Research Interests

I am a physicist interested both in experiment and in theory, and enjoy working with my colleagues and students. With torsion balances, we have tested Einstein's equivalence principle, searched for new forces weaker than gravity, and measured the Casimir force. With mass-spectrometric methods we measured the lifetimes of the 128Te and 130Te for double-beta decay, the longest ever to be measured, and there from deduced the limits on the Majorana mass of the neutrinos. Theoretically, my focus is on astrophysics and cosmology, especially their interconnections with basic physics. We have investigated how, particles are accelerated to relativistic energies, how they are transported through interstellar and intergalactic space, emit secondary radiations, and give rise to phenomena like cosmic rays, supernova remnants, pulsars and quasars. We calculated the flux of cosmic-ray neutrinos and formulated strategies for the study of neutrino-interactions in underground laboratories. In the context of the hot big bang origin for the universe, we could calculate the present-day number-density of neutrinos and other weekly interacting neutral particles, and thence derived strict bounds on their rest mass - either less than a few eV or greater than a few GeV. The consequences of near saturation of these bounds are dramatic: these particles will constitute 'dark matter' in the universe, which gravitationally dominates over the normal matter in the formation and dynamics of the galaxies, generically forming invisible halos around galactic systems and thus providing an explanation for the virial discrepancy and rotation curves of galactic systems. These considerations stimulated the now vibrant field of astroparticle physics.

Membership Type

International Member

Election Year


Primary Section

Section 13: Physics

Secondary Section

Section 12: Astronomy