2,598 research outputs found
Remarks on a Proposed Super-Kamiokande Test for Quantum Gravity Induced Decoherence Effects
Lisi, Marrone, and Montanino have recently proposed a test for quantum
gravity induced decoherence effects in neutrino oscillations observed at
Super-Kamiokande. We comment here that their equations have the same
qualitative form as the energy conserving objective state vector reduction
equations discussed by a number of authors. However, using the Planckian
parameter value proposed to explain state vector reduction leads to a neutrino
oscillation effect many orders of magnitude smaller than would be detectable at
Super-Kamiokande. Similar estimates hold for the Ghirardi, Rimini, and Weber
spontaneous localization approach to state vector reduction, and our remarks
are relevant as well to proposed meson and meson tests of gravity
induced decoherence.Comment: 10 pages, plain Tex, no figure
Problems and Aspects of Energy-Driven Wavefunction Collapse Models
Four problematic circumstances are considered, involving models which
describe dynamical wavefunction collapse toward energy eigenstates, for which
it is shown that wavefunction collapse of macroscopic objects does not work
properly. In one case, a common particle position measuring situation, the
apparatus evolves to a superposition of macroscopically distinguishable states
(does not collapse to one of them as it should) because each such
particle/apparatus/environment state has precisely the same energy spectrum.
Second, assuming an experiment takes place involving collapse to one of two
possible outcomes which is permanently recorded, it is shown in general that
this can only happen in the unlikely case that the two apparatus states
corresponding to the two outcomes have disjoint energy spectra. Next, the
progressive narrowing of the energy spectrum due to the collapse mechanism is
considered. This has the effect of broadening the time evolution of objects as
the universe evolves. Two examples, one involving a precessing spin, the other
involving creation of an excited state followed by its decay, are presented in
the form of paradoxes. In both examples, the microscopic behavior predicted by
standard quantum theory is significantly altered under energy-driven collapse,
but this alteration is not observed by an apparatus when it is included in the
quantum description. The resolution involves recognition that the statevector
describing the apparatus does not collapse, but evolves to a superposition of
macroscopically different states.Comment: 17 page
Non-Markovian quantum state diffusion for absorption spectra of molecular aggregates
In many molecular systems one encounters the situation where electronic
excitations couple to a quasi-continuum of phonon modes. That continuum may be
highly structured e.g. due to some weakly damped high frequency modes. To
handle such a situation, an approach combining the non-Markovian quantum state
diffusion (NMQSD) description of open quantum systems with an efficient but
abstract approximation was recently applied to calculate energy transfer and
absorption spectra of molecular aggregates [Roden, Eisfeld, Wolff, Strunz, PRL
103 (2009) 058301]. To explore the validity of the used approximation for such
complicated systems, in the present work we compare the calculated
(approximative) absorption spectra with exact results. These are obtained from
the method of pseudomodes, which we show to be capable of determining the exact
spectra for small aggregates and a few pseudomodes. It turns out that in the
cases considered, the results of the two approaches mostly agree quite well.
The advantages and disadvantages of the two approaches are discussed
Optical discrimination between spatial decoherence and thermalization of a massive object
We propose an optical ring interferometer to observe environment-induced
spatial decoherence of massive objects. The object is held in a harmonic trap
and scatters light between degenerate modes of a ring cavity. The output signal
of the interferometer permits to monitor the spatial width of the object's wave
function. It shows oscillations that arise from coherences between energy
eigenstates and that reveal the difference between pure spatial decoherence and
that coinciding with energy transfer and heating. Our method is designed to
work with a wide variety of masses, ranging from the atomic scale to
nano-fabricated structures. We give a thorough discussion of its experimental
feasibility.Comment: 2 figure
Pasture top-dressing in New Hampshire, Bulletin, no. 320
The Bulletin is a publication of the New Hampshire Agricultural Experiment Station, College of Life Sciences and Agriculture, University of New Hampshire, Durham, New Hampshire
Spontaneous Collapse of Unstable Quantum Superposition State: A Single-Particle Model of Modified Quantum Dynamics
We propose a modified dynamics of quantum mechanics, in which classical
mechanics of a point mass derives intrinsically in a massive limit of a
single-particle model. On the premise that a position basis plays a special
role in wavefunction collapse, we deduce to formalize spontaneous localization
of wavefunction on the analogy drawn from thermodynamics, in which a
characteristic energy scale and a time scale are introduced to separate quantum
and classical regimes.Comment: 2figs., contribution to Xth ICQO 200
Cobalt deficiency in New Hampshire cattle, sheep, and goats, Station Bulletin, no.411
The Bulletin is a publication of the New Hampshire Agricultural Experiment Station, College of Life Sciences and Agriculture, University of New Hampshire, Durham, New Hampshire
Generalized stochastic Schroedinger equations for state vector collapse
A number of authors have proposed stochastic versions of the Schr\"odinger
equation, either as effective evolution equations for open quantum systems or
as alternative theories with an intrinsic collapse mechanism. We discuss here
two directions for generalization of these equations. First, we study a general
class of norm preserving stochastic evolution equations, and show that even
after making several specializations, there is an infinity of possible
stochastic Schr\"odinger equations for which state vector collapse is provable.
Second, we explore the problem of formulating a relativistic stochastic
Schr\"odinger equation, using a manifestly covariant equation for a quantum
field system based on the interaction picture of Tomonaga and Schwinger. The
stochastic noise term in this equation can couple to any local scalar density
that commutes with the interaction energy density, and leads to collapse onto
spatially localized eigenstates. However, as found in a similar model by
Pearle, the equation predicts an infinite rate of energy nonconservation
proportional to , arising from the local double commutator in
the drift term.Comment: 24 pages Plain TeX. Minor changes, some new references. To appear in
Journal of Physics
Self-Referential Noise and the Synthesis of Three-Dimensional Space
Generalising results from Godel and Chaitin in mathematics suggests that
self-referential systems contain intrinsic randomness. We argue that this is
relevant to modelling the universe and show how three-dimensional space may
arise from a non-geometric order-disorder model driven by self-referential
noise.Comment: Figure labels correcte
Quantum noise and stochastic reduction
In standard nonrelativistic quantum mechanics the expectation of the energy
is a conserved quantity. It is possible to extend the dynamical law associated
with the evolution of a quantum state consistently to include a nonlinear
stochastic component, while respecting the conservation law. According to the
dynamics thus obtained, referred to as the energy-based stochastic Schrodinger
equation, an arbitrary initial state collapses spontaneously to one of the
energy eigenstates, thus describing the phenomenon of quantum state reduction.
In this article, two such models are investigated: one that achieves state
reduction in infinite time, and the other in finite time. The properties of the
associated energy expectation process and the energy variance process are
worked out in detail. By use of a novel application of a nonlinear filtering
method, closed-form solutions--algebraic in character and involving no
integration--are obtained for both these models. In each case, the solution is
expressed in terms of a random variable representing the terminal energy of the
system, and an independent noise process. With these solutions at hand it is
possible to simulate explicitly the dynamics of the quantum states of
complicated physical systems.Comment: 50 page
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