Mahan\u27s Concepts of Sea Power

I would submit to you that Admiral Mahan him­self was only secondarily a propagandist for his views and pri­marily an analytical historian who derived from his studies and writings demonstrable cause and effect relationships between sea power and national greatness

Accelerated-Cherenkov radiation and signatures of radiation reaction

In this manuscript we examine an accelerated charged particle moving through an optical medium, and explore the emission of accelerated-Cherenkov radiation. The particle's reaction to acceleration creates a low-frequency spectral cutoff in the Cherenkov emission that has a sharp resonance at the superluminal threshold. Moreover, the effect of recoil on the radiation is incorporated kinematically through the use of an Unruh-DeWitt detector by setting an energy gap, i.e., the change in electron energy, to the recoil energy of the emitted photon. The simultaneous presence of recoil and acceleration conspire to produce a localized resonance peak in the emission. These theoretical considerations could be used to construct high precision tests of radiation reaction using Cherenkov emission under acceleration.Comment: 18 pages, 8 figures. As appears in The New Journal of Physic

Ultrafast Multiharmonic Plasmon Generation by Optically Dressed Electrons

Interactions between electrons and photons are a source of rich physics from atomic to astronomical scales. Here, we examine a new kind of electron-photon interaction in which an electron, modulated by light, radiates multiple harmonics of plasmons. The emitted plasmons can be femtosecond in duration and nanometer in spatial scale. The extreme subwavelength nature of the plasmons lowers the necessary input light intensity by at least 4 orders of magnitude relative to state-of-the-art strong-field processes involving bound or free electrons. The results presented here reveal a new means of ultrafast (10–1000 fs) interconversion between photonic and plasmonic energy, and a general scheme for generating spatiotemporally shaped ultrashort pulses in optical materials. More generally, our results suggest a route towards realizing analogues of fascinating physical phenomena like nonlinear Compton scattering in plasmonics and nanophotonics with relatively low intensities, slow electrons, and on nanometer length scales.United States. Department of Energy (Grant DE-FG02-97ER25308)United States. Army Research Office (Contract W911NF-18-2-0048)United States. Army Research Office (Contract W911NF-13-D-0001

Modeling and Control of Large-Scale Adversarial Swarm Engagements

We theoretically and numerically study the problem of optimal control of large-scale autonomous systems under explicitly adversarial conditions, including probabilistic destruction of agents during the simulation. Large-scale autonomous systems often include an adver sarial component, where different agents or groups of agents explicitly compete with one another. An important component of these systems that is not included in current theory or modeling frameworks is random destruction of agents in time. In this case, the modeling and optimal control framework should consider the attrition of agents as well as their position. We propose and test three numerical modeling schemes, where survival probabilities of all agents are smoothly and continuously decreased in time, based on the relative positions of all agents during the simulation. In particular, we apply these schemes to the case of agents defending a high-value unit from an attacking swarm. We show that these models can be successfully used to model this situation, provided that attrition and spatial dynamics are coupled. Our results have relevance to an entire class of adversarial autonomy situations, where the positions of agents and their survival probabilities are both important.ONR SoA programNPS CRUSER progra

Constructing “Designer Atoms” via Resonant Graphene-Induced Lamb Shifts

The properties of an electron in an atom or molecule are not fixed; rather they are a function of the optical environment of the emitter. Not only is the spontaneous emission a function of the optical environment, but also the underlying wave functions and energy levels, which are modified by the potential induced by quantum fluctuations of the electromagnetic field. In free space, this modification of atomic levels and wave functions is very weak and generally hard to observe due to the prevalence of other perturbations like fine structure. Here, we explore the possibility of highly tailorable electronic structure by exploiting large Lamb shifts in tunable electromagnetic environments such as graphene, whose optical properties are dynamically controlled via doping. The Fermi energy can be chosen so that the Lamb shift is very weak, but it can also be chosen so that the shifts become more prominent than the fine structure of the atom and even potentially the Coulomb interaction with the nucleus. Potential implications of this idea include being able to electronically shift an unfavorable emitter structure into a favorable one, a new approach to probe near-field physics in fluorescence, and a way to access regimes of physics where vacuum fluctuations are not a weak perturbation but rather the dominant physics. Keywords: graphene plasmonics; Lamb shift; light-matter interactions; quantum electrodynamicsUnited States. Army Research Office (Grant W911NF-13-D-0001)United States. Department of Energy (Award DE-FG02-97ER25308

