8,020 research outputs found
Comment on "Separability of quantum states and the violation of Bell-type inequalities"
The statement of E.R. Loubenets, Phys. Rev. A 69, 042102 (2004), that
separable states can violate classical probabilistic constraints is based on a
misleading definition of classicality, which is much narrower than Bell's
concept of local hidden variables. In a Bell type setting the notion of
classicality used by Loubenets corresponds to the assumption of perfect
correlations if the same observable is measured on both sides. While it is
obvious that most separable states do not satisfy this assumption, this does
not constitute "non-classical" behaviour in any usual sense of the word.Comment: 1 page, accepted by Phys. Rev.
A stellar census of the nearby, young 32 Orionis group
The 32 Orionis group was discovered almost a decade ago and despite the fact
that it represents the first northern, young (age ~ 25 Myr) stellar aggregate
within 100 pc of the Sun ( pc), a comprehensive survey for members
and detailed characterisation of the group has yet to be performed. We present
the first large-scale spectroscopic survey for new (predominantly M-type)
members of the group after combining kinematic and photometric data to select
candidates with Galactic space motion and positions in colour-magnitude space
consistent with membership. We identify 30 new members, increasing the number
of known 32 Ori group members by a factor of three and bringing the total
number of identified members to 46, spanning spectral types B5 to L1. We also
identify the lithium depletion boundary (LDB) of the group, i.e. the luminosity
at which lithium remains unburnt in a coeval population. We estimate the age of
the 32 Ori group independently using both isochronal fitting and LDB analyses
and find it is essentially coeval with the {\beta} Pictoris moving group, with
an age of Myr. Finally, we have also searched for circumstellar disc
hosts utilising the AllWISE catalogue. Although we find no evidence for warm,
dusty discs, we identify several stars with excess emission in the WISE W4-band
at 22 {\mu}m. Based on the limited number of W4 detections we estimate a debris
disc fraction of per cent for the 32 Ori group.Comment: Accepted for publication in MNRAS; 24 pages, 17 figures and 10 table
Proposal to demonstrate the non-locality of Bohmian mechanics with entangled photons
Bohmian mechanics reproduces all statistical predictions of quantum
mechanics, which ensures that entanglement cannot be used for superluminal
signaling. However, individual Bohmian particles can experience superluminal
influences. We propose to illustrate this point using a double double-slit
setup with path-entangled photons. The Bohmian velocity field for one of the
photons can be measured using a recently demonstrated weak-measurement
technique. The found velocities strongly depend on the value of a phase shift
that is applied to the other photon, potentially at spacelike separation.Comment: 6 pages, 4 figure
Esmase skisofreenia farmakoteraapia Eestis: võrdlus kohaliku ja rahvusvaheliste ravijuhistega
Psühhooside farmakoteraapia ja ravijuhised on eri riikides erinevad. Uuringu eesmärgiks oli analüüsida ja kirjeldada esmaste skisofreeniaepisoodide farmakoteraapiat Eestis. Töös analüü-
siti septembrist 2005 kuni septembrini 2006 Põhja-Eesti Regionaalhaigla ja TÜ Kliinikumi psühhiaatriakliinikutesse hospitaliseeritud skisofreenia ja skisotüüpse häirega patsientide farmakoteraapiat. Vaadeldi manustatud ravimite annuseid, antipsühhootikumide polüteraapia esinemise sagedust ning atüüpiliste ja konventsionaalsete antipsühhootikumide määramise sagedust. Tulemusi võrreldi kohalike ja rahvusvaheliste ravijuhistega. Esmase skisofreenia farmakoteraapia Eestis on suures osas vastavuses Eesti ja rahvusvaheliste ravijuhistega, kuid sageli kasutati konventsionaalseid antipsühhootikume ja levinud oli polüteraapia antipsühhootikumidega. Tõenduspõhise farmakoteraapia soodustamiseks oleks otstarbekas ajakohastada Eesti ravijuhiseid.
Eesti Arst 2008; 87(9):601−60
Toroidal Perturbations of Friedmann-Robertson-Walker Universes
Explicit expressions are found for the axisymmetric metric perturbations of
the closed, flat and open FRW universes caused by toroidal motions of the
cosmic fluid. The perturbations are decomposed in vector spherical harmonics on
2-spheres, but the radial dependence is left general. Solutions for general
odd-parity -pole perturbations are given for either angular velocities or
angular momenta prescribed. In particular, in case of closed universes the
solutions require a special treatment of the Legendre equation.Comment: 13 page
Realisation of Hardy's Thought Experiment
We present an experimental realisation of Hardy's thought experiment [Phys.
Rev. Lett. {\bf 68}, 2981 (1992)], using photons. The experiment consists of a
pair of Mach-Zehnder interferometers that interact through photon bunching at a
beam splitter. A striking contradiction is created between the predictions of
quantum mechanics and local hidden variable based theories. The contradiction
relies on non-maximally entangled position states of two particles.Comment: 5 page
Experimental test of nonlocal realistic theories without the rotational symmetry assumption
We analyze the class of nonlocal realistic theories that was originally
considered by Leggett [Found. Phys. 33, 1469 (2003)] and tested by us in a
recent experiment [Nature (London) 446, 871 (2007)]. We derive an
incompatibility theorem that works for finite numbers of polarizer settings and
that does not require the previously assumed rotational symmetry of the
two-particle correlation functions. The experimentally measured case involves
seven different measurement settings. Using polarization-entangled photon
pairs, we exclude this broader class of nonlocal realistic models by
experimentally violating a new Leggett-type inequality by 80 standard
deviations.Comment: Published versio
Hidden-variable theorems for real experiments
It has recently been questioned whether the Kochen-Specker theorem is
relevant to real experiments, which by necessity only have finite precision. We
give an affirmative answer to this question by showing how to derive
hidden-variable theorems that apply to real experiments, so that non-contextual
hidden variables can indeed be experimentally disproved. The essential point is
that for the derivation of hidden-variable theorems one does not have to know
which observables are really measured by the apparatus. Predictions can be
derived for observables that are defined in an entirely operational way.Comment: 4 page
An Exploratory Examination of Burnout in NCAA Division II Athletes
The purpose of this study was to assess the causes of burnout among student-athletes in Division II institutions. The authors distributed the Athlete Burnout Questionnaire (ABQ) to 125 undergraduate student-athletes enrolled at three Division II colleges and universities. The athletes competed in various sports. A 2 (Gender) × 2 (Type of Scholarship) × 2 (School Status) analysis of variance revealed that women and men reported different levels of burnout dependent upon type of scholarship. Men with no scholarship reported the lowest levels of burnout among the three types (None/Academic/Athletic), whereas women with no type of scholarship reported the highest levels of burnout. The authors discuss the results and offer implications, limitations, and future directions
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