arXiv subjects

Nirmal Ghorai

Publications and source records attributed to Nirmal Ghorai.

2 recordsLinked to original sources

arXiv2026

Towards celestial CFT dual of 4d conformal gravity

We compute tree-level celestial operator product expansions (OPE) in a bosonic sub-sector of the Berkovits-Witten conformal supergravity from the scattering amplitudes in the MHV configuration. While the OPE between a leading soft graviton current for a positive helicity graviton and any of the primary operators exhibits the same singularity structure as in a gravitational theory with two-derivative kinetic terms, the OPE of a subleading soft graviton current with a positive helicity hard graviton primary operator receives corrections, as a consequence of the non-universal nature of the subleading soft graviton theorem in the bulk. Remarkably, the subleading soft graviton terms remain consistent with the Ward identity of the chiral $\mathfrak{sl}(2,\mathbb{R}) $ current algebra, albeit with a different realisation where particle-changing operators play a role. Our analysis suggests that the dual celestial CFT continues to enjoy at least the chiral $\mathfrak{bms}_4$ symmetry, though in a non-trivial way, and possibly a conformal extension of it.

hep-th↗

arXiv2026

Celestial dual of conformal gravity MHV amplitudes: an OPE analysis

In an earlier paper [arXiv:2511.03669] we extracted the OPE of celestial CFT operator duals of positive helicity graviton and scalar particles from the Mellin transformed relevant MHV amplitudes of conformal gravity, realised as the bosonic subsector of the Berkovits-Witten theory. A soft theorem analysis of bulk MHV amplitudes established that this conformal gravity exhibits a chiral $\mathfrak{bms}_4$ symmetry on the celestial sphere with the associated $\mathfrak{sl}(2,\mathbb{R})$ current algebra, which acquires a non-trivial central extension, unlike the Einstein gravity. Here we construct a $2d$ chiral CFT free-field realisation of the relevant chiral $\mathfrak{bms}_4$ algebra in terms of three free scalars ($ϕ_i$) and three $(β_i,γ_i)$ ghost pairs, and propose vertex operators for the positive-helicity graviton primary $G^{++}_Δ(z,\bar{z})$ as well as the scalar primary $Φ_Δ(z,\bar{z})$, and compute their OPEs. These OPEs reproduce exactly those obtained from the bulk conformal gravity MHV amplitudes, providing a concrete celestial dual description of its MHV sector.

hep-th↗