C S Warke

Microscopic band-mixing calculations in154,156Gd

A many-body microscopic band-mixing formulation of variation after projection of angular momentum and conservation of nucleon number is used to study the yrast band and first excitedKπ=0+ band in the doubly even nuclei154,156Gd. The computed energy spectra and the interband and intra-band B (E2) values are in good agreement with corresponding experimental data. Connection with the phenomenological model of Stephens and Simon is discussed, bringing out the role played by thei13/2 neutron pair in the microscopic formalism.

Field localization and particle confinement effects on pair creation by Schwinger’s mechanism

AbstractSolutions of the Dirac equation in the presence of a static uniform electric fieldɛ in thez-direction and a linear confining potentialAz, are obtained. Generalized reflection and transmission coefficients are derived for such divergent potentials forɛ >A/e. The eigenspectrum and corresponding localized eigenfunctions forɛ <A/e are obtained from the reflection coefficient and the continuum solutions respectively. The rate for the electric field to decay into pairs is derived from the transmission coefficient. Neglecting nonabelian effects in quantum chromodynamics we identify the fieldɛ with a colour electric field and the produced particles with a quark and an antiquark. By considering a cylindrical geometry, we thus obtain a generalization of Schwinger’s formula, for the fieldɛ in a finite spatial region with the quark (antiquark) being confined in thez direction by the linear potentialAz and in the perpendicular direction by the MIT bag boundary condition. The result is used to qualitatively study Schwinger’s mechanism of quark-gluon plasma (QGP) formation in ultrarelativistic heavy ion collisions. It is found that the critical strength of the field required to create

Isobaric degrees of freedom in nuclei as determined from nonrelativistic quark model

q\bar q

Microscopic calculations in odd-A nuclei

pairs is enhanced,ɛc(A) >ɛc(A = 0). The rate of pair creation for constantɛ, decreases for non-zeroA, implying longer QGP formation times. Because ofɛc(A) >ɛc(0), QGP is predicted to be formed in the early stages of the nuclear collision. The finite size effects and the MIT bag boundary condition effects on QGP formation are also discussed.

Schwinger’s effective lagrangian from reflection and transmission amplitudes

A microscopic theory has been provided for propagation of solitons in superfluid4He films at temperatureT=0°K.

Electric and magnetic polarizabilities of nucleon and QCD quark models

Isobaric degrees of freedom δδ in nuclei are determined from the quark cluster model of a nucleus. These additional degrees of freedom are brought in by the coloured quark exchange between different nucleon clusters present in nuclei. They are found to be important in the region of momentum transfer near 3.5 fm−1. The mass dependence of these isobaric degrees of freedom in nuclei turns out to beA5/6.

Side-bands in170Yb

The expressions for baryon number violating nuclear partial decay widths are derived from the interactions as predicted by grand unified theories. Theory predicts that the baryon number violating proton decay inside the nucleus is hindered relative to the free proton decay rate. In the case of closed shell nuclei, the meson spin-isospin dependence of the partial width is the same as that for the nucleon decay. The branching ratios of decay amplitudes depend on the nuclear binding energies. Nuclear structure introduces lepton energy spread of ±49.5 MeV for light closed shell nuclei, while it does not affect the back to back emission of lepton-meson pair.

An explicit spin-isospin dependence of the nucleon partial decay amplitudes

The odd-A nuclei 153Eu and 153Gd are studied together with the doubly even nucleus 154Gd using a microscopic method of variation after angular momentum projection with conversation of the nucleon number in each projected state. The calculated energies of the yrast bands in 154Gd and the ground and excited bands in 153Gd and 153Eu are in fair agreement with the corresponding experimental data. The role played by the i13/2 neutron pair in these nuclei is discussed.