C. S. Unnikrishnan

AIGO: a southern hemisphere detector for the worldwide array of ground-based interferometric gravitational wave detectors

This paper describes the proposed AIGO detector for the worldwide array of interferometric gravitational wave detectors. The first part of the paper summarizes the benefits that AIGO provides to the worldwide array of detectors. The second part gives a technical description of the detector, which will follow closely the Advanced LIGO design. Possible technical variations in the design are discussed.

Penning collisions of laser-cooled metastable helium atoms

Abstract:We present experimental results on the two-body loss rates in a magneto-optical trap of metastable helium atoms. Absolute rates are measured in a systematic way for several laser detunings ranging from -5 to -30 MHz and at different intensities, by monitoring the decay of the trap fluorescence. The dependence of the two-body loss rate coefficient β on the excited state ( 23P2) and metastable state ( 23S1) populations is also investigated. From these results we infer a rather uniform rate constant Ksp = (1±0.4)×10-7 cm3/s.

The electrical neutrality of atoms and of bulk matter

The equality of the charges of the electron and the proton, and the charge neutrality of the neutron are of great significance in the fundamental theory of particles. This equality suggests a deep symmetry between leptons and quarks that is not yet revealed in other experiments. The electrical neutrality of bulk matter is a direct result of this characteristic of the fundamental charges, with important consequences for precise tests of fundamental physical laws and for electrical metrology. The question is of interest also in cosmology. In this paper, we discuss the experimental evidence for the equality of the fundamental electrical charges, its implications and the possibility of improved experiments.

Comment on "Sonoluminescence as Quantum Vacuum Radiation"

We argue that the available experimental data is not compatible with models of sonoluminescence which invoke dynamical properties of the interface without regard to the compositional properties of the trapped gas inside the bubble.

Does a superconductor shield gravity

Abstract Recently there were some experimental observations which were interpreted as due to a shielding of the gravitational interaction by a superconducting disc in a static configuration as well as when set in rotation. We examine the experiments in detail and point out some difficulties which should be eliminated before reliable results can be claimed. The data from these experiments provide an internal check on the correctness of the hypothesis and we argue that the observed results are inconsistent with the hypothesis of shielding and therefore they are not shielding of the Earths gravity. Our preliminary experiments in the static case do not show any evidence for the reported shielding.

A simple and inexpensive electronic wavelength-meter using a dual-output photodiode

In this Note we describe the design, construction, and calibration of an electronic wavelength-meter using a wavelength-sensitive dual-output photodiode. The device was constructed using electronic circuitry and then calibrated using various laser sources in the wavelength range 500–850 nm. This is an inexpensive device compared to the other similar devices available commercially. It is very useful for the determination of the wavelengths of diode lasers. It works well with multi-mode light, and there are no stringent alignment requirements. It is extremely compact and essentially a “pocket wavemeter.” The wavelength range for the operation of the wavelength-meter is 450 to 900 nm and it gives 1–3 nm accuracy, depending on the wavelength.

Correlation functions, Bell's inequalities and the fundamental conservation laws

I derive the correlation function for a general theory of two-valued spin variables that satisfy the fundamental conservation law of angular momentum. The unique theory-independent correlation function is identical to the quantum-mechanical correlation function. I prove that any theory of correlations of such discrete variables satisfying the fundamental conservation law of angular momentum violates Bells inequalities. Taken together with Bells theorem, this result has far-reaching implications. No theory satisfying Einstein locality, reality in the EPR-Bell sense, and the validity of the conservation law can be constructed. Therefore, all local hidden-variable theories are incompatible with fundamental symmetries and conservation laws.

Do leptons generate gravity? First laboratory constraints obtained from some G experiments and possibility of a new decisive constraint

Abstract The equivalence of the active and passive gravitational masses has been tested in the laboratory to an accuracy of about 5 parts in 10 5 . However, this level of sensitivity is not enough to answer the important question whether leptons generate gravity. We point out that some of the contemporary experiments aimed at re-determining the Newtonian gravitational constant, G , have reached the level of sensitivity required to provide the first meaningful result from a direct experiment on this important issue. Stronger constraints on the hypothesis that leptons do not generate gravity could be more decisively provided by still other G experiments if their aimed sensitivities are maintained in experiments with different sets of source masses.

Some comments on the two prism tunnelling experiment

Abstract We show that the two prism tunnelling experiment of Mizobuchi and Ohtake [Phys. Lett. A 168 (1992) 1] does not verify the quantum optical prediction due to insufficient statistical precision in the anticoincidence measurement. We reanalyze their data and show that the observed number of coincidences is actually even larger than what is expected from a classical coherent light source.

Evaporative Cooling of Atoms to Quantum Degeneracy in an Optical Dipole Trap

We discuss our experimental results on forced evaporative cooling of cold rubidium 87Rb atoms to quantum degeneracy in an Optical Dipole Trap. The atoms are first trapped and cooled in a magneto-optical trap (MOT) loaded from a continuous beam of cold atoms [1]. More than 1010 atoms are trapped in the MOT and then about 108 atoms are transferred to a Quasi-Electrostatic Trap (QUEST) formed by tightly focused CO2 laser (λ = 10.6μm) beams intersecting at their foci in an orthogonal configuration in the horizontal plane. Before loading the atoms into the dipole trap, the phase-space density of the atomic ensemble was increased making use of sub-doppler cooling at large detuning and the temporal dark MOT technique. In a MOT the phase-space density of the atomic ensemble is six orders of magnitude less than what is required to achieve quantum degeneracy. After transferring atoms into the dipole trap efficiently, phase-space density increases by a factor of 103. Further increase in phase-space density to quantum degeneracy is achieved by forced evaporative cooling of atoms in the dipole trap. The evaporative cooling process involves a gradual reduction of the trap depth by ramping down the trapping laser intensity over a second. The temperature of the cold atomic cloud was measured by time-of-flight (TOF) technique. The spatial distribution of the atoms is measured using absorption imaging. We report results of evaporative cooling in a single beam and in a crossed double-beam dipole traps. Due to the large initial phase space density, and large initial number of atoms trapped, the quantum phase transition occurs after about 600 ms of evaporative cooling in our optimized crossed dipole trap.