on orthogonal branes, we show that the construction admits observable $n-\bar{n}$ oscillation while naturally suppressing the proton decay rates. Consistent with other low-energy observables, the model also accommodates baryogenesis at $\mathcal{O}$(10 TeV) scale.

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arXiv2022

Kalb-Ramond field induced cosmological bounce in generalized teleparallel gravity

One of the important open questions in high-energy physics is to understand the lack of evidence of Kalb-Ramond (KR) field, in particular in the present day cosmology. In this paper we aim to address this issue by showing that a bounce scenario in the evolution of the Universe strongly advocates their elusiveness, even if their energy density was very large to start with. We consider the Kalb-Ramond field and its effects in the context of generalized teleparallel gravity in (3+1) dimensions. Teleparallel gravity is a description of gravitation in which the tetrads are the dynamical degrees of freedom, and the torsion arising from fields with spin are accommodated naturally as field strength tensors. In order to describe the coupling prescription, we address the correct generalization of the Fock-Ivanenko derivative operator for an n-form tensor field. By varying with respect to the tetrads, this rank-2 field is shown to source the teleparallel equivalent of Einstein's equations. We study the possibility of reproducing two well-known cosmological bounce scenarios, namely, symmetric bounce and matter bounce in four-dimensional spacetime with with the Friedmann-Lemaitre-Robertson-Walker metric and observe that the solution requires the KR field energy density to be localized near the bounce. The crucial result in our work is that this feature also naturally explains the lack of cosmological evidence of the rank-2 field in the present day Universe for the matter-bounce scenario. Thus, among the bouncing cosmologies, latter is favored over the former.

gr-qc↗