arXiv subjects

Roberto Bonezzi

Publications and source records attributed to Roberto Bonezzi.

At least 19 recordsLinked to original sources

arXiv2026

Color-kinematics duality from an algebra of superforms

Color-kinematics duality states that the kinematic numerators of the cubic tree-level Yang-Mills scattering amplitudes obey the same symmetry properties that the color factors obey due to the Jacobi identity. We present a novel strategy for deriving this duality, based on the differential forms on a superspace. This space of superforms carries a generalization of a Batalin-Vilkovisky (BV) algebra (BV$^{\square}$ algebra). We show that the homotopy algebra of color-stripped Yang-Mills theory is obtained as a quotient of this space in which a subspace, which is an ideal `up to homotopy', is modded out. This algebra is a subsector of a BV$_{\infty}^{\square}$ algebra. Deriving the latter would provide a first-principle proof of color-kinematics duality from field theory.

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arXiv2025

Yang-Mills kinematic algebra via homotopy transfer from a worldline operator algebra

The homotopy Lie or $L_{\infty}$ algebra encoding Yang-Mills theory is the tensor product of a color Lie algebra with the kinematic $C_{\infty}$ algebra. We derive this $C_{\infty}$ algebra, via homotopy transfer, from a strict operator algebra of a worldline theory, realized as an associative star product algebra. This gives a homotopy transfer interpretation to worldline vertex operators introduced in previous work.

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arXiv2025

The Double Copy of Maximal Supersymmetry in $D=10$

We continue the program of using homotopy algebras to obtain off-shell, local and gauge redundant derivations of the double copy relations between gauge theory and gravity. We apply it to $N=1$ super-Yang-Mills theory in $D=10$ in order to obtain type IIA or type IIB supergravity, at least to cubic order in fields. Furthermore, we show how the super-Lie algebra of global supersymmetries, acting on the homotopy algebra of $N=1$ super-Yang-Mills theory, double copies to the maximal supersymmetry of supergravity.

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arXiv2025

Gluon amplitudes in first quantization

We compute tree-level gluon amplitudes as worldline correlators of vertex operators in a bosonic spinning particle model. In this framework, the particle's position degrees of freedom are extended by complex bosonic variables that encode its spin. In the free theory, the model exhibits a first-class constraint algebra whose gauging ensures the unitarity of the quantum theory. This algebra is a contraction of the $sl(2,\mathbb{R})$ algebra, which is by itself a subalgebra of the Virasoro algebra. In string theory, gauging the Virasoro algebra plays a similar role. Our model admits a consistent truncation to describe a pure spin-1 particle. Non-abelian interactions are introduced by using BRST techniques, which allow us to extract the vertex operators of the theory as suitable deformations of the BRST charge. BRST invariance is central to ensuring the consistency of the tree-level amplitudes analyzed in this work. We discuss connections with similar worldline constructions and comment on the potential relevance of this framework for uncovering the structures underlying the double-copy program in gauge and gravitational theories.

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arXiv2025

Worldline geometries for scattering amplitudes

In this paper, we construct the path integral for infinite and semi-infinite scalar worldlines. We show that, at the asymptotic endpoints, on-shell physical states can be generated by inserting vertex operators at infinity. This procedure implements automatically the LSZ reduction, thus leading to a direct worldline representation of scattering amplitudes. To obtain it, we introduce generalized vertex operators, to be viewed as the gluing of entire tree subdiagrams to a given worldline. We demonstrate that the subdiagrams themselves are given, via a recursive relation, by correlation functions on the semi-infinite line. In this sense, the approach we take is fully first-quantized, in that it does not need any field theoretic quantity as input. We envisage that, when suitably extended to gauge theories, it could provide useful insights in addressing current research issues, such as color-kinematics duality.

