A Method for Measuring the Weak Value of Spin for Metastable Atoms

A method for measuring the weak value of spin for atoms is proposed using a variant of the original Stern–Gerlach apparatus. A full simulation of an experiment for observing the real part of the weak value using the impulsive approximation has been carried out. Our predictions show a displacement of the beam of helium atoms in the metastable 23S1 state, Δw, that is within the resolution of conventional microchannel plate detectors indicating that this type of experiment is feasible. Our analysis also determines the experimental parameters that will give an accurate determination of the weak value of spin. Preliminary experimental results are shown for helium, neon and argon in the 23S1 and 3P2 metastable states, respectively.

A Method for Measuring the Real Part of the Weak Value of Spin for Metastable Atoms

A method for measuring the real part of the weak value of spin for non-zero rest mass atoms is presented using a variant on the original Stern-Gerlach apparatus. The experiment utilises helium in the metastable 23S1 state. A full simulation for observing the real part of the weak value using the impulsive approximation has been carried out and it predicts a displacement of the beam, Δw, that is within the resolution of our detector. It also indicates how this shift might be increased. The full analysis also indicated that there is a limit, L, to the applicability of the weak value approximation and has been evaluated for our apparatus. This experiment has the possibility to be expanded to utilise other nobal gas species such as neon and argon in the 3P2 metastable state, but we shall restrict this paper to metastable helium only.

Bar Destruction Mechanism by External Interactions

To investigate bar destruction by a vertical head-on galaxy encounter, the dynamical evolution after the instantaneous momentum change of the impulsive approximation of a vertical head-on galaxy encounter, and the instability of finite amplitude one-armed perturbations to barred structure, are investigated by 2-dimensional N-body simulations.Preliminary results show that off-center vertical head-on collisions induce bar destruction but collisions in which the colliding galaxy passes through the very center of the target galaxy do not induce bar destruction.

Galactic Disk Shocks on Globular Clusters

We study tidal shocking on globular clusters by N-body simulation. The results, which cover a range of cluster and disk parameters, are compared with the impulsive approximation.

Secular evolutionary trends in ellipticals and bulges due to mergers

Using basically the impulsive approximation and a modification of the method used by Alladin S.M., (1965, Ap.J.,141, 768), and described in detail in Chatterjee T.K., (1990, IAU Col.,124, 519, 569) we study the evolution of binary interacting galaxies, leading ultimately to mergers. Each collision is characterised by the initial separation between the galaxies and the relative velocity therein. In each case the orbital evolution and largescale structural changes in the galaxies are studied by taking into account the change in relative velocity due to dynamical friction, leading ultimately to mergers. The evolution is considered from a time when the gravitational interaction between the progenitor pairs is physically significant (Chatterjee, 1992, Astroph. Sp.Sc., in press).

A Statistical Study of Merging Galaxies-Theory and Observations

A study of the expected frequency of merging galaxies is conducted, using the impulsive approximation. Results indicate that if we consider mergers involving galaxy pairs without halos in a single crossing time or orbital period, the expected frequency of mergers is two orders of magnitude below the observed value for the present epoch. If we consider mergers invovling several orbital periods or crossing times, the expected frequency goes up by an order of magnitude. Preliminary calculation indicate that if we consider galaxy mergers between pairs with massive halos, the merger is very much hastened.

A Dynamical Proximity Analysis of Interacting Galaxy Pairs

Using the impulsive approximation to study the velocity changes of stars during disk-sphere collisions and a method due to Bottlinger to study the post collision orbits of stars, the formation of various types of interacting galaxies is studied as a function of the distance of closest approach between the two galaxies.

Energy Transfer during the Tidal Encounter of Disc Galaxies

Numerical simulations of merging galaxies do not include a disc component due to bar instability modes. Analytic work is based upon the impulsive approximation which leads to energy loss by the perturber. However, for the perturber to become bound we need consider parabolic encounters. Here we present an analytic technique suitable for all types of encounters.

Merger Cross-Sections of Colliding Galaxies

The velocities of escape of colliding galaxies obtained under the impulsive approximation are compared to those obtained from N-body simulations.