10,092 research outputs found
Gyroscopic Precession and Inertial Forces in Axially Symmetric Stationary Spacetimes
We study the phenomenon of gyroscopic precession and the analogues of
inertial forces within the framework of general relativity. Covariant
connections between the two are established for circular orbits in stationary
spacetimes with axial symmetry. Specializing to static spacetimes, we prove
that gyroscopic precession and centrifugal force both reverse at the photon
orbits. Simultaneous non-reversal of these in the case of stationary spacetimes
is discussed. Further insight is gained in the case of static spacetime by
considering the phenomena in a spacetime conformal to the original one.
Gravi-electric and gravi-magnetic fields are studied and their relation to
inertial forces is established.Comment: 21 pages, latex, no figures, http://202.41.67.76/~nayak/gpifass.te
Novel epoxy powder for manufacturing thick-section composite parts under vacuum-bag-only conditions. Part II: Experimental validation and process investigations
Validations of a one-dimensional process model are carried out by manufacturing thick-section glass-fibre reinforced composite laminates with a low-exotherm epoxy powder. An experimental apparatus is developed which heats the laminates from one side while insulating the remaining sides (i.e. approximating one-dimensional heat transfer conditions). The experimental results are analysed and used to validate process models for the epoxy powder system. Process simulations are performed to analyse the influence of material format, laminate thickness change, and heating methods (i.e. one-sided heating vs two-sided heating, and heated tooling vs oven heating). It is shown that epoxy powder eliminates the risk of ‘thermal runaway’, but thermal and cure gradients persist for a conventional processing cycle. Methods to inhibit the evolution of these gradients are explored using process simulations. These methods include modifying the temperature cycle and using multiple epoxy powders with varied latent curing properties
Chemically reacting and radiating nanofluid flow past an exponentially stretching sheet in a porous medium
The influence of non-uniform permeability, thermal radiation and variable chemical reaction on three-dimensional flow of an incompressible nanofluid over an exponentially-stretching sheet in association with a convective boundary condition has been investgated. In the present study, a new micro-convection model known as Patel model has been employed to enhance the thermal conductivity and hence the heat transfer capability of nanofluids. In the present analysis, base fluids such as water, 30% ethylene glycol, 50% ethylene glycol and nanoparticles such as Cu, Ag and Fe3O4 have been considered. With the help of some suitable transformations the governing partial differential equationsare converted into a set of ordinary differential equations which have beeen then solved numerically by using fourth-order Runge-Kutta method along with shooting technique. The influence of various embedded physical parameters have been explored through graphs for velocity, temperature, concentration, skin friction, local Nusselt and Sherwood numbers. The resistive force offered by the porous matrix belittles the momentum boundary layer and helps in growing the temperature and concentration boundary layers. Fluid temperature is an increasing function of radiation parameter Rd and Biot’s number Bi whereas concentration field is a decreasing function of Schmidt number Sc and chemical reaction parameter γ
Exotic resonant level models in non-Abelian quantum Hall states coupled to quantum dots
In this paper we study the coupling between a quantum dot and the edge of a
non-Abelian fractional quantum Hall state. We assume the dot is small enough
that its level spacing is large compared to both the temperature and the
coupling to the spatially proximate bulk non-Abelian fractional quantum Hall
state. We focus on the physics of level degeneracy with electron number on the
dot. The physics of such a resonant level is governed by a -channel Kondo
model when the quantum Hall state is a Read-Rezayi state at filling fraction
or its particle-hole conjugate at . The
-channel Kondo model is channel symmetric even without fine tuning any
couplings in the former state; in the latter, it is generically channel
asymmetric. The two limits exhibit non-Fermi liquid and Fermi liquid
properties, respectively, and therefore may be distinguished. By exploiting the
mapping between the resonant level model and the multichannel Kondo model, we
discuss the thermodynamic and transport properties of the system. In the
special case of , our results provide a novel venue to distinguish between
the Pfaffian and anti-Pfaffian states at filling fraction . We present
numerical estimates for realizing this scenario in experiment.Comment: 18 pages, 2 figures. Clarified final discussio
Open Luttinger liquids
We study the problem of Luttinger liquids interacting with an active
