39 results found
Adamo T, Ilderton A, 2019, Gluon helicity flip in a plane wave background, Journal of High Energy Physics, Vol: 2019, Pages: 1-26, ISSN: 1029-8479
We compute the leading probability for a gluon to flip helicity state upon traversing a background plane wave gauge field in pure Yang-Mills theory and QCD, with an arbitrary number of colours and flavours. This is a one-loop calculation in perturbative gauge theory around the gluonic plane wave background, which is treated without approximation (i.e., to all orders in the coupling). We introduce a background-dressed version of the spinor helicity formalism and use it to obtain simple formulae for the flip amplitude with pure external gluon polarizations. We also give in-depth examples for gauge group SU(2), and evaluate both the high- and low-energy limits. Throughout, we compare and contrast with the calculation of photon helicity flip in strong-field QED.
Adamo T, Casali E, Mason L, et al., 2019, Plane wave backgrounds and colour-kinematics duality, Journal of High Energy Physics, Vol: 2019, Pages: 1-28, ISSN: 1029-8479
We consider perturbative gauge theory on a fixed Yang-Mills plane wave background, describing its Feynman rules in detail. Using these rules, the tree-level 4-point gluon amplitude is computed. As an application, we investigate whether some notion of colour-kinematics duality — a relation between the colour and kinematic constituents of the amplitude — holds on the plane wave background. Although the duality is obstructed, the obstruction has an interesting and highly-constrained structure. This plane wave version of colour-kinematics duality reduces on a flat background to the well-known identities underpinning the BCJ relations for colour-ordered partial amplitudes, and constrains representations of tree-level amplitudes beyond 4-points.
Adamo T, Casali E, Nekovar S, 2019, Ambitwistor string vertex operators on curved backgrounds, Journal of High Energy Physics, Vol: 2019, ISSN: 1029-8479
We present vertex operators for ambitwistor strings around generic Yang-Mills, gravity and NS-NS backgrounds. The requirement that vertex operators lie in the BRST cohomology of the worldsheet theory enforces the appropriate linear equations of motion (as well as gauge fixing conditions) for the respective perturbations in these backgrounds. Due to the nature of ambitwistor strings, no approximation is taken and all calculations around the backgrounds are exact.
Adamo T, Skinner D, Williams J, 2018, Minitwistors and 3d Yang-Mills-Higgs theory, Journal of Mathematical Physics, Vol: 59, ISSN: 1089-7658
We construct a minitwistor action for Yang–Mills–Higgs (YMH) theory in three dimensions. The Feynman diagrams of this action will construct perturbation theory around solutions of the Bogomolny equations in much the same way that MHV (maximally helicity violating) diagrams describe perturbation theory around the self-dual Yang Mills equations in four dimensions. We also provide a new formula for all tree amplitudes in YMH theory (and its maximally supersymmetric extension) in terms of degree d maps to minitwistor space. We demonstrate its relationship to the Roiban-Spradlin-Volovich-Witten (RSVW) formula in four dimensions and show that it generates the correct MHV amplitudes at d = 1 and factorizes correctly in all channels for all degrees.
Adamo T, Casali E, Nekovar S, 2018, Yang-Mills theory from the worldsheet, Physical Review D, Vol: 98, ISSN: 2470-0010
We give a new description of classical Yang-Mills theory by coupling a two-dimensional chiral conformal field theory (which gives the tree-level S matrix of Yang-Mills theory at genus zero) to a background non-Abelian gauge field. The resulting model is solvable, and when the gravitational degrees of freedom are decoupled, the nonlinear Yang-Mills equations are imposed as an exact worldsheet anomaly cancellation condition. When gravitational modes are reinstated, we find gauge anomalies analogous to those appearing in heterotic string theory.
