Summary of research interests
Black hole jets
- Relativistic jets formation and collimation in M87
- Physics of the central engine in gamma-ray bursts (GRBs)
Multi-messenger astroparticle physics
- Physics of cosmic rays accelerators
- Origin of ultrahigh energy cosmic-ray anisotropies
- Propagation of ultra-high energy cosmic rays in Galactic and extragalactic magnetic fields
- Production of γ-rays, neutrinos from GRBs (core-collapse supernovae and binary neutrons star mergers)
- Production of cosmogenic γ-rays and neutrinos backgrounds
Interdisciplinary research on the origin of Life
- Origin of biological homochirality
- Polarized cosmic radiation and enantioselective mutagenesis
- Cosmic-ray shower calculations at different astrophysical environments targets for the search of life
My CV can be downloaded here. An updated list of publications can be found here.
Research achievements
The origin of black hole jets
My research work related to relativistic jets is principally focused on the physics of their central engine. It has connections with recent observations, like the emission ring around the M87 black hole recently reported by the Event Horizon Telescope, or gamma-ray bursts -- flashes of highly energetic gamma rays lasting from less than a second to several minutes and producing as much energy as the sun will emit during its entire 10-billion-year life! Gamma-ray bursts are associated with the formation of relativistic jets around stellar mass black holes, shortly after the collapse of a massive star or the merger of two neutron stars.
My principal achievements in this field are listed below:
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I studied the jet formation around Kerr black holes during my PhD by constructing self-similar solutions to the GRMHD equations, and also during my first postdoc by calculating GRMHD inflow-outflow solutions where the rotational energy can be extracted from the black hole. There is a critical energy load for the Blandford-Znajek mechanism to operate.
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I applied the model to the central engine of gamma-ray bursts jets using a realistic plasma injection profile derived from neutrino-antineutrino annihilation above the black hole's horizon.
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I studied the collimation of magnetic jets by disc winds. The M87 jet profile can be reproduced if the jet is collimated by a hydrodynamical disk wind with luminosity ~20% of the jet luminosity. The HST-1 knot can be due to the focusing of the magnetized jet due to the change in the pressure profile around the Bondi radius.
Currently, I study the processes at play in the magnetosphere of the spinning black hole in M87 allowing energy transport from the hole to the disc.
The origin of ultra-high energy cosmic rays and neutrinos
My research work related to cosmic-rays has connections with recent discoveries, like the dipole anisotropy recently reported by the Pierre Auger Observatory, or the multi-messenger aspects of cosmic-ray propagation.
My principal achievements in this field are listed below:
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During my PhD, I co-authored a numerical code to calculate the acceleration of cosmic rays at gamma-ray bursts internal shocks, including all the relevant energy loss processes experienced by nuclei. We predicted a softer proton component as a distinctive signature of gamma-ray bursts.
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I studied the Galactic-to-extragalactic cosmic-ray transition and showed that a simple generic model with a softer proton component can account for the evolution of the spectrum and composition observed by KASCADE-Grande and Auger.
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I showed the implications of the Fermi-LAT and IceCube data regarding the extragalactic diffuse-ray gamma-ray and neutrino backgrounds on the ultra-high energy cosmic-ray origin. Sources that have a large cosmological evolution are excluded, as they would overproduce the rate of these secondary messengers.
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I calculated the lifetime of small scale anisotropies in the interstellar turbulence, and showed that the lifetime of a cosmic-ray hot spot over a 5 years observation period depends on the direction of the source.
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I investigated the origin of cosmic ray anisotropies, with a focus on interpretation of the first significant large scale anisotropy reported by the Pierre Auger Collaboration. I authored a code to calculate the anisotropy of cosmic rays from the large scale structure, using constrained cosmological simulations. The observed energy dependence of the dipole anisotropy is a natural consequence of the evolution of the size of the cosmic rays observable universe (due to the GZK effect).
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I mentored a student (Chen Ding) during two years to study the energy dependence of the direction of the dipole. This study shows that the direction and amplitude of the dipole anisotropy is well accounted for when the cosmic-ray source distribution follows the large scale structure, using the Jansson and Farrar state-of-the-art model for the Galactic magnetic field (In the press).
The origin of biological homochirality
I became fascinated by the problem of biological homochirality in 2004, with the launch of Rosetta mission. One of the goal of the mission was to search for enantiomeric excesses in a comet. The origin of biological homochirality has been an intense field of research and debate since its discovery by Pasteur in 1848. The weak force, one of the fundamental forces operating in nature, is parity-violating. Therefore, the weak force has been invoked to be responsible for the homochirality in biological molecules ever since its discovery in the 1950s. Cosmic rays, or more precisely, the secondary muons they produce, are caused by a decay involving the weak force and are, hence, spin-polarized. At ground level, 85% of the cosmic radiation dose comes from muons. We proposed that muons could induce persistent structural changes in helical polymers, thereby enabling the emergence of biological homochirality through enantioselective mutagenesis (Globus & Blandford, 2020).
My principal achievements in this field are listed below:
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The difference in the probability of ionization by a spin-polarized cosmic ray is higher for helical polymers of different handedness - such as left and right-handed DNA - than for simple enantiomers such as amino acids or sugars.
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This ionization difference, translated in a difference in the mutation rate, can influence the evolution of primitive self-replicating polymers, and lead to the emergence of homochirality. In the press, invited news items in Nature and in Scientific American
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We predicted that the biological response depends on the polarization on the radiation and calculated the spin-polarized radiation doses at different environments (Mars, Venus, Titan, small bodies of the solar system).
We are developing the experiments to test this idea with collaborators at the University of California Santa-Cruz.