environment. We are particularly interested in how dissipation affects the
response and correlation functions of non-isolated Luttinger liquids. We show
that the exchange of particles, energy, and momentum lead to changes in the
exponents characterizing the various correlations functions. We discuss the
importance of the zero mode physics in this context.Comment: Revtex, 4 pages. Final version published in PR
Multiplicity Fluctuations in the Pion-Fireball Gas
The pion number fluctuations are considered in the system of pions and large
mass fireballs decaying finally into pions. A formulation which gives an
extension of the model of independent sources is suggested. The grand canonical
and micro-canonical ensemble formulations of the pion-fireball gas are
considered as particular examples.Comment: 13 pages, 4 figure
Large Noncollinearity and Spin Reorientation in the Novel Mn2RhSn Heusler Magnet
Noncollinear magnets provide essential ingredients for the next generation
memory technology. It is a new prospect for the Heusler materials, already well
known due to the diverse range of other fundamental characteristics. Here, we
present a combined experimental and theoretical study of novel noncollinear
tetragonal Mn2RhSn Heusler material exhibiting unusually strong canting of its
magnetic sublattices. It undergoes a spin-reorientation transition, induced by
a temperature change and suppressed by an external magnetic field. Because of
the presence of Dzyaloshinskii-Moriya exchange and magnetic anisotropy, Mn2RhSn
is suggested to be a promising candidate for realizing the Skyrmion state in
the Heusler family
Tailoring discrete quantum walk dynamics via extended initial conditions: Towards homogeneous probability distributions
We study the evolution of initially extended distributions in the coined
quantum walk on the line by analyzing the dispersion relation of the process
and its associated wave equations. This allows us, in particular, to devise an
initially extended condition leading to a uniform probability distribution
whose width increases linearly with time, with increasing homogeneity.Comment: 4 pages, 2 figure
Retrieval of sea surface velocities using sequential Ocean Colour Monitor (OCM) data
The Indian remote sensing satellite, IRS-P4 (Oceansat-I) launched on May 26th, 1999 carried two sensors on board, i.e., the Ocean Colour Monitor (OCM) and the Multi-frequency Scanning Microwave Radiometer (MSMR) dedicated for oceanographic research. Sequential data of IRS-P4 OCM has been analysed over parts of both east and west coast of India and a methodology to retrieve sea surface current velocities has been applied. The method is based on matching suspended sediment dispersion patterns, in sequential two time lapsed images. The pattern matching is performed on a pair of atmospherically corrected and geo-referenced sequential images by Maximum Cross-Correlation (MCC) technique. The MCC technique involves computing matrices of cross-correlation coefficients and identifying correlation peaks. The movement of the pattern can be calculated knowing the displacement of windows required to match patterns in successive images. The technique provides actual flow during a specified period by integrating both tidal and wind influences. The current velocities retrieved were compared with synchronous data collected along the east coast during the GSI cruise ST-133 of R.V. Samudra Kaustubh in January 2000. The current data were measured using the ocean current meter supplied by the Environmental Measurement and CONtrol (EMCON), Kochi available with the Geological Survey of India, Marine Wing. This current meter can measure direction and magnitude with an accuracy of ±5‡ and 2% respectively. The measurement accuracies with coefficient of determination (R2 ) of 0.99, for both magnitude (cm.s-1) and direction (deg.) were achieved
STIRAP transport of Bose-Einstein condensate in triple-well trap
The irreversible transport of multi-component Bose-Einstein condensate (BEC)
is investigated within the Stimulated Adiabatic Raman Passage (STIRAP) scheme.
A general formalism for a single BEC in M-well trap is derived and analogy
between multi-photon and tunneling processes is demonstrated. STIRAP transport
of BEC in a cyclic triple-well trap is explored for various values of detuning
and interaction between BEC atoms. It is shown that STIRAP provides a complete
population transfer at zero detuning and interaction and persists at their
modest values. The detuning is found not to be obligatory. The possibility of
non-adiabatic transport with intuitive order of couplings is demonstrated.
Evolution of the condensate phases and generation of dynamical and geometric
phases are inspected. It is shown that STIRAP allows to generate the
unconventional geometrical phase which is now of a keen interest in quantum
computing.Comment: 9 pages, 6 figures. To be published in Laser Physics (v. 19, n.4,
2009
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