Adamo T, Nakach S, Tseytlin AA, 2018, Scattering of conformal higher spin fields, Journal of High Energy Physics, Vol: 2018, ISSN: 1029-8479
We develop a formalism for describing the most general notion of tree-level scattering amplitudes in 4d conformal higher spin theory. As conformal higher spin fields obey higher-derivative equations of motion, there are many distinct on-shell external states which may contribute to their scattering, some of which grow polynomially with time, leading to ill-defined amplitudes. We characterize the set of admissible scattering states which produce finite tree amplitudes, noting that there are more such states than just standard massless higher spins obeying two-derivative equations of motion. We use conformal gravity as a prime example, where the set of scattering states includes the usual Einstein graviton and a ‘ghost’ massless spin 1 particle. An extension of the usual spinor helicity formalism allows us to encode these scattering states efficiently in terms of ‘twistor-spinors’. This leads to compact momentum space expressions for all finite tree-level 3-point amplitudes of conformal higher spin theory. While some of these 3-point amplitudes vanish (including all those with only standard two-derivative higher spin external states), there are many others which are non-vanishing. We also comment on the generalization to scattering of conformal higher spins in AdS4.
Adamo T, Casali E, Mason L, et al., 2017, Amplitudes on plane waves from ambitwistor strings, Journal of High Energy Physics, Vol: 2017, ISSN: 1029-8479
In marked contrast to conventional string theory, ambitwistor strings remainsolvable worldsheet theories when coupled to curved background fields. We use this fact toconsider the quantization of ambitwistor strings on plane wave metric and plane wave gaugefield backgrounds. In each case, the worldsheet model is anomaly free as a consequenceof the background satisfying the field equations. We derive vertex operators (in bothfixed and descended picture numbers) for gravitons and gluons on these backgrounds fromthe worldsheet CFT, and study the 3-point functions of these vertex operators on theRiemann sphere. These worldsheet correlation functions reproduce the known results for3-point scattering amplitudes of gravitons and gluons in gravitational and gauge theoreticplane wave backgrounds, respectively.
Adamo T, Monteiro R, Poulo MF, 2017, Space-time CFTs from the Riemann sphere, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2017, ISSN: 1029-8479
We consider two-dimensional chiral, first-order conformal field theories governing maps from the Riemann sphere to the projective light cone inside Minkowski space — the natural setting for describing conformal field theories in two fewer dimensions. These theories have a SL(2) algebra of local bosonic constraints which can be supplemented by additional fermionic constraints depending on the matter content of the theory. By computing the BRST charge associated with gauge fixing these constraints, we find anomalies which vanish for specific target space dimensions. These critical dimensions coincide precisely with those for which (biadjoint) cubic scalar theory, gauge theory and gravity are classically conformally invariant. Furthermore, the BRST cohomology of each theory contains vertex operators for the full conformal multiplets of single field insertions in each of these space-time CFTs. We give a prescription for the computation of three-point functions, and compare our formalism with the scattering equations approach to on-shell amplitudes.
Adamo T, Hahnel P, McLoughlin T, 2017, Conformal higher spin scattering amplitudes from twistor space, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2017, ISSN: 1029-8479
We use the formulation of conformal higher spin (CHS) theories in twistor space to study their tree-level scattering amplitudes, finding expressions for all three-point MHV¯¯¯¯¯¯¯¯¯¯¯¯MHV¯ amplitudes and all MHV amplitudes involving positive helicity conformal gravity particles and two negative helicity higher spins. This provides the on-shell analogue for the covariant coupling of CHS fields to a conformal gravity background. We discuss the restriction of the theory to a ghost-free unitary subsector, analogous to restricting conformal gravity to general relativity with a cosmological constant. We study the flat-space limit and show that the restricted amplitudes vanish, supporting the conjecture that in the unitary sector the S-matrix of CHS theories is trivial. However, by appropriately rescaling the amplitudes we find non-vanishing results which we compare with chiral flat-space higher spin theories.
