Abstract theory of pointwise decay with applications to wave and Schr\"odinger equations

We prove pointwise in time decay estimates via an abstract conjugate operator method. This is then applied to a large class of dispersive equations.Comment: Fixed a reference. To appear in Annales Henri Poincar\'

Chiral perturbation theory of muonic hydrogen Lamb shift: polarizability contribution

The proton polarizability effect in the muonic-hydrogen Lamb shift comes out as a prediction of baryon chiral perturbation theory at leading order and our calculation yields for it: $\Delta E^{(\mathrm{pol})} (2P-2S) = 8^{+3}_{-1}\, \mu$eV. This result is consistent with most of evaluations based on dispersive sum rules, but is about a factor of two smaller than the recent result obtained in {\em heavy-baryon} chiral perturbation theory. We also find that the effect of $\Delta(1232)$-resonance excitation on the Lamb-shift is suppressed, as is the entire contribution of the magnetic polarizability; the electric polarizability dominates. Our results reaffirm the point of view that the proton structure effects, beyond the charge radius, are too small to resolve the `proton radius puzzle'.Comment: 16 pages, 5 figure

Pseudorehearsal in actor-critic agents with neural network function approximation

Catastrophic forgetting has a significant negative impact in reinforcement learning. The purpose of this study is to investigate how pseudorehearsal can change performance of an actor-critic agent with neural-network function approximation. We tested agent in a pole balancing task and compared different pseudorehearsal approaches. We have found that pseudorehearsal can assist learning and decrease forgetting

Pseudorehearsal in actor-critic agents with neural network function approximation

Catastrophic forgetting has a significant negative impact in reinforcement learning. The purpose of this study is to investigate how pseudorehearsal can change performance of an actor-critic agent with neural-network function approximation. We tested agent in a pole balancing task and compared different pseudorehearsal approaches. We have found that pseudorehearsal can assist learning and decrease forgetting

Forward doubly-virtual Compton scattering off the nucleon in chiral perturbation theory: the subtraction function and moments of unpolarized structure functions

The forward doubly-virtual Compton scattering (VVCS) off the nucleon contains a wealth of information on nucleon structure, relevant to the calculation of the two-photon-exchange effects in atomic spectroscopy and electron scattering. We report on a complete next-to-leading-order (NLO) calculation of low-energy VVCS in chiral perturbation theory ($\chi$PT). Here we focus on the unpolarized VVCS amplitudes $T_1(\nu, Q^2)$ and $T_2(\nu, Q^2)$, and the corresponding structure functions $F_1(x, Q^2)$ and $F_2(x,Q^2)$. Our results are confronted, where possible, with "data-driven" dispersive evaluations of low-energy structure quantities, such as nucleon polarizabilities. We find significant disagreements with dispersive evaluations at very low momentum-transfer $Q$; for example, in the slope of polarizabilities at zero momentum-transfer. By expanding the results in powers of the inverse nucleon mass, we reproduce the known "heavy-baryon" expressions. This serves as a check of our calculation, as well as demonstrates the differences between the manifestly Lorentz-invariant (B$\chi$PT) and heavy-baryon (HB$\chi$PT) frameworks.Comment: 31 pages, 11 figures, 1 table; supplemented material: 1 Mathematica notebook; minor modifications, published versio

Mejora en la distribución de áreas y equipos en el proceso de introducción y práctica en la especialidad de mecánica automotriz, del SENATI Callao Ventanilla

El autor no autorizó la publicación de la tesis

Análisis de métodos de evaluación de la sección transversal de radar y de los parámetros que inciden en ella para buques de superficie

This article presents an analysis of the different modeling methods for predicting the radar cross section of surface ships. In the analysis, we studied the effect of different factors in vessel construction regarding the amount of electromagnetic energy returning to a radar source, such as the handling of shapes, use of different materials, and vessel size. We can see the different evaluation methods of the radar cross section and the software tools available to determine an appropriate methodology for adoption by the Colombian Navy and their subsequent integration with the design process and optimization of warships.En este artículo se presenta un análisis de los diferentes métodos de modelado para la predicción de la sección transversal de radar (RCS) de buques de superficie. Dentro del análisis, se estudia el efecto de los diferentes factores constructivos del buque sobre la cantidad de energía electromagnética que regresa a una fuente de radar, como son el manejo de formas, el uso de diferentes materiales y el tamaño del buque. Se aprecian los diferentes métodos de evaluación de la sección transversal de radar y las herramientas de software disponibles con el fin de determinar una metodología adecuada para su adopción por parte de la Armada de Colombia, y su posterior integración con el proceso de diseño y optimización de buques de guerra

High photon flux table-top coherent extreme ultraviolet source

High harmonic generation (HHG) enables extreme ultraviolet radiation with table-top setups. Its exceptional properties, such as coherence and (sub)-femtosecond pulse durations, have led to a diversity of applications. Some of these require a high photon flux and megahertz repetition rates, e.g. to avoid space charge effects in photoelectron spectroscopy. To date this has only been achieved with enhancement cavities. Here, we establish a novel route towards powerful HHG sources. By achieving phase-matched HHG of a megahertz fibre laser we generate a broad plateau (25 eV - 40 eV) of strong harmonics, each containing more than $10^{12}$ photons/s, which constitutes an increase by more than one order of magnitude in that wavelength range. The strongest harmonic (H25, 30 eV) has an average power of 143 $\mu$W ($3\cdot10^{13}$ photons/s). This concept will greatly advance and facilitate applications in photoelectron or coincidence spectroscopy, coherent diffractive imaging or (multidimensional) surface science