arXiv subjects

Jack Holden

Publications and source records attributed to Jack Holden.

6 recordsLinked to original sources

arXiv2026

Instanton condensation and a new phase of BPS black holes

We analyse the 1/16-BPS superconformal index for BPS black holes at equal charge in $AdS_5 \times S_5$, uncovering evidence for a new instability in the microcanonical ensemble along the small black hole saddle. This is indicated by instanton condensation in the matrix model description of the index. This instability occurs for black holes of radius close to, but below, the scale at which black holes become `small', and implies a new dominant phase in this region. We propose a connection to the partially deconfined phase in the field theory dual description. This would resolve recent confusion about the location of the partially deconfined phase in the BPS phase diagram and promises new avenues for understanding confinement, partial deconfinement, and the encoding of colour degrees of freedom under the holographic map. We also motivate the importance of instantons in partial deconfinement from a matrix model perspective.

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arXiv2025

Supersymmetric Holomorphic Masses in AdS/CFT with Flavour

In type IIB supergravity (SUGRA), in the extremal background of a number N_c of D3-branes we consider a number N_f of probe D7-branes extended along all four D3-brane directions, (x_0,x_1,x_2,x_3). Using (x_2,x_3) to define complex coordinates (z,\bar{z}) and defining the D7-branes' worldvolume scalars as (y,\bar{y}), we prove that any holomorphic function y(z) or antiholomorphic function y(\bar{z}) is a BPS solution of the D7-branes' equations of motion preserving N=(4,0) or (0,4) supersymmetry (SUSY) along (x_0,x_1), respectively. In the near-horizon geometry, five-dimensional Anti-de Sitter (AdS) spacetime times a five-sphere, the AdS/Conformal Field Theory correspondence states that type IIB SUGRA is holographically dual to four-dimensional N=4 supersymmetric SU(N_c) Yang-Mills theory at large N_c and large 't Hooft coupling, and the N_f D7-branes are dual to N_f N=2 hypermultiplets in the fundamental representation, i.e. flavour fields. Our D7-brane solutions are dual to a position-dependent hypermultiplet mass m that is holomorphic, m(z), or antiholomorphic, m(\bar{z}). We provide field theory proofs, valid for any N_c, N_f, and 't Hooft coupling, that such m preserve N=(4,0) or (0,4) SUSY along (x_0,x_1). We also perform holographic calculations with probe D7-branes to show that the theory with such m has zero energy and zero expectation value of the mass operator, and that a zero of m is dual to a superconformal defect described by chiral fermions along (x_0,x_1).

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arXiv2025

New phases in QCD at finite temperature and chemical potential

Understanding the phases of quantum chromodynamics (QCD) at finite temperature and baryon density is crucial for describing matter in heavy-ion collisions and the interior of neutron stars. While the transition from the confined phase to the deconfined phase has been extensively studied at vanishing chemical potential, recent theoretical work suggests the existence of intermediate phases with partial deconfinement, where only a subset of the color degrees of freedom is deconfined. In this paper, we study the generalization of partial deconfinement in QCD in the Veneziano large-$N_{\rm c}$ limit ($N_{\rm f}/N_{\rm c}$ fixed) to finite baryon chemical potential. We find that the partially deconfined phase has finer structure, and hence that there are four phases in QCD at finite temperature and moderately large chemical potential: complete confinement, complete deconfinement, and two kinds of partial deconfinement. A key ingredient is the refined understanding of the meaning of the 'Gross-Witten-Wadia point', i.e., the opening of a gap in the distribution of Polyakov line phases: either string condensation or baryon condensation causes the GWW transition. As a by-product, we observe the emergence of the QCD critical point from the interplay between baryon condensation and partial deconfinement. While our approach is necessarily qualitative due to the fermion sign problem, it provides a unified theoretical framework for understanding the rich phase structure of dense QCD matter and offers new perspectives on the location and nature of the QCD critical point.

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arXiv2024

Wilson Loops and Random Matrices

Linear confinement with Casimir scaling of the string tension in confining gauge theories is a consequence of a certain property of the Polyakov loop related to random matrices. This mechanism does not depend on the details of the theories (neither the gauge group nor dimensions) and explains approximate Casimir scaling below string-breaking length. In this paper, we study 3d SU(2) pure Yang-Mills theory numerically and find the same random-matrix behavior for rectangular Wilson loops. We conjecture that this is a universal feature of strongly coupled confining gauge theories.

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arXiv2023

Linear confinement in the partially-deconfined phase

We consider the partially-deconfined saddle of large-$N$ pure Yang-Mills theory lying between confined and deconfined phases, in which the color degrees of freedom split into confined and deconfined sectors. Based on the microscopic mechanism of deconfinement, we argue that a flux tube is formed in the confined sector and a linear confinement potential is generated. The string tension should not depend on the size of the confined sector. We provide evidence by studying the finite-temperature strong-coupling lattice gauge theory. In particular, we make analytic predictions assuming linear confinement in the confined sector, and then confirm these by numerical simulations. We discuss some implications of the conjecture to QCD and holography.

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arXiv2021

Global Symmetries and Partial Confinement

In gauge theories, spontaneous breaking of the centre symmetry provides a precise definition of deconfinement. In large-$N$ gauge theories, evidence has emerged recently that between confined and deconfined phases a partially-deconfined phase can appear, in which only a subset of colours deconfine. In the partially-deconfined phase, the centre symmetry is spontaneously broken, raising the question of whether an order parameter exists that can distinguish completely- and partially-deconfined phases. We present two examples in gauge theories of global symmetries that are spontaneously broken in the confined phase and preserved in the deconfined phase, and we show that this symmetry is spontaneously broken in the partially-deconfined phase. As a result, in these theories the transition from complete to partial deconfinement is accompanied by the spontaneous breaking of a global symmetry. The two examples are CP symmetry in $\mathcal{N}=1$ super-Yang-Mills with a massive gluino and theta-angle $θ=π$, and chiral symmetry in a strongly-coupled lattice gauge theory. For $\mathcal{N}=1$ SYM we also present numerical evidence that the same phenomenon occurs at finite $N \geq 30$. We thus conjecture that global symmetries may provide order parameters to distinguish completely and partially deconfined phases generically, including at finite $N$.

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