Professor of Physics and Astronomy
Office:
4-915, PAB (click to see the map)
Phone: +1 310 825 4814
My public
key
Ultrahigh-energy cosmic rays[1] present a puzzle. It is difficult to
understand
why a single cosmic particle should carry as much energy as a bullet!
The
origin of these extreme cosmic rays remains unclear. In addition,
interactions
with the cosmic microwave background should have prevented the most
energetic
particles from reaching us. The resolution of this puzzle may teach us
about
physics beyond the Standard Model.
Ultrahigh-energy cosmic neutrinos can
help understand the physics of particle interactions at energies well
beyond
the reach of terrestrial accelerators[2].
Read
about this in Nature
science
update and in AIP
Physics
News Update.
Q-balls are non-topological solitons that owe their stability to a conservation of some global charge. Baryonic Q-balls appear in every supersymmetric extension of the Standard Model [3]. If supersymmetry exists, stable Q-balls could be copiously produced at the end of inflation and may now exist as a form of dark matter [4]. Experimental search for relic Q-balls is under way[5]. Read a New Scientist article and also a story in AIP Physics News Update.
Pulsar velocities and dark matter. Pulsar velocities (100 to 1600 km/s) present an outstanding puzzle in astrophysics. Pulsars are magnetized rotating neutron stars, which are born in supernova explosions of ordinary stars. Most of the energy released in the explosions, 1053 erg, is carried away by neutrinos. A 1% asymmetry in the distribution of these neutrinos can give the nascent pulsar a kick powerful enough to explain the observed velocities of pulsars. We showed that such an asymmetry could result from neutrino conversions in the hot magnetized nuclear matter of a cooling neutron star [6]. In the event of a nearby supernova, one may be able to observe gravity waves from a pulsar acelerated by the neutrino emission [7]. It intriguing that the same sterile neutrino needed to explain the pulsar kicks can make up the dark matter in the universe. Sterile neutrinos can also play a role in the formation of the first stars [8], and they may open a window on the new physics at the electroweak scale [9]. Read about sterile neutrinos, dark matter, and the pulsar kicks: Nature (2006), Economist (2006), New Scientist (2006), CERN Courier (2006), AIP Physics News Update, New Scientist (1996), Sky and Telescope (1997).
Baryogenesis. Although every particle has its antiparticle, there is no
antimatter
in the observed universe. The process in which the matter-antimatter
asymmetry
was produced in the early universe, called baryogenesis[10],
remains a mystery. We showed that the baryon asymetry
could have
arisen from standard electroweak interactions at the end of inflation[11]. Another appealing scenario is
Affleck-Dine baryogenesis, which can generate both ordinary
matter and dark
matter [10].
G.Gelmini and A. Kusenko, Phys.Rev.Lett.84:1378,2000
2. A.Kusenko and T.Weiler, Phys.Rev.Lett.88:161101,2002
3.A. Kusenko, Phys.Lett.B405:108,1997
4. A. Kusenko and M. Shaposhnikov, Phys.Lett.B418:46,1997
5. A. Kusenko et al., Phys.Rev.Lett. 80:3185,1998
A.Kusenko and P. Steinhardt, Phys.Rev.Lett. 87:141301,2001
G.Gelimini,A. Kusenko, and Nussinov, Phys.Rev.Lett. 89:101302,2002
6.
A.Kusenko
and G.Segrè, Phys.Rev.Lett. 77:4872,1996;
Phys.Lett.B396:197,1997;
Phys.Rev.Lett. 79:2751,1997; Phys.Rev.D
59:061302,1999; G. Fuller, A. Kusenko, I.Mocioiu, S.Pascoli,
Phys.Rev. D68:103002 (2003); C. Fryer and A. Kusenko, ApJ.S
163:335,2006.
7. L.C. Loveridge, Phys. Rev. D69, 024008 (2004).
8. P. Biermann and A. Kusenko, Phys.Rev.Lett. 96, 091301 (2006); J.Stasielak, P. Biermann, and A. Kusenko, ApJ 654, 290 (2007).
9. A. Kusenko, Phys. Rev. Lett. 97, 241301 (2006).
10. M. Dine and A. Kusenko, Rev.Mod.Phys.76:1 (2004)
11. J.Garcia-Bellido, D.Grigorev, A.Kusenko, M.Shaposhnikov, Phys. Rev. D60,123504(1999); J.M.Cornwall and A.Kusenko, Phys. Rev. D61, 103510 (2000); J.M.Cornwall, D.Grigoriev, and A.Kusenko, Phys.Rev.D64:123518,2001