17,813 research outputs found
Quintessential Inflation in a thawing realization
We study quintessential inflation with an inverse hyperbolic type potential
, where ,
and "n" are parameters of the theory. We obtain a bound on
for different values of the parameter n. The spectral index and the
tensor-to-scalar-ratio fall in the bound given by the Planck 2015
data for for certain values of . However for
there exist values of for which the spectral index and the
tensor-to-scalar-ratio fall only within the bound of the Planck
data. Furthermore, we show that the scalar field with the given potential can
also give rise to late time acceleration if we invoke the coupling to massive
neutrino matter. We also consider the instant preheating mechanism with Yukawa
interaction and put bounds on the coupling constants for our model using the
nucleosynthesis constraint on relic gravity waves produced during inflation.Comment: 11 page
Method of measuring cross-flow vortices by use of an array of hot-film sensors
The invention is a method for measuring the wavelength of cross-flow vortices of air flow having streamlines of flow traveling across a swept airfoil. The method comprises providing a plurality of hot-film sensors. Each hot-film sensor provides a signal which can be processed, and each hot-film sensor is spaced in a straight-line array such that the distance between successive hot-film sensors is less than the wavelength of the cross-flow vortices being measured. The method further comprises determining the direction of travel of the streamlines across the airfoil and positioning the straight-line array of hot film sensors perpendicular to the direction of travel of the streamlines, such that each sensor has a spanwise location. The method further comprises processing the signals provided by the sensors to provide root-mean-square values for each signal, plotting each root-mean-square value as a function of its spanwise location, and determining the wavelength of the cross-flow vortices by noting the distance between two maxima or two minima of root-mean-square values
Cosmic acceleration from coupling of baryonic and dark matter components: Analysis and diagnostics
In this paper, we examine a scenario in which late-time cosmic acceleration
might arise due to the coupling between baryonic matter and dark matter without
the presence of extra degrees of freedom. In this case, one can obtain
late-time acceleration in Jordan frame and not in Einstein frame. We consider
two different forms of parametrization of the coupling function, and put
constraints on the model parameters by using an integrated datasets of Hubble
parameter, Type Ia supernova and baryon acoustic oscillations. The models under
consideration are consistent with the observations. In addition, we perform the
statefinder and diagnostics, and show that the models exhibit a
distinctive behavior due to the phantom characteristic in future which is a
generic feature of the underlying scenario.Comment: 15 pages, 5 figure
A Langevin analysis of fundamental noise limits in Coherent Anti-Stokes Raman Spectroscopy
We use a Langevin approach to analyze the quantum noise in Coherent
Anti-Stokes Raman Spectroscopy (CARS) in several experimental scenarios: with
continuous wave input fields acting simultaneously and with fast sequential
pulsed lasers where one field scatters off the coherence generated by other
fields; and for interactions within a cavity and in free space. In all the
cases, the signal as well as the quantum noise due to spontaneous decay and
decoherence in the medium are shown to be described by the same general
expression. Our theory in particular shows that for short interaction times,
the medium noise is not important and the efficiency is limited only by the
intrinsic quantum nature of the photon. We obtain fully analytic results
\emph{without} making an adiabatic approximation, the fluctuations of the
medium and the fields are self solved consistently.Comment: 12 pages, 1 figur
Off Resonant Pumping for Transition from Continuous to Discrete Spectrum and Quantum Revivals in Systems in Coherent States
We show that in parametrically driven systems and, more generally, in systems
in coherent states, off-resonant pumping can cause a transition from a
continuum energy spectrum of the system to a discrete one, and result in
quantum revivals of the initial state. The mechanism responsible for quantum
revivals in the present case is different from that in the non-linear
wavepacket dynamics of systems such as Rydberg atoms. We interpret the reported
phenomena as an optical analog of Bloch oscillations realized in Fock space and
propose a feasible scheme for inducing Bloch oscillations in trapped ions.Comment: 5 pages, 4 figures, submitted to Jnl. of Optics
DC field induced enhancement and inhibition of spontaneous emission in a cavity
We demonstrate how spontaneous emission in a cavity can be controlled by the
application of a dc field. The method is specially suitable for Rydberg atoms.
We present a simple argument for the control of emission.Comment: 3-pages, 2figure. accepted in Phys. Rev.
Origin of the anomalous magnetic circular dichroism spectral shape in ferromagnetic (Ga,Mn)As: Impurity bands inside the band gap
The electronic structure of a prototype dilute magnetic semiconductor (DMS),
Ga1-xMnxAs, is studied by magnetic circular dichroism (MCD) spectroscopy. We
prove that the optical transitions originated from impurity bands cause the
strong positive MCD background. The MCD signal due to the E0 transition from
the valence band to the conduction band is negative indicating that the p-d
exchange interactions between the p-carriers and d-spin is antiferromagnetic.
The negative E0 MCD signal also indicates that the hole-doping of the valence
band is not so large as previously assumed. The impurity bands seem to play
important roles for the ferromagnetism of Ga1-xMnxAs.Comment: 13 pages, 3 figure
Evaluation of Labeling Strategies for Rotating Maps
We consider the following problem of labeling points in a dynamic map that
allows rotation. We are given a set of points in the plane labeled by a set of
mutually disjoint labels, where each label is an axis-aligned rectangle
attached with one corner to its respective point. We require that each label
remains horizontally aligned during the map rotation and our goal is to find a
set of mutually non-overlapping active labels for every rotation angle so that the number of active labels over a full map rotation of
2 is maximized. We discuss and experimentally evaluate several labeling
models that define additional consistency constraints on label activities in
order to reduce flickering effects during monotone map rotation. We introduce
three heuristic algorithms and compare them experimentally to an existing
approximation algorithm and exact solutions obtained from an integer linear
program. Our results show that on the one hand low flickering can be achieved
at the expense of only a small reduction in the objective value, and that on
the other hand the proposed heuristics achieve a high labeling quality
significantly faster than the other methods.Comment: 16 pages, extended version of a SEA 2014 pape
Analysis of MAGSAT data of the Indian region
Progress in the development of software for reading MAGSAT data tapes and for the reduction of anomaly data, and in the preparation of data for magnetic anomaly maps is reported
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