Gauge-Higgs Unification on Flat Space Revised

Models with gauge-Higgs unification on a flat space are typically affected by common problems, the main of which are the prediction of a too small top and Higgs mass and a too low compactification scale. We show how, by breaking the SO(4,1) Lorentz symmetry in the bulk and introducing a Z_2 ``mirror'' symmetry, a potentially realistic model arises, in which all these problems are solved.Comment: 4 pages, 1 figure, to appear in Proceedings of SUSY06, the 14th International Conference on Supersymmetry and the Unification of Fundamental Interactions, UC Irvine, California, 12-17 June 200

The causes of the debt crisis in Europe and the role of regional integration

The factors that allow the launch of a speculative attack, such as those on he government debts of Greece, Spain, Portugal, Ireland and Italy in 2010, are always multiple. In this case, they can be found in some simultaneous events (e.g. the regional German elections of the 9th of May), in some previous faulty behaviors of the governments under attack, and in some defects of the institutional organization of the European Monetary Union. Those who believe that the operation of market forces (and of financial speculation) is always able to bring about efficiency tend to stress the role played by the faulty behaviors of the authorities. Those holding a different standpoint tend to blame the faults in the institutional organization that have prevented the authorities from operating effectively against the speculative attack. For those having faith in the “market efficiency hypothesis”, the government of Greece and of the other countries under attack failed to take advantage of the positive trend of the world economy before the financial crisis.

Flavor hierarchies from dynamical scales

One main obstacle for any beyond the SM (BSM) scenario solving the hierarchy problem is its potentially large contributions to electric dipole moments. An elegant way to avoid this problem is to have the light SM fermions couple to the BSM sector only through bilinears, $\bar ff$. This possibility can be neatly implemented in composite Higgs models. We study the implications of dynamically generating the fermion Yukawa couplings at different scales, relating larger scales to lighter SM fermions. We show that all flavor and CP-violating constraints can be easily accommodated for a BSM scale of few TeV, without requiring any extra symmetry. Contributions to B physics are mainly mediated by the top, giving a predictive pattern of deviations in $\Delta F=2$ and $\Delta F=1$ flavor observables that could be seen in future experiments.Comment: 25 pages, 5 figures; v2: corrections in some estimate

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 one-loop approximation. We show that at temperatures of order $T\sim 1/L$, 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 transition.Comment: 4 pages, 2 figures, contribution to the Proceedings of the Int. Europhysics Conf. on High Energy Physics (HEP2005), July 21-27 2005, Lisboa, Portuga

Probing light top partners with CP violation

We investigate CP-violating effects induced by light top partners in composite Higgs theories. We find that sizable contributions to the dipole moments of the light SM quarks and leptons are generically generated at the two-loop level through Barr-Zee-type diagrams. The present constraints on the electron and neutron electric dipole moments translate into bounds on top partner masses of order few TeV and are competitive with the reach of LHC direct searches. Interestingly, we find that CP-violation effects are sensitive to the same operators that control top partner single production. Near-future improvements in the determination of the electron dipole moment will extend the reach on top partner masses beyond the 5 - 10 TeV range.Comment: 31 pages, 10 figures; v2: typos corrected, matches published versio

Top Partners Searches and Composite Higgs Models

Colored fermionic partners of the top quark are well-known signatures of the Composite Higgs scenario and for this reason they have been and will be subject of an intensive experimental study at the LHC. Performing an assessment of the theoretical implications of this experimental effort is the goal of the present paper. We proceed by analyzing a set of simple benchmark models, characterized by simple two-dimensional parameter spaces where the results of the searches are conveniently visualized and their impact quantified. We only draw exclusion contours, in the hypothesis of no signal, but of course our formalism could equally well be used to report discoveries in a theoretically useful format.Comment: 32 pages, 15 figure

A Scheme to Coordinate Monetary and Fiscal Policies in the Euro Area

The paper deals with the problems of coordination between monetary and fiscal policies in the Euro area. It examines how the existing institutions handle these problems and presents a proposal to reorganize them. The paper points out that, contrary to what is often stated by the literature, there is a need for coordination between monetary and fiscal policies when both cyclical (short-run) and structural (long-run) problems are dealt with. Then it assesses how coordination is carried out under the existing institutional arrangements, summarizes the main literature that has dealt, in recent years, with the need to modify them and proposes a new scheme, which intends to make them work effectively.European Monetary Union, policy coordination, Stability and Growth Pact