arXiv subjects

Vijay Nenmeli

Publications and source records attributed to Vijay Nenmeli.

7 recordsLinked to original sources

arXiv2026

The Energy-Momentum-News Complex near Future Null Infinity

We study asymptotically flat vacuum solutions of general relativity in three and four dimensions, with an emphasis on the geometric structures that emerge near null infinity. We construct asymptotic solutions to the three- and four-dimensional Einstein equations near future null infinity, which is a conformal Carroll manifold, starting from the most general Carroll metric data allowed by the Einstein equations. We use a Carroll-covariant version of Bondi--Sachs gauge, whose residual transformations act on the boundary Carroll geometry and shear as boundary diffeomorphisms, Weyl transformations and Carroll boosts. We then define a boundary energy-momentum-news complex at future null infinity by varying a suitably renormalised action with respect to the boundary Carroll metric data and shear. This involves adding boundary terms to the Einstein--Hilbert action on a cut-off surface near future null infinity. The boundary energy-momentum-news complex obeys two relations due to the boundary diffeomorphism and Weyl gauge invariance of the renormalised action. A third relation, due to the Carroll boost, is anomalous, and the corresponding anomaly is obtained from the variation of the renormalised action. Together, these Ward-type identities obeyed by the boundary energy-momentum-news complex lead to a Carroll-covariant generalisation of the Bondi loss equations.

hep-th↗

arXiv2026

On Carrollian Loop Amplitudes for Gauge Theory and Gravity

Carrollian amplitudes are scattering amplitudes of massless particles written in position space at null infinity. We study various aspects of Carrollian amplitudes for gauge theory and gravity at loop level using primarily the modified Mellin prescription of [1]. Finite one-loop four-point Carrollian amplitudes in gauge theory are shown to maintain an analytic structure similar to tree level results. We compute the one-loop four-point Carrollian MHV amplitudes in planar $N=4$ super Yang-Mills theory, which are expressed as differential operators acting on tree level Carrollian amplitudes. This result is generalized to all loop orders using the Bern-Dixon-Smirnov (BDS) formula. Similar structures are observed at one-loop for Carrollian MHV amplitudes in $N=8$ supergravity. We next consider $2\to 2$ scattering of massless scalars via gravitational interactions in the eikonal regime and show that the corresponding Carrollian amplitudes exhibit logarithmic behavior in the `Carroll time' $u$. We compute the discontinuities of these Carrollian amplitudes up to $O(G^3)$ and show that they are descendants of Carrollian Born amplitudes. We observe similar logarithmic behavior in Carrollian amplitudes associated with the one-loop scalar box diagram. The dependence of this amplitude on dual scaling dimensions also differs from standard tree level results. Finally, we further study the infrared (IR) divergences of Carrollian amplitudes in massless scalar QED, gravity, and Yang-Mills theory. We show that Carrollian amplitudes in these theories naturally factorize, allowing us to provide an IR-safe definition for these objects.

hep-th↗

arXiv2026

From AdS to Flat Space: Massive Spin-2 Fields

We analyze a bulk effective field theory in AdS containing a U(1)-charged massive spin-2 field coupled to a gauge field, by performing the required holographic renormalization, and computing the one and two-point functions. We then compute the renormalized bulk three-point function involving two massive spin-2 fields and one gauge field. Matching with the CFT 3-point correlator of two non-conserved spin-2 operators and a conserved current, we obtain explicit mappings between the bulk minimal and gyromagnetic couplings and the boundary OPE data. Finally, we take the flat-space limit of the momentum space CFT correlator and verify that the resulting amplitude matches the expected flat-space structure.

hep-th↗

arXiv2025

Boundary Energy-Momentum Tensors for Asymptotically Flat Spacetimes

We consider 3D and 4D asymptotically flat spacetimes near future null infinity endowed with the most general allowed Carroll geometry. We define a boundary energy-momentum tensor by varying the on-shell action with respect to the Carroll metric data. This requires adding counterterms to the Einstein-Hilbert action. We show that, in 4D, the shear is on par with the Carroll metric data. Their combined response defines a boundary energy-momentum-news complex whose diffeomorphism Ward identity is equivalent to the Bondi mass and angular momentum loss equations. Weyl invariance leads to an identity for the trace of the energy-momentum tensor, and local Carroll boosts are anomalous in 3D and in 4D.

hep-th↗

arXiv2023

Order and Chaos in the $SU(2)$ Matrix Model: Ergodicity and Classical Phases

We study the classical non-linear dynamics of the $SU(2)$ Yang-Mills matrix model introduced in [1] as a low-energy approximation to two-color QCD. Restricting to the spin-0 sector of the model, we unearth an unexpected tetrahedral symmetry, which endows the dynamics with an extraordinarily rich structure. Amongst other things, we find that the spin-0 sector contains co-existing chaotic sub-sectors as well as nested chaotic basins, and displays alternation between regular and chaotic dynamics as energy is varied. The symmetries also grant us a considerable amount of analytic control which allows us to make several quantitative observations. Next, by noting that several features of the model have natural thermodynamic interpretations, we switch from our original chaos-theoretic viewpoint to a more statistical perspective. By so doing, we see that the classical spin-0 sector has a rich phase structure, arising from ergodicity breaking, which we investigate in depth. Surprisingly, we find that many of these classical phases display numerous similarities to previously discovered quantum phases of the spin-0 sector [2], and we explore these similarities in a heuristic fashion.

hep-th↗

arXiv2022

When and why do zero-modes cause a divergence in the entanglement entropy?

We examine the correlations between divergences in ground state entanglement entropy and emergent zero-modes of the underlying Hamiltonian in the context of one-dimensional Bosonic and Fermionic chains. Starting with a pair of coupled Bosonic degrees of freedom, we show that zero modes are necessary, but not sufficient for entanglement entropy divergences. We then list sufficient conditions that identify divergences. Next, we extend our analysis to Bosonic chains, where we demonstrate that zero modes of the entanglement Hamiltonian provide a signature for divergences independent of the entanglement Hamiltonian. We then generalize our results to one-dimensional Fermionic lattices for a chain of staggered Fermions which is a discretized version of the Dirac field. We find that the methods detailed for Bosonic chains have Fermionic analogs and follow this up with a numerical study of the entanglement in the Fermionic chain. Finally, we discuss our results in light of the factorization algebra theorem.

quant-ph↗

arXiv2021

Maximal momentum GUP leads to quadratic gravity

Quantum theories of gravity predict interesting phenomenological features such as a minimum measurable length and maximum momentum. We use the Generalized Uncertainty Principle (GUP), which is an extension of the standard Heisenberg Uncertainty Principle motivated by Quantum Gravity, to model the above features. In particular, we use a GUP with modelling maximum momentum to establish a correspondence between the GUP-modified dynamics of a massless spin-2 field and quadratic (referred to as Stelle) gravity. In other words, Stelle gravity can be regarded as the classical manifestation of a maximum momentum and the related GUP. We explore the applications of Stelle gravity to cosmology and specifically show that Stelle gravity applied to a homogeneous and isotropic background leads to inflation with an exit. Using the above, we obtain strong bounds on the GUP parameter from CMB observations. Unlike previous works, which fixed only upper bounds for GUP parameters, we obtain both \emph{lower and upper bounds} on the GUP parameter.

gr-qc↗