Related papers: Self-duality, Helicity and Higher-loop Euler-Heise…
We establish the existence of an exact non-perturbative self-duality in a variety of quantum impurity problems, including the Luttinger liquid or quantum wire with impurity. The former is realized in the fractional quantum Hall effect,…
We develop the derivative expansion of the one-loop ${\cal N}=4$ SYM effective action depending both on ${\cal N}=2$ vector multiplet and on hypermultiplet background fields. We get a new derivation of the complete ${\cal N}=4$…
We combine the unitarity method with the six-dimensional helicity formalism of Cheung and O'Connell to construct loop-level scattering amplitudes. As a first example, we construct dimensionally regularized QCD one-loop four-point…
Colour-kinematics duality is the conjecture of a group theory-like structure for the kinematic dependence of scattering amplitudes in gauge theory and gravity. This structure has been verified at tree level in various ways, but similar…
We construct a general Lagrangian, quadratic in the field strengths of $n$ abelian gauge fields, which interpolates between BI actions of n abelian vectors and actions, quadratic in the vector field-strengths, describing Maxwell fields…
Though the one-loop amplitudes of the Higgs boson to massless gauge bosons are finite because there is no direct interaction at tree-level in the Standard Model, a well-defined regularization scheme is still required for their correct…
Duality is an indispensable tool for describing the strong-coupling dynamics of gauge theories. However, its actual realization is often quite subtle: quantities such as the partition function can transform covariantly, with degrees of…
A canonical analysis of the first-order two-dimensional Einstein-Hilbert action has shown it to have no physical degrees of freedom and to possess an unusual gauge symmetry with a symmetric field $\xi_{\mu\nu}$ acting as a gauge function.…
This is a summary of the analysis of the one-loop effective action in Z_2-orbifold compactifications of type-I theory presented in references [1,2]. We show how, for non-abelian group factors, the threshold effects are ultraviolet finite…
We study one-loop low-energy effective action in the hypermultiplet sector for ${\cal N}=2$ superconformal models. Any such a model contains ${\cal N}=2$ vector multiplet and some number of hypermultiplets. Gauge group $G$ is assumed to be…
We study the heterotic string compactified on K3 x T^2 near the line T=U, where the effective action becomes singular due to an SU(2) gauge symmetry enhancement. By `integrating in' the light W^\pm vector multiplets we derive a quantum…
Functional methods can be applied to the quantum effective action to efficiently determine counterterms and matching conditions for effective field theories. We extend the toolbox to two-loop order and beyond and show how to evaluate the…
We investigate the gauge/gravity duality in the interaction between two spherical membranes in the 11-dimensional pp-wave background. On the supergravity side, we find the solution to the field equations at locations close to a spherical…
We perform a supergraph computation of the effective Kaehler potential at one and two loops for general four dimensional N=1 supersymmetric theories described by arbitrary Kaehler potential, superpotential and gauge kinetic function. We…
We study the one-loop effective action for a generic two-dimensional dilaton gravity theory conformally coupled to $N$ matter fields. We obtain an explicit expression for the effective action in the weak-coupling limit under a suitable…
In 4-D heterotic superstrings, the dilaton and antisymmetric tensor fields belong to a linear N=1 supersymmetric multiplet L. We study the lagrangian describing the coupling of one linear multiplet to chiral and gauge multiplets in global…
Based on the gauge independent decomposition of the non-Abelian gauge field into the dual potential and the valence potential, we calculate the one loop effective action of SU(2) QCD in an arbitrary constant monopole background, using the…
We study the helicity amplitudes of the process \gamma \gamma \to \gamma \gamma at high energy, which in the standard and SUSY models first arise at the one-loop order. In the standard model (SM), the diagrams involve W and charged quark…
Conventional Lagrangian formulations of gauge and gravity theories emphasize compactness and off-shell symmetry. This often obscures the structure of on-shell physical observables. In this work, we present a constructive framework that…
Self-dual Yang-Mills and Einstein gravity in Euclidean AdS$_4$ are useful toy models because they can be described by simple scalar Lagrangians exhibiting a new manifestation of the colour/kinematics duality, as recently shown by two of the…