61,403 research outputs found
Inertial frame rotation induced by rotating gravitational waves
We calculate the rotation of the inertial frames within an almost flat
cylindrical region surrounded by a pulse of non-axially-symmetric gravitational
waves that rotate about the axis of our cylindrical polar coordinates. Our
spacetime has only one Killing vector. It is along the z-axis and hypersurface
orthogonal. We solve the Einstein equations to first order in the wave
amplitude and superpose such linearized solutions to form a wave pulse. We then
solve the relevant Einstein equation to second order in the amplitude to find
the rotation of inertial frames produced by the pulse. The rotation is without
time delay. The influence of gravitational wave angular momentum on the
inertial frame demonstrates that Mach's principle can not be expressed in terms
of the influence of the stress-energy-momentum tensor alone but must involve
also influences of gravitational wave energy and angular momentum.Comment: Scheduled to appear in Class. and Quantum Grav. July 2008, "inertial"
added in titl
On Fast Linear Gravitational Dragging
A new formula is given for the fast linear gravitational dragging of the
inertial frame within a rapidly accelerated spherical shell of deep potential.
The shell is charged and is electrically accelerated by an electric field whose
sources are included in the solution.Comment: 4 pages, 1 figur
Causal Quantum Theory and the Collapse Locality Loophole
Causal quantum theory is an umbrella term for ordinary quantum theory
modified by two hypotheses: state vector reduction is a well-defined process,
and strict local causality applies. The first of these holds in some versions
of Copenhagen quantum theory and need not necessarily imply practically
testable deviations from ordinary quantum theory. The second implies that
measurement events which are spacelike separated have no non-local
correlations. To test this prediction, which sharply differs from standard
quantum theory, requires a precise theory of state vector reduction.
Formally speaking, any precise version of causal quantum theory defines a
local hidden variable theory. However, causal quantum theory is most naturally
seen as a variant of standard quantum theory. For that reason it seems a more
serious rival to standard quantum theory than local hidden variable models
relying on the locality or detector efficiency loopholes.
Some plausible versions of causal quantum theory are not refuted by any Bell
experiments to date, nor is it obvious that they are inconsistent with other
experiments. They evade refutation via a neglected loophole in Bell experiments
-- the {\it collapse locality loophole} -- which exists because of the possible
time lag between a particle entering a measuring device and a collapse taking
place. Fairly definitive tests of causal versus standard quantum theory could
be made by observing entangled particles separated by light
seconds.Comment: Discussion expanded; typos corrected; references adde
Bell nonlocality, signal locality and unpredictability (or What Bohr could have told Einstein at Solvay had he known about Bell experiments)
The 1964 theorem of John Bell shows that no model that reproduces the
predictions of quantum mechanics can simultaneously satisfy the assumptions of
locality and determinism. On the other hand, the assumptions of \emph{signal
locality} plus \emph{predictability} are also sufficient to derive Bell
inequalities. This simple theorem, previously noted but published only
relatively recently by Masanes, Acin and Gisin, has fundamental implications
not entirely appreciated. Firstly, nothing can be concluded about the
ontological assumptions of locality or determinism independently of each other
-- it is possible to reproduce quantum mechanics with deterministic models that
violate locality as well as indeterministic models that satisfy locality. On
the other hand, the operational assumption of signal locality is an empirically
testable (and well-tested) consequence of relativity. Thus Bell inequality
violations imply that we can trust that some events are fundamentally
\emph{unpredictable}, even if we cannot trust that they are indeterministic.
This result grounds the quantum-mechanical prohibition of arbitrarily accurate
predictions on the assumption of no superluminal signalling, regardless of any
postulates of quantum mechanics. It also sheds a new light on an early stage of
the historical debate between Einstein and Bohr.Comment: Substantially modified version; added HMW as co-autho
Charting the evolution of the ages and metallicities of massive galaxies since z=0.7
The stellar populations of intermediate-redshift galaxies can shed light onto
the growth of massive galaxies in the last 8 billion years. We perform deep,
multi-object rest-frame optical spectroscopy with IMACS/Magellan of ~70
galaxies in the E-CDFS with redshift 0.6522.7 and
stellar mass >10^{10}Msun. Following the Bayesian approach adopted for previous
low-redshift studies, we constrain the stellar mass, mean stellar age and
stellar metallicity of individual galaxies from stellar absorption features. We
characterize for the first time the dependence of stellar metallicity and age
on stellar mass at z~0.7 for all galaxies and for quiescent and star-forming
galaxies separately. These relations for the whole sample have a similar shape
as the z=0.1 SDSS analog, but are shifted by -0.28 dex in age and by -0.13 dex
in metallicity, at odds with simple passive evolution. We find that no
additional star formation and chemical enrichment are required for z=0.7
quiescent galaxies to evolve into the present-day quiescent population.
