Kabir Bajaj | Searcharxiv

arXiv2026

Wilson coefficients from a non-renormalization theorem in 2D SYM

Matrix string theory (arXiv:hep-th/9703030, arXiv:hep-th/9701025, arXiv:hep-th/9710009) is a conjectured duality between two-dimensional maximally supersymmetric $U(N)$ Yang-Mills theory and type-IIA string theory in ten-dimensional Minkowski spacetime. The IR description of this gauge theory is governed by the symmetric product orbifold $(\mathbb{R}^8)^N/S_N$ CFT. The leading irrelevant deformation from this IR fixed point is the Dijkgraaf-Verlinde-Verlinde operator, which comes with an unknown Wilson coefficient. We determine this coefficient using non-renormalization arguments from the UV gauge theory. The result is consistent with the matrix string theory conjecture and gives a first-principles check of the relation between $g_{\rm YM}$ and the string coupling. We also comment on the prospects for fixing further Wilson coefficients using similar methods.

hep-th↗

arXiv2024

Grey Galaxies in $AdS_5$

It has recently been conjectured \cite{Kim:2023sig} that the end point of the rotational superradiant instability of black holes in $AdS_4$ is a Grey Galaxy: an $\omega=1$ black hole sitting at the centre of $AdS_4$, surrounded by a large disk of rapidly rotating gravitons and other bulk fields. In this paper we study Grey Galaxies in $AdS_5$. In this case, the rotational group is of rank 2, and so has two distinct angular velocities $\omega_1$ and $\omega_2$. We demonstrate that $AdS_5$ hosts two qualitatively distinct Grey Galaxy phases: the first with either $\omega_1\approx 1$ or $\omega_2\approx 1$, and the second with both angular velocities $\approx 1$. We use these results to present a conjecture for a part of the phase diagram of ${\cal N}=4$ Yang-Mills (as a function of energy and the two angular momenta) that displays several phase transitions between regular black holes and various Grey Galaxy phases. We present an explicit gravitational construction of the phases in which $\omega_1$ and $\omega_2$ are both parametrically close to unity, and demonstrate that the corresponding boundary stress tensor is the sum of two pieces. The first is the stress tensor of the central black hole. The second - the contribution of the bulk gas - takes the form of the stress tensor of an equilibrated boundary conformal fluid, rotating at the given angular speeds $\omega_i$. We also briefly comment on the structure of Grey Galaxies in $AdS_D$ for $D > 5$.

hep-th↗