Poul H. Damgaard

Minimal basis for gauge theory amplitudes.

Identities based on monodromy for integrations in string theory are used to derive relations between different color-ordered tree-level amplitudes in both bosonic and supersymmetric string theory. These relations imply that the color-ordered tree-level n-point gauge theory amplitudes can be expanded in a minimal basis of (n-3)! amplitudes. This result holds for any choice of polarizations of the external states and in any number of dimensions.

The momentum kernel of gauge and gravity theories

We derive an explicit formula for factorizing an n-point closed string amplitude into open string amplitudes. Our results are phrased in terms of a momentum kernel which in the limit of infinite string tension reduces to the corresponding field theory kernel. The same momentum kernel encodes the monodromy relations which lead to the minimal basis of color-ordered amplitudes in Yang-Mills theory. There are interesting consequences of the momentum kernel pertaining to soft limits of amplitudes. We also comment on surprising links between gravity and certain combinations of kinematic and color factors in gauge theory.

The microscopic spectral density of the QCD Dirac operator

We derive the microscopic spectral density of the Dirac operator in

Gravity and Yang-Mills amplitude relations

SU(N_c\geq 3)

Universality of random matrices in the microscopic limit and the Dirac operator spectrum

Yang-Mills theory coupled to

Monodromy and Jacobi-like Relations for Color-Ordered Amplitudes

N_f

Proof of gravity and Yang-Mills amplitude relations

fermions in the fundamental representation. An essential technical ingredient is an exact rewriting of this density in terms of integrations over the super Riemannian manifold

Universal spectral correlators and massive Dirac operators

Gl(N_f+1|1)

Distribution of the k-th smallest Dirac operator eigenvalue

. The result agrees exactly with earlier calculations based on Random Matrix Theory.

Partially quenched chiral perturbation theory and the replica method

Using only general features of the S matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.