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arXiv2025

The Double Copy of Maximal Supersymmetry in $D=4$

We realize off-shell, local and gauge invariant $N=8$ supergravity in $D=4$, to cubic order in fields, as the double copy of $N=4$ super Yang-Mills theory (SYM). Employing the homotopy algebra approach, we show that, thanks to a redundant formulation for the fermionic fields, the kinematic algebra $K$ of $N=4$ SYM is compatible with an action of the global supersymmetry algebra. The double copy space is then a subspace of $K\otimes{\widetilde K}$ that inherits an $L_{\infty}$ algebra on which the two copies of the $N=4$ action combine into an action of the $N=8$ supersymmetry algebra, with a corresponding enhancement of the $R$-symmetry group to $SU(8)$.

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arXiv2024

Vertex operators for the kinematic algebra of Yang-Mills theory

The kinematic algebra of Yang-Mills theory can be understood in the framework of homotopy algebras: the $L_{\infty}$ algebra of Yang-Mills theory is the tensor product of the color Lie algebra and a kinematic space that carries a $C_{\infty}$ algebra. There are also hidden structures that generalize Batalin-Vilkovisky algebras, which explain color-kinematics duality and the double copy but are only partially understood. We show that there is a representation of the $C_{\infty}$ algebra, in terms of vertex operators, on the Hilbert space of a first-quantized worldline theory. To this end we introduce $A_{\infty}$ morphisms, which define the vertex operators and which inject the $C_{\infty}$ algebra into the strictly associative algebra of operators on the Hilbert space. We also take first steps to represent the hidden structures on the same space.

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arXiv2024

Yang-Mills theory from the worldline

We construct off-shell vertex operators for the bosonic spinning particle. Using the language of homotopy algebras, we show that the full nonlinear structure of Yang-Mills theory, including its gauge transformations, is encoded in the commutator algebra of the worldline vertex operators. To do so, we deform the worldline BRST operator by coupling it to a background gauge field and show that the coupling is consistent on a suitable truncation of the Hilbert space. On this subspace, the square of the BRST operator is proportional to the Yang-Mills field equations, which we interpret as an operator Maurer-Cartan equation for the background. This allows us to define further vertex operators in different ghost numbers, which correspond to the entire $L_\infty$ algebra of Yang-Mills theory. Besides providing a precise map of a fully nonlinear field theory into a worldline model, we expect these results will be valuable to investigate the kinematic algebra of Yang-Mills, which is central to the double copy program.

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arXiv2024

Double Copy of 3D Chern-Simons Theory and 6D Kodaira-Spencer Gravity

We apply an algebraic double copy construction of gravity from gauge theory to three-dimensional (3D) Chern-Simons theory. The kinematic algebra ${\cal K}$ is the 3D de Rham complex of forms equipped, for a choice of metric, with a graded Lie algebra that is equivalent to the Schouten-Nijenhuis bracket on polyvector fields. The double copied gravity is defined on a subspace of ${\cal K}\otimes \bar{\cal K}$ and yields a topological double field theory for a generalized metric perturbation and two 2-forms. This local and gauge invariant theory is non-Lagrangian but can be rendered Lagrangian by abandoning locality. Upon fixing a gauge this reduces to the double copy of Chern-Simons theory previously proposed by Ben-Shahar and Johansson. Furthermore, using complex coordinates in $\mathbb{C}^3$ this theory is related to six-dimensional (6D) Kodaira-Spencer gravity in that truncating the two 2-forms and one equation yields the Kodaira-Spencer equations on a 3D real slice of $\mathbb{C}^3$. The full 6D Kodaira-Spencer theory can instead be obtained as a consistent truncation of a chiral double copy.

