arXiv subjects

Jieming Lin

Publications and source records attributed to Jieming Lin.

5 recordsLinked to original sources

arXiv2026

M5 Instantons in ABJM

We study the existence of supersymmetric M5-brane instantons in asymptotically AdS$_4 \times S^7/\mathbf{Z}_k$ geometries of M-theory, dual to the ABJM theory. The supersymmetric embeddings of these instantons are determined by the M5-brane $\kappa$-symmetry, which forces them to localise to the equivariant fixed points in the asymptotically AdS$_4$ geometry, and wrap $(S^3\times S^3)/\mathbf{Z}_k $. At the quantum level we find that the one-loop partition function of these instantons vanishes, suggesting that the bulk partition function is instead to be expanded in terms of supergravity modes and M2-brane instantons, in line with known results for the $S^3$ partition function of the dual ABJM theory.

hep-th↗

arXiv2026

$Spin(n,n)\times\mathbb{R}^+$ Generalised Geometry and Consistent Truncations on Branes

In this note we show how the consistent truncations on half-supersymmetric branes of Leung and Stelle and Lin, Skrzypek and Stelle fit into the general exceptional generalised geometry analysis of Cassani \emph{et al.}. Each solution defines a torsion-free $Spin(n)$ structure in the $Spin(n,n)\times \mathbb{R}^+$ generalised geometry introduced by Strickland--Constable, where $n$ is the dimension of the space transverse to the brane. Embedding this into the appropriate exceptional generalised geometry then defines the truncation. As a by-product we derive a new consistent truncation on the IIA NS5-brane to six-dimensional $\mathcal{N}=(2,0)$ supergravity coupled to a tensor mutliplet, and new consistent truncations on the D6- and D7-branes to seven- and eight-dimensional pure half-maximal supergravity respectively.

hep-th↗

arXiv2025

Scalar-induced gravitational waves in spatially covariant gravity

We investigate scalar-induced gravitational waves (SIGWs) in the framework of spatially covariant gravity (SCG), a broad class of Lorentz-violating modified gravity theories respecting only spatial diffeomorphism invariance. Extending earlier SCG formulations, we compute the general kernel function for SIGWs on a flat Friedmann-Lema\^itre-Robertson-Walker background, focusing on polynomial-type SCG Lagrangians up to $d=3$, where $d$ denotes the total number of derivatives in each monomial. We derive explicit expressions for the kernel in the case of power-law time evolution of the coefficients, and restrict attention to the subset of SCG operators whose tensor modes propagate at the speed of light, thereby avoiding late-time divergences in the fractional energy density of SIGWs. Instead of the usual Newtonian gauge, the breaking of time reparametrization symmetry in SCG necessitates a unitary gauge analysis. We compute the energy density of SIGWs for representative parameter combinations, finding distinctive deviations from general relativity (GR), including scale-dependent modifications to both the amplitude and the spectral shape. Our results highlight the potential of stochastic GW background measurements to probe spatially covariant gravity and other Lorentz-violating extensions of GR.

gr-qc↗

arXiv2025

Interplay of Intersecting Branes and Consistent Embeddings

We explore consistent truncations from 10d/11d supergravity to supergravity theories on brane worldvolumes. Supersymmetric black-brane solutions to these lower-dimensional theories can be uplifted to 10d/11d supergravity and interpreted as intersecting-brane solutions with a particular smearing pattern. We survey this novel family of intersecting-brane solutions which also includes cases that are not related to previously known consistent truncations. Turning the argument on its head, we argue that the knowledge of such solutions allows us to generate appropriate embedding ans\"atze for consistent truncations. We demonstrate this by deriving new consistent embeddings of pure 5d $\mathcal{N}=4$ supergravity on D4-branes in type IIA theory and of pure 6d $\mathcal{N}=(1,1)$ supergravity on NS5-branes in type IIB theory.

hep-th↗

arXiv2024

Compactification on Calabi-Yau threefolds: Consistent truncation to pure supergravity

We study compactifications of eleven- and ten-dimensional maximal supergravity on Calabi-Yau threefolds. We explicitly construct truncations to pure supergravity with eight supercharges in five and four dimensions and show that they are consistent, i.e. that every solution of the lower-dimensional equations of motion fully solves the higher-dimensional ones. We furthermore match the supersymmetry transformations and demonstrate the consistency to full non-linear order in fermions. Our construction is independent of the choice of Calabi-Yau threefold and only involves the universal structures such as the K\"ahler form and the holomorphic three-form, in agreement with implicit constructions in the generalised geometry literature. As an immediate application, we embed four-dimensional extremal black holes in the higher-dimensional supergravities. We furthermore propose Ans\"atze for consistent truncations on all universal structures, leading to supergravities with additional matter multiples. An extensive list of equations of motion and supersymmetry transformations for various supergravity theories is provided in the appendix.

hep-th↗