Ballistic Deposition: Global Scaling and Local Time Series.

Complexity can emerge from extremely simple rules. A paradigmatic example of this is the model of ballistic deposition (BD), a simple model of sedimentary rock growth. In two separate Problem-in-Lieu-of Thesis studies, BD was investigated numerically in (1+1)-D on a lattice. Both studies are combined in this document. For problem I, the global interface roughening (IR) process was studied in terms of effective scaling exponents for a generalized BD model. The model used incorporates a tunable parameter B to change the cooperation between aggregating particles. Scaling was found to depart increasingly from the predictions of Kardar-Parisi-Zhang theory both with decreasing system sizes and with increasing cooperation. For problem II, the local single column evolution during BD rock growth was studied via statistical analysis of time series. Connections were found between single column time series properties and the global IR process

Atom chip setup for cold Rydberg atom experiments

The design, construction and characterization of an atom chip apparatus for cold Rydberg atom experiments with 87Rb is presented. The apparatus is designed to investigate interactions between Rydberg atoms and the nearby chip surface, as well as the dynamics of Rydberg atoms in a double well. The proposed interrogation scheme is Rydberg electromagnetically induced transparency (Rydberg EIT). Magnetic trapping potentials used to load the chip with atoms are calculated. The atom number and temperature during various phases of the loading sequence are measured using absorption imaging. The room-temperature 4-level ladder-type Rydberg EIT system, in which the 3-level Rydberg EIT system is coupled via microwaves to a second Rydberg state, is investigated experimentally. EIT transmission spectra for different microwave powers and different polarizations of optical fields and microwaves are presented. It is shown that, to explain the observed polarization effects in the probe transmission lineshape, all magnetic sublevels, including the hyperfine structure of both Rydberg levels, have to be taken into account. The corresponding 52-level theory is discussed. Calculations of long-range multipolar Rydberg-atom Rydberg-atom interaction potentials are also presented and discussed

Spinor dynamics in an antiferromagnetic spin-1 thermal Bose gas

We present experimental observations of coherent spin-population oscillations in a cold thermal, Bose gas of spin-1 sodium-23 atoms. The population oscillations in a multi-spatial-mode thermal gas have the same behavior as those observed in a single-spatial-mode antiferromagnetic spinor Bose Einstein condensate. We demonstrate this by showing that the two situations are described by the same dynamical equations, with a factor of two change in the spin-dependent interaction coefficient, which results from the change to particles with distinguishable momentum states in the thermal gas. We compare this theory to the measured spin population evolution after times up to a few hundreds of ms, finding quantitative agreement with the amplitude and period. We also measure the damping time of the oscillations as a function of magnetic field.Comment: 5 pages, 3 figure

Stromatolites: why do we care?

Article discussing stromatolites. The authors apply the method of Diffusion Entropy (DE) to the study of stromatolites by means of a two-dimensional procedure that makes it possible for us to compare the DE analysis to the results of a compression method