arXiv subjects

S. R. Haridev

Publications and source records attributed to S. R. Haridev.

3 recordsLinked to original sources

arXiv2026

Inflationary trispectrum of gauge fields from scalar and tensor exchanges

In this paper, we compute the inflationary trispectrum of primordial gauge fields generated through the scalar and tensor exchanges in models with spectator $U(1)$ gauge fields which are kinetically coupled to the inflaton. Focusing on the connected four-point autocorrelation function of gauge fields, we derive exact analytical expressions for the full trispectrum of both electric and magnetic fields using the in-in formalism and cosmological diagrammatic rules, and explore their respective contributions in specific momentum configurations. For the scalar exchange, we find that the trispectrum signal in the equisided configuration grows with the exchange momentum and reaches its maximum in the flattened limit. However, in the counter collinear limit, we show that the non-linearity parameter associated with the trispectrum scales quadratically with the corresponding parameter of the cross-correlation bispectrum of magnetic fields and curvature perturbations, thereby establishing a hierarchical relation between the higher- and lower-order correlation functions. For the tensor exchange, the trispectrum displays a richer angular dependence, reflecting the sensitivity to the orientation of the momentum quadrilateral with respect to the tensor polarisation, producing characteristic angular modulations in the trispectrum. Detecting such angular signatures in future high-precision cosmological observations would provide a novel window into tensor-mediated interactions in the early universe.

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arXiv2025

RG studies of scalar-field models of long-range interactions

In this work we studies the long-range interactions in non-gravitational field theories and their behaviour in the deep infrared. To model such effects, we consider a nonlocal scalar theory obtained by adding a $ϕ\Box^{-1}ϕ$ term to the local action. Using the functional renormalisation group, we analyse its infrared fixed-point structure. Within the LPA, we show that nonlocality modifies phase-transition patterns and can induce symmetry breaking. Extending the LPA beyond polynomial truncations, we examine the convexity property of the effective potential as $k\rightarrow 0$ and find that the flow becomes singular for $λ^{2}>0$ before reaching the deep infrared. In the LPA$'$ framework, we find that the infrared-stable fixed point is the nonlocal Gaussian fixed point. We then generalise the model to $ϕ\Box^{σ/2}ϕ$ and analyse how the infrared properties depend on $σ$. With appropriate scaling choices, we show that the infrared behaviour remains unchanged up to $σ=d/2$ and follows Sak's prediction up to $σ=2$. Finally, we study higher-derivative cases within the LPA, focusing on $σ=4$, which corresponds to isotropic Lifshitz criticality, and obtain results consistent with earlier work.

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arXiv2022

Revisiting Vacuum Energy in Compact Spacetimes

We revisit the calculation of vacuum energy density in compact spacetimes. For the general case of $k$ compact spatial dimensions in $p+k$ dimensional Minkowski spacetime, we calculate the Casimir force on a piston placed in the presence of external electromagnetic fields. We observe that while the presence of a strong external magnetic field reduces the intensity of the Casimir force, the presence of an electric field enhances it instead. We discuss various physical cases, and also derive the particle production rate in the presence of such external fields in compact spacetimes. We observe that the pair production rate is enhanced in the presence of a piston.

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