Boson half-integer spin particles cannot be bosons and integer spin particles cannot be fermions. In large systems, the difference between bosonic and fermionic statistics is only apparent at large densities — when their wave functions overlap. At low densities, both types of statistics are well approximated by Maxwell–Boltzmann statistics, which is described by classical mechanics. All observed elementary particles are either fermions or bosons. The observed elementary bosons are all gauge bosons: photons, W and Z bosons, gluons, except the Higgs boson which is a scalar boson. Finally, many approaches to quantum gravity postulate a force carrier for gravity, the graviton,
Palash Baran Pal neutrino physics, Pal has done important work related to grand unification theory and statistical field theory (popularly called thermal field theory). Some of his works deal with the quantum field theoretic calculations of self-energies of photon and neutrino in a background of charged particles (as electrons, positrons or charged weak gauge bosons) in thermal equilibrium. Pal has also ventured into calculations where the background for various elementary particle processes includes a thermal bath of charged particles in presence of constant magnetic field. Palash Pal is also well known for his teaching and has taught various topics of modern physics in