The nuclear theory group at VECC is engaged in exploring nuclear dynamics at energies extending from low to extreme relativistic energies. At a microscopic level, an effective Nucleon - Nucleon interaction is used to investigate nuclear processes such as proton and alpha-decay rates and also nuclear properties like nuclear equation of state. Cross sections of photonuclear reactions and neutron induced reactions are calculated. Fission dynamics of hot and rotating compound nuclei are studied extensively using Langevin equations. Neutron multiplicities and evaporation residue cross-sections from fusion-fission reactions are systematically investigated in order to find the magnitude of nuclear dissipation. At intermediate energies nuclear multi- fragmentation becomes the dominant process for which statistical methods are exploited. Nuclear properties such as symmetry energy are being investigated by comparing the predictions of the statistical model with experimental data.
A new state of matter called quark gluon plasma (QGP), that existed shortly after the Big Bang may be created by colliding heavy ions at ultra-relativistic energies. QGP is believed to be the most perfect fluid ever discovered. Members of the theory division, VECC, are actively engaged in dynamical modelling of relativistic heavy ion collisions to understand the important issues like, initial conditions, thermalisation, equation of state, transport properties etc. Effects of viscosity on several experimentally measured quantities like elliptic flow and transverse momentum distribution of hadrons and photons are investigated by evolving heavy ion collisions in space and time using relativistic hydrodynamics. Works on the systematic of photon and dilepton productions in ultra-relativistic heavy ion collisions including Hanbury Brown Twiss intensity interferometry with electromagnetically interacting particles are being pursued rigorously. The elliptic flow of the matter produced in nuclear collisions at relativistic energies probed by real photons and lepton pairs are shown to be an effective technique for the detection of QGP. In addition, the role of heavy quarks in probing the properties of QGP is examined in detail. Investigation of hadronic properties in hot and dense matter using effective theories of strong interaction constitutes another important sphere of activity in the theory division. In particular, the spectral properties of light vector mesons, nucleons and pions are evaluated at non-zero temperature and baryon density using thermal field theory and its effects on the photon and dilepton spectra are investigated.