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arXiv2023

Tree-level Scattering Amplitudes via Homotopy Transfer

We formalize the computation of tree-level scattering amplitudes in terms of the homotopy transfer of homotopy algebras, illustrating it with scalar $\phi^3$ and Yang-Mills theory. The data of a (gauge) field theory with an action is encoded in a cyclic homotopy Lie or $L_{\infty}$ algebra defined on a chain complex including a space of fields. This $L_{\infty}$ structure can be transported, by means of homotopy transfer, to a smaller space that, in the massless case, consists of harmonic fields. The required homotopy maps are well-defined since we work with the space of finite sums of plane-wave solutions. The resulting $L_{\infty}$ brackets encode the tree-level scattering amplitudes and satisfy generalized Jacobi identities that imply the Ward identities. We further present a method to compute color-ordered scattering amplitudes for Yang-Mills theory, using that its $L_{\infty}$ algebra is the tensor product of the color Lie algebra with a homotopy commutative associative or $C_{\infty}$ algebra. The color-ordered scattering amplitudes are then obtained by homotopy transfer of $C_{\infty}$ algebras.

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arXiv2023

Weakly Constrained Double Field Theory as the Double Copy of Yang-Mills Theory

Weakly constrained double field theory, in the sense of Hull and Zwiebach, captures the subsector of string theory on toroidal backgrounds that includes gravity, $B$-field and dilaton together with all of their massive Kaluza-Klein and winding modes, which are encoded in doubled coordinates subject to the `weak constraint'. Due to the complications of the weak constraint, this theory was only known to cubic order. Here we construct the quartic interactions for the case that all dimensions are toroidal and doubled. Starting from the kinematic $C_{\infty}$ algebra ${\cal K}$ of pure Yang-Mills theory and its hidden Lie-type algebra, we construct the $L_{\infty}$ algebra of weakly constrained double field theory on a subspace of the `double copied' tensor product space ${\cal K}\otimes\bar{\cal K}$, by doing homotopy transfer to the weakly constrained subspace and performing a non-local shift that is well-defined on the torus. We test the resulting three-brackets, and establish their uniqueness up to cohomologically trivial terms, by verifying the Jacobi identities up to homotopy for the gauge sector.

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arXiv2023

Gravity = Yang-Mills

This essay's title is justified by discussing a class of Yang-Mills-type theories of which standard Yang-Mills theories are special cases but which is broad enough to include gravity as a double field theory. We use the framework of homotopy algebras, where conventional Yang-Mills theory is the tensor product ${\cal K}\otimes \frak{g}$ of a `kinematic' algebra ${\cal K}$ with a color Lie algebra $\frak{g}$. The larger class of Yang-Mills-type theories are given by the tensor product of ${\cal K}$ with more general Lie-type algebras of which ${\cal K}$ itself is an example, up to anomalies that can be cancelled for the tensor product with a second copy $\bar{\cal K}$. Gravity is then given by ${\cal K}\otimes \bar{\cal K}$.

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arXiv2023

Gauge independent kinematic algebra of self-dual Yang-Mills theory

The double copy programme relies crucially on the so-called color-kinematics duality which, in turn, is widely believed to descend from a kinematic algebra possessed by gauge theories. In this paper we construct the kinematic algebra of gauge invariant and off-shell self-dual Yang-Mills theory, up to trilinear maps. This structure is a homotopy algebra of the same type as the ones recently uncovered in Chern-Simons and full Yang-Mills theories. To make contact with known results for the self-dual sector, we show that it reduces to the algebra found by Monteiro and O'Connell upon taking light-cone gauge and partially solving the self-duality constraints. Finally, we test a double copy prescription recently proposed in [1] and reproduce self-dual gravity.

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arXiv2023

Weakly constrained double field theory: the quartic theory

Double field theory was originally introduced as the subsector of closed string field theory on a toroidal background given by the massless fields together with all their massive Kaluza-Klein and winding modes. These massive modes are encoded in the dependence of the massless fields on doubled toroidal coordinates, subject to the so-called 'weak constraint'. This theory was constructed by Hull and Zwiebach in 2009 to cubic order in fields, but due to the weak constraint it is a highly non-trivial problem to extend this to quartic and higher order. In this letter we announce and outline the construction of weakly constrained double field theory to quartic order, in which all coordinates are toroidal and doubled. To this end we use the framework of homotopy algebras and obtain double field theory as a double copy of the kinematic homotopy algebra of Yang-Mills theory.

