Session C5: SPS I

N-body Simulations of Dwarf Galaxies

The effects of gravitational interactions on the evolution of dwarf irregular galaxies are explored through the use of N-body simulations. Numerous studies have been performed on N-body simulations of dwarf galaxies, with most focused on modeling the tidal interactions of satellite and host galaxies. Here, two general scenarios are considered: the interaction of two dwarf galaxies, and a single dwarf galaxy nearby a large spiral galaxy. Initial conditions for each galaxy model were produced using GalactICS, with N-body simulations being run through GADGET 2. The dwarf models consist of disk and halo components, with a total of 40,000 particles per galaxy. A galaxy cluster is included in the simulation using a gravitational potential function introduced into the GADGET 2 code. Each scenario is run both with and without the cluster potential present. Additionally, a single dwarf galaxy in the presence of the cluster potential is simulated. Within each general case, various combinations of initial galaxy position and velocity are considered. The results of the simulations imply that global environment (group / cluster membership) has more impact on dwarf galaxy evolution compared to local environment (presence of nearby neighbor).   

Mutual Friction in Neutron Star Cores

Neutron stars are the super-dense remnants of stars which had masses of 8-25 solar masses. A typical neutron star has a mass of 1.4 solar masses compressed into a ball having a radius of about 10km. The neutron star core, about 1km below the crust of a NS, is a fluid of protons and neutrons. Due to the motion of this fluid, certain observable effects, such as glitches, can be seen in the behavior of NSs. These effects are believed to occur due to effects such as the mutual friction, the interaction between the neutron and proton fluids arising due to nuclear forces. The coupling time constant is related to the mutual friction and is a measure of how tightly the fluid is coupled to the behavior of the crust, and models can be verified by observing effects arising due to this coupling. This project looked at current models for the mutual friction and coupling time and looked at avenues for improving these models.   

Constraining modified gravity parameters for testing General Relativity

We test several of the parameters of Einstein’s theory of General Relativity for consistency with cosmological observations. We use data from PLANCK 2015 for cosmic microwave background radiation, CFHTLenS data for weak lensing, SDSS LRG surveys for the Integrated Sachs Wolfe-galaxy cross correlation, baryon acoustic oscillations, compilations of supernovae data, the WiggleZ matter power spectrum, the Hubble Parameter data and Big Bang nucleosynthesis priors. For testing General Relativity with cosmological data, we use cosmoMC, Markov Chain Monte Carlo code for constraining cosmological parameters. Specifically, we use a modified version integrated with the ISiTGR modules which parameterize the equations of motion for General Relativity. We present two dimensional contour graphs and tables of constraints on the General relativity parameters. Our preliminary results suggest tension between the theoretical General Relativity values and our observed values.   

Comparison of lateral retention forces for sessile and pendant water drops on a solid surface

A sessile drop is produced by placing the drop on top of a solid surface and a pendant drop is produced by placing the drop on the bottom of the surface. When we place both of these drops on a Plexiglas surface, and then we spin the surface with an increasing angular velocity, one would expect the pendant drop to be easier to slide off the surface. On the contrary, the pendant drop is harder slide. This effect was first discovered in [R. Tadmor et al, Phys. Rev. Lett. 103, 266101 (1999)], and it has been recently demonstrated using a very simple apparatus in [R. de la Madrid et al, Am. J. Phys. 83, 531 (2015)]. However, there is still not known why the effect happens. In this talk, I will present an experimental arrangement that "The Drop Team" intends to use to elucidate the origin of this effect.   

Construction of a hardware-modified printer to print on multiple surface types

Printing has applications varying from convenience to necessity. Low-cost printers are limited in width to 8.5 inches on paper. Construction is in progress for a hardware-modified printer designed to print on multiple surface types and sizes with a minimal budget. The project requires an easy to use interface. A custom micro-controlled circuit is being used to automate control in addition to pre-existing printer driver software.   

Analyzing the Tacoma Narrows Bridge Collapse Using the Physics of Free Fall

75 years ago the Tacoma Narrows Bridge collapsed, an event well known because it was captured on film and is shown in video format in physics classrooms to this day. Using the physics of free fall and Tracker software for video analysis, we can determine the frame rate of the original 16mm movie camera and can answer the question: Does the video show the free fall sped up, slowed down, or at the correct speed as observed by eyewitnesses on November 7, 1940.