J. R. Espinosa

Changes in precipitation and temperature extremes in Central America and northern South America, 1961–2003

[1]xa0In November 2004, a regional climate change workshop was held in Guatemala with the goal of analyzing how climate extremes had changed in the region. Scientists from Central America and northern South America brought long-term daily temperature and precipitation time series from meteorological stations in their countries to the workshop. After undergoing careful quality control procedures and a homogeneity assessment, the data were used to calculate a suite of climate change indices over the 1961–2003 period. Analysis of these indices reveals a general warming trend in the region. The occurrence of extreme warm maximum and minimum temperatures has increased while extremely cold temperature events have decreased. Precipitation indices, despite the large and expected spatial variability, indicate that although no significant increases in the total amount are found, rainfall events are intensifying and the contribution of wet and very wet days are enlarging. Temperature and precipitation indices were correlated with northern and equatorial Atlantic and Pacific Ocean sea surface temperatures. However, those indices having the largest significant trends (percentage of warm days, precipitation intensity, and contribution from very wet days) have low correlations to El Nino–Southern Oscillation. Additionally, precipitation indices show a higher correlation with tropical Atlantic sea surface temperatures.

On the Naturalness of Higgs inflation

We critically examine the recent claim that the standard model (SM) Higgs boson H could drive inflation in agreement with observations if |H|{sup 2} has a strong coupling {xi}{approx}10{sup 4} to the Ricci curvature scalar. We first show that the effective-theory approach upon which that claim is based ceases to be valid beyond a cutoff scale {lambda}=m{sub p}/{xi}, where m{sub p} is the reduced Planck mass. We then argue that knowing the Higgs potential profile for the field values relevant for inflation (|H|>m{sub p}/{radical}({xi})>>{lambda}) requires knowledge of the ultraviolet completion of the SM beyond {lambda}. In absence of such microscopic theory, the extrapolation of the pure SM potential beyond {lambda} is unwarranted and the scenario is akin to other ad hoc inflaton potentials afflicted with significant fine-tuning. The appealing naturalness of this minimal proposal is therefore lost.

First Glimpses at Higgs’ face

A bstractThe 8 TeV LHC Higgs search data just released indicates the existence of a scalar resonance with mass ~ 125 GeV. We examine the implications of the data reported by ATLAS, CMS and the Tevatron collaborations on understanding the properties of this scalar by performing joint fits on its couplings to other Standard Model (SM) particles. We discuss and characterize to what degree this resonance has the properties of the SM Higgs, and consider what implications can be extracted for New Physics in a (mostly) model-independent fashion. We find that, if the Higgs couplings to fermions and weak vector bosons are allowed to differ from their standard values, the SM is ~ 2σ from the best fit point to the current data. Fitting to a possible invisible decay branching ratio, we find BRinv ≃ 0.05 ± 0.32 (95% C.L.). We also discuss and develop some ways of using the data in order to bound or rule out models which modify significantly the properties of this scalar resonance, and apply these techniques to the current global dataset.

Fingerprinting Higgs suspects at the LHC

A bstractWe outline a method for characterizing deviations from the properties of a Standard Model (SM) Higgs boson. We apply it to current data in order to characterize up to which degree the SM Higgs boson interpretation is consistent with experiment. We find that the SM Higgs boson is consistent with the current data set at the 82 % confidence level, based on data of excess events reported by CMS and ATLAS, which are interpreted to be related to the mass scale mh ∼ 124 − 126 GeV, and on published CLs exclusion regions. We perform a global fit in terms of two parameters characterizing the deviation from the SM value in the gauge and fermion couplings of a Higgs boson. We find two minima in the global fit and identify observables that can remove this degeneracy. An update for Moriond 2012 data is included in the appendix, which finds that the SM Higgs boson is now consistent with the current data set at only the 89 % confidence level (which corresponds to ∼ 2 σ tension compared to the best fit point).

Higgs windows to new physics through d = 6 operators: constraints and one-loop anomalous dimensions

A bstractThe leading contributions from heavy new physics to Higgs processes can be captured in a model-independent way by dimension-six operators in an effective Lagrangian approach. We present a complete analysis of how these contributions affect Higgs couplings. Under certain well-motivated assumptions, we find that 8 CP-even plus 3 CP-odd Wilson coefficients parametrize the main impact in Higgs physics, as all other coefficients are constrained by non-Higgs SM measurements. We calculate the most relevant anomalous dimensions for these Wilson coefficients, which describe operator mixing from the heavy scale down to the electroweak scale. This allows us to find the leading-log corrections to the predictions for the Higgs couplings in specific models, such as the MSSM or composite Higgs, which we find to be significant in certain cases.

