1,165 research outputs found
Bell inequality and CP violation in the neutral kaon system
For the entangled neutral kaon system we formulate a Bell inequality
sensitive to CP violation in mixing. Via this Bell inequality we obtain a bound
on the leptonic CP asymmetry which is violated by experimental data.
Furthermore, we connect the Bell inequality with a decoherence approach and
find a lower bound on the decoherence parameter which practically corresponds
to Furry's hypothesis.Comment: 10 pages, latex, no figure
Violation of a Bell inequality in particle physics experimentally verified?
Relevant aspects for testing Bell inequalities with entangled meson-antimeson
systems are analyzed. In particular, we argue that the result of A. Go, J. Mod.
Optics 51, 991 (2004), which nicely illustrate the quantum entanglement of
B-meson pairs, cannot be considered as a Bell-test refuting local realism.Comment: 9 page
A Bethe-Salpeter model for light mesons: spectra and decays
The spectra and electroweak decay properties of light mesons are analyzed
within the framework of the instantaneous Bethe-Salpeter equation. The
interaction kernel comprises alternative spin-structures for a parameterization
of confinement and a residual quark-antiquark interaction based on instanton
effects. It is shown that only with a vector confinement the parameters can be
chosen such as to yield an excellent description of the light pseudoscalar and
vector mesons including weak and two photon decays. However it is found that it
is not possible to reconcile this with the Regge behavior of higher lying meson
states with the same parameter set.Comment: 12 pages, RevTeX, TK-93-1
Revealing Bell's Nonlocality for Unstable Systems in High Energy Physics
Entanglement and its consequences - in particular the violation of Bell
inequalities, which defies our concepts of realism and locality - have been
proven to play key roles in Nature by many experiments for various quantum
systems. Entanglement can also be found in systems not consisting of ordinary
matter and light, i.e. in massive meson--antimeson systems. Bell inequalities
have been discussed for these systems, but up to date no direct experimental
test to conclusively exclude local realism was found. This mainly stems from
the fact that one only has access to a restricted class of observables and that
these systems are also decaying. In this Letter we put forward a Bell
inequality for unstable systems which can be tested at accelerator facilities
with current technology. Herewith, the long awaited proof that such systems at
different energy scales can reveal the sophisticated "dynamical" nonlocal
feature of Nature in a direct experiment gets feasible. Moreover, the role of
entanglement and CP violation, an asymmetry between matter and antimatter, is
explored, a special feature offered only by these meson-antimeson systems.Comment: 6 pages, 3 figure
Multipartite entangled states in coupled quantum dots and cavity-QED
We investigate the generation of multipartite entangled state in a system of
N quantum dots embedded in a microcavity and examine the emergence of genuine
multipartite entanglement by three different characterizations of entanglement.
At certain times of dynamical evolution one can generate multipartite entangled
coherent exciton states or multiqubit states by initially preparing the
cavity field in a superposition of coherent states or the Fock state with one
photon, respectively. Finally we study environmental effects on multipartite
entanglement generation and find that the decay rate for the entanglement is
proportional to the number of excitons.Comment: 9 pages, 4 figures, to appear in Phys. Rev.
