6,945 research outputs found
Triple solutions for the one-dimensional p-Laplacian
We give conditions on f involving pairs of lower and upper solutions which lead to the existence of at least three solutions to the two point boundary value problem
(|u\u27|p -2 u\u27) = q(t) f(t,u,u\u27) on (0,1), u(0) = u(1) = 0
Oscillation of higher order difference equations via comparison
In this paper we shall present some new oscillation criteria for difference equations of the form
x(n) + q(n)f(x[n - ]) = 0
and
x(n) = q(t)f(x[n - ]) + p(n)F(x[n + ])
via comparison with some difference equations of lower order whose oscillatory behavior are known
A Fresh Approach to the Study of Atmosphere Turbidity
The problem of assessment of atmospheric turbidity caused by aerosol particles, viz., dust, smoke, haze, and other atmospheric pollutants, apart from the effect of variable water vapour content of the atmosphere, has been studied afresh. The basic concept underlying Linke's turbidity factor, T has been found to be theoretically sound, although its quantitative formulation suffers from one major defect, viz, its 'virtual variation' with air mass. This error has been traced to defective formulation of the quantitative expression for T. A 'Rational turbidity factor', Tr, has been proposed which is likely to overcome the limitations of Linke's turbidity factor, T. A nomogram has been development for quick evaluation of Tr, and the effect of altitude has also been considered
Topological transitions in dissipatively coupled Su-Schrieffer-Heeger models
Non-Hermitian topological phenomena have gained much interest among
physicists in recent years. In this paper, we expound on the physics of
dissipatively coupled Su-Schrieffer-Heeger (SSH) lattices, specifically in
systems with bosonic and electrical constituents. In the context of electrical
circuits, we demonstrate that a series of resistively coupled LCR circuits
mimics the topology of a dissipatively coupled SSH model. In addition, we
foreground a scheme to construct dissipatively coupled SSH lattices involving a
set of non-interacting bosonic oscillators weakly coupled to engineered
reservoirs of modes possessing substantially small lifetimes when compared to
other system timescales. Further, by activating the coherent coupling between
bosonic oscillators, we elucidate the emergence of non-reciprocal dissipative
coupling which can be controlled by the phase of the coherent interaction
strength precipitating in phase-dependent topological transitions and skin
effect. Our analyses are generic, apropos of a large class of systems
involving, for instance, optical and microwave settings, while the circuit
implementation represents the most straightforward of them.Comment: 10 pages, 9 figure
Robust transmission of non-Gaussian entanglement over optical fibers
We show how the entanglement in a wide range of continuous variable
non-Gaussian states can be preserved against decoherence for long-range quantum
communication through an optical fiber. We apply protection via
decoherence-free subspaces and quantum dynamical decoupling to this end. The
latter is implemented by inserting phase shifters at regular intervals inside the fiber, where is roughly the ratio of the speed of light
in the fiber to the bath high-frequency cutoff. Detailed estimates of relevant
parameters are provided using the boson-boson model of system-bath interaction
for silica fibers, and is found to be on the order of a millimeter.Comment: 9 pages, 2 figures, RevTeX4, submitted to PR
Exact time evolution and master equations for the damped harmonic oscillator
Using the exact path integral solution for the damped harmonic oscillator it
is shown that in general there does not exist an exact dissipative Liouville
operator describing the dynamics of the oscillator for arbitrary initial bath
preparations. Exact non-stationary Liouville operators can be found only for
particular preparations. Three physically meaningful examples are examined. An
exact new master equation is derived for thermal initial conditions. Second,
the Liouville operator governing the time-evolution of equilibrium correlations
is obtained. Third, factorizing initial conditions are studied. Additionally,
one can show that there are approximate Liouville operators independent of the
initial preparation describing the long time dynamics under appropriate
conditions. The general form of these approximate master equations is derived
and the coefficients are determined for special cases of the bath spectral
density including the Ohmic, Drude and weak coupling cases. The connection with
earlier work is discussed.Comment: to be published in Phys. Rev.
An analysis of dynamical suppression of spontaneous emission
It has been shown recently [see, for example, S.-Y. Zhu and M. O. Scully,
Phys. Rev. Lett. {\bf 76}, 388 (1996)] that a dynamical suppression of
spontaneous emission can occur in a three-level system when an external field
drives transitions between a metastable state and {\em two} decaying states.
What is unusual in the decay scheme is that the decaying states are coupled
directly by the vacuum radiation field. It is shown that decay dynamics
required for total suppression of spontaneous emission necessarily implies that
the level scheme is isomorphic to a three-level lambda system, in which the
lower two levels are {\em both} metastable, and each is coupled to the decaying
state. As such, the total suppression of spontaneous emission can be explained
in terms of conventional dark states and coherent population trapping.Comment: 8 pages, 3 figure
- …