Browsing by Author "Castano-Yepes, Jorge David"

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    Anisotropic photon emission from gluon fusion and splitting in a strong magnetic background: The two-gluon one-photon vertex
    (2022) Ayala, Alejandro; Castano-Yepes, Jorge David; Hernandez, L. A.; Mizher, Ana Julia; Tejeda-Yeomans, Maria Elena; Zamora, R.
    Having in mind the pre-equilibrium stage in peripheral heavy-ion collisions as a possible scenario for the production of electromagnetic radiation, we compute the two-gluon one-photon vertex in the presence of an intense magnetic field at one-loop order. The quarks in the loop are taken such that two of them occupy the lowest Landau level, with the third one occupying the first excited Landau level. When the field strength is the largest of the energy (squared) scales, the tensor basis describing this vertex corresponds to two of the three-vector particles polarized in the longitudinal direction whereas the third one is polarized in the transverse direction. However, when the photon energy is of the same order as or larger than the field strength, the explicit one-loop computation contains extra tensor structures that spoil the properties of the basis compared with the case when the field strength is the largest of the energy scales, which signals that the calculation is incomplete. Nevertheless, by projecting the result onto the would-be basis, we show that the squared amplitude for processes involving two gluons and one photon exhibits the expected properties such as a preferred in-plane photon emission and a slightly decreasing strength for an increasing magnetic-field strength. We comment on possible venues to improve the one-loop calculation that include accounting for progressive occupation of the three quarks of the lowest and first-excited Landau levels such that, still working in the large field limit, a more complete description can be achieved when the photon energy increases.
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    Computing the gravitational acceleration within the World Pendulum Alliance as an application of the remote laboratory methodology
    (2023) Torres-Payoma, Freddy; Herrera, Diana; Triana, Karla; Neira-Quintero, Laura; Castano-Yepes, Jorge David
    This paper describes a method for calculating gravitational acceleration using simple pendulums available through the World Pendulum Alliance. This network comprises fourteen institutions across eight countries, each providing a pendulum that can be accessed remotely via the Internet. We demonstrate how to measure the pendulum's period for N oscillations, discussing the importance of repetitions and samples in minimizing experimental uncertainty. We then use the averaged period value to compute the local gravitational acceleration, accounting for corrections due to the moment of inertia of the system. Finally, we analyze the geographical location of each pendulum to explore the dependence of gravity on latitude, longitude, and altitude and discuss its implications for the Earth's shape. We believe this tool will be useful for physics courses at the introductory and university levels due to its remote access features and its relevance to fundamental concepts.
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    Fermion self-energy and effective mass in a noisy magnetic background
    (2024) Castano-Yepes, Jorge David; Munoz, Enrique
    In this article, we consider the propagation of QED fermions in the presence of a classical background magnetic field with white-noise stochastic fluctuations. The effects of the magnetic field fluctuations are incorporated into the fermion and photon propagators in a quasiparticle picture, which we developed in previous works using the replica trick. By working in the very strong-field limit, here we explicitly calculate the fermion self-energy involving radiative contributions at first order in alpha(em), in order to obtain the noise-averaged mass of the fermion propagating in the fluctuating magnetized medium. Our analytical results reveal a leading double-logarithmic contribution similar to[ln vertical bar eB vertical bar =m(2))](2) to the mass, with an imaginary part representing a spectral broadening proportional to the magnetic noise autocorrelation Delta. While a uniform magnetic field already breaks Lorentz invariance, inducing the usual separation into two orthogonal subspaces (perpendicular and parallel with respect to the field), the presence of magnetic noise further breaks the remaining symmetry, thus leading to distinct spectral widths associated with fermion and antifermion, and their spin projection in the quasiparticle picture.
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    Ground state and polarization of a hydrogenlike atom near a Weyl semimetal
    (2023) Castano-Yepes, Jorge David; Nader, D. J.; Martin-Ruiz, A.
    In this paper we study the effects of a topological Weyl semimetal (WSM) upon the ground state and polarization of a hydrogen-like atom near its surface. The WSM is assumed to be in the equilibrium state and at the neutrality point, such that the interaction between the atomic charges and the material is fully described (in the nonretarded regime) by axion electrodynamics, which is an experimentally observable signature of the anomalous Hall effect in the bulk of the WSM. The atom-WSM interaction provides additional contributions to the Casimir-Polder potential thus modifying the energy spectra and wave function, which now becomes distance dependent. Using variational methods, we solve the corresponding Schrodinger equation for the atomic electron. The ground state and the polarization are analyzed as a function of the atom-surface distance, and we directly observe the effects of the nontrivial topology of the material by comparing our results with that of a topologically trivial sample. We also study the impact of the medium's permittivity by assuming a hydrogen atom in vacuum, and a donor impurity in the semiconductors gallium arsenide (GaAs) and gallium phosphide (GaP). We find that the topological interaction behaves as an effective-attractive charge so that the electronic cloud tends to be polarized to the interface of materials. Moreover, the loss of wave-function normalization is interpreted as a critical location from below which the bound state is broken.