Dynamic effects of electromagnetic wave on a damped two-level atom

We studied the dynamic effects of an electromagnetic(EM) wave with circular polarization on a two-level damped atom. The results demonstrate interesting ac Stark split of energy levels of damped atom. The split levels have different energies and lifetimes, both of which depend on the interaction and the damping rate of atom. When the frequency of the EM wave is tuned to satisfy the resonance condition in the strong coupling limit, the transition probability exhibits Rabi oscillation. Momentum transfer between atom and EM wave shows similar properties as the transition probability under resonance condition. For a damped atom interacting with EM field, there exists no longer stable state. More importantly, if the angular frequency of the EM wave is tuned the same as the atomic transition frequency and its amplitude is adjusted appropriately according to the damping coefficients, we can prepare a particular 'Dressed State' of the coupled system between atom and EM field and can keep the system coherently in this 'Dressed state' for a very long time. This opens another way to prepare coherent atomic states.Comment: latex, 2 figure

Upstream Volatility in the Supply Chain: The Machine Tool Industry as a Case Study

Working Draft, May 1995Cyclicality is a well known and accepted fact of life in market-driven economies. Less well known or understood, however, is the phenomenon of amplification as one looks "upstream" in the industrial supply chain. This paper discusses and explains the amplification phenomenon and its implications through the lens of one "upstream" industry that is notorious for the intensity of the business cycles it faces: the machine tool industry. Using a sparse simulation model, we have replicated much of the behavior seen in the industrial world in which machine tool companies operate. This model has allowed us to test and confirm many of our hypotheses. Two results stand out. Even though machine tool builders can do little to reduce their production volatility through choice of forecast rule, a longer view of the future leads companies to retain more of their skilled workforce. This is often cited as one of the advantages that European and Japanese companies have enjoyed: lower skilled employee turnover. The second, and most important result is that machine tool customers can do a great deal to reduce the volatility for machine tool builders through their choice of order forecast rule. Companies which use a longer horizon over which to forecast orders tend to impose less of their own volatility upon their supply base.MIT -- Leaders for Manufacturing, the International Motor Vehicle Program, the Industrial Performance Center, the International Center for Research on the Management of Technology, and the Japan Program; Chrysler, Intel, Sematech, and Texas Instruments

An Investigation of Cloud Cavitation about a Sphere

Cloud cavitation occurrence about a sphere is investigated in a variable pressure water tunnel using still and high-speed photography. The model sphere, 0.15 m in diameter, was sting mounted within a 0.6 m square test section and tested at a constant Reynolds number of 1.5 x 106 with cavitation numbers varying between 0.36 and 1.0. High-speed photographic recordings were made at 6 kHz for several cavitation numbers. Shedding phenomena and frequency content is investigated by means of pixel intensity time series data using wavelet analysis. The boundary layer at cavity separation is shown to be laminar for all cavitation numbers, with Kelvin-Helmholtz instability the main mechanism for cavity break up and cloud formation at high cavitation numbers. At intermediate cavitation numbers, cavity lengths allow the development of re-entrant jet phenomena providing a mechanism for shedding of large scale Karman-type vortices similar to those for low mode shedding in single-phase subcritical flow. This shedding mode is eliminated at low cavitation numbers with the onset of supercavitation

The Electron Spectral Function in Two-Dimensional Fractionalized Phases

We study the electron spectral function of various zero-temperature spin-charge separated phases in two dimensions. In these phases, the electron is not a fundamental excitation of the system, but rather ``decays'' into a spin-1/2 chargeless fermion (the spinon) and a spinless charge e boson (the chargon). Using low-energy effective theories for the spinons (d-wave pairing plus possible N\'{e}el order), and the chargons (condensed or quantum disordered bosons), we explore three phases of possible relevance to the cuprate superconductors: 1) AF*, a fractionalized antiferromagnet where the spinons are paired into a state with long-ranged N\'{e}el order and the chargons are 1/2-filled and (Mott) insulating, 2) the nodal liquid, a fractionalized insulator where the spinons are d-wave paired and the chargons are uncondensed, and 3) the d-wave superconductor, where the chargons are condensed and the spinons retain a d-wave gap. Working within the $Z_2$ gauge theory of such fractionalized phases, our results should be valid at scales below the vison gap. However, on a phenomenological level, our results should apply to any spin-charge separated system where the excitations have these low-energy effective forms. Comparison with ARPES data in the undoped, pseudogapped, and superconducting regions is made.Comment: 10 page

Weak force detection using a double Bose-Einstein condensate

A Bose-Einstein condensate may be used to make precise measurements of weak forces, utilizing the macroscopic occupation of a single quantum state. We present a scheme which uses a condensate in a double well potential to do this. The required initial state of the condensate is discussed, and the limitations on the sensitivity due to atom collisions and external coupling are analyzed.Comment: 12 pages, 2 figures, Eq.(41) has been correcte

