Gluon Regge trajectory at two loops from Lipatov's high energy effective action

We present the derivation of the two-loop gluon Regge trajectory using Lipatov's high energy effective action and a direct evaluation of Feynman diagrams. Using a gauge invariant regularization of high energy divergences by deforming the light-cone vectors of the effective action, we determine the two-loop self-energy of the reggeized gluon, after computing the master integrals involved using the Mellin-Barnes representations technique. The self-energy is further matched to QCD through a recently proposed subtraction prescription. The Regge trajectory of the gluon is then defined through renormalization of the reggeized gluon propagator with respect to high energy divergences. Our result is in agreement with previous computations in the literature, providing a non-trivial test of the effective action and the proposed subtraction and renormalization framework.Comment: 22 page

Dijet Production at Large Rapidity Separation in N=4 SYM

Ratios of azimuthal angle correlations between two jets produced at large rapidity separation are studied in the N=4 super Yang-Mills theory (MSYM). It is shown that these observables, which directly prove the SL(2,C) symmetry present in gauge theories in the Regge limit, exhibit an excellent perturbative convergence. They are compared to those calculated in QCD for different renormalization schemes concluding that the momentum-substraction (MOM) scheme with the Brodsky-Lepage-Mackenzie (BLM) scale-fixing procedure captures the bulk of the MSYM results.Comment: 13 pages, 7 figure

Dynamical Mass Generation and Confinement in Maxwell-Chern-Simons Planar Quantum Electrodynamics

We study the non-perturbative phenomena of Dynamical Mass Generation and Confinement by truncating at the non-perturbative level the Schwinger-Dyson equations in Maxwell-Chern-Simons planar quantum electrodynamics. We obtain numerical solutions for the fermion propagator in Landau gauge within the so-called rainbow approximation. A comparison with the ordinary theory without the Chern-Simons term is presented.Comment: 9 pages, 9 figures; prepared for the XIV Mexican School of Particles and Fields, 4-12 November 2010, Morelia, Michoacan, Mexic

Resumming large higher-order corrections in non-linear QCD evolution

Linear and non-linear QCD evolutions at high energy suffer from severe issues related to convergence, due to higher order corrections enhanced by large double and single transverse logarithms. We resum double logarithms to all orders by taking into account successive soft gluon emissions strongly ordered in lifetime. We further resum single logarithms generated by the first non-singular part of the splitting functions and by the one-loop running of the coupling. The resulting collinearly improved BK equation admits stable solutions, which are used to successfully fit the HERA data at small-x for physically acceptable initial conditions and reasonable values of the fit parameters.Comment: 4 pages, 4 figures, based on talk given at Hard Probes 2015, 29 June - 3 July 2015, Montreal, Canad

Resummation of Large Logarithms in the Rapidity Evolution of Color Dipoles

Perturbative corrections beyond leading-log accuracy to BFKL and BK equations, describing the rapidity evolution of QCD scattering amplitudes at high energy, exhibit strong convergence problems due to radiative corrections enhanced by large single and double transverse logs. We identify explicitly the physical origin of double transverse logs and resum them directly in coordinate space as appropriate for BK equation, in terms of an improved local-in-rapidity evolution kernel. Numerical results show the crucial role of double-logarithmic resummation for BK evolution, which is stabilized and slowed down by roughly a factor of two.Comment: 6 pages, 4 figures; Proceedings of the XXIII International Workshop on Deep-Inelastic Scattering (27 April-May 1 2015, Dallas (USA)

Health in my community: Conducting and evaluating photovoice as a tool to promote environmental health and leadership among Latino/a youth

BackgroundThe PhotoVoice method has shown substantial promise for work with youth in metropolitan areas, yet its potential for use with Latino youth from agricultural areas has not been well documented.ObjectivesThis project was designed to teach environmental health to 15 high school youth while building their individual and community capacity for studying and addressing shared environmental concerns. The project also aimed to test the utility of PhotoVoice with Latino agricultural youth.MethodsFifteen members of the Youth Community Council (YCC), part of a 15-year project with farmworker families in Salinas, CA, took part in a 12-week PhotoVoice project. Their pictures captured the assets and strengths of their community related to environmental health, and were then analyzed by participants. A multi-pronged evaluation was conducted.ResultsYCC members identified concerns such as poor access to affordable, healthy foods and lack of safe physical spaces in which to play, as well as assets, including caring adults and organizations, and open spaces in surrounding areas. Participants presented their findings on radio, television, at local community events, and to key policy makers. The youth also developed two action plans, a successful 5K run/walk and a school recycling project, still in progress. Evaluation results included significant changes in such areas as perceived ability to make presentations, leadership, and self-confidence, as well as challenges including transportation, group dynamics, and gaining access to people in power.ConclusionThe PhotoVoice method shows promise for environmental health education and youth development in farmworker communities

