1,686 research outputs found
Measuring measurement--disturbance relationships with weak values
Using formal definitions for measurement precision {\epsilon} and disturbance
(measurement backaction) {\eta}, Ozawa [Phys. Rev. A 67, 042105 (2003)] has
shown that Heisenberg's claimed relation between these quantities is false in
general. Here we show that the quantities introduced by Ozawa can be determined
experimentally, using no prior knowledge of the measurement under investigation
--- both quantities correspond to the root-mean-squared difference given by a
weak-valued probability distribution. We propose a simple three-qubit
experiment which would illustrate the failure of Heisenberg's
measurement--disturbance relation, and the validity of an alternative relation
proposed by Ozawa
Kinetic energy driven superconductivity, the origin of the Meissner effect, and the reductionist frontier
Is superconductivity associated with a lowering or an increase of the kinetic
energy of the charge carriers? Conventional BCS theory predicts that the
kinetic energy of carriers increases in the transition from the normal to the
superconducting state. However, substantial experimental evidence obtained in
recent years indicates that in at least some superconductors the opposite
occurs. Motivated in part by these experiments many novel mechanisms of
superconductivity have recently been proposed where the transition to
superconductivity is associated with a lowering of the kinetic energy of the
carriers. However none of these proposed unconventional mechanisms explores the
fundamental reason for kinetic energy lowering nor its wider implications. Here
I propose that kinetic energy lowering is at the root of the Meissner effect,
the most fundamental property of superconductors. The physics can be understood
at the level of a single electron atom: kinetic energy lowering and enhanced
diamagnetic susceptibility are intimately connected. According to the theory of
hole superconductivity, superconductors expel negative charge from their
interior driven by kinetic energy lowering and in the process expel any
magnetic field lines present in their interior. Associated with this we predict
the existence of a macroscopic electric field in the interior of
superconductors and the existence of macroscopic quantum zero-point motion in
the form of a spin current in the ground state of superconductors (spin
Meissner effect). In turn, the understanding of the role of kinetic energy
lowering in superconductivity suggests a new way to understand the fundamental
origin of kinetic energy lowering in quantum mechanics quite generally
The Evolution of Universe with th B-I Type Phantom Scalar Field
We considered the phantom cosmology with a lagrangian ,
which is original from the nonlinear Born-Infeld type scalar field with the
lagrangian . This cosmological model can explain the
accelerated expansion of the universe with the equation of state parameter
. We get a sufficient condition for a arbitrary potential to admit a
late time attractor solution: the value of potential at the critical
point should be maximum and large than zero. We study a specific
potential with the form of
via phase plane
analysis and compute the cosmological evolution by numerical analysis in
detail. The result shows that the phantom field survive till today (to account
for the observed late time accelerated expansion) without interfering with the
nucleosynthesis of the standard model(the density parameter
at the equipartition epoch), and also avoid the
future collapse of the universe.Comment: 17 pages, 10 figures,typos corrected, references added,figures added
and enriched, title changed, main result remaine
Weak value of Dwell time for Quantum Dissipative spin-1/2 System
The dwell time is calculated within the framework of time dependent weak
measurement considering dissipative interaction between a spin half system and
the environment. Caldirola and Montaldi's method of retarded Schroedinger
equation is used to study the dissipative system. The result shows that
inclusion of dissipative interaction prevents zero time tunneling.Comment: This work is original. arXiv admin note: text overlap with
arXiv:0807.1357, arXiv:quant-ph/9611018, arXiv:quant-ph/9501015 by other
author
Cosmology in Nonlinear Born-Infeld Scalar Field Theory With Negative Potentials
The cosmological evolution in Nonlinear Born-Infeld(hereafter NLBI) scalar
field theory with negative potentials was investigated. The cosmological
solutions in some important evolutive epoches were obtained. The different
evolutional behaviors between NLBI and linear(canonical) scalar field theory
have been presented. A notable characteristic is that NLBI scalar field behaves
as ordinary matter nearly the singularity while the linear scalar field behaves
as "stiff" matter. We find that in order to accommodate current observational
accelerating expanding universe the value of potential parameters and
must have an {\it upper bound}. We compare different cosmological
evolutions for different potential parameters .Comment: 18 pages, 18 figures, some references added, revised version for
Int.J.Mod.Phys.A, appeared in Int.J.Mod.Phys.
A double-slit `which-way' experiment on the complementarity--uncertainty debate
A which-way measurement in Young's double-slit will destroy the interference
pattern. Bohr claimed this complementarity between wave- and particle behaviour
is enforced by Heisenberg's uncertainty principle: distinguishing two positions
a distance s apart transfers a random momentum q \sim \hbar/s to the particle.
This claim has been subject to debate: Scully et al. asserted that in some
situations interference can be destroyed with no momentum transfer, while
Storey et al. asserted that Bohr's stance is always valid. We address this
issue using the experimental technique of weak measurement. We measure a
distribution for q that spreads well beyond [-\hbar/s, \hbar/s], but
nevertheless has a variance consistent with zero. This weakvalued
momentum-transfer distribution P_{wv}(q) thus reflects both sides of the
debate.Comment: 13 pages, 4 figure
Fractal Characterizations of MAX Statistical Distribution in Genetic Association Studies
Two non-integer parameters are defined for MAX statistics, which are maxima
of simpler test statistics. The first parameter, , is the
fractional number of tests, representing the equivalent numbers of independent
tests in MAX. If the tests are dependent, . The second
parameter is the fractional degrees of freedom of the chi-square
distribution that fits the MAX null distribution. These two
parameters, and , can be independently defined, and can be
non-integer even if is an integer. We illustrate these two parameters
using the example of MAX2 and MAX3 statistics in genetic case-control studies.
We speculate that is related to the amount of ambiguity of the model
inferred by the test. In the case-control genetic association, tests with low
(e.g. ) are able to provide definitive information about the disease
model, as versus tests with high (e.g. ) that are completely uncertain
about the disease model. Similar to Heisenberg's uncertain principle, the
ability to infer disease model and the ability to detect significant
association may not be simultaneously optimized, and seems to measure the
level of their balance
A Comparison of Quintessence and Nonlinear Born-Infeld Scalar Field Using Gold Supernova data
We study the Non-Linear Born-Infeld(NLBI) scalar field model and quintessence
model with two different potentials( and ). We
investigate the differences between those two models. We explore the equation
of state parameter w and the evolution of scale factor in both NLBI
scalar field and quintessence model. The present age of universe and the
transition redshift are also obtained. We use the Gold dataset of 157 SN-Ia to
constrain the parameters of the two models. All the results show that NLBI
model is slightly superior to quintessence model.Comment: 17 pages, 10 figures, some references adde
Ground state correlations and mean-field in O: Part II
We continue the investigations of the O ground state using the
coupled-cluster expansion [] method with realistic nuclear
interaction. In this stage of the project, we take into account the three
nucleon interaction, and examine in some detail the definition of the internal
Hamiltonian, thus trying to correct for the center-of-mass motion. We show that
this may result in a better separation of the internal and center-of-mass
degrees of freedom in the many-body nuclear wave function. The resulting ground
state wave function is used to calculate the "theoretical" charge form factor
and charge density. Using the "theoretical" charge density, we generate the
charge form factor in the DWBA picture, which is then compared with the
available experimental data. The longitudinal response function in inclusive
electron scattering for O is also computed.Comment: 9 pages, 7 figure
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