Estudio de la co-evolución asíncrona situada para la resolución de problemas dinámicos descentralizados en ingeniería

[Resumen] Esta tesis doctoral propone una técnica de computación evolutiva denominada Co-evolución Asíncrona Situada (CeAS) y estudia su aplicación en la resolución de un tipo particular de problemas de optimización dentro de la ingeniería, aquellos que están sujetos a cambios en tiempo real y cuya resolución en forma distribuida aporta ventajas intrínsecas si estas soluciones se basan en interacciones locales, y por tanto, se resuelven de forma descentralizada. El CeAS surge como combinación de las técnicas que propone el campo de los Sistemas Complejos para la generación y análisis de sistemas dinámicos, y de los procedimientos que estudia el campo de la Inteligencia Artificial Distribuida para coordinar un grupo de agentes hacia un objetivo común. Este enfoque nos permitirá obtener sistemas que se autoorganizan para resolver un problema global. En el desarrollo de esta tesis se plantea una metodología para la transformación de un problema dinámico descentralizado al dominio del CeAS y una segunda metodología de análisis de los resultados obtenidos, inspirada en aquellas que realizan en el campo de los Sistemas Complejos. Además, se desarrolla una herramienta computacional denominada Waspbed que permite definir, simular y analizar un problema planteado en el CeAS. En resumen, se propone un enfoque totalmente original a la resolución distribuída de problemas de optimización en ingeniería que abre un nuevo campo de investigación y desarrollo con grandes perspectivas de futuro

Robust determination of the major merger fraction at z = 0.6 in Groth Strip

(Abridged) We measure the fraction of galaxies undergoing disk-disk major mergers (f_m) at intermediate redshifts (0.35 <= z < 0.85) by studying the asymmetry index A of galaxy images. Results are provided for B- and Ks-band absolute magnitude selected samples from the Groth strip in the GOYA photometric survey. Three sources of systematic error are carefully addressed: (i) we avoid morphological K-corrections, (ii) we measure asymmetries in artificially redshifted to z_d = 0.75 galaxies to lead with loss of morphological information with redshift, and (iii) we take into account the observational errors in z and A, that tend to overestimate the merger fraction, by maximum likelihood techniques. We find: (i) our data allow for a robust merger fraction to be provided for a single redshift bin centered at z=0.6. (ii) Merger fractions have low values: f_m = 0.045 for M_B <= -20 galaxies, and f_m = 0.031 for M_Ks <= -23.5 galaxies. And, (iii) failure to address the effects of the observational errors leads to overestimating f_m by factors of 10%-60%. Combining our results with those on literature, and parameterizing the merger fraction evolution as f_m(z) = f_m(0)(1+z)^m, we obtain that m = 2.9 +- 0.8, and f_m(0) = 0.012 +- 0.004$. Assuming a Ks-band mass-to-light ratio not varying with luminosity, we infer that the merger rate of galaxies with stellar mass M >= 3.5x10^10 M_Sun is R_m = 1.6x10^-4 Mpc^-3 Gyr^-1. When we compare with previous studies at similar redshifts, we find that the merger rate decreases when mass increases.Comment: Accepted for publication in ApJ. 11 pages, 7 figures, 3 tables. Formatted with emulateap

Growth of galactic bulges by mergers. II. Low-density satellites

Satellite accretion events have been invoked for mimicking the internal secular evolutionary processes of bulge growth. However, N-body simulations of satellite accretions have paid little attention to the evolution of bulge photometric parameters, to the processes driving this evolution, and to the consistency of this evolution with observations. We want to investigate whether satellite accretions indeed drive the growth of bulges, and whether they are consistent with global scaling relations of bulges and discs. We perform N-body models of the accretion of satellites onto disc galaxies. A Tully-Fisher (M \propto V_{rot}^ {alpha_TF}) scaling between primary and satellite ensures that density ratios, critical to the outcome of the accretion, are realistic. We carry out a full structural, kinematic and dynamical analysis of the evolution of the bulge mass, bulge central concentration, and bulge-to-disc scaling relations. The remnants of the accretion have bulge-disc structure. Both the bulge-to-disc ratio (B/D) and the Sersic index (n) of the remnant bulge increase as a result of the accretion, with moderate final bulge Sersic indices: n = 1.0 to 1.9. Bulge growth occurs no matter the fate of the secondary, which fully disrupts for alpha_TF=3 and partially survives to the remnant center for alpha_TF = 3.5 or 4. Global structural parameters evolve following trends similar to observations. We show that the dominant mechanism for bulge growth is the inward flow of material from the disc to the bulge region during the satellite decay. The models confirm that the growth of the bulge out of disc material, a central ingredient of secular evolution models, may be triggered externally through satellite accretion.Comment: Accepted for publication in A&A, 20 pages, 11 figures. Figs. 1 and 2 are low resolution ones: high-resolution versions available under request to the author

Measurement of D ±s production asymmetry in pp collisions at √s=7 and 8 TeV

The inclusive D ±s production asymmetry is measured in pp collisions collected by the LHCb experiment at centre-of-mass energies of √s=7 and 8 TeV. Promptly produced D ±s mesons are used, which decay as D ±s → ϕπ±, with ϕ → K+K−. The measurement is performed in bins of transverse momentum, pT, and rapidity, y, covering the range 2.5 < pT < 25.0 GeV/c and 2.0 < y < 4.5. No kinematic dependence is observed. Evidence of nonzero D ±s production asymmetry is found with a significance of 3.3 standard deviations.S

