Affiliation: | Department of Physics, Presidency College, Calcutta 700073, India;Department of Physics, Maulana Azad College, Calcutta 700 013, India;The Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy;Instituto de Fisica, UFF, Boa Viagem, CEP 24210-340, Niteroi, RJ, Brazil |