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arXiv2022

Gauge invariant double copy of Yang-Mills theory: the quartic theory

We give an explicit gauge invariant, off-shell and local double copy construction of gravity from Yang-Mills theory to quartic order. To this end we use the framework of homotopy algebras, and we identify a rich new algebraic structure associated to color-stripped Yang-Mills theory. This algebra, which is a generalization of a Batalin-Vilkovisky algebra, is the underlying structure necessary for double copy. We give a self-contained introduction into these algebras by illustrating them for Chern-Simons theory in three dimensions. We then construct N = 0 supergravity in the form of double field theory in terms of the algebraic Yang-Mills building blocks to quartic order in interactions. As applications of the same universal formula, we re-derive the 4-graviton scattering amplitude and compute a chiral form of the Courant algebroid gauge structure of double field theory.

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arXiv2022

Gauge-invariant coefficients in perturbative quantum gravity

Heat kernel methods are useful for studying properties of quantum gravity. We recompute here the first three heat kernel coefficients in perturbative quantum gravity with cosmological constant to ascertain which ones are correctly reported in the literature. They correspond to the counterterms needed to renormalize the one-loop effective action in four dimensions. They may be evaluated at arbitrary dimensions $D$, in which case they identify only a subset of the divergences appearing in the effective action for $D\geq 6$. Generically, these coefficients depend on the gauge-fixing choice adopted in quantizing the Einstein-Hilbert action. However, they become gauge-invariant once evaluated on-shell, i.e. using Einstein's field equations with cosmological constant. We identify them and use them as a benchmark for checking alternative approaches to perturbative quantum gravity. One such approach describes the graviton in first-quantization through the use of the action of the ${\cal N}=4$ spinning particle, characterized by four supersymmetries on the worldline and a set of worldline gauge invariances. This description has been used for computing the gauge-invariant coefficients as well. We verify their correctness at $D=4$, but find a mismatch at arbitrary $D$ when comparing with the benchmark fixed earlier. We interpret this result as signaling that the path integral quantization of the ${\cal N}=4$ spinning particle should be amended. We perform this task by fixing the correct counterterm that must be used in the worldline path integral quantization of the ${\cal N}=4$ spinning particle to make it consistent in arbitrary dimensions.

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arXiv2022

The Gauge Structure of Double Field Theory follows from Yang-Mills Theory

We show that to cubic order double field theory is encoded in Yang-Mills theory. To this end we use algebraic structures from string field theory as follows: The $L_{\infty}$-algebra of Yang-Mills theory is the tensor product ${\cal K}\otimes \mathfrak{g}$ of the Lie algebra $\mathfrak{g}$ of the gauge group and a `kinematic algebra' ${\cal K}$ that is a $C_{\infty}$-algebra. This structure induces a cubic truncation of an $L_{\infty}$-algebra on the subspace of level-matched states of the tensor product ${\cal K}\otimes \bar{\cal K}$ of two copies of the kinematic algebra. This $L_{\infty}$-algebra encodes double field theory. More precisely, this construction relies on a particular form of the Yang-Mills $L_{\infty}$-algebra following from string field theory or from the quantization of a suitable worldline theory.

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arXiv2021

Duality invariant string beta functions at two loops

We compute, for cosmological backgrounds, the $O(d,d;\mathbb{R})$ invariant beta functions for the sigma model of the bosonic string at two loops. This yields an independent first-principle derivation of the order $\alpha'$ corrections to the cosmological target-space equations. To this end we revisit the quantum consistency of Tseytlin's duality invariant formulation of the worldsheet theory. While we confirm the absence of gravitational (and hence Lorentz) anomalies, our results show that the minimal subtraction scheme is not applicable, implying significant technical complications at higher loops. To circumvent these we then change gears and use the Polyakov action for cosmological backgrounds, applying a suitable perturbation scheme that, although not $O(d,d;\mathbb{R})$ invariant, allows one to efficiently determine the $O(d,d;\mathbb{R})$ invariant beta functions.

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