Adamo T, Skinner D, Williams J, 2016, Twistor methods for AdS5, JOURNAL OF HIGH ENERGY PHYSICS, Vol: 2016, ISSN: 1029-8479
We consider the application of twistor theory to five-dimensional anti-de Sitter space. The twistor space of AdS5 is the same as the ambitwistor space of the four-dimensional conformal boundary; the geometry of this correspondence is reviewed for both the bulk and boundary. A Penrose transform allows us to describe free bulk fields, with or without mass, in terms of data on twistor space. Explicit representatives for the bulk-to-boundary propagators of scalars and spinors are constructed, along with twistor action functionals for the free theories. Evaluating these twistor actions on bulk-to-boundary propagators is shown to produce the correct two-point functions.
Adamo T, Casali E, Roehrig KA, et al., 2015, On tree amplitudes of supersymmetric Einstein-Yang-Mills theory, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Adamo T, 2015, Gravity with a cosmological constant from rational curves, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Adamo T, 2015, General relativity as a two-dimensional CFT, INTERNATIONAL JOURNAL OF MODERN PHYSICS D, Vol: 24, ISSN: 0218-2718
Adamo T, Casali E, 2015, Perturbative gauge theory at null infinity, PHYSICAL REVIEW D, Vol: 91, ISSN: 2470-0010
Adamo T, Casali E, 2015, Scattering equations, supergravity integrands, and pure spinors, JOURNAL OF HIGH ENERGY PHYSICS, Pages: 1-28, ISSN: 1029-8479
Adamo T, Casali E, Skinner D, 2015, A worldsheet theory for supergravity, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Adamo T, Casali E, Skinner D, 2014, Perturbative gravity at null infinity, CLASSICAL AND QUANTUM GRAVITY, Vol: 31, ISSN: 0264-9381
Adamo T, Casali E, Skinner D, 2014, Ambitwistor strings and the scattering equations at one loop, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Adamo T, 2014, Worldsheet factorization for twistor-strings, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Adamo T, Mason L, 2014, Conformal and Einstein gravity from twistor actions, CLASSICAL AND QUANTUM GRAVITY, Vol: 31, ISSN: 0264-9381
Adamo T, Mason L, 2013, Twistor-strings and gravity tree amplitudes, CLASSICAL AND QUANTUM GRAVITY, Vol: 30, ISSN: 0264-9381
Adamo T, Groechenig M, 2013, Moduli stacks of maps for supermanifolds, ADVANCES IN THEORETICAL AND MATHEMATICAL PHYSICS, Vol: 17, Pages: 1303-1342, ISSN: 1095-0761
Adamo T, Mason L, 2012, Maximally helicity-violating diagrams in twistor space and the twistor action, PHYSICAL REVIEW D, Vol: 86, ISSN: 1550-7998
Adamo T, Mason L, 2012, Einstein supergravity amplitudes from twistor-string theory, CLASSICAL AND QUANTUM GRAVITY, Vol: 29, ISSN: 0264-9381
Adamo TM, Newman ET, Kozameh C, 2012, Null Geodesic Congruences, Asymptotically-Flat Spacetimes and Their Physical Interpretation, LIVING REVIEWS IN RELATIVITY, Vol: 15, ISSN: 2367-3613
Adamo T, 2011, Correlation functions, null polygonal Wilson loops, and local operators, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Adamo T, Bullimore M, Mason L, et al., 2011, Scattering amplitudes and Wilson loops in twistor space, JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, Vol: 44, ISSN: 1751-8113
Adamo T, Bullimore M, Mason L, et al., 2011, A prooof of the correlation function/supersymmetric Wilson loop correspondence, JOURNAL OF HIGH ENERGY PHYSICS, ISSN: 1029-8479
Adamo TM, Newman ET, 2011, Light cones in relativity: Real, complex, and virtual, with applications, PHYSICAL REVIEW D, Vol: 83, ISSN: 2470-0010
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