We discuss how the renormalization group can be used to derive effective nuclear interactions. Starting from the model-independent low-momentum interaction Vlow k, we successively integrate out high-lying particle and hole states from momentum shells around the Fermi surface as proposed by Shankar. The renormalization group approach allows for a systematic calculation of induced interactions an...

In Ref.[1] we used the XY model to investigate numerically the finite–size scaling (FSS) properties of the superfluid density of superfluid films with respect to the film thickness H . The superfluid density ρs is related to the helicity modulus Υ of the XY model through ρs = (m/h̄) Υ where m denotes the mass of the helium atom[2]. We used rather thin films up to H = 24 and found that we were ab...

We study the correlation energy associated with the pair fluctuations in BCS theory. We use a schematic two-level pairing model and discuss the behavior of the correlation energy across shell closures, including the even-odd differences. It is shown that the random phase approximation (RPA) to the ground state energy reproduces the exact solutions quite well both in the normal fluid and in the ...

Two theoretical models are developed and tested to understand a particular mode of superfluid vibration called third sound. In particular we are trying to explain a brief lapse in third sound in early 4He film development on a carbon nanotube substrate. We use a resonant cavity of nanotubes at 1.3 K and introduce 4He gas. Using a variable-frequency heat pulse and a thermometer, we utilize the t...

The development of superfluid weak links has led both to the discovery of new physical phenomena and also to the development of superfluid helium quantum interference devices (SHeQUIDs). We describe the physics underlying the SHeQUID and present a brief overview of the current state of this promising technology. Superfluid 4He and 3He are described by the Landau two fluid model [1] augmented by...

We present a model of a freely precessing neutron star which is then compared against pulsar observations. The aim is to draw conclusions regarding the structure of the star, and test theoretical ideas of crust-core coupling and superfluidity. We argue that, on theoretical grounds, it is likely that the core neutron superfluid does not participate in the free precession of the crust. We apply o...

Superfluid He4 is a promising target material for direct detection of light (<1 GeV) dark matter. Possible signal channels available readout in this medium include prompt photons, triplet excimers, and roton phonon quasiparticles. The relative yield these signals has implications the sensitivity discrimination power superfluid matter detector. Using 16 cm3 volume 1.75 K read out by six immersed...

A model is presented of the A transition in superfluid helium in which fluctuations near the transition are approximated by distinct regions of normal fluid and superfluid. The macroscopic viscosity of such a medium is computed. The ion mobility is also computed, taking into account a region of normal fluid around the ion induced by electrostriction. The results are, for the viscosity, TJ, TJ t...

This doctoral thesis consists of experimental studies on rotating superfluid helium-3 at millikelvin temperatures. Superfluid He provides an example of ordered systems where quantum phenomena are visible on a macroscopic scale. The order parameter is described by a 3×3 complex matrix leading to different superfluid phases with different properties. The A and B phases support topologically diffe...