2,915 research outputs found
The local content of all pure two-qubit states
The (non-)local content in the sense of Elitzur, Popescu, and Rohrlich (EPR2)
[Phys. Lett. A 162, 25 (1992)] is a natural measure for the (non-)locality of
quantum states. Its computation is in general difficult, even in low
dimensions, and is one of the few open questions about pure two-qubit states.
We present a complete solution to this long-lasting problem.Comment: 9 pages, 3 figure
Is Communication Complexity Physical?
Recently, Brassard et. al. conjectured that the fact that the maximal
possible correlations between two non-local parties are the quantum-mechanical
ones is linked to a reasonable restriction on communication complexity. We
provide further support for the conjecture in the multipartite case. We show
that any multipartite communication complexity problem could be reduced to
triviality, had Nature been more non-local than quantum-mechanics by a quite
small gap for any number of parties. Intriguingly, the multipartite
nonlocal-box that we use to show the result corresponds to the generalized Bell
inequality that manifests maximal violation in respect to a local
hidden-variable theory
Jubilee March / music by Samuel Brown; words by Samuel Brown
Cover: four caricature drawings of African Americans, in one, a group, dressed in finery, processes into a ballroom; in another, a group sits around a table eating watermelons; in another, a rural family dances a country dance; the final drawing is of a family preparing food in a kitchen; Publisher: J. R. Bell (Leavenworth)https://egrove.olemiss.edu/sharris_a/1012/thumbnail.jp
Discovery of pulsations, including possible pressure modes, in two new extremely low mass, He-core white dwarfs
We report the discovery of the second and third pulsating extremely low mass
white dwarfs (WDs), SDSS J111215.82+111745.0 (hereafter J1112) and SDSS
J151826.68+065813.2 (hereafter J1518). Both have masses < 0.25 Msun and
effective temperatures below 10,000 K, establishing these putatively He-core
WDs as a cooler class of pulsating hydrogen-atmosphere WDs (DAVs, or ZZ Ceti
stars). The short-period pulsations evidenced in the light curve of J1112 may
also represent the first observation of acoustic (p-mode) pulsations in any WD,
which provide an exciting opportunity to probe this WD in a complimentary way
compared to the long-period g-modes also present. J1112 is a Teff = 9590 +/-
140 K and log(g) = 6.36 +/- 0.06 WD. The star displays sinusoidal variability
at five distinct periodicities between 1792-2855 s. In this star we also see
short-period variability, strongest at 134.3 s, well short of expected g-modes
for such a low-mass WD. The other new pulsating WD, J1518, is a Teff = 9900 +/-
140 K and log(g) = 6.80 +/- 0.05 WD. The light curve of J1518 is highly
non-sinusoidal, with at least seven significant periods between 1335-3848 s.
Consistent with the expectation that ELM WDs must be formed in binaries, these
two new pulsating He-core WDs, in addition to the prototype SDSS
J184037.78+642312.3, have close companions. However, the observed variability
is inconsistent with tidally induced pulsations and is so far best explained by
the same hydrogen partial-ionization driving mechanism at work in classic
C/O-core ZZ Ceti stars.Comment: 9 pages, 5 figures, accepted to The Astrophysical Journa
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Western North Pacific Tropical Cyclone Tracks in CMIP5 Models: Statistical Assessment Using a Model-Independent Detection and Tracking Scheme
Past studies have shown that tropical cyclone (TC) projection results can be sensitive to different types of TC tracking schemes, and that the relative adjustments of detection criteria to accommodate different models may not necessarily provide a consistent platform for comparison of projection results. Here, future climate projections of TC activity in the western North Pacific basin (WNP, defined from 0°–50°N and 100°E–180°) are assessed with a model-independent detection and tracking scheme. This scheme is applied to models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) forced under the historical and representative concentration pathway 8.5 (RCP8.5) conditions. TC tracks from the observed records and independent models are analyzed simultaneously with a curve-clustering algorithm, allowing observed and model tracks to be projected onto the same set of clusters (k = 9). Four of the nine clusters were projected to undergo significant changes in TC frequency. Straight-moving TCs in the South China Sea were projected to significantly decrease. Projected increases in TC frequency were found poleward of 20°N and east of 160°E, consistent with changes in ascending motion, as well as vertical wind shear and relative humidity respectively. Projections of TC track exposure indicated significant reductions for southern China and the Philippines and significant increases for the Korean peninsula and Japan, although very few model TCs reached the latter subtropical regions in comparison to the observations. The use of a fundamentally different detection methodology that overcomes the detector/tracker bias gives increased certainty to projections as best as low-resolution simulations can offer
Radius constraints from high-speed photometry of 20 low-mass white dwarf binaries
We carry out high-speed photometry on 20 of the shortest-period, detached
white dwarf binaries known and discover systems with eclipses, ellipsoidal
variations (due to tidal deformations of the visible white dwarf), and Doppler
beaming. All of the binaries contain low-mass white dwarfs with orbital periods
less than 4 hr. Our observations identify the first eight tidally distorted
white dwarfs, four of which are reported for the first time here, which we use
to put empirical constraints on the mass-radius relationship for extremely
low-mass (<0.30 Msun) white dwarfs. We also detect Doppler beaming in several
of these binaries, which confirms the high-amplitude radial-velocity
variability. All of these systems are strong sources of gravitational
radiation, and long-term monitoring of those that display ellipsoidal
variations can be used to detect spin-up of the tidal bulge due to orbital
decay.Comment: 14 pages, 5 figures, accepted for publication in The Astrophysical
Journa
Four-photon interference: a realizable experiment to demonstrate violation of EPR postulates for perfect correlations
Bell's theorem reveals contradictions between the predictions of quantum
mechanics and the EPR postulates for a pair of particles only in situations
involving imperfect statistical correlations. However, with three or more
particles, contradictions emerge even for perfect correlations. We describe an
experiment which can be realized in the laboratory, using four-photon entangled
states generated by parametric down-conversion, to demonstrate this
contradiction at the level of perfect correlations.Comment: publishe
Classical simulation of entanglement swapping with bounded communication
Entanglement appears under two different forms in quantum theory, namely as a
property of states of joint systems and as a property of measurement
eigenstates in joint measurements. By combining these two aspects of
entanglement, it is possible to generate nonlocality between particles that
never interacted, using the protocol of entanglement swapping. We show that
even in the more constraining bilocal scenario where distant sources of
particles are assumed to be independent, i.e. to share no prior randomness,
this process can be simulated classically with bounded communication, using
only 9 bits in total. Our result thus provides an upper bound on the
nonlocality of the process of entanglement swapping.Comment: 6 pages, 1 figur
The association of handgrip strength and mortality: What does it tell us and what can we do with it?
© Copyright 2019, Mary Ann Liebert, Inc., publishers 2019. The relationship between grip strength and mortality is often used to underscore the importance of resistance exercise in physical activity guidelines. However, grip strength does not appear to appreciably change following traditional resistance training. Thus, grip strength could be considered reflective of strength independent of resistance exercise. If true, grip strength is not necessarily informing us of the importance of resistance exercise as an adult, but potentially highlighting inherent differences between individuals who are stronger at baseline compared to their weaker counterpart. The purpose of this article is to discuss: (1) potential factors that may influence grip strength and (2) hypothesize strategies that may be able to influence grip strength and ultimately attain a higher baseline level of strength. Although there appears to be a limited ability to augment grip strength as an adult, there may be critical periods during growth/development during which individuals can establish a higher baseline. Establishing a high baseline of strength earlier in life may have long-term implications related to mortality and disease
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