Stoppage of Light Made Flexible by an Additional Control Field

We show how the application of a coupling field connecting the two lower metastable states of a Lambda system facilitates stoppage of light in a coheren tly driven Doppler broadened atomic medium via electromagnetic induced transparencyComment: 11 pages, 3 figures, typed in Latex, Accepted in JM

Causality in Propagation of a Pulse in a Nonlinear Dispersive Medium

We investigate the causal propagation of the pulse through dispersive media by very precise numerical solution of the coupled Maxwell-Bloch equations without any approximations about the strength of the input field. We study full nonlinear behavior of the pulse propagation through solid state media like ruby and alexandrite. We have demonstrated that the information carried by the discontinuity, {\it i.e}, front of the pulse, moves inside the media with velocity $c$ even though the peak of the pulse can travel either with sub-luminal or with super-luminal velocity. We extend the argument of Levi-Civita to prove that the discontinuity would travel with velocity $c$ even in a nonlinear medium.Comment: 4 pages, 4 figures, 2 table

Sub and Super-Luminal Propagation of Intense Pulses in Media with Saturated and Reverse Absorption

We develop models for the propagation of intense pulses in solid state media which can have either saturated absorption or exhibit reverse absorption . We show that the experiments of Bigelow {\it et al.}[Phys. Rev. Lett. {\bf 90}, 113903 (2003); Science {\bf 301}, 200 (2003).] on subluminal propagation in Ruby and superluminal propagation in Alexandrite are well explained by modelling them as three level and four level systems coupled to Maxwell equations. We present results well beyond the traditional pump-probe approach.Comment: 4 pages, 6 figure

Plus-Minus Player Ratings for Soccer

The paper presents plus–minus ratings for use in association football (soccer). We first describe the general plus–minus methodology as used in basketball and ice-hockey and then adapt it for use in soccer. The usual goal-differential plus–minus is considered before two new variations are proposed. For the first variation, we present a methodology to calculate an expected goals plus–minus rating. The second variation makes use of in-play probabilities of match outcome to evaluate an expected points plus–minus rating. We use the ratings to examine who are the best players in European football, and demonstrate how the players’ ratings evolve over time. Finally, we shed light on the debate regarding which is the strongest league. The model suggests the English Premier League is the strongest, with the German Bundesliga a close runner-up

Non-steady wind turbine response to daytime atmospheric turbulence.

Relevant to drivetrain bearing fatigue failures, we analyse non-steady wind turbine responses from interactions between energy-dominant daytime atmospheric turbulence eddies and the rotating blades of a GE 1.5 MW wind turbine using a unique dataset from a GE field experiment and computer simulation. Time-resolved local velocity data were collected at the leading and trailing edges of an instrumented blade together with generator power, revolutions per minute, pitch and yaw. Wind velocity and temperature were measured upwind on a meteorological tower. The stability state and other atmospheric conditions during the field experiment were replicated with a large-eddy simulation in which was embedded a GE 1.5 MW wind turbine rotor modelled with an advanced actuator line method. Both datasets identify three important response time scales: advective passage of energy-dominant eddies (≈25-50 s), blade rotation (once per revolution (1P), ≈3 s) and sub-1P scale (s) response to internal eddy structure. Large-amplitude short-time ramp-like and oscillatory load fluctuations result in response to temporal changes in velocity vector inclination in the aerofoil plane, modulated by eddy passage at longer time scales. Generator power responds strongly to large-eddy wind modulations. We show that internal dynamics of the blade boundary layer near the trailing edge is temporally modulated by the non-steady external flow that was measured at the leading edge, as well as blade-generated turbulence motions.This article is part of the themed issue 'Wind energy in complex terrains'