Tailoring the energy distribution and loss of 2D plasmons

The ability to tailor the energy distribution of plasmons at the nanoscale has many applications in nanophotonics, such as designing plasmon lasers, spasers, and quantum emitters. To this end, we analytically study the energy distribution and the proper field quantization of 2D plasmons with specific examples for graphene plasmons. We find that the portion of the plasmon energy contained inside graphene (energy confinement factor) can exceed 50%, despite graphene being infinitely thin. In fact, this very high energy confinement can make it challenging to tailor the energy distribution of graphene plasmons just by modifying the surrounding dielectric environment or the geometry, such as changing the separation distance between two coupled graphene layers. However, by adopting concepts of parity-time symmetry breaking, we show that tuning the loss in one of the two coupled graphene layers can simultaneously tailor the energy confinement factor and propagation characteristics, causing the phenomenon of loss-induced plasmonic transparency.Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (W911NF-13-D-0001)United States. Department of Energy. Office of Science. Solid-State Solar Thermal Energy Conversion Center (DESC0001299)National Science Foundation (U.S.) (1122374)National Science Foundation (U.S.) (DMR-1419807)China Scholarship Council (201506320075

Controlling Cherenkov angles with resonance transition radiation

Cherenkov radiation provides a valuable way to identify high energy particles in a wide momentum range, through the relation between the particle velocity and the Cherenkov angle. However, since the Cherenkov angle depends only on material's permittivity, the material unavoidably sets a fundamental limit to the momentum coverage and sensitivity of Cherenkov detectors. For example, Ring Imaging Cherenkov detectors must employ materials transparent to the frequency of interest as well as possessing permittivities close to unity to identify particles in the multi GeV range, and thus are often limited to large gas chambers. It would be extremely important albeit challenging to lift this fundamental limit and control Cherenkov angles as preferred. Here we propose a new mechanism that uses constructive interference of resonance transition radiation from photonic crystals to generate both forward and backward Cherenkov radiation. This mechanism can control Cherenkov angles in a flexible way with high sensitivity to any desired range of velocities. Photonic crystals thus overcome the severe material limit for Cherenkov detectors, enabling the use of transparent materials with arbitrary values of permittivity, and provide a promising option suited for identification of particles at high energy with enhanced sensitivity.Comment: There are 16 pages and 4 figures for the manuscript. Supplementary information with 18 pages and 5 figures, appended at the end of the file with the manuscript. Source files in Word format converted to PDF. Submitted to Nature Physic

Childhood Bullying Victimization, Emotion Regulation, Rumination, Distress Tolerance, and Depressive Symptoms: A Cross-National Examination Among Young Adults In Seven Countries

Existing research suggests a robust association between childhood bullying victimization and depressive symptoms in adulthood, but less is known about potential mediators of this link. Furthermore, there is limited cross-national research evaluating similarities and differences in bullying victimization and its associations with mental health. The current study addressed gaps in the literature by evaluating cognitive and affective responses to stress (i.e., emotion regulation, rumination, and distress tolerance) as potential mediators of the link between recalled bullying victimization and current depressive symptoms among 5909 (70.6% female) college students from seven countries. Results revealed specific indirect associations of bullying victimization through distress tolerance and three out of four facets of rumination, as well as a persistent direct association of childhood bullying on adulthood depression. Emotion regulation strategies were not significantly associated with bullying victimization and did not mediate its association with depressive symptoms. Constrained multigroup models indicated that results were invariant across country and gender. Findings provide evidence of statistical mediation in a cross-sectional sample and await replication in prospective studies. Rumination and distress tolerance may be promising targets for resilience-promoting interventions among children experiencing peer victimization. Ongoing research is needed to clarify cross-national patterns in childhood bullying, identify additional mediators accounting for the remaining direct association, and evaluate emotion regulation as a potential moderator of associations between bullying victimization and adult mental health