591 research outputs found
Multiplicity of periodic solutions for systems of weakly coupled parametrized second order differential equations
We prove a multiplicity result of periodic solutions for a system of second order differential equations having asymmetric nonlinearities. The proof is based on a recent generalization of the Poincar\ue9\u2013Birkhoff fixed point theorem provided by Fonda and Ure\uf1a
Exponential behavior of a quantum system in a macroscopic medium
An exponential behavior at all times is derived for a solvable dynamical
model in the weak-coupling, macroscopic limit. Some implications for the
quantum measurement problem are discussed, in particular in connection with
dissipation.Comment: 8 pages, report BA-TH/94-17
Suppression of Zeno effect for distant detectors
We describe the influence of continuous measurement in a decaying system and
the role of the distance from the detector to the initial location of the
system. The detector is modeled first by a step absorbing potential. For a
close and strong detector, the decay rate of the system is reduced; weaker
detectors do not modify the exponential decay rate but suppress the long-time
deviations above a coupling threshold. Nevertheless, these perturbing effects
of measurement disappear by increasing the distance between the initial state
and the detector, as well as by improving the efficiency of the detector.Comment: 4 pages, 4 figure
Quantum Zeno effect in a probed downconversion process
The distorsion of a spontaneous downconvertion process caused by an auxiliary
mode coupled to the idler wave is analyzed. In general, a strong coupling with
the auxiliary mode tends to hinder the downconversion in the nonlinear medium.
On the other hand, provided that the evolution is disturbed by the presence of
a phase mismatch, the coupling may increase the speed of downconversion. These
effects are interpreted as being manifestations of quantum Zeno or anti-Zeno
effects, respectively, and they are understood by using the dressed modes
picture of the device. The possibility of using the coupling as a nontrivial
phase--matching technique is pointed out.Comment: 11 pages, 4 figure
'Sexercise': Working out heterosexuality in Jane Fondaâs fitness books
This is an Author's Accepted Manuscript of an article published in Leisure Studies, 30(2), 237 - 255, 2011, copyright Taylor & Francis, available online at: http://www.tandfonline.com/10.1080/02614367.2010.523837.This paper explores the connection between the promotion of heterosexual norms in womenâs fitness books written by or in the name of Jane Fonda during the 1980s and the commodification of womenâs fitness space in both the public and private spheres. The paper is set in the absence of overt discussions of normative heterosexuality in leisure studies and draws on critical heterosexual scholarship as well as the growing body of work theorising geographies of corporeality and heterosexuality. Using the principles of media discourse analysis, the paper identifies three overlapping characteristics of heterosexuality represented in Jane Fondaâs fitness books, and embodied through the exercise regimes: respectable heterosexual desire, monogamous procreation and domesticity. The paper concludes that the promotion and prescription of exercise for women in the Jane Fonda workout books centred on the reproduction and embodiment of heterosexual corporeality. Set within an emerging commercial landscape of womenâs fitness in the 1980s, such exercise practices were significant in the legitimation and institutionalisation of heteronormativity
Complex Scaled Spectrum Completeness for Coupled Channels
The Complex Scaling Method (CSM) provides scattering wave functions which
regularize resonances and suggest a resolution of the identity in terms of such
resonances, completed by the bound states and a smoothed continuum. But, in the
case of inelastic scattering with many channels, the existence of such a
resolution under complex scaling is still debated. Taking advantage of results
obtained earlier for the two channel case, this paper proposes a representation
in which the convergence of a resolution of the identity can be more easily
tested. The representation is valid for any finite number of coupled channels
for inelastic scattering without rearrangement.Comment: Latex file, 13 pages, 4 eps-figure
The role of initial state reconstruction in short and long time deviations from exponential decay
We consider the role of the reconstruction of the initial state in the
deviation from exponential decay at short and long times. The long time decay
can be attributed to a wave that was, in a classical-like, probabilistic sense,
fully outside the initial state or the inner region at intermediate times,
i.e., to a completely reconstructed state, whereas the decay during the
exponential regime is due instead to a non-reconstructed wave. At short times
quantum interference between regenerated and non-regenerated paths is
responsible for the deviation from the exponential decay. We may thus conclude
that state reconstruction is a ``consistent history'' for long time deviations
but not for short ones.Comment: 4 pages, 6 figure
The various power decays of the survival probability at long times for free quantum particle
The long time behaviour of the survival probability of initial state and its
dependence on the initial states are considered, for the one dimensional free
quantum particle. We derive the asymptotic expansion of the time evolution
operator at long times, in terms of the integral operators. This enables us to
obtain the asymptotic formula for the survival probability of the initial state
, which is assumed to decrease sufficiently rapidly at large .
We then show that the behaviour of the survival probability at long times is
determined by that of the initial state at zero momentum . Indeed,
it is proved that the survival probability can exhibit the various power-decays
like for an arbitrary non-negative integers as ,
corresponding to the initial states with the condition as .Comment: 15 pages, to appear in J. Phys.
The decay law can have an irregular character
Within a well-known decay model describing a particle confined initially
within a spherical potential shell, we consider the situation when the
undecayed state has an unusual energy distribution decaying slowly as
; the simplest example corresponds to a wave function constant
within the shell. We show that the non-decay probability as a function of time
behaves then in a highly irregular, most likely fractal way.Comment: 4 pages, 3 eps figure
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