Bell-inequality violation with "thermal" radiation
The model of a quantum-optical device for a conditional preparation of
entangled states from input mixed states is presented. It is demonstrated that
even thermal or pseudo-thermal radiation can be entangled in such a way, that
Bell-inequalities are violated
A 15.7-minAMâCVn binary discovered in K2
We present the discovery of SDSSâJ135154.46â064309.0, a short-period variable observed using 30-mincadence photometry in K2 Campaign 6. Follow-up spectroscopy and high-speed photometry support a classification as a new member of the rare class of ultracompact accreting binaries known as AMâCVn stars. The spectroscopic orbital period of 15.65 ± 0.12âmin makes this system the fourth-shortest-period AMâCVn known, and the second system of this type to be discovered by the Kepler spacecraft. The K2 data show photometric periods at 15.7306 ± 0.0003âmin, 16.1121 ± 0.0004âmin, and 664.82 ± 0.06âmin, which we identify as the orbital period, superhump period, and disc precession period, respectively. From the superhump and orbital periods we estimate the binary mass ratio q = M2/M1= 0.111 ± 0.005, though this method of mass ratio determination may not be well calibrated for helium-dominated binaries. This system is likely to be a bright foreground source of gravitational waves in the frequency range detectable by Laser Interferometer Space Antenna, and may be of use as a calibration source if future studies are able to constrain the masses of its stellar components
The Similarity Hypothesis in General Relativity
Self-similar models are important in general relativity and other fundamental
theories. In this paper we shall discuss the ``similarity hypothesis'', which
asserts that under a variety of physical circumstances solutions of these
theories will naturally evolve to a self-similar form. We will find there is
good evidence for this in the context of both spatially homogenous and
inhomogeneous cosmological models, although in some cases the self-similar
model is only an intermediate attractor. There are also a wide variety of
situations, including critical pheneomena, in which spherically symmetric
models tend towards self-similarity. However, this does not happen in all cases
and it is it is important to understand the prerequisites for the conjecture.Comment: to be submitted to Gen. Rel. Gra
Charged cosmic strings interacting with gravitational and electromagnetic waves
Under a particular choice of the Ernst potential, we solve analytically the
Einstein-Maxwell equations to derive a new exact solution depending on five
parameters: the mass, the angular-momentum (per unit mass), the
electromagnetic-field strength, k, the parameter-p and the Kerr-NUT parameter,
l. This (Petrov Type D) solution is cylindrically-symmetric and represents the
curved background around a charged, rotating cosmic string, surrounded by
gravitational and electromagnetic waves, under the influence of the Kerr-NUT
parameter. A C-energy study in the radiation zone suggests that both the
incoming and the outgoing radiation is gravitational, strongly focused around
the null direction and preserving its profile. In this case, the absence of the
k-parameter from the C-energy implies that, away from the linear defect the
electromagnetic field is too weak to contribute to the energy-content of the
cylindrically-symmetric space-time under consideration. In order to explain
this result, we have evaluated the Weyl and the Maxwell scalars near the axis
of the linear defect and at the spatial infinity. Accordingly, we have found
that the electromagnetic field is concentrated (mainly) in the vicinity of the
axis, while falling-off prominently at large radial distances. However, as long
as k differs from unity, the non-zero Kerr-NUT parameter enhances those
scalars, both near the axis and at the spatial infinity, introducing some sort
of gravitomagnetic contribution.Comment: 18 pages, Springer_Latex, accepted for publication in General
Relativity and Gravitatio
Black Hole Spin via Continuum Fitting and the Role of Spin in Powering Transient Jets
The spins of ten stellar black holes have been measured using the
continuum-fitting method. These black holes are located in two distinct classes
of X-ray binary systems, one that is persistently X-ray bright and another that
is transient. Both the persistent and transient black holes remain for long
periods in a state where their spectra are dominated by a thermal accretion
disk component. The spin of a black hole of known mass and distance can be
measured by fitting this thermal continuum spectrum to the thin-disk model of
Novikov and Thorne; the key fit parameter is the radius of the inner edge of
the black hole's accretion disk. Strong observational and theoretical evidence
links the inner-disk radius to the radius of the innermost stable circular
orbit, which is trivially related to the dimensionless spin parameter a_* of
the black hole (|a_*| < 1). The ten spins that have so far been measured by
this continuum-fitting method range widely from a_* \approx 0 to a_* > 0.95.
The robustness of the method is demonstrated by the dozens or hundreds of
independent and consistent measurements of spin that have been obtained for
several black holes, and through careful consideration of many sources of
systematic error. Among the results discussed is a dichotomy between the
transient and persistent black holes; the latter have higher spins and larger
masses. Also discussed is recently discovered evidence in the transient sources
for a correlation between the power of ballistic jets and black hole spin.Comment: 30 pages. Accepted for publication in Space Science Reviews. Also to
appear in hard cover in the Space Sciences Series of ISSI "The Physics of
Accretion onto Black Holes" (Springer Publisher). Changes to Sections 5.2,
6.1 and 7.4. Section 7.4 responds to Russell et al. 2013 (MNRAS, 431, 405)
who find no evidence for a correlation between the power of ballistic jets
and black hole spi
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