arXiv subjects

Chris D. White

Publications and source records attributed to Chris D. White.

At least 19 recordsLinked to original sources

arXiv2026

Probing new physics in the top sector using quantum information

Recent studies have shown that quantitative concepts from quantum information theory can play a role in analysing collider physics, including elucidating new physics. In this paper, we study various QI measures including magic, trace distance and fidelity distance, in generic new physics scenarios modelled by the Standard Model Effective Field Theory. We argue that such measures can indeed show up differences with respect to the pure Standard Model, and we compare our results with similar findings for the concurrence discussed previously in the literature. We examine the relative sensitivity of different measures to new physics in two-dimensional bins of the top pair invariant mass and scattering angle, finding that the concurrence, magic and trace distance each emerge as the best measure in at least some regions of the phase space. This highlights the importance of exploring multiple quantum information measures in the hunt for beyond the Standard Model physics.

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arXiv2026

Non-topological solitons in biadjoint scalar field theory

Biadjoint scalar theory has been widely studied, due to its being closely related to the double copy correspondence linking gauge, gravity and related theories. In this paper, we continue a programme of work in elucidating non-linear solutions of this theory, and find a family of new solutions that are richer and more complex than previous cases. Using an ansatz that can be embedded in any choice of non-abelian colour groups, we demonstrate the existence of non-topological solitons, whose existence is protected by carrying a U(1) charge associated with certain rotations in colour space. The solutions are time-dependent, and closely related to the well-known Q-ball solutions in other scalar field theories. We also show explicitly that our solution set contains those that are stable under small perturbations within a consistent truncation of the theory, and have finite energy in addition to being localised.

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arXiv2026

Hawking Radiation meets the Double Copy

We describe an electromagnetic system which is related to black hole production with Hawking radiation through the double copy. We consider the scattering of a massless scalar particle through a collapsing electromagnetic background -- the single copy of Vaidya -- and identify the Feynman diagrams that exponentiate in the geometric-optics limit. The Bogoliubov coefficients obtained from the diagrammatic approach are reproduced by a semiclassical ray-tracing computation of null rays in this same background. We discuss the thermodynamic interpretation of the resulting number distribution in light of the double copy.

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arXiv2026

Non-local nonstabiliserness in Gluon and Graviton Scattering

The property of non-stabiliserness, or ``magic'', is of interest in quantum computing due to its role in developing fault-tolerant quantum algorithms with genuine computational advantage over classical counterparts. There has been much interest in quantifying magic in various physical systems, in order to probe how to produce and enhance it. The production of magic has previously been quantified in gluon and graviton scattering, in the so-called helicity basis relating particle spins with momentum directions. For a basis-independent statement, one should instead use the recently developed concept of non-local non-stabiliserness, and our aim in this paper is to derive how this varies for gluon and graviton scattering processes. Our results show that, for many initial states, including those produced with polarised beams, the helicity basis coincides with a basis in which the non-local magic is manifest, providing a physical motivation for using the helicity basis to study quantum information quantities. However, this property breaks upon adding additional operators to the Yang-Mills Lagrangian, as would be the case in new physics scenarios.

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arXiv2026

Double soft graviton factors from the gravitational Wilson line

The description of low-energy (``soft") gravitons using universal theorems continues to attract attention. In this paper, we consider the emission of two soft gravitons, using a previously developed formalism that describes (next-to) soft graviton emission in terms of generalised Wilson lines (GWLs). Based on Schwinger's proper time methods, the GWL allows for a systematic accounting of graviton emission from external hard particles in the amplitude, as well as from three-graviton vertices located off the individual worldlines. By combining these effects, previously derived results for the leading double soft graviton theorem are recovered. Still, the formalism allows us to go further in deriving new universal double soft graviton terms at subleading order in the momentum expansion. We further demonstrate how gauge invariance can be utilized to account for double soft graviton emissions within the non-radiative amplitude, including the effects of non-zero initial positions of the hard particles. Our results can be packaged into an exponential dressing operator, and we comment on possible applications to the effective field theory for binary scattering processes.

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arXiv2026

Classical strings and the double copy

The double copy is by now a well-established relationship between scattering amplitudes and classical solutions in gauge and gravity (field) theories, and is itself inspired by amplitude relations in string theory. In this paper, we generalise the classical double copy to the motion of strings, taking as a case study the motion of an open string in a background abelian gauge field. We argue that the double copy of this situation is a closed string moving in a spacetime background arising as the double copy of the gauge theory background. The gauge theory background we consider is that of a constant electric field, which has a critical value beyond which the open string motion is pathological. We find no counterpart of this behaviour in the double copy, and interpret this result. We then examine how the closed string nevertheless still knows about the single copy gauge theory. Our results pave the way for more systematic study of the double copy in a classical string context, thus going beyond the KLT relations for amplitudes in flat space.