Strong electroweak phase transitions in the Standard Model with a singlet

Abstract It is well known that the electroweak phase transition (EWPhT) in extensions of the Standard Model with one real scalar singlet can be first-order for realistic values of the Higgs mass. We revisit this scenario with the most general renormalizable scalar potential systematically identifying all regions in parameter space that develop, due to tree-level dynamics, a potential barrier at the critical temperature that is strong enough to avoid sphaleron wash-out of the baryon asymmetry. Such strong EWPhTs allow for a simple mean-field approximation and an analytic treatment of the free-energy that leads to very good theoretical control and understanding of the different mechanisms that can make the transition strong. We identify a new realization of such mechanism, based on a flat direction developing at the critical temperature, which could operate in other models. Finally, we discuss in detail some special cases of the model performing a numerical calculation of the one-loop free-energy that improves over the mean-field approximation and confirms the analytical expectations.

The cosmological Higgstory of the vacuum instability

A bstractThe Standard Model Higgs potential becomes unstable at large field values. After clarifying the issue of gauge dependence of the effective potential, we study the cosmological evolution of the Higgs field in presence of this instability throughout inflation, reheating and the present epoch. We conclude that anti-de Sitter patches in which the Higgs field lies at its true vacuum are lethal for our universe. From this result, we derive upper bounds on the Hubble constant during inflation, which depend on the reheating temperature and on the Higgs coupling to the scalar curvature or to the inflaton. Finally we study how a speculative link between Higgs meta-stability and consistence of quantum gravity leads to a sharp prediction for the Higgs and top masses, which is consistent with measured values.

Probing for invisible Higgs decays with global fits

A bstractWe demonstrate by performing a global fit on Higgs signal strength data that large invisible branching ratios (Brinv) for a Standard Model (SM) Higgs particle are currently consistent with the experimental hints of a scalar resonance with mass mh ~ 124 GeV. For this mass, we find Brinv< 0.64 (95% CL) from a global fit to individual channel signal strengths supplied by ATLAS, CMS and the Tevatron collaborations. Novel tests that can be used to improve the prospects of experimentally discovering the existence of a Brinv with future data are proposed. These tests are based on the combination of all visible channel Higgs signal strengths, and allow us to examine the required reduction in experimental and theoretical errors in this data that would allow a more significantly bounded invisible branching ratio to be experimentally supported. We examine in some detail how our conclusions and method are affected when a scalar resonance at this mass scale has couplings deviating from the SM ones.

A Link between Bone Mineral Density and Serum Adiponectin and Visfatin Levels in Acromegaly

CONTEXTnTwo adipokines highly expressed in fat mass, adiponectin with antiinflammatory and antiatherogenic properties and visfatin with an insulin-mimetic effect, are potential contributors to bone metabolism. In acromegaly, data on adiponectin are contradictory, and there are no data on visfatin.nnnOBJECTIVESnThe aim of the study was to evaluate adiponectin and visfatin in acromegaly, compared to control subjects, and to analyze their relationship with body composition and bone markers.nnnMETHODSnBone markers [osteocalcin, total amino-terminal propeptide of type 1 procollagen (total P1NP), carboxy-terminal telopeptide (beta-Crosslaps)], body composition (by dual-energy x-ray absorptiometry), adiponectin (by ELISA), and visfatin (by immunoanalysis)] were evaluated in 60 acromegalic patients (24 males and 36 females) and in 105 age- and gender-matched healthy controls (33 males and 72 females). Acromegalic patients were classified as controlled, with normal IGF-I and nadir GH no greater than 1 microg/liter (n = 41), or active (n = 19).nnnRESULTSnAcromegalic patients had lower adiponectin (P < 0.01), more lean body mass (P < 0.01), more total body mass (P < 0.01), higher bone formation markers (osteocalcin and total P1NP, P < 0.05 and P < 0.01, respectively), but less bone resorption markers (beta-Crosslaps, P < 0.001) than controls. No differences in visfatin and BMD were found between patients and controls. Adiponectin correlated negatively with BMD (r = -0.374; P < 0.05) and lean mass (r = -0.301; P < 0.05) and positively with age (r = 0.341; P < 0.001) in acromegaly. Visfatin correlated negatively with BMD (r = -0.359; P < 0.05). BMD was the predictor for adiponectin and visfatin.nnnCONCLUSIONSnAcromegalic patients present hypoadiponectinemia and a favorable bone marker profile. Adiponectin and visfatin could be a link between fat mass and bone in acromegaly.

Taming Infrared Divergences in the Effective Potential

A bstractThe Higgs effective potential in the Standard Model (SM), calculated perturbatively, generically suffers from infrared (IR) divergences when the (field-dependent) tree-level mass of the Goldstone bosons goes to zero. Such divergences can affect both the potential and its first derivative and become worse with increasing loop order. In this paper we show that these IR divergences are spurious, we perform a simple resummation of all IR-problematic terms known (up to three loops) and explain how to extend the resummation to cure all such divergences to any order. The method is of general applicability and would work in scenarios other than the SM. Our discussion has some bearing on a scenario recently proposed as a mechanism for gauge mediation of scale breaking in the ultraviolet, in which it is claimed that the low-energy Higgs potential is non-standard. We argue that all non-decoupling effects from the heavy sector can be absorbed in the renormalization of low-energy parameters leading to a SM-like effective theory.