arXiv subjects

Md. Abhishek

Publications and source records attributed to Md. Abhishek.

8 recordsLinked to original sources

arXiv2026

Cosmological Correlators in Gauge Theory and Gravity from EAdS

In this work we examine in more detail the map between late-time correlators in de Sitter space and boundary correlators in Euclidean anti-de Sitter space, elaborating on the general construction presented in arXiv:2007.09993 and arXiv:2109.02725 for EFTs of bosonic spinning fields. This map may be phrased as an equivalence between the generating functional of late-time correlators in the Schwinger--Keldysh formalism and the generating functional for boundary correlators in the corresponding EAdS theory. We extend the construction to gauge bosons and gravitons, and clarify additional subtleties that appear in even boundary dimensions. We give the resulting EAdS Feynman rules for scalar QED, pure Yang--Mills theory and Einstein gravity in dS space, illustrating them with contact and tree-level exchange diagrams. The sinusoidal factors relating dS and EAdS diagrams lead to selection rules for late-time falloffs, with possible residual local terms only in IR-divergent cases. Finally, we emphasise that the relation between dS and EAdS propagators is manifest in Mellin space, and we provide new expressions for gauge-boson and graviton propagators in axial/temporal gauge, including their longitudinal components. These results provide a practical framework for studying cosmological correlators involving gauge fields and gravitons.

hep-th↗

arXiv2024

Looking for the $G_2$ Higgs Branch of 4D Rank 1 SCFTs

The Schur index of the Higgs branch of 4-dimensional $\mathcal{N}=2$ SCFTs is related to the spectrum of non-unitary 2-dimensional CFTs. The rank 1 case has been shown to lead to the non-unitary CFTs with Deligne-Cvitanovic (DC) exceptional sequence of Lie groups. We show that a subsequence $(A_0, A_{\frac{1}{2}}, A_1, A_2, D_4)$ within the non-unitary sequence is related to a subsequence in the Mathur-Mukhi-Sen (MMS) sequence of unitary theories. We show that 2D non-unitary $G_2$ theory is related to unitary $E_6$ theory, and using this result along with the Galois conjugation, we propose that the $G_2$ Higgs branch is a sub-branch of the $E_6$ Higgs branch.

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arXiv2024

On-shell functions on the Coulomb branch of $\mathcal{N}=4$ SYM

We study on-shell functions in the kinematic space for the Coulomb branch of $\mathcal{N}=4$ SYM. We construct BCFW bridges that help us build bigger on-shell functions. As a consequence, we provide on-shell diagram formulations for BCFW shifts that correspond to various mass configurations. We will use this to calculate the quadruple cut for the one-loop amplitude on the Coulomb branch and maximal cuts for higher-loops. We make preliminary comments on finding the inequivalent set of on-shell functions for the Coulomb branch.

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arXiv2024

Loop Amplitudes in the Coulomb Branch of $\mathcal{N}=4$ Super-Yang-Mills Theory

We study four point planar loop amplitudes at an arbitrary point in the Coulomb branch of $\mathcal{N}=4$ super-Yang-Mills theory. We study two particle unitary cuts up to four loop order. We explicitly verify that bubble and triangle graphs do not contribute at one loop level and show that the results hold at higher loop level as well. We also write down an all loop recursion relation for two particle reducible graphs for four point amplitudes.

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arXiv2023

Effect of Minimal Length on Landau Diamagnetism and de Haas-van Alphen Effect

We study Landau diamagnetism in the framework of generalised uncertainty principle(GUP). We calculate the correction to magnetisation and susceptibility by constructing the grand partition function of diamagnetic material in this framework. We explicitly show that Curie's law gets a temperature independent correction which vanishes when quantum gravity effects are neglected. We further consider the low temperature limit to find how GUP affects the de Haas-van Alphen effect.

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arXiv2022

Scattering Amplitudes and BCFW in $\mathcal{N}=2^{\ast}$ Theory

We use massive spinor helicity formalism to study scattering amplitudes in $\mathcal{N}=2^*$ super-Yang-Mills theory in four dimensions. We compute the amplitudes at an arbitrary point in the Coulomb branch of this theory. We compute amplitudes using projection from $\mathcal{N}=4$ theory and write three point amplitudes in a convenient form using special kinematics. We then compute four point amplitudes by carrying out massive BCFW shifts of the amplitudes. We find some of the shifted amplitudes have a pole at $z=\infty$. Taking the residue at $z=\infty$ into account ensures little group covariance of the final result.

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arXiv2021

One-loop integrand from generalised scattering equations

Generalised bi-adjoint scalar amplitudes, obtained from integrations over moduli space of punctured $\mathbb{CP}^{k-1}$, are novel extensions of the CHY formalism. These amplitudes have realisations in terms of Grassmannian cluster algebras. Recently connections between one-loop integrands for bi-adjoint cubic scalar theory and $\mathcal{D}_n$ cluster polytope have been established. In this paper using the $\text{Gr}\left(3,6\right)$ cluster algebra, we relate the singularities of $\left(3,6\right)$ amplitude to four-point one-loop integrand in the bi-adjoint cubic scalar theory through the $\mathcal{D}_{4}$ cluster polytope. We also study factorisation properties of the $(3,6)$ amplitude at various boundaries in the worldsheet.

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arXiv2021

Double Soft Theorem for Generalised Biadjoint Scalar Amplitudes

We study double soft theorem for the generalised biadjoint scalar field theory whose amplitudes are computed in terms of punctures on $\mathbb{CP}^{k-1}$. We find that whenever the double soft limit does not decouple into a product of single soft factors, the leading contributions to the double soft theorems come from the degenerate solutions, otherwise the non degenerate solutions dominate. Our analysis uses the regular solutions to the scattering equations. Most of the results are presented for $k=3$ but we show how they generalise to arbitrary $k$. We have explicit analytic results, for any $k$, in the case when soft external states are adjacent.

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