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arXiv2025

Quantum Information meets High-Energy Physics: Input to the update of the European Strategy for Particle Physics

Some of the most astonishing and prominent properties of Quantum Mechanics, such as entanglement and Bell nonlocality, have only been studied extensively in dedicated low-energy laboratory setups. The feasibility of these studies in the high-energy regime explored by particle colliders was only recently shown and has gathered the attention of the scientific community. For the range of particles and fundamental interactions involved, particle colliders provide a novel environment where quantum information theory can be probed, with energies exceeding by about 12 orders of magnitude those employed in dedicated laboratory setups. Furthermore, collider detectors have inherent advantages in performing certain quantum information measurements, and allow for the reconstruction of the state of the system under consideration via quantum state tomography. Here, we elaborate on the potential, challenges, and goals of this innovative and rapidly evolving line of research and discuss its expected impact on both quantum information theory and high-energy physics.

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arXiv2025

The double copy as a doppelgänger

The double copy relates scattering amplitudes and classical solutions in non-abelian gauge theories and gravity. As such, it is usually expressed in the conventional second-order formalisms in both theories corresponding to standard Yang-Mills theory, and the Einstein--Hilbert action in General Relativity. In this paper, we instead consider alternative formulations of gravity, which are known to terminate at finite order in the coupling at Lagrangian level. We focus in particular on the Chern--Simons--Witten (CSW) formulation in 2+1 dimensions, and argue that the double copy then becomes a doppelgänger relationship between gauge theory and gravity, allowing straightforward replacement of generators and structure constants in both theories. We show how explicit (multiple) static point-source solutions can be mapped in the two approaches, and use the CSW formalism to examine when double copies are expected to be possible, and when not. In addition, we present an explicit double copy between the Wong equations for colour charges, and the Mathisson-Papapetrou-Dixon equations for spinning particles, that extends also to higher dimensions.

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arXiv2025

Spin versus Magic: Lessons from Gluon and Graviton Scattering

The quantum property of non-stabiliserness, also known as magic, plays a key role in designing quantum computing systems. How to produce, manipulate and enhance magic remains mysterious, such that concrete examples of physical systems that manifest magic behaviour are sought after. In this paper, we study two-particle scattering of gluons and gravitons in Yang--Mills theory and General Relativity, as well as their supersymmetric extensions. This provides an interesting case of two-qubit systems, differing only in the physical spin of the qubits. We show that magic is generically produced in both theories, and also show that magic typically decreases as the spin of the qubits increases. The maximal magic in each case is found to be substantially less than the known upper bound. Differences in the profile of magic generation can be traced to the known physics of each theory, as manifested in relations between their respective scattering amplitudes. Our case study may provide useful insights into understanding magic in other systems.

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arXiv2025

Topological modes, non-locality and the double copy

The double copy connects scattering amplitudes and other objects in gauge and gravity theories. Open conceptual issues include whether non-local information in gravity theories can be generated from the double copy, and how the double copy should be practically implemented in unseen cases. In this paper, we consider topological theories (with and without mass) in 2+1 dimensions, and argue that this makes a useful playground for exploring non-locality. In particular, topological modes of the gauge field arise, themselves associated with non-trivial global behaviour, and it is not clear {\it a priori} how to double copy them. We settle this issue, and clarify the role of BCJ shifts in modifying how topological modes contribute. We show how our conclusions apply to four- and five-point scattering amplitudes in topological gauge / gravity theories, as a by-product obtaining greatly simplified analytic expressions for the four-point amplitudes.

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arXiv2025

Time-dependent solutions of biadjoint scalar field theories

Biadjoint scalar field theories appear in the study of scattering amplitudes and classical solutions in gauge, gravity and related theories. In this paper, we present new exact solutions of biadjoint scalar field theory, showing that time-dependent solutions are possible and analytically tractable. We generalise the theory to include mass and / or quartic terms, and also a coupling to a constant background field. This allows for more exact solutions, which make contact with previous soliton literature. We also find bounded solutions, in contrast to all known previous examples. Our results may be useful for the study of non-perturbative aspects of the double copy between gauge theories and gravity. We also speculate as to their possible practical applications.

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arXiv2024

The magic of top quarks

In recent years, there has been increasing collaboration between the fields of quantum computing and high energy physics, including using LHC processes such as top (anti-)quark pair production to perform high energy tests of quantum entanglement. In this proceeding, I will review another interesting property from quantum computing ("magic"), that is needed to make quantum computers with genuine computational advantage over their classical counterparts. How to make and enhance magic in general quantum systems is an open question, such that new insights are always useful. To this end, I will show that the LHC naturally produces magic top quarks, providing a novel playground for further study in this area.