Evidence for the decay B0S→K¯∗0μ+μ−

A search for the decay B0S→K¯∗0μ+μ− is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb−1 of integrated luminosity collected during pp collisions with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the B0S→K¯∗0μ+μ− decay is determined to be B(B0s→K¯∗0μ+μ−)=[2.9±1.0(stat)±0.2(syst)±0.3(norm)]×10−8, where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement.S

Measurement of the CKM angle γ using B± → DK± with D → K0Sπ+π−, K0SK+K− decays

A binned Dalitz plot analysis of B± → DK± decays, with D → K 0Sπ+π− and D → K 0SK+K−, is used to perform a measurement of the CP-violating observables x± and y±, which are sensitive to the Cabibbo-Kobayashi-Maskawa angle γ. The analysis is performed without assuming any D decay model, through the use of information on the strong-phase variation over the Dalitz plot from the CLEO collaboration. Using a sample of proton-proton collision data collected with the LHCb experiment in 2015 and 2016, and corresponding to an integrated luminosity of 2.0 fb−1, the values of the CP violation parameters are found to be x− = (9.0 ± 1.7 ± 0.7 ± 0.4) × 10−2, y− = (2.1 ± 2.2 ± 0.5 ± 1.1) × 10−2, x+ = (−7.7 ± 1.9 ± 0.7 ± 0.4) × 10−2, and y+ = (−1.0 ± 1.9 ± 0.4 ± 0.9) × 10−2. The first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty (on the strong-phase measurements. These values are used to obtain γ = (87 + 11− 12)∘, rB = 0.086 + 0.013− 0.014, and δB = (101±11)°, where rB is the ratio between the suppressed and favoured B-decay amplitudes and δB is the corresponding strong-interaction phase difference. This measurement is combined with the result obtained using 2011 and 2012 data collected with the LHCb experiment, to give γ = (80 + 10− 9)∘, rB = 0.080 ± 0.011, and δB = (110 ± 10)°.S

Evidence for an ηc(1S)π− resonance in B0 → ηc(1S)K+π− decays

A Dalitz plot analysis of B0 → ηc(1S)K +π− decays is performed using data samples of pp collisions collected with the LHCb detector at centre-of-mass energies of √s = 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 4.7 fb−1. A satisfactory description of the data is obtained when including a contribution representing an exotic ηc(1S)π− resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096 ± 20 +18 −22 MeV and 152±58 +60 −35 MeV, respectively. The spin-parity assignments J P = 0+ and J P = 1− are both consistent with the data. In addition, the first measurement of the B0 → ηc(1S)K +π− branching fraction is performed and gives B(B0→ ηc(1S)K +π−) = (5.73 ± 0.24 ± 0.13 ± 0.66) × 10−4, where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractionsS

Studies of the resonance structure in D0→K∓π±π±π∓ decays

Amplitude models are constructed to describe the resonance structure of D0 → K− π + π + π − and D0 → K+ π − π − π + decays using pp collision data collected at centre-of-mass energies of 7 and 8 TeV with the LHCb experiment, corresponding to an integrated luminosity of 3.0 f b−1. The largest contributions to both decay amplitudes are found to come from axial resonances, with decay modes D0 → a1(1260) +K− and D0 → K1(1270/1400) + π − being prominent in D0 → K− π + π + π − and D0 → K+ π − π − π +, respectively. Precise measurements of the lineshape parameters and couplings of the a1(1260) +, K1(1270) − and K(1460) − resonances are made, and a quasi model-independent study of the K(1460) − resonance is performed. The coherence factor of the decays is calculated from the amplitude models to be RK3π = 0.459 ± 0.010 (stat) ± 0.012 (syst)±0.020 (model), which is consistent with direct measurements. These models will be useful in future measurements of the unitary-triangle angle γ and studies of charm mixing and CP violationS

Observation of the decay B¯0s→χc2K+K− in the ϕ mass region

The B¯0s→χc2K+K− decay mode is observed and its branching fraction relative to the corresponding χc1 decay mode, in a ±15 MeV/c2 window around the ϕ mass, is found to be B(B¯0s→χc2K+K−)B(B¯0s→χc1K+K−)=(17.1±3.1±0.4±0.9)%, where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative χc decays. The decay mode B¯0s→χc1K+K− allows the B0s mass to be measured as m(B0s)=5366.83±0.25±0.27 MeV/c2, where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the B 0s mass is made.S

Measurement of ϒ production in pp collisions at √s=13 TeV

The production cross-sections of ϒ(1S), ϒ(2S) and ϒ(3S) mesons in proton-proton collisions at √s=13 TeV are measured with a data sample corresponding to an integrated luminosity of 277 ± 11 pb−1 recorded by the LHCb experiment in 2015. The ϒ mesons are reconstructed in the decay mode ϒ → μ+μ−. The differential production cross-sections times the dimuon branching fractions are measured as a function of the ϒ transverse momentum, pT, and rapidity, y, over the range 0 < pT < 30 GeV/c and 2.0 < y < 4.5. The ratios of the cross-sections with respect to the LHCb measurement at s√=8 TeV are also determined. The measurements are compared with theoretical predictions based on NRQCD.S