582 research outputs found
Truly unentangled photon pairs without spectral filtering
We demonstrate that an integrated silicon microring resonator is capable of
efficiently producing photon pairs that are completely unentangled; such pairs
are a key component of heralded single photon sources. A dual-channel
interferometric coupling scheme can be used to independently tune the quality
factors associated with the pump and signal and idler modes, yielding a
biphoton wavefunction with Schmidt number arbitrarily close to unity. This will
permit the generation of heralded single photon states with unit purity.Comment: 5 pages, 3 figure
Homothetic Wyman Spacetimes
The time-dependent, spherically symmetric, Wyman sector of the Unified Field
Theory is shown to be equivalent to a self-gravitating scalar field with a
positive-definite, repulsive self-interaction potential. A homothetic symmetry
is imposed on the fundamental tensor, and the resulting autonomous system is
numerically integrated. Near the critical point (between the collapsing and
non-collapsing spacetimes) the system displays an approximately periodic
alternation between collapsing and dispersive epochs.Comment: 15 pages with 6 figures; requires amsart, amssymb, amsmath, graphicx;
formatted for publication in Int. J. Mod. Phys.
Geodesic and Path Motion in the Nonsymmetric Gravitational Theory
We study the problem of test-particle motion in the Nonsymmetric
Gravitational Theory (NGT) assuming the four-velocity of the particle is
parallel-transported along the trajectory. The predicted motion is studied on a
static, spherically symmetric background field, with particular attention paid
to radial and circular motions. Interestingly, it is found that the proper time
taken to travel between any two non-zero radial positions is finite. It is also
found that circular orbits can be supported at lower radii than in General
Relativity for certain forms of motion.
We present three interactions which could be used as alternate methods for
coupling a test-particle to the antisymmetric components of the NGT field. One
of these takes the form of a Yukawa force in the weak-field limit of a static,
spherically symmetric field, which could lead to interesting phenomenology.Comment: 17 pages, REVTeX 3.0 with amssymb.st
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Real-world heart rate norms in the Health eHeart study.
Emerging technology allows patients to measure and record their heart rate (HR) remotely by photoplethysmography (PPG) using smart devices like smartphones. However, the validity and expected distribution of such measurements are unclear, making it difficult for physicians to help patients interpret real-world, remote and on-demand HR measurements. Our goal was to validate HR-PPG, measured using a smartphone app, against HR-electrocardiogram (ECG) measurements and describe out-of-clinic, real-world, HR-PPG values according to age, demographics, body mass index, physical activity level, and disease. To validate the measurements, we obtained simultaneous HR-PPG and HR-ECG in 50 consecutive patients at our cardiology clinic. We then used data from participants enrolled in the Health eHeart cohort between 1 April 2014 and 30 April 2018 to derive real-world norms of HR-PPG according to demographics and medical conditions. HR-PPG and HR-ECG were highly correlated (Intraclass correlationâ=â0.90). A total of 66,788 Health eHeart Study participants contributed 3,144,332 HR-PPG measurements. The mean real-world HR was 79.1 bpmâ±â14.5. The 95th percentile of real-world HR was â€110 in individuals aged 18-45, â€100 in those aged 45-60 and â€95 bpm in individuals older than 60 years old. In multivariable linear regression, the number of medical conditions, female gender, increasing body mass index, and being Hispanic was associated with an increased HR, whereas increasing age was associated with a reduced HR. Our study provides the largest real-world norms for remotely obtained, real-world HR according to various strata and they may help physicians interpret and engage with patients presenting such data
The Dynamical Instability of Static, Spherically Symmetric Solutions in Nonsymmetric Gravitational Theories
We consider the dynamical stability of a class of static,
spherically-symmetric solutions of the nonsymmetric gravitational theory. We
numerically reproduce the Wyman solution and generate new solutions for the
case where the theory has a nontrivial fundamental length scale \mu^{-1}. By
considering spherically symmetric perturbations of these solutions we show that
the Wyman solutions are generically unstable.Comment: 13 pages, uses amslatex, graphicx and subfigure package
Unconditional remote entanglement using second-harmonic generation and twin two-mode squeezed vacuum states
We propose a photonics-based, continuous-variable (CV) form of remote
entanglement utilizing strictly second-order nonlinear optical interactions
that does not require the implementation of a state-projective measurement
(i.e. remote entanglement without conditioning). This scheme makes use of two
separate down-converters, wherein the corresponding nonlinear crystals are
driven by strong classical fields as prescribed by the parametric
approximation, as well as a fully quantum mechanical model of nondegenerate
second harmonic generation (SHG) whose evolution is described by the trilinear
Hamiltonian of the form . By driving the SHG process
with the signal modes of the two down-converters, we show entanglement
formation between the generated second-harmonic mode (SH-mode) and the
non-interacting joint-idler subsystem without the need for any state-reductive
measurements on the interacting modes
Osservazioni distributive e cariologiche su Sternbergia colchiciflora Waldt. et Kit. (Amaryllidaceae) nel Parco Nazionale del Pollino
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