From Storage and Retrieval of Pulses to Adiabatons

We investigate whether it is possible to store and retrieve the intense probe pulse from a $\Lambda$-type homogeneous medium of cold atoms. Through numerical simulations we show that it is possible to store and retrieve the probe pulse which are not necessarily weak. As the intensity of the probe pulse increases, the retrieved pulse remains a replica of the original pulse, however there is overall broadening and loss of the intensity. These effects can be understood in terms of the dependence of absorption on the intensity of the probe. We include the dynamics of the control field, which becomes especially important as the intensity of the probe pulse increases. We use the theory of adiabatons [Grobe {\it et al.} Phys. Rev. Lett. {\bf 73}, 3183 (1994)] to understand the storage and retrieval of light pulses at moderate powers.Comment: 15 pages, 7 figures, typed in RevTe

Accelerated Design of Block Copolymers: An Unbiased Exploration Strategy via Fusion of Molecular Dynamics Simulations and Machine Learning

Star block copolymers (s-BCPs) have potential applications as novel surfactants or amphiphiles for emulsification, compatbilization, chemical transformations and separations. s-BCPs are star-shaped macromolecules comprised of linear chains of different chemical blocks (e.g., solvophilic and solvophobic blocks) that are covalently joined at one junction point. Various parameters of these macromolecules can be tuned to obtain desired surface properties, including the number of arms, composition of the arms, and the degree-of-polymerization of the blocks (or the length of the arm). This makes identification of the optimal s-BCP design highly non-trivial as the total number of plausible s-BCPs architectures is experimentally or computationally intractable. In this work, we use molecular dynamics (MD) simulations coupled with reinforcement learning based Monte Carlo tree search (MCTS) to identify s-BCPs designs that minimize the interfacial tension between polar and non-polar solvents. We first validate the MCTS approach for design of small- and medium-sized s-BCPs, and then use it to efficiently identify sequences of copolymer blocks for large-sized s-BCPs. The structural origins of interfacial tension in these systems are also identified using the configurations obtained from MD simulations. Chemical insights on the arrangement of copolymer blocks that promote lower interfacial tension were mined using machine learning (ML) techniques. Overall, this work provides an efficient approach to solve design problems via fusion of simulations and ML and provide important groundwork for future experimental investigation of s-BCPs sequences for various applications

A Knob for Changing Light Propagation from Subluminal to Superluminal

We show how the application of a coupling field connecting the two lower metastable states of a lambda-system can produce a variety of new results on the propagation of a weak electromagnetic pulse. In principle the light propagation can be changed from subluminal to superluminal. The negative group index results from the regions of anomalous dispersion and gain in susceptibility.Comment: 6 pages,5 figures, typed in RevTeX, accepted in Phys. Rev.

Slow Light in Doppler Broadened Two level Systems

We show that the propagation of light in a Doppler broadened medium can be slowed down considerably eventhough such medium exhibits very flat dispersion. The slowing down is achieved by the application of a saturating counter propagating beam that produces a hole in the inhomogeneous line shape. In atomic vapors, we calculate group indices of the order of 10^3. The calculations include all coherence effects.Comment: 6 pages, 5 figure

Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)

The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the India-based Neutrino Observatory (INO) is designed to study the atmospheric neutrinos and antineutrinos separately over a wide range of energies and path lengths. The primary focus of this experiment is to explore the Earth matter effects by observing the energy and zenith angle dependence of the atmospheric neutrinos in the multi-GeV range. This study will be crucial to address some of the outstanding issues in neutrino oscillation physics, including the fundamental issue of neutrino mass hierarchy. In this document, we present the physics potential of the detector as obtained from realistic detector simulations. We describe the simulation framework, the neutrino interactions in the detector, and the expected response of the detector to particles traversing it. The ICAL detector can determine the energy and direction of the muons to a high precision, and in addition, its sensitivity to multi-GeV hadrons increases its physics reach substantially. Its charge identification capability, and hence its ability to distinguish neutrinos from antineutrinos, makes it an efficient detector for determining the neutrino mass hierarchy. In this report, we outline the analyses carried out for the determination of neutrino mass hierarchy and precision measurements of atmospheric neutrino mixing parameters at ICAL, and give the expected physics reach of the detector with 10 years of runtime. We also explore the potential of ICAL for probing new physics scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration, Contents identical with the version published in Pramana - J. Physic