Theory of Elementary Particles, Astroparticle Physics, and Phenomenology (TEPAPP)

TEPAPP news: 

●      Professor Graciela Gelmini was elected to National Academy of Sciences of Argentina

●      Professor Alexander Kusenko has accepted a position of Associate Editor, Review of Modern Physics, in charge of Theoretical Elementary Particle Physics

●      Dr. Zac Picker has joined the group as a new Postdoctoral Fellow

Research Highlights

The oldest black holes in the universe

Primordial black holes could have formed in the Big Bang long before the first stars and galaxies formed.  These first black holes can account for dark matter if they are very small – smaller than the wavelength of visible light.   If dark matter contains a large number of microscopic black holes, a neutron star in the galactic center can be invaded by a black hole which ultimately destroys the neutron star, converting it to a one-two solar mass black hole.  It appears that mysterious G objects, recently discovered by UCLA astronomers in the galactic center could be explained by  such solar-mass black holes. This is discussed in a paper co-authored by TEPAPP researchers and UCLA astronomers: “G Objects and Primordial Black Holes”  by Marcos Flores, Alex Kusenko, Andrea Ghez, Smadar Naoz [1]. Professor Andrea Ghez describes G objects as very unusual because “These objects look like gas but behave like stars, and survive the gravitational tidal forces of the supermassive black hole in the galactic center.” The possible explanation may be that the G objects are clouds of gas held together by the gravitational pull of a solar-mass black hole in their interiors. 

Professor Kusenko, together with his student Marcos Flores and postdoc Zac Picker explored the formation of primordial black holes in the early universe, as well as observational signatures and constraints on the oldest black holes in the universe.  The formation of primordial black holes can be confirmed by the future  observations of gravitational waves . 

Sterile Neutrinos

Another dark matter candidate is a sterile neutrino, an extremely weakly interacting cousin of the active neutrinos.  Professor Gelmini and Professor Kusenko received funding from the UC National Laboratories division of the University of California Office of the President for theoretical work on this subject, while UCLA Professors Paul Hamilton and Eric Hudson are leading an experimental proposal called HUNTER, which is an ambitious attempt to discover sterile neutrinos using a combination of atomic, molecular, and optical physics and nuclear physics techniques.  In a recent paper, Professor Gelmini and collaborators explored production of sterile neutrinos from evaporating primordial black holes.  Professor Kusenko joined the UCLA astronomers Professor Tommaso Treu and Dr. Ioana Zelko in setting observational limits on sterile neutrinos using gravitational lensing.