Cavity QED with Multiple Hyperfine Levels

We calculate the weak-driving transmission of a linearly polarized cavity mode strongly coupled to the D2 transition of a single Cesium atom. Results are relevant to future experiments with microtoroid cavities, where the single-photon Rabi frequency g exceeds the excited-state hyperfine splittings, and photonic bandgap resonators, where g is greater than both the excited- and ground-state splitting.Comment: 6 pages, 10 figure

Hydrogen Embrittlement of Aluminum: the Crucial Role of Vacancies

We report first-principles calculations which demonstrate that vacancies can combine with hydrogen impurities in bulk aluminum and play a crucial role in the embrittlement of this prototypical ductile solid. Our studies of hydrogen-induced vacancy superabundant formation and vacancy clusterization in aluminum lead to the conclusion that a large number of H atoms (up to twelve) can be trapped at a single vacancy, which over-compensates the energy cost to form the defect. In the presence of trapped H atoms, three nearest-neighbor single vacancies which normally would repel each other, aggregate to form a trivacancy on the slip plane of Al, acting as embryos for microvoids and cracks and resulting in ductile rupture along the these planes.Comment: To appear in Phys. Rev. Let

Stratigraphy, Geochronology and Detrital Zircon Provenance of Two Silicic Ash Layers at Hagerman Fossil Beds National Monument, Idaho

Hagerman Fossil Beds National Monument (HAFO) is home to the world-famous Hagerman Horse Quarry. This site gives important insight into Pliocene age paleontology. Absolute ages of this site have been elusive, although researchers have assumed the site to be around 3.2 Ma. This study sought to determine more precise ages for the previously documented Hagerman Horse Quarry and Peters Gulch ash layers at HAFO thereby defining a more specific date for the Hagerman fossil assemblage, and to describe and interpret their sedimentary horizons. Detailed stratigraphic columns were created to describe sedimentary layers and establish marker beds. The sedimentology and stratigraphy are consistent with that of fluvial/flood plain depositional environments. Two ash samples were collected and analyzed using U/Pb zircon geochronology via laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Similar to previous studies, the majority of zircon crystals in these volcanic ashes are detrital in origin, ranging in age from 4 Ma to Precambrian. While the depositional age of these ash beds remains elusive, the detrital ages were grouped into three major volcanic events and described in order to identify the source of the detrital zircons and hosting sediment. These source areas include the Atlanta Lobe of the Idaho Batholith (80 – 100 Ma), the Challis Volcanic Group (45 – 52 Ma), and rhyolitic Yellowstone-Snake River Plain volcanics (4 – 17 Ma)

Mechanics of hydrogen-dislocation-impurity interactions: part 1- increasing shear modulus

The effect of hydrogen on dislocation-dislocation and dislocation-impurity atom interactions is studied under conditions where hydrogen is in equilibrium with local stresses and in systems where hydrogen increases the shear modulus. In the case of two edge dislocations (plain strain) the effect of hydrogen is modeled through a continous distribution of dilatation lines whose strength depends on the local hydrogen concentration. The hydrogen distribution in the atmospheres is adjusted to minimize the energy of the system as the dislocations approach each other. The iterative finite element analysis used to calculate the hydrogen distribution accounts for the stress relaxation associated with the hydrogen induced volume and the elastic moduli changes due to hydrogen. The interactions between the dislocations are calculated accounting for all the stress fields due to dislocations and hydrogen atmospheres. An analytical formula is suggested for the hydrogen induced reduction in the magnitude of the shear stress exerted between the dislocations along the slip system. Modeling of the hydrogen effect on the edge dislocation-interstitial solute atom interaction is discussed using a finite element analysis and a formula is developed for the calculation of the dislocation-solute atom interaction energy in the presence of hydrogen. In this paper the numerical results are presented for the case where hydrogen increases the shear modulus of the metallic system. A significant decrease of the edge dislocation-intersititial solid atom interaction energy was observed when the dislocation-solute distance is approximately less than 2 Burgers vectors. This can be attributed almost entirely to the modulus change due to hydrogen. The effect of hydrogen on the screw dislocation-intersitial solute interaction was investigated. Numerical results indicate that, depeneding on the orientation of the tetragonal axis of the carbon distortion field, hydrogen may strengthen or weaken the interaction. The present model provides strong support for the hydrogen shielding mechanism wherby hydrogen diminishes the local stress fields from dislocation and solutes which act as barriers to the dislocation motion

