On the Cut-off Estimate in Lifshitz Five Dimensional Field Theories

We analyze if and to what extent the high energy behaviour of five-dimensional (5D) gauge theories can be improved by adding certain higher dimensional operators of "Lifshitz" type, without breaking the ordinary four-dimensional Lorentz symmetries. We show that the UV behaviour of the transverse gauge field polarizations can be improved by the Lifshitz operators, while the longitudinal polarizations get strongly coupled at energies lower than the ones in ordinary 5D theories, spoiling the usefulness of the construction in non-abelian gauge theories. We conclude that the improved behaviour as effective theories of the ordinary 5D models is not only related to locality and 5D gauge symmetries, but is a special property of the standard theories defined by the lowest dimensional operators.Comment: 18 pages, one appendix; v2: minor improvements, to appear in Phys. Rev. D; v3: one typo fixed, incorrect argument at the end of section 5 removed, acknowledgments added, conclusions unchanged, supersedes published version v

A note on supersymmetric D-brane dynamics

We study the spin dependence of D-brane dynamics in the Green-Schwarz formalism of boundary states. In particular we show how to interpret insertion of supercharges on the boundary state as sources of non-universal spin effects in D-brane potentials. In this way we find for a generic (D)p-brane, potentials going like $v^{4-n}/r^{7-p+n}$ corresponding to interactions between the different components of the D-brane supermultiplet. From the eleven dimensional point of view, these potentials arise from the exchange of field strengths corresponding to the graviton and the three form, coupled non-minimally to the branes. We show how an annulus computation truncated to its massless contribution is enough to reproduce these next-to-leading effects, meaning in particular that the one-loop (M)atrix theory effective action should encode all the spin dependence of low-energy supergravity interactions.Comment: LaTex file, 12 pages, no figures, some corrections in last section and references added; version to appear in Physics Letters

A Simple UV-Completion of QED in 5D

We construct a Lifshitz-like version of five-dimensional (5D) QED which is UV - completed and reduces at low energies to ordinary 5D QED. The UV quantum behaviour of this theory is very smooth. In particular, the gauge coupling constant is finite at all energy scales and at all orders in perturbation theory. We study the IR properties of this theory, when compactified on a circle, and compare the one-loop energy dependence of the coupling in the Lifshitz theory with that coming from the standard 5D QED effective field theory. The range of validity of the 5D effective field theory is found to agree with the more conservative version of Naive Dimensional Analysis.Comment: 24 pages, 7 figures; v2: Minor improvements, matches journal versio

The Electroweak phase transition in models with gauge-Higgs unification

The dynamics of five dimensional Wilson line phases at finite temperature is studied in the oneloop approximation. We show that at temperatures of order T 3c 1/L, where L is the length of the compact space, the gauge symmetry is always restored and the electroweak phase transition appears to be of first order. We focus on a specific model where the Wilson line phase is identified with the Higgs field (gauge-Higgs unification). The transition is of first order even for values of the Higgs mass above the current experimental limit. If large localized gauge kinetic terms are present, the transition might be strong enough to give baryogenesis at the electroweak transitio

Fermion conformal bootstrap in 4d

We apply numerical conformal bootstrap techniques to the four-point function of a Weyl spinor in 4d non-supersymmetric CFTs. We find universal bounds on operator dimensions and OPE coefficients, including bounds on operators in mixed symmetry representations of the Lorentz group, which were inaccessible in previous bootstrap studies. We find discontinuities in some of the bounds on operator dimensions, and we show that they arise due to a generic yet previously unobserved fake primary effect, which is related to the existence of poles in conformal blocks. We show that this effect is also responsible for similar discontinuities found in four-fermion bootstrap in 3d, as well as in the mixed-correlator analysis of the 3d Ising CFT. As an important byproduct of our work, we develop a practical technology for numerical approximation of general 4d conformal blocks

Gaugino condensation in an improved heterotic M-theory

Gaugino condensation is discussed in the context of a consistent new version of low energy heterotic M-theory. The four dimensional reduction of the theory is described, based on simple boson and fermion backgrounds. This is generalised to include gaugino condenstates and various background fluxes, some with non-trivial topology. It is found that condensate and quantised flux contributions to the four-dimensional superpotential contain no corrections due to the warping of the higher dimensional metric.Comment: 11 pages, 4 figures, LaTe

Orbifold resolutions with general profile

A very general class of resolved versions of the C/Z_N, T^2/Z_N and S^1/Z_2 orbifolds is considered and the free theory of 6D chiral fermions studied on it. As the orbifold limit is taken, localized 4D chiral massless fermions are seen to arise at the fixed points. Their number, location and chirality is found to be independent on the detailed profile of the resolving space and to agree with the result of hep-th/0409229, in which a particular resolution was employed. As a consistency check of the resolution procedure, the massive equation is numerically studied. In particular, for S^1/Z_2, the "resolved" mass--spectrum and wave functions in the internal space are seen to correctly reproduce the usual orbifold ones, as the orbifold limit is taken.Comment: 28 pages, 3 figures, typos corrected, references adde