Biennial Report 2005-2007 - Saha Institute of Nuclear Physics

Theoretical Physics 31.2.1.2 Topological charge in the broken phase of the renormalized 1+1 dimensionallattice φ 4 theoryWe identify kink configurations in the broken phase using a lattice regulator with antiperiodicboundary conditions. With a suitable definition of the topological charge in the renormalizedtheory we demonstrate invariance of the charge of the renormalized theory in the broken symmetryphase.Asit K De, A Harindranath, Jyotirmoy Maiti, Tilak SinhaTheo1.2.1.3 Study of Lattice QCD with 2 Flavors of Wilson Quarks using Gaussian SmearingA detailed study has been initiated involving the pion and the rho mass and their decay constantsas functions of quark mass (determined from PCAC) using PP, AA, AP and PA operators withboth smeared sources and sinks (P and A stand respectively for the pseudoscalar and the axialvector densities). This will prove very useful for the study of the chiral regime where accuratevalues of quantities are required to make any conclusion.Asit K De, A Harindranath, Jyotirmoy MaitiTheo1.2.1.4 Study of Static Quark Potential and the Scale therefrom in Lattice QCD withDynamical QuarksProperties of QCD with dynamical light quarks are yet to be understood fully. Determination ofthe lattice scale from the study of static interquark potentials when the sea quarks are light is madecomplicated by the fact that the potential itself and the scale determined seem to depend on thevalue of the sea quark mass in lattice units. We have initiated a study to possibly disentangle thescale-violating (cut-off dependent) part from the scaling part. If this is possible, then only one cantalk about a mass-independent renormalization scheme for the lattice theory and this would alsomake matching to continuum schemes like MS ¯ simple.Asit K De, A Harindranath, Jyotirmoy MaitiTheo1.2.1.5 Quasinormal Modes, Gravity Waves and Black HolesThe study of quasinormal modes (a type of gravity waves) are of great importance in understandingthe properties of black holes. The BTZ black hole provides us with an opportunity to analyze manyproperties of the qnm’s in an analytical fashion. In this work we provide a systematic way of derivingthe qnm frequencies of BTZ black hole based on the underlying symmetry principles. Our methodutilizes the various geometric and topological aspects of the BTZ black hole and provides a novelmethod to analyze the associated qnm’s.Kumar S Gupta, S Sen†Theo