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A. Gallegos

Publications and source records attributed to A. Gallegos.

7 recordsLinked to original sources
arXiv2022

Vanishing Poynting observers and electromagnetic field classification in Kerr and Kerr-Newman spacetimes

We consider electromagnetic fields having an angular momentum density in a locally non-rotating reference frame in Schwarzschild, Kerr, and Kerr-Newman spacetimes. The nature of such fields is assessed with two families of observers, the locally non-rotating ones and those of vanishing Poynting flux. The velocity fields of the vanishing-Poynting observers in the locally non-rotating reference frames are determined using the 3+1 decomposition formalism. From a methodological point of view, and considering a classification of the electromagnetic field based on its invariants, it is convenient to separate the consideration of the vanishing-Poynting observers into two cases corresponding to the pure and non-pure fields, additionally if there are regions where the field rotates with the speed of light (light surfaces) it becomes necessary to split these observers into two subfamilies. We present several examples of relevance in astrophysics and general relativity, such as pure rotating dipolar-like magnetic fields and the electromagnetic field of the Kerr-Newman solution. For the latter example, we see that vanishing-Poynting observers also measure a vanishing super-Poynting vector, confirming recent results in the literature. Finally, for all non-null electromagnetic fields, we present the 4-velocity fields of vanishing Poynting observers in an arbitrary spacetime.

gr-qc↗
arXiv2021

Dynamics of a ring of three unidirectionally coupled Duffing oscillators with time-dependent damping

We study dynamics of a ring of three unidirectionally coupled double-well Duffing oscillators for three different values of the damping coefficient: fixed dumping, proportional to time, and inversely proportional to time. The dynamics in all cases is analyzed through time series, Fourier and Hilbert transforms, Poincaré sections, as well as bifurcation diagrams and Lyapunov exponents with respect to the coupling strength. In the first case, we observe a well-known route from a stable steady state to hyperchaos through Hopf bifurcation and a series of torus bifurcations, as the coupling strength is increased. In the second case, the system is highly dissipative and converges into one of stable equilibria. Finally, in the third case, transient toroidal hyperchaos takes place.

nlin.CD↗
arXiv2014

Ermakov Systems with Multiplicative Noise

Using the Euler-Maruyama numerical method, we present calculations of the Ermakov-Lewis invariant and the dynamic, geometric, and total phases for several cases of stochastic parametric oscillators, including the simplest case of the stochastic harmonic oscillator. The results are compared with the corresponding numerical noiseless cases to evaluate the effect of the noise. Besides, the noiseless cases are analytic and their analytic solutions are briefly presented. The Ermakov-Lewis invariant is not affected by the multiplicative noise in the three particular examples presented in this work, whereas there is a shift effect in the case of the phases

nlin.CD↗
arXiv2010

Charge asymmetries in e+e- -> pi+ pi- gamma at the phi resonance

We consider the forward-backward pion charge asymmetry for the e^{+}e^{-}\toπ^{+}π^{-}γprocess. At tree level we consider bremsstrahlung and double resonance contributions. Although the latter contribution is formally sub-leading, it is enhanced at low dipion invariant mass due to $ρ$ resonant effects. We consider also four alternative models to describe the final state radiation at the loop level: Resonance Chiral Perturbation Theory, Unitarized Chiral Perturbation Theory, Kaon Loop Model and Linear Sigma Model. The last three models yield results compatible with experimental data. The Kaon Loop Model requires an energy dependent phase to achieve the agreement.

hep-ph↗
arXiv2003

$ππ$ Invariant mass spectrum in $V'\to V~ππ$ and the $f_0(600)$ pole

We consider the phenomenological description of the two pion invariant mass spectrum in the $V' \to V ππ$ decays. We study the parametrization of the amplitude involving both $S$ and $D$ wave contributions. From a fit to the two pion decays of the $ Υ(nS)$ and $Ψ(nS)$ we determine the $f_0 (600)$ mass and width to be $m_{f_0}=528 \pm 32$ MeV and $Γ_{f_0}=413\pm 45$ MeV. The mass and width values we report correspond to the real and imaginary part of the S matrix pole respectively.

hep-ph↗
arXiv2003

On the mass, width and coupling constants of the f0(980)

Using the pole approach we determine the mass and width of the $f_0(980)$; in particular, we analyze the possibility that two nearby poles are associated to it. We restrict our analysis to a neighborhood of the resonance, using $ππ$ data for the phase shift and inelasticity, and the invariant mass spectrum of the $J/ψ\toϕππ, ϕK\bar K$ decays. The formalism we use is based on unitarity and a generalized version of the Breit-Wigner parameterization. We find that a single pole describes the $f_0(980)$, the precise position depending upon the $ππ$ data used. As a byproduct, values for the $g_{f_0ππ}$ and $g_{f_0K\bar K}$ coupling constants are obtained.

hep-ph↗