However, this must be accompanied by the quenching of a fraction of z=0.7
Mstar>10^{11}Msun star-forming galaxies with metallicities comparable to those
of quiescent galaxies, thus increasing the scatter in age without affecting the
metallicity distribution. However rapid quenching of the entire population of
massive star-forming galaxies at z=0.7 would be inconsistent with the
age/metallicity--mass relation for the population as a whole and with the
metallicity distribution of star-forming galaxies only, which are on average
0.12 dex less metal-rich than their local counterparts. This indicates chemical
enrichment until the present in at least a fraction of the z=0.7 massive
star-forming galaxies.[abridged]Comment: accepted for publication on ApJ, 26 pages, 13 figure
Electromagnetic Magic: The Relativistically Rotating Disk
A closed form analytic solution is found for the electromagnetic field of the
charged uniformly rotating conducting disk for all values of the tip speed
up to . For it becomes the Magic field of the Kerr-Newman black hole
with set to zero.
The field energy, field angular momentum and gyromagnetic ratio are
calculated and compared with those of the electron.
A new mathematical expression that sums products of 3 Legendre functions each
of a different argument, is demonstrated.Comment: 10 pages, one figur
Stronger two-observer all-versus-nothing violation of local realism
We introduce a two-observer all-versus-nothing proof of Bell's theorem which
reduces the number of required quantum predictions from 9 [A. Cabello, Phys.
Rev. Lett. 87, 010403 (2001); Z.-B. Chen et al., Phys. Rev. Lett. 90, 160408
(2003)] to 4, provides a greater amount of evidence against local realism,
reduces the detection efficiency requirements for a conclusive experimental
test of Bell's theorem, and leads to a Bell's inequality which resembles
Mermin's inequality for three observers [N. D. Mermin, Phys. Rev. Lett. 65,
1838 (1990)] but requires only two observers.Comment: REVTeX4, 5 page
Bell's inequality and the coincidence-time loophole
This paper analyzes effects of time-dependence in the Bell inequality. A
generalized inequality is derived for the case when coincidence and
non-coincidence [and hence whether or not a pair contributes to the actual
data] is controlled by timing that depends on the detector settings. Needless
to say, this inequality is violated by quantum mechanics and could be violated
by experimental data provided that the loss of measurement pairs through
failure of coincidence is small enough, but the quantitative bound is more
restrictive in this case than in the previously analyzed "efficiency loophole."Comment: revtex4, 3 figures, v2: epl document class, reformatted w slight
change
From Einstein's Theorem to Bell's Theorem: A History of Quantum Nonlocality
In this Einstein Year of Physics it seems appropriate to look at an important
aspect of Einstein's work that is often down-played: his contribution to the
debate on the interpretation of quantum mechanics. Contrary to popular opinion,
Bohr had no defence against Einstein's 1935 attack (the EPR paper) on the
claimed completeness of orthodox quantum mechanics. I suggest that Einstein's
argument, as stated most clearly in 1946, could justly be called Einstein's
reality-locality-completeness theorem, since it proves that one of these three
must be false. Einstein's instinct was that completeness of orthodox quantum
mechanics was the falsehood, but he failed in his quest to find a more complete
theory that respected reality and locality. Einstein's theorem, and possibly
Einstein's failure, inspired John Bell in 1964 to prove his reality-locality
theorem. This strengthened Einstein's theorem (but showed the futility of his
quest) by demonstrating that either reality or locality is a falsehood. This
revealed the full nonlocality of the quantum world for the first time.Comment: 18 pages. To be published in Contemporary Physics. (Minor changes;
references and author info added
Pseudo-Dirac Neutrino Scenario: Cosmic Neutrinos at Neutrino Telescopes
Within the "pseudo-Dirac" scenario for massive neutrinos the existence of
sterile neutrinos which are almost degenerate in mass with the active ones is
hypothesized. The presence of these sterile neutrinos can affect the flavor
composition of cosmic neutrinos arriving at Earth after traveling large
distances from astrophysical objects. We examine the prospects of neutrino
telescopes such as IceCube to probe the very tiny mass squared differences
10^(-12) eV^2<\Delta m^2<10^(-19) eV^2, by analyzing the ratio of -track
events to shower-like events. Considering various sources of uncertainties
which enter this analysis, we examine the capability of neutrino telescopes to
verify the validity of the pseudo-Dirac neutrino scenario and especially to
discriminate it from the conventional scenario with no sterile neutrino. We
also discuss the robustness of our results with respect to the uncertainties in
the initial flavor ratio of neutrinos at the source.Comment: 24 pages, 5 figure
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