Two Composite Higgs Doublets: Is it the Low Energy Limit of a Natural Strong Electroweak Symmetry Breaking Sector ?

In this paper, we construct an effective model that describes the electroweak symmetry breaking sector by means of composite Higgs-like scalars, following the ideas of Minimal Walking Technicolor (MWT). We argue that, because of the general failure of Extended Technicolor (ETC) to explain the mass of the top quark, it is necessary to introduce two composite Higgs bosons: one of them originated by a MWT-ETC sector and the other one produced by a Topcolor sector. We focus on the phenomenological differences between the light composite Higgs present in our model and the fundamental Higgs boson predicted by the Standard Model and their production at the LHC. We show that in this scheme the main production channel of the lighter Higgs boson are the associated production with a gauge boson and $WW$ fusion but not the gluon-gluon fusion channel which is substantially suppressed.Comment: Version accepted in Modern Physics Letters

Endogenous retirement and public pension system reform in Spain

All around the world , developed countries have resorted to parametric reforms of their Social Security systems, in an attempt to lessen the impact of the population aging. In particular, pension formulae have been modified to reduce the generosity of the systems and to induce longer working careers. In this paper we explore the capacity of these reforms to alleviate the expected financial difficulties of current PAYG systems. This is accomplished by developing and Heterogeneous Agents, Applied General Equilibrium model where individuals can freely adjust their retirement ages in response to the incentives provided by the pension regulations. This inclusion is relevant, as parametric changes tend to significantly alter retirement incentives. We find that the calibrated model successfully reproduces the basic stylized facts of retirement behavior in Spain. In particular, it mimics the early retirement pattern of low income workers under the effects of minimum pensions. The model is then used to explore the effects of several changes in pension formula, including the reform actually implemented in 1997. The general conclusion is that parametric changes can significantly improve the financial condition of the system, but are far away from being able to fully restoring it

Axigluon Phenomenology using ATLAS dijet data

In recent years, there has been a renewed interest on axigluons as part of a possible extension of strong interactions at high energies. In this work, we use recent ATLAS measurements of the dijet spectrum in order to set limits on the axigluon mass and coupling to quarks. We pay special attention to the methodology used to extract the resonant contribution from theoretical simulations. Finally, we present some predictions for the next LHC run at $\sqrt{s}=14$ TeV

Endogenous Retirement and Public Pension System Reform in Spain

All around the world, population aging has spurred developed countries to reform their PAYG pension systems. In particular, delaying legal retirement ages and reducing the generosity of pension benefits have been widely implemented changes. In this paper we assess how successful those policies can be in the case of the Spanish economy, and compare with the results obtained by the already implemented reforms (1997 and 2001). This evaluation is accomplished in a heterogeneous-agents, applied general equilibrium model where individuals can adjust their retirement ages in response to changes in pension rules. We check the ability of the model to reproduce the basic stylized facts of retirement behavior (specially the pattern of early retirement induced by minimum pensions). We then use to model to explore the impact of pension reforms. We find that already implemented changes actually increase the implicit liabilities of the system, while delaying the legal retirement age to 68 may roughly halve the size of the current pension debt.Pension System Reform, Applied General Equilibrium, Retirement.

Limits on a Strong Electroweak Sector from e^+ e^- -> 2gamma + missing E at LEP2

We study the process $e^+ e^- \to \gamma \gamma \nu \bar{\nu}$ in the context of a strong electroweak symmetry breaking model, which can be a source of events with two photons and missing energy at LEP2. We investigate bounds on the model assuming that no deviation is observed from the Standard Model within a given experimental error.Comment: 7 pages, Latex, one figur

The effect of pension rules on retirement monetary incentives with an application to pension reforms in Spain

In this work we theoretically disentangle the effects of pension provisions on a variety of financial incentives to retirement, trying to reconcile them with some key Spanish retirement patterns. We find that the "average" individual, who is never affected by any cap of contributions or benefits, has weak incentives to retire early and strong incentives to retire at the normal retirement age. Alternatively, individuals at the bottom of the wage distribution have strong incentives to retire as early as possible, because ot the interaction between age-related penalties and the minimun pension. Both findings perfectly accommodate the retirement hazard of medium and low earners respectively. In contrast, high earners (those that have their contributions capped) despite having strong incentives to retire at the Early Retirement Age, do not do so. This is because, for those workers, financial incentives are not a good proxy for the marginal utility from working. Finally, we analyze the reasons behind the failure of the 1997 reform in improving the sustainability of the Spanish public pension system

On the Quantum Chromodynamics of a Massive Vector Field in the Adjoint Representation

In this paper, we explore the possibility of constructing the quantum chromodynamics of a massive color-octet vector field without introducing higher structures like extended gauge symmetries, extra dimensions or scalar fields. We show that gauge invariance is not enough to constraint the couplings. Nevertheless the requirement of unitarity fixes the values of the coupling constants, which otherwise would be arbitrary. Additionally, it opens a new discrete symmetry which makes the coloron stable and avoid its resonant production at a collider. On the other hand, a judicious definition of the gauge fixing terms modifies the propagator of the massive field making it well-behaved in the ultra-violet limit. The relation between our model and the more general approach based on extended gauge symmetries is also discussed.Comment: Subsection 2.1 rewritten in order to make it more pedagogical. This version match the text accepted in IJMP