Rita C. Anjos

Ultra high energy cosmic rays and possible signature of black strings

Ultra high energy cosmic rays (UHECRs) probably originate in extreme conditions in which extra dimension effects might be important. In this paper we calculate the correction in black hole accretion mechanisms due to extra dimension effects in the static and rotating cases. A parametrization of the external Kerr horizons in both cases is presented and analysed. We use previous calculations of upper limits on the UHECR flux to set limits on the UHECR production efficiency of nine sources. The upper limit on the UHECR luminosity calculation is based on GeV-TeV gamma-ray measurements. The total luminosity due to the accretion mechanism is compared to the upper limit on UHECRs. The dependence of the UHECR production efficiency upper limit on black hole mass is also presented and discussed

Luminosity of ultrahigh energy cosmic rays and bounds on magnetic luminosity of radio-loud active galactic nuclei

We investigate the production of magnetic flux from rotating black holes in active galactic nuclei (AGNs) and compare it with the upper limit of ultrahigh energy cosmic ray (UHECR) luminosities, calculated from observed integral flux of GeV-TeV gamma rays for nine UHECR AGN sources. We find that, for the expected range of black hole rotations (0.44<a<0.80), the corresponding bounds of theoretical magnetic luminosities from AGNs coincides with the calculated UHECR luminosity. We argue that such result possibly can contribute to constrain AGN magnetic and dynamic properties as phenomenological tools to explain the requisite conditions to proper accelerate the highest energy cosmic rays.

Central accumulation of magnetic flux in massive Seyfert galaxies as a possible engine to trigger ultrahigh energy cosmic rays

In the present paper we investigate the production of ultrahigh energy cosmic rays (UHECRs) from Seyferts. We discuss the UHECR luminosities obtained by two possible engine trigger models: pure radiative transfer and the energy extraction from poloidal magnetic flux. The first case is modeled by Kerr slim disk or Bondi accretion mechanisms. Since it is assumed that the broadband spectra of Seyferts indicate that at least the outer portions of their accretion disks are cold and geometrically thin, and since our results point that the consequent radiative energy transfer is inefficient, we build the second approach based on massive Seyferts with sufficient central poloidal magnetic field to trigger an outflow of magnetically driven charged particles capable to explain the observed UHECRs and gamma rays in Earth experiments from a given Seyfert source.

Luminosity of ultrahigh energy cosmic rays as a probe of black strings

Ultrahigh energy cosmic rays (UHECRs) can originate from extragalactic sources as Active Galactic Nuclei. We propose a mechanism to calculate bounds on the upper limits of the AGN luminosity fraction that can be converted into UHECRs. This result comes from the mechanism powered by central black holes to produce the AGN luminosity and observation of UHECRs and gamma-rays from experiments to reconstruct proton and iron luminosities of a given AGN source.

Generalization of conserved charges for Toda models

The soliton solutions to Toda models receive a zero curvature representation of their equations of motion, i.e. there exist potentials, (Aμ ), that are functional of the fields of the theory and which belong to a Kac-Moody algebra G such that the zero curvature condition is equivalent to the equations of motion. For the construction of the soliton solutions and conserved charges it is required an integer gradation of the Kac-Moody algebra and a “vacuum solution”, such that the potentials evaluated on it belong to an Abelian subalgebra. The conserved charges are then constructed using the dressing method.

The influence of the observatory latitude on the study of ultra high energy cosmic rays

Recent precision measurements of the Ultra High Energy Cosmic Rays (UHECR) arrival directions, spectrum and parameters related to the mass of the primary particle have been done by the HiRes, Pierre Auger and Telescope Array (TA) Observatories. In this paper, distributions of arrival directions of events in the nearby Universe are assumed to correlate with sources in the 2MASS Redshift Survey (2MRS), IRAS 1.2 Jy Survey, Palermo Swift-BAT and Swift-BAT catalogs, and the effect of the latitude of the observatory on the measurement of the energy spectrum and on the capability of measuring anisotropy is studied. The differences between given latitudes on the northern and southern hemispheres are quantified. It is shown that the latitude of the observatory: a) has an influence on the total flux measured and b) imposes an important limitation on the capability of measuring an anisotropic sky.

Estimative of conversion fractions of AGN magnetic luminosity to produce ultra high energy cosmic rays from the observation of Fermi-LAT gamma rays

A fraction of the magnetic luminosity (LB) produced by Kerr black holes in some active galactic nuclei (AGNs) can produce the necessary energy to accelerate ultra high energy cosmic rays (UHECRs) beyond the GZK limit, observed, e.g., by the Pierre Auger experiment. Nevertheless, the direct detection of those UHECRs has a lack of information about the direction of the source from where those cosmic rays are coming, since charged particles are deflected by the intergalactic magnetic field. This problem arises the needing of alternative methods to evaluate the luminosity of UHECRs (LCR) from a given source. Methods proposed in literature range from the observation of upper limits in gamma rays to the observation of upper limits in neutrinos produced by cascade effects during the propagation of UHECRs. In this aspect, the present work proposes a method to calculate limits of the main possible conversion fractions ηCR = LCR/LB for nine UHECR AGN Seyfert sources based on the respective observation of gamma ray ...

Stability of perturbed geodesics in nD axisymmetric spacetimes

The eect of self-gravity of a disk matter is evaluated by the simplest modes of oscillation frequencies for perturbed circular geodesics. It is plotted the radial profiles of free oscillations of an equatorial circular geodesic perturbed within the orbital plane or in the vertical direction. The calculation is carried out to geodesics of an axisymmetric n-dimensional spacetime. The profiles are computed by examples of disks embeded in five-dimensional or six-dimensional spacetime, where it is studied the motion of free test particles for three axisymmetric cases: (i) the Newtonian limit of a general proposed 5D and 6D axisymmetric spacetime; (ii) a simple Randall-Sundrum 5D spacetime; (iii) general 5D and 6D Randall-Sundrum spacetime. The equation of motion of such particles is derived and the stability study is computed for both horizontal and vertical directions, to see how extra dimensions could aect the system. In particular, we investigate a disk constructed from Miyamoto-Nagai and Chazy-Curzon with a cut parameter to generate a disk potential. Those solutions have a simple extension for extra dimensions in the case (i), and by solving vacuum Einstein field equations for a kind of Randall-SundrumWeyl metric in cases (ii) and (iii). We find that it is possible to compute a range of possible solutions where such perturbed geodesics are stable. Basicaly, the stable solutions appear, for the radial direction, in special cases when the system has 5D and in all cases when the system has 6D; and, for the axial direction, in all cases when the system has both 5D or 6D.

Estudo da equação de Fokker-Planck para os potenciais de Hulthén e de Morse generalizado via supersimetria

Neste trabalho utiliza-se o formalismo da supersimetria em mecânica quântica para obter e estudar o comportamento das solucoes analiticas da equacao de Fokker-Planck para os potenciais de Hulthen e de Morse generalizado.