arXiv subjects

Babli Khatun

Publications and source records attributed to Babli Khatun.

5 recordsLinked to original sources

arXiv2026

All Order Gravitational Wave Tails for Subleading Post-Newtonian Expansion

The low-frequency gravitational waveform emitted in a classical scattering process contains an infinite tower of late- and early-time tail terms of the form $u^{-r}(\ln|u|)^{r-1}$, $r \geq 1$. In the Newtonian limit, the coefficients of this entire tower have recently been shown to be universal, i.e. fixed by the asymptotic data of the scattering objects alone. At the retained order in the velocity expansion, these leading-logarithmic tails are determined to all orders in Newton's constant $G$. We extend this result to the first subleading order in the post-Newtonian expansion of the asymptotic states. We consider scattering of an arbitrary number of incoming and outgoing nonrelativistic objects interacting only through gravity at long range, and we derive the complete tower of tail terms at this order. The correction arises from the first subleading term in the retardation expansion and is determined by the asymptotic Newtonian trajectories of the massive particles. Its coefficients are again determined entirely by the asymptotic trajectories and are independent of the details of the interaction. For $2\to2$ scattering, the leading-logarithmic series can be summed in closed form. Our results agree with a relativistic conjecture proposed in earlier work arXiv:2610.07134.

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arXiv2026

All-Orders Classical Soft Graviton Theorems in the Newtonian Limit and Beyond

The classical soft graviton theorem aims to determine certain terms in the early- and late-time tails of the gravitational waveform produced in a scattering process, using only the asymptotic momenta of the scattered objects. In this paper we find an infinite series of leading-logarithmic tail terms in the Newtonian limit, where the incoming and outgoing particles move slowly, but the scattering itself can be violent. The all-orders conjecture of Alessio, Di Vecchia and Heissenberg agrees with our results for two-particle scattering, but does not hold in general when the initial or final state contains three or more particles. We also propose an all-orders conjecture for these tails beyond the Newtonian limit, but do not prove it. Nevertheless, the conjecture passes several nontrivial consistency checks.

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arXiv2026

Reconstructing cosmological correlators via dispersion: from cutting to dressing rules

In this work, we investigate how cosmological correlators can be reconstructed by applying the momentum-space dispersion formula to their discontinuities, treating them as functions of momentum variables associated with the corresponding de Sitter Witten diagrams. We focus on conformally coupled and massless polynomial scalar interactions (both IR-divergent and IR-convergent), and consider tree-level de Sitter Witten diagrams. We explicitly utilize the single-cut discontinuity relations, or cutting rules, involving the cosmological correlators recently constructed in arXiv:2512.20720. For diagrams with multiple interaction vertices, we apply the dispersion formula by cutting all internal lines in the diagram one by one, successively, thereby allowing us to reconstruct the full correlator using only lower-point contact-level objects and their discontinuity data, up to contact diagram ambiguities. We also rediscover how the cosmological correlators on the late-time slice of de Sitter space can be obtained from flat-space Feynman diagrams via a set of dressing rules. Our starting point, being the cutting rules for the cosmological correlators, also emphasizes how basic principles, such as unitarity for in-in correlators, can lead us to the dressing rules, which were previously derived in literature following a different method.

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arXiv2025

A single-cut discontinuity for cosmological correlators from unitarity and analyticity

We derive discontinuity relations, also known as cutting rules, and explore the analytic properties of cosmological correlators, fundamental observables of the primordial universe. Our emphasis is on how these relations arise from unitarity and hermitian analyticity in interacting quantum field theories on de Sitter space-time. Instead of analyzing wave-function coefficients, we apply these relations directly to cosmological correlators. By studying conformally coupled and massless scalar fields with $ϕ^n$ self-interactions, we demonstrate that the discontinuity of a cosmological correlator can be expressed as a sum of products of lower-point discontinuities, stemming from a single-cut of one internal line in the corresponding tree-level exchange Witten diagram. Notably, beyond lower-point correlators, the decomposition of the discontinuities of cosmological correlators includes contributions from auxiliary elements that consist of both the real and imaginary parts of the lower-point wave-function coefficients, which have not been reported in the existing literature. Interestingly, depending on whether $n$ is even or odd in a $ϕ^n$ interaction, these different lower-point discontinuities contribute as the leading or sub-leading piece in the late-time limit to the discontinuity relations. Additionally, our single-cut discontinuity relation leads to a decomposition rule for the residue of the cosmological correlators at partial energy singularities, incorporating contributions from these auxiliary objects. Through explicit calculations in several models, we confirm that our discontinuity relations are consistent with results from the in-in formalism. While primarily developed using tree-level exchanges with polynomial interactions, we also demonstrate that our framework can be extended to include loop corrections and cases with derivative interactions.

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arXiv2025

All Order Classical Electromagnetic Soft Theorems

If a set of charged objects collide in space and the fragments disperse, then this process will emit electromagnetic waves. Classical soft photon theorem determines the constant term and the leading power law fall-off of the wave-form at late and early times in terms of only the momenta and charges of the incoming and outgoing objects. In this paper we determine an infinite set of subleading terms in the late and early time expansion of the wave-form, which also depend only on the momenta and charges of the incoming and outgoing particles. For two-particle scattering, we derive a resummed low-frequency electromagnetic wave-form, as well as the resummed wave-form at early and late times. In this analysis we ignore the effect of long range gravitational interaction, but our result is unaffected by any other short range interactions among the objects.

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