Peer Evaluation of Video Lab Reports in a Blended Introductory Physics Course

The Georgia Tech blended introductory calculus-based mechanics course emphasizes scientific communication as one of its learning goals, and to that end, we gave our students a series of four peer-evaluation assignments intended to develop their abilities to present and evaluate scientific arguments. Within these assignments, we also assessed students' evaluation abilities by comparing their evaluations to a set of expert evaluations. We summarize our development efforts and describe the changes we observed in student evaluation behavior.Comment: 4 pages, 1 table, 2 figures, submitted to Summer 2014 PERC Proceeding

Pregenomic RNA encapsidation analysis of eleven missense and nonsense polymerase mutants of human hepatitis B virus

We characterized 11 DNA polymerase mutants of human hepatitis B virus (HBV) which contain single missense or nonsense mutations in the various domains within this gene. Except for mutant 738, a tight association between DNA replication and RNA packaging of these missense pol mutants was observed. Further analysis of HBV core particle-associated RNA indicated that only the 3.5-kb core-specific RNA, but not the precore-specific RNA, is selectively packaged in this tissue culture system. Previously, we have demonstrated that only the 3.5-kb core-specific RNA can serve as an efficient template for pol translation. Taken together, our results suggest that selectivity of HBV RNA packaging occurs as a result of selective translation of pol-containing mRNAs. Furthermore, our data suggest that the RNA encapsidation domain of pol overlaps with all of the domains of pol involved in the synthesis of terminal protein, as well as DNA replication. Finally, on the basis of gradient centrifugation analysis, a pol defect appeared to have no negative effect on the assembly or stability of core particles. A new method to assay RNA encapsidation, as well as potential RNase H activity, is reported

The Initial State of Students Taking an Introductory Physics MOOC

As part of a larger research project into massively open online courses (MOOCs), we have investigated student background, as well as student participation in a physics MOOC with a laboratory component. Students completed a demographic survey and the Force and Motion Conceptual Evaluation at the beginning of the course. While the course is still actively running, we have tracked student participation over the first five weeks of the eleven-week course.Comment: Accepted to PERC Proceedings 201

The mixed black hole partition function for the STU model

We evaluate the mixed partition function for dyonic BPS black holes using the recently proposed degeneracy formula for the STU model. The result factorizes into the OSV mixed partition function times a proportionality factor. The latter is in agreement with the measure factor that was recently conjectured for a class of N=2 black holes that contains the STU model.Comment: 14 page

Finite resolution measurement of the non-classical polarization statistics of entangled photon pairs

By limiting the resolution of quantum measurements, the measurement induced changes of the quantum state can be reduced, permitting subsequent measurements of variables that do not commute with the initially measured property. It is then possible to experimentally determine correlations between non-commuting variables. The application of this method to the polarization statistics of entangled photon pairs reveals that negative conditional probabilities between non-orthogonal polarization components are responsible for the violation of Bell's inequalities. Such negative probabilities can also be observed in finite resolution measurements of the polarization of a single photon. The violation of Bell's inequalities therefore originates from local properties of the quantum statistics of single photon polarization.Comment: 15 pages, 5 figures and 1 table, new figure to illustrate results, improved explanation of statistical analysi

d-Wave Pairing Correlation in the Two-Dimensional t-J Model

The pair-pair correlation function of the two-dimensional t-J model is studied by using the power-Lanczos method and an assumption of monotonic behavior. In comparison with the results of the ideal Fermi gas, we conclude that the 2D t-J model does not have long range d-wave superconducting correlation in the interesting parameter range of $J/t \leq 0.5$. Implications of this result will also be discussed.Comment: 4 pages, 6 figures, accepted by PR

Low energy physical properties of high-Tc superconducting Cu oxides: A comparison between the resonating valence bond and experiments

In a recent review by Anderson and coworkers\cite{Vanilla}, it was pointed out that an early resonating valence bond (RVB) theory is able to explain a number of unusual properties of high temperature superconducting (SC) Cu-oxides. Here we extend previous calculations \cite{anderson87,FC Zhang,Randeria} to study more systematically low energy physical properties of the plain vanilla d-wave RVB state, and to compare results with the available experiments. We use a renormalized mean field theory combined with variational Monte Carlo and power Lanczos methods to study the RVB state of an extended $t-J$ model in a square lattice with parameters suitable for the hole doped Cu-oxides. The physical observable quantities we study include the specific heat, the linear residual thermal conductivity, the in-plane magnetic penetration depth, the quasiparticle energy at the antinode $(\pi, 0)$, the superconducting energy gap, the quasiparticle spectra and the Drude weight. The traits of nodes (including $k_{F}$, the Fermi velocity $v_{F}$ and the velocity along Fermi surface $v_{2}$), as well as the SC order parameter are also studied. Comparisons of the theory and the experiments in cuprates show an overall qualitative agreement, especially on their doping dependences.Comment: 12 pages, 14 figures, 1 tabl

Singularities of N=1 Supersymmetric Gauge Theory and Matrix Models

In N=1 supersymmetric U(N) gauge theory with adjoint matter $\Phi$ and polynomial tree-level superpotential $W(\Phi)$, the massless fluctuations about each quantum vacuum are generically described by $U(1)^n$ gauge theory for some n. However, by tuning the parameters of $W(\Phi)$ to non-generic values, we can reach singular vacua where additional fields become massless. Using both the matrix model prescription and the strong-coupling approach, we study in detail three examples of such singularities: the singularities of the n=1 branch, intersections of n=1 and n=2 branches, and a class of N=1 Argyres-Douglas points. In all three examples, we find that the matrix model description of the low-energy physics breaks down in some way at the singularity.Comment: 29 pages, 1 figure. Revised section 1, fixed misprints in section 3.1, added clarifications and reference