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arXiv2024

Deriving Weyl double copies with sources

The Weyl double copy is a relationship between classical solutions in gauge and gravity theories, and has previously been applied to vacuum solutions in both General Relativity and its generalisations. There have also been suggestions that the Weyl double copy should extend to solutions with non-trivial sources. In this paper, we provide a systematic derivation of sourced Weyl double copy formulae, using spinorial methods previously established for ${\cal N}=0$ supergravity. As a cross-check, we rederive the same formulae using a tensorial approach, which then allows us to extend our arguments to sources containing arbitrary powers of the inverse radial coordinate. We also generalise our results to include the Kerr-Newman black hole, clarifying previous alternative double copy formulae presented in the literature. Our results extend the validity of the Weyl double copy, and may be useful for further astrophysical applications of this correspondence.

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arXiv2024

The magic of entangled top quarks

Recent years have seen an increasing body of work examining how quantum entanglement can be measured at high energy particle physics experiments, thereby complementing traditional table-top experiments. This raises the question of whether more concepts from quantum computation can be examined at colliders, and we here consider the property of magic, which distinguishes those quantum states which have a genuine computational advantage over classical states. We examine top anti-top pair production at the LHC, showing that nature chooses to produce magic tops, where the amount of magic varies with the kinematics of the final state. We compare results for individual partonic channels and at proton-level, showing that averaging over final states typically increases magic. This is in contrast to entanglement measures, such as the concurrence, which typically decrease. Our results create new links between the quantum information and particle physics literatures, providing practical insights for further study.

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arXiv2024

The Uncertainty Principle and Classical Amplitudes

We study the variance in the measurement of observables during scattering events, as computed using amplitudes. The classical regime, characterised by negligible uncertainty, emerges as a consequence of an infinite set of relationships among multileg, multiloop amplitudes in a momentum-transfer expansion. We discuss two non-trivial examples in detail: the six-point tree and the five-point one-loop amplitudes in scalar QED. We interpret these relationships in terms or a coherent exponentiation of radiative effects in the classical limit which generalises the eikonal formula, and show how to recover the impulse, including radiation reaction, from this generalised eikonal. Finally, we incorporate the physics of spin into our framework.

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arXiv2024

What can abelian gauge theories teach us about kinematic algebras?

The phenomenon of BCJ duality implies that gauge theories possess an abstract kinematic algebra, mirroring the non-abelian Lie algebra underlying the colour information. Although the nature of the kinematic algebra is known in certain cases, a full understanding is missing for arbitrary non-abelian gauge theories, such that one typically works outwards from well-known examples. In this paper, we pursue an orthogonal approach, and argue that simpler abelian gauge theories can be used as a testing ground for clarifying our understanding of kinematic algebras. We first describe how classes of abelian gauge fields are associated with well-defined subgroups of the diffeomorphism algebra. By considering certain special subgroups, we show that one may construct interacting theories, whose kinematic algebras are inherited from those already appearing in a related abelian theory. Known properties of (anti-)self-dual Yang-Mills theory arise in this way, but so do new generalisations, including self-dual electromagnetism coupled to scalar matter. Furthermore, a recently obtained non-abelian generalisation of the Navier-Stokes equation fits into a similar scheme, as does Chern-Simons theory. Our results provide useful input to further conceptual studies of kinematic algebras.

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arXiv2023

Exponentiation of soft quark effects from the replica trick

In this paper, we show that multiple maximally soft (anti-)quark and gluon emissions exponentiate at the level of either the amplitude or cross-section. We first show that such emissions can be captured by introducing new soft emission operators, which serve to generalise the well-known Wilson lines describing emissions of maximally soft gluons. Next, we prove that vacuum expectation values of these operators exponentiate using the replica trick, a statistical-physics argument that has previously been used to demonstrate soft-gluon exponentiation properties in QCD. The obtained results are general, i.e. not tied to a particular scattering process. We illustrate our arguments by demonstrating the exponentiation of certain real and virtual corrections affecting subleading partonic channels in deep-inelastic scattering.

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arXiv2023

Next-to-soft radiation from a different angle

Soft and collinear radiation in collider processes can be described in a universal way, that is independent of the underlying process. Recent years have seen a number of approaches for probing whether radiation beyond the leading soft approximation can also be systematically classified. In this paper, we study a formula that captures the leading next-to-soft QCD radiation affecting processes with both final- and initial-state partons, by shifting the momenta in the non-radiative squared amplitude. We first examine W+jet production, and show that a previously derived formula of this type indeed holds in the case in which massive colour singlet particles are present in the final state. Next, we develop a physical understanding of the momentum shifts, showing precisely how they disrupt the well-known angular ordering property of leading soft radiation.

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