Cavity QED with Single Atoms and Photons

Recent experimental advances in the field of cavity quantum electrodynamics (QED) have opened new possibilities for control of atom-photon interactions. A laser with "one and the same atom" demonstrates the theory of laser operation pressed to its conceptual limit. The generation of single photons on demand and the realization of cavity QED with well defined atomic numbers N = 0, 1, 2,... both represent important steps toward realizing diverse protocols in quantum information science. Coherent manipulation of the atomic state via Raman transitions provides a new tool in cavity QED for in situ monitoring and control of the atom-cavity system. All of these achievements share a common point of departure: the regime of strong coupling. It is thus interesting to consider briefly the history of the strong coupling criterion in cavity QED and to trace out the path that research has taken in the pursuit of this goal

Zener Disaccommodation In Dilute F.C.C. Co-Ti Alloys

The magnetic Dis accommodation, i.e., the time dependence of the low field magnetic permeability, was investigated in cobalt base alloys containing 0-5.1 at.% (0-4.2 wt.%) titanium in the temperature range 400-700°C. A strong temperature dependence of the Dis accommodation observed in the range 430-530°C could be accounted for predominantly by a single first order relaxation process. Analyzing the data in terms of (a) a single exponential relaxation, (b) a lognormal distribution of relaxation times, and (c) a sum of exponential relaxations, it was shown that the relaxation strength varies as the square of the titanium concentration and that the relaxation is characterized by an activation enthalpy of 69 ± 1 kcal/mole and a τ0 of the order of 10-16 sec. The Dis accommodation was attributed to the reorientation of substitutional solute atom (titanium) pairs. From the temperature dependence of the relaxation strength the binding energy of Ti atom pairs was determined to be 0.17 ± 0.08 eV. © 1968

Interstitial Solute Trapping In Irradiated And Quenched Iron

The interaction of interstitial carbon and nitrogen solutes with defects produced by low temperature neutron irradiation and by quenching was studied in high purity and Ferrovac E iron. Magnetic Dis accommodation techniques were applied to determine the interstitial solute content after irradiation and upon annealing. Doses of about 1017 neutrons/cm2 caused the trapping of about 20 ppm (atomic) interstitial solutes at 65 (carbon) and 40°C (nitrogen). Trapping of carbon in a Ferrovac E iron alloy occurred during a fast quench from 880°C. After trapping, the interstitial solutes reappeared in solid solution at 300 (carbon, neutron irradiation), 200 (nitrogen, neutron irradiation), and 620°C (carbon, quenching). Various possibilities for the defect traps were considered and it was concluded that trapping of the interstitial solutes occurred at iron interstitial clusters after neutron irradiation and at vacancy type defects after quenching. Copyright © 1968 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinhei

Observation of the Vacuum-Rabi Spectrum for One Trapped Atom

The transmission spectrum for one atom strongly coupled to the field of a high-finesse optical resonator is observed to exhibit a clearly resolved vacuum-Rabi splitting characteristic of the normal modes in the eigenvalue spectrum of the atom-cavity system. A new Raman scheme for cooling atomic motion along the cavity axis enables a complete spectrum to be recorded for an individual atom trapped within the cavity mode, in contrast to all previous measurements in cavity QED that have required averaging over many atoms.Comment: 5 pages with 4 figure

Stable marriage with general preferences

We propose a generalization of the classical stable marriage problem. In our model, the preferences on one side of the partition are given in terms of arbitrary binary relations, which need not be transitive nor acyclic. This generalization is practically well-motivated, and as we show, encompasses the well studied hard variant of stable marriage where preferences are allowed to have ties and to be incomplete. As a result, we prove that deciding the existence of a stable matching in our model is NP-complete. Complementing this negative result we present a polynomial-time algorithm for the above decision problem in a significant class of instances where the preferences are asymmetric. We also present a linear programming formulation whose feasibility fully characterizes the existence of stable matchings in this special case. Finally, we use our model to study a long standing open problem regarding the existence of cyclic 3D stable matchings. In particular, we prove that the problem of deciding whether a fixed 2D perfect matching can be extended to a 3D stable matching is NP-complete, showing this way that a natural attempt to resolve the existence (or not) of 3D stable matchings is bound to fail.Comment: This is an extended version of a paper to appear at the The 7th International Symposium on Algorithmic Game Theory (SAGT 2014