Sumit Kumar Garg

We study the theoretical constraints on the scalar sector of the alternative left-right model (ALRM), an E 6 -motivated extension of the Standard Model based on the gauge group S U ( 3 ) c ⊗ S U ( 2 ) L ⊗ S U ( 2 ) R ′ ⊗ U ( 1 ) B − L , supplemented by a global U ( 1 ) S symmetry. We derive the complete set of tree-level perturbative unitarity constraints on the model, resulting in 14 independent conditions on the quartic scalar couplings. When combined with the boundedness-from-below conditions and the requirement of positive-definite scalar mass-squared eigenvalues, this yields significantly more stringent restrictions on the parameter space than either set alone. We then perform a one-loop renormalization group analysis, evolving the model parameters up to a high-energy cutoff scale, and requiring that the vacuum stability, the unitarity, and the perturbativity conditions are preserved throughout. The renormalization group evolution is found to restrict the allowed parameter space considerably beyond the tree-level bounds, with the constraints on the quartic couplings becoming more stringent as the cutoff scale is raised. Consequently, the physical scalar masses in the model acquire upper bounds. For the right-hand symmetry breaking scale, v R = 10 TeV and requiring theoretical consistency up to 10 16 GeV , we obtain m H 1 ± ≲ 6.5 TeV , m H 2 ± ≲ 1.5 TeV , and m H 1 0 ≃ m A 1 ≲ 1.5 TeV , with all bounds scaling with v R . These findings offer a predictive and falsifiable framework for searches of the extended Higgs sector of the ALRM at the current and future collider experiments.

A bstract: We investigate the sensitivity of the LHC to flavour-changing neutral current interactions involving the top quark and a photon using a model-independent effective field theory framework, focusing on two complementary processes: single top production via qg → tγ and the rare decay t → qγ in top pair events. To enhance signal discrimination, we employ a range of deep learning classifiers, including multi-layer perceptrons, graph attention networks and transformers, and compare them against a traditional cut-based analysis. Our results demonstrate that attention-based architectures, in particular transformer networks, significantly outperform other strategies, yielding up to a factor of five improvement in the expected exclusion limits. In particular, we show that at the high-luminosity LHC, rare top branching ratios can be probed down to values as low as 10 ^{− 6} . Our results thus highlight the significant potential of attention-based architectures for improving the sensitivity to new physics signatures in top quark processes at colliders.

We explore constraints on the parameter space of the alternative left-right model originating from the leptonic sector. Our analyses focuses on both lepton-flavor-conserving observables, particularly the anomalous magnetic moment of the muon, and lepton-flavor-violating processes like μ → e γ decay and μ − e conversions in nuclei. While contributions to the anomalous magnetic moment fall below the measured values at 2 σ , current and future experimental sensitivities to flavor-violating branching rations of the Standard Model leptons are expected to impose lower bounds on the mass of the peculiar S U ( 2 ) R gauge boson of the model. This provides complementary constraints relative to existing limits, which are indirect and derived from collider bounds on the mass of the associated neutral gauge boson Z ′ . Published by the American Physical Society 2025

We discuss conditions under which a deterministic sequence of real numbers, interpreted as the set of eigenvalues of a Hamiltonian, can exhibit features usually associated to random matrix spectra. A key diagnostic is the spectral form factor (SFF) — a linear ramp in the SFF is often viewed as a signature of random matrix behavior. Based on various explicit examples, we observe conditions for linear and power law ramps to arise in deterministic spectra. We note that a very simple spectrum with a linear ramp is E _n ~ log n. Despite the presence of ramps, these sequences do not exhibit conventional level repulsion, demonstrating that the lore about their concurrence needs refinement. However, when a small noise correction is added to the spectrum, they lead to clear level repulsion as well as the (linear) ramp. We note some remarkable features of logarithmic spectra, apart from their linear ramps: they are closely related to normal modes of black hole stretched horizons, and their partition function with argument s = β + it is the Riemann zeta function ζ(s). An immediate consequence is that the spectral form factor is simply −ζ|(it)|². Our observation that log spectra have a linear ramp, is closely related to the Lindelöf hypothesis on the growth of the zeta function. With elementary numerics, we check that the slope of a best fit line through |ζ(it)|² on a log-log plot is indeed 1, to the fourth decimal. We also note that truncating the Riemann zeta function sum at a finite integer N causes the would-be-eternal ramp to end on a plateau.

A bstract: Black holes are believed to have the fast scrambling properties of random matrices. If the fuzzball proposal is to be a viable model for quantum black holes, it should reproduce this expectation. This is considered challenging, because it is natural for the modes on a fuzzball microstate to follow Poisson statistics. In a previous paper, we noted a potential loophole here, thanks to the modes depending not just on the n -quantum number, but also on the J -quantum numbers of the compact dimensions. For a free scalar field ϕ , by imposing a Dirichlet boundary condition ϕ = 0 at the stretched horizon, we showed that this J -dependence leads to a linear ramp in the Spectral Form Factor (SFF). Despite this, the status of level repulsion remained mysterious. In this letter, motivated by the profile functions of BPS fuzzballs, we consider a generic profile ϕ = ϕ ₀ ( θ ) instead of ϕ = 0 at the stretched horizon. For various notions of genericity (eg. when the Fourier coefficients of ϕ ₀ ( θ ) are suitably Gaussian distributed), we find that the J -dependence of the spectrum exhibits striking evidence of level repulsion, along with the linear ramp. We also find that varying the profile leads to natural interpolations between Poisson and Wigner-Dyson(WD)-like spectra. The linear ramp in our previous work can be understood as arising via an extreme version of level repulsion in such a limiting spectrum. We also explain how the stretched horizon/fuzzball is different in these aspects from simply putting a cut-off in flat space or AdS (i.e., without a horizon).