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Constraints on the Variation of G from Primordial Nucleosynthesis
We study here the effect of a varying G on the evolution of the early Universe and, in particular, on primordial nucleosynthesis. This variation of G is modelled using the Brans-Dicke theory as well as a more general class ...
Exact Friedmann Solutions in Higher-Order Gravity Theories
We find the general behaviour of homogeneous and isotropic cosmological models in some fourth-order theories of gravity. Explicit, exact, general solutions are given for both empty universes and those filled with a perfect ...
Islands in the landscape
The string theory landscape consists of many metastable de Sitter vacua, populated by eternal inflation. Tunneling between these vacua gives rise to a dynamical system, which asymptotically settles down to an equilibrium ...
Modified Gravity and Cosmology
In this review we present a thoroughly comprehensive survey of recent work on modified theories of gravity and their cosmological consequences. Amongst other things, we cover General Relativity, Scalar-Tensor, Einstein-Aether, ...
Interactions as intertwiners in 4D QFT
In a recent paper we showed that the correlators of free scalar field theory in four dimensions can be constructed from a two dimensional topological field theory based on so(4,2) equivariant maps (intertwiners). The free ...
Decay of the Cosmic Vacuum Energy
In his 2005 review, Gravity and the Thermodynamics of Horizons, Paddy suggested that a vacuum in thermal equilibrium with a bath of radiation should have a gradually diminishing energy. We work through the consequences of ...
Geometrical Aspects of An Abelian (2,0) Action
(Springer Verlag (Germany), 2020-04)
We explore various geometrical aspects of an action for six-dimensional chiral 2-forms based on the formalism of 1903.12196. We elucidate the coupling to general backgrounds and construct the full supersymmetric completion ...
Type-B Anomaly Matching and the 6D (2,0) Theory
(Springer Verlag (Germany), 2020)
We study type-B conformal anomalies associated with $\frac{1}{2}$-BPS Coulomb-branch operators in 4D $\mathcal N=2$ superconformal field theories. When the vacuum preserves the conformal symmetry these anomalies coincide ...
Permutations and the combinatorics of gauge invariants for general N
Group algebras of permutations have proved highly useful in solving a number of problems in large N gauge theories. I review the use of permutations in classifying gauge invariants in one-matrix and multi-matrix models and ...
(Mis-)Matching Type-B Anomalies on the Higgs Branch
(Springer Verlag (Germany), 2021)
Building on arXiv:1911.05827, we uncover new properties of type-B conformal anomalies for Coulomb-branch operators in continuous families of 4D $\mathcal{N}=2$ SCFTs. We study a large class of such anomalies on the Higgs ...