Community Detection in Quantum Complex Networks

Determining community structure is a central topic in the study of complex networks, be it technological, social, biological or chemical, in static or interacting systems. In this paper, we extend the concept of community detection from classical to quantum systems---a crucial missing component of a theory of complex networks based on quantum mechanics. We demonstrate that certain quantum mechanical effects cannot be captured using current classical complex network tools and provide new methods that overcome these problems. Our approaches are based on defining closeness measures between nodes, and then maximizing modularity with hierarchical clustering. Our closeness functions are based on quantum transport probability and state fidelity, two important quantities in quantum information theory. To illustrate the effectiveness of our approach in detecting community structure in quantum systems, we provide several examples, including a naturally occurring light-harvesting complex, LHCII. The prediction of our simplest algorithm, semiclassical in nature, mostly agrees with a proposed partitioning for the LHCII found in quantum chemistry literature, whereas our fully quantum treatment of the problem uncovers a new, consistent, and appropriately quantum community structure.Comment: 16 pages, 4 figures, 1 tabl

Laser-induced plasma generation of terahertz radiation using three incommensurate wavelengths

We present the generation of THz radiation by focusing ultrafast laser pulses with three incommensurate wavelengths to form a plasma. The three colors include 800 nm and the variable IR signal and idler outputs from an optical parametric amplifier. We observe that stable THz is generated when all three colors are present, with a peak-to-peak field strength of ~200 kV cm^(−1) and a relatively broad, smooth spectrum extending out to 6 THz, without any strong dependence on the selection of signal and idler IR wavelengths (in the range from 1300 to 2000 nm). We confirm that three colors are indeed needed, and we present plasma current modeling that corroborates our observations

The Myth of Strategic and Tactical Airlift

In the 21st century, our ability to quickly and decisively deliver combat forces and equipment is of the utmost importance in achieving our national security objectives. The swiftness and flexibility of the US Air Force’s mobility airlift fleet is the key to executing a rapid global mobility strategy. The operational effectiveness and efficiency of military air transportation relies on the expertise and intuition of Air Mobility Command’s (AMC) mobility planners. Working in coordination with the United States Transportation Command (USTRANSCOM) and geographic combatant commands (GCC), AMC is responsible for the tasking and tracking of almost 900 daily mobility sorties worldwide. Using a hub-and-spoke model, mobility planners conceptualize airlift requirements and routes as either tactical or strategic in nature. Airlift assets are also considered this way. Tactical aircraft (usually C-130 variants) are smaller and are used primarily for intratheater airlift within a defined area of responsibility (AOR). Strategic aircraft (C-5B/M, C-17A) have larger payload capacities and extended ranges, making them useful for intertheater transportation between two different AORs or GCCs

Laser-induced plasma generation of terahertz radiation using three incommensurate wavelengths

We present the generation of THz radiation by focusing ultrafast laser pulses with three incommensurate wavelengths to form a plasma. The three colors include 800 nm and the variable IR signal and idler outputs from an optical parametric amplifier. We observe that stable THz is generated when all three colors are present, with a peak-to-peak field strength of ~200 kV cm^(−1) and a relatively broad, smooth spectrum extending out to 6 THz, without any strong dependence on the selection of signal and idler IR wavelengths (in the range from 1300 to 2000 nm). We confirm that three colors are indeed needed, and we present plasma current modeling that corroborates our observations

The Panchromatic Hubble Andromeda Treasury. VI. The reliability of far-ultraviolet flux as a star formation tracer on sub-kpc scales

We have used optical observations of resolved stars from the Panchromatic Hubble Andromeda Treasury (PHAT) to measure the recent (< 500 Myr) star formation histories (SFHs) of 33 FUV-bright regions in M31. The region areas ranged from ~$10^4$ to $10^6$ pc$^2$, which allowed us to test the reliability of FUV flux as a tracer of recent star formation on sub-kpc scales. The star formation rates (SFRs) derived from the extinction-corrected observed FUV fluxes were, on average, consistent with the 100-Myr mean SFRs of the SFHs to within the 1$\sigma$ scatter. Overall, the scatter was larger than the uncertainties in the SFRs and particularly evident among the smallest regions. The scatter was consistent with an even combination of discrete sampling of the initial mass function and high variability in the SFHs. This result demonstrates the importance of satisfying both the full-IMF and the constant-SFR assumptions for obtaining precise SFR estimates from FUV flux. Assuming a robust FUV extinction correction, we estimate that a factor of 2.5 uncertainty can be expected in FUV-based SFRs for regions smaller than $10^5$ pc$^2$, or a few hundred pc. We also examined ages and masses derived from UV flux under the common assumption that the regions are simple stellar populations (SSPs). The SFHs showed that most of the regions are not SSPs, and the age and mass estimates were correspondingly discrepant from the SFHs. For those regions with SSP-like SFHs, we found mean discrepancies of 10 Myr in age and a factor of 3 to 4 in mass. It was not possible to distinguish the SSP-like regions from the others based on integrated FUV flux.Comment: Accepted for publication in The Astrophysical Journa

Calculation of nonzero-temperature Casimir forces in the time domain

We show how to compute Casimir forces at nonzero temperatures with time-domain electromagnetic simulations, for example using a finite-difference time-domain (FDTD) method. Compared to our previous zero-temperature time-domain method, only a small modification is required, but we explain that some care is required to properly capture the zero-frequency contribution. We validate the method against analytical and numerical frequency-domain calculations, and show a surprising high-temperature disappearance of a non-monotonic behavior previously demonstrated in a piston-like geometry.Comment: 5 pages, 2 figures, submitted to Physical Review A Rapid Communicatio