Efecto de la fertilización sobre la producción de un fruto forestal comestible: el piñón de pino piñonero (Pinus pinea L.) en Andalucía Occidental

The pine nut from the stone pine (Pinus pinea L.) is the most important edible fruit in mediterranean forests. Despite this fact, there is a lack of knowledge regarding the application of agronomy techniques in stands of this species to increase pine nut production. Our study focuses on the effect of mineral fertilization on cone production and size, which in turn, are closely related to nut yield and quality. Cone production and quality was analysed in a randomized experiment installed in south west Spain, comparing the effect of different doses of lime superphosphate, dolomite and potassium. A significant short term increase in cone production and quality exists as a consequence of fertilization, especially in those treatments involving the addition of larger quantity of dolomite. Nevertheless, effect of mineral fertilization on cone yield and quality was lower than expected, so further increments might be achieved through nitrogenous and organic fertilizations to improve soil structure in these sandy soils.El piñón de Pinus pinea L. es el fruto forestal comestible más importante en los bosques mediterráneos. Pese a esto, existe una falta de conocimiento científico acerca de la aplicación de prácticas agronómicas sobre las masas forestales de la especie al objeto de mejorar la producción de piñón. Nuestro trabajo se centra en el análisis del efecto de la fertilización mineral sobre la producción y el tamaño de las piñas, variables muy relacionadas con la cantidad y calidad de piñón. Entre 1993-1999 se realizó el seguimiento de la producción y la calidad de la piña en un experimente aleatorizado instalado en el SO de España, donde se comparaban diferentes dosis de superfosfato de cal, dolomita y cloruro potásico. Se ha detectado una respuesta positiva a la fertilización en la cantidad y calidad de las piñas producidas, especialmente en los tratamientos que planteaban la incorporación de una mayor cantidad de dolomita. El efecto de la fertilización mineral sobre la cantidad y calidad de piña ha sido menor que el esperado, por lo que futuros trabajos deben plantear la necesidad de incorporar fertilizantes nitrogenados y materia orgánica para mejorar la estructura en estos suelos arenosos

Fast Incoherent OFDR Interrogation of FBG Arrays Using Sparse Radio Frequency Responses

[EN] We present two implementations of fast, discrete incoherent optical frequency-domain reflectometers (I-OFDR) for the interrogation of equally spaced fiber Bragg grating (FBG) arrays, based on the determination of the array's radio frequency (RF) response at a sparse number of frequencies. FBG reflectivities are determined by use of the inverse discrete Fourier transform (IDFT) of the sparse RF response, in a dynamic range limited by crosstalk induced by FBG positioning errors. The first implementation employs the complete, vector RF response at a number of frequencies equal to the number N of FBGs in the array. In the second, the introduction of a reference reflector allows for an interrogation using the power (phaseless) RF response in 4N - 1 frequencies. Demodulation based on IDFT leads to total interrogation times determined by the network analyzer scan time, which can be as low as 10 mu s per FBG. Depending on the interrogation technique, electrical bandwidth requirements are 12 GHz in our array with 10-cm separation. We implemented both techniques in a N = 10 array, inducing decays in reflectivity by 10 dB in one or several FBGs. Unambiguous detection of FBG decays was obtained in both interrogation methods. Additional tests performed on the measured reflectivities also show that measurement linearity is preserved in the 10-dB decay range. As discrete I-OFDR systems, the proposed techniques show the possibility to reach compromises between interrogation time and dynamic range or accuracy in reflectivity measurements, using the number of interrogation frequencies and the sensor topology.This work was supported in part by Infraestructura GVA-FEDER operative program 2007-2013 and in part by the Spanish MINECO through Project TEC2017-88029-R. The work of J. Clement Bellido was supported by the GVA VALi+d scholarship ACIF/2016/214. The work of J. Hervas was supported by the Spanish MEC scholarship FPU13/04675.Clement, J.; Hervás-Peralta, J.; Madrigal-Madrigal, J.; Maestre, H.; Torregrosa, G.; Fernandez-Pousa, CR.; Sales Maicas, S. (2018). Fast Incoherent OFDR Interrogation of FBG Arrays Using Sparse Radio Frequency Responses. Journal of Lightwave Technology. 36(19):4393-4400. https://doi.org/10.1109/JLT.2018.2821199S43934400361