Optimal generalization of power filters for gravitational wave bursts, from single to multiple detectors

Searches for gravitational wave signals which do not have a precise model describing the shape of their waveforms are often performed using power detectors based on a quadratic form of the data. A new, optimal method of generalizing these power detectors so that they operate coherently over a network of interferometers is presented. Such a mode of operation is useful in obtaining better detection efficiencies, and better estimates of the position of the source of the gravitational wave signal. Numerical simulations based on a realistic, computationally efficient hierarchical implementation of the method are used to characterize its efficiency, for detection and for position estimation. The method is shown to be more efficient at detecting signals than an incoherent approach based on coincidences between lists of events. It is also shown to be capable of locating the position of the source.Comment: 16 pages, 5 figure

Effect of annealing on glassy dynamics and non-Fermi liquid behavior in UCu_4Pd

Longitudinal-field muon spin relaxation (LF-muSR) experiments have been performed in unannealed and annealed samples of the heavy-fermion compound UCu_4Pd to study the effect of disorder on non-Fermi liquid behavior in this material. The muon spin relaxation functions G(t,H) obey the time-field scaling relation G(t,H) = G(t/H^gamma) previously observed in this compound. The observed scaling exponent gamma = 0.3 pm 0.1, independent of annealing. Fits of the stretched-exponential relaxation function G(t) = exp[-(Lambda t)^K] to the data yielded stretching exponentials K < 1 for all samples. Annealed samples exhibited a reduction of the relaxation rate at low temperatures, indicating that annealing shifts fluctuation noise power to higher frequencies. There was no tendency of the inhomogeneous spread in rates to decrease with annealing, which modifies but does not eliminate the glassy spin dynamics reported previously in this compound. The correlation with residual resistivity previously observed for a number of NFL heavy-electron materials is also found in the present work.Comment: 4 pages, 3 figures, submitted to 10th International Conference on Muon Spin Rotation, Relaxation, and Resonance, Oxford, UK, August 200

On the Geometry and Mass of Static, Asymptotically AdS Spacetimes, and the Uniqueness of the AdS Soliton

We prove two theorems, announced in hep-th/0108170, for static spacetimes that solve Einstein's equation with negative cosmological constant. The first is a general structure theorem for spacetimes obeying a certain convexity condition near infinity, analogous to the structure theorems of Cheeger and Gromoll for manifolds of non-negative Ricci curvature. For spacetimes with Ricci-flat conformal boundary, the convexity condition is associated with negative mass. The second theorem is a uniqueness theorem for the negative mass AdS soliton spacetime. This result lends support to the new positive mass conjecture due to Horowitz and Myers which states that the unique lowest mass solution which asymptotes to the AdS soliton is the soliton itself. This conjecture was motivated by a nonsupersymmetric version of the AdS/CFT correspondence. Our results add to the growing body of rigorous mathematical results inspired by the AdS/CFT correspondence conjecture. Our techniques exploit a special geometric feature which the universal cover of the soliton spacetime shares with familiar ``ground state'' spacetimes such as Minkowski spacetime, namely, the presence of a null line, or complete achronal null geodesic, and the totally geodesic null hypersurface that it determines. En route, we provide an analysis of the boundary data at conformal infinity for the Lorentzian signature static Einstein equations, in the spirit of the Fefferman-Graham analysis for the Riemannian signature case. This leads us to generalize to arbitrary dimension a mass definition for static asymptotically AdS spacetimes given by Chru\'sciel and Simon. We prove equivalence of this mass definition with those of Ashtekar-Magnon and Hawking-Horowitz.Comment: Accepted version, Commun Math Phys; Added Remark IV.3 and supporting material dealing with non-uniqueness arising from choice of special cycle on the boundary at infinity; 2 new citations added; LaTeX 27 page

The curvature perturbation at second order

We give an explicit relation, up to second-order terms, between scalar-field fluctuations defined on spatially-flat slices and the curvature perturbation on uniform-density slices. This expression is a necessary ingredient for calculating observable quantities at second-order and beyond in multiple-field inflation. We show that traditional cosmological perturbation theory and the `separate universe' approach yield equivalent expressions for superhorizon wavenumbers, and in particular that all nonlocal terms can be eliminated from the perturbation-theory expressions

Constraining Galileon inflation

In this short paper, we present constraints on the Galileon inflationary model from the CMB bispectrum. We employ a principal-component analysis of the independent degrees of freedom constrained by data and apply this to the WMAP 9-year data to constrain the free parameters of the model. A simple Bayesian comparison establishes that support for the Galileon model from bispectrum data is at best weak