776 research outputs found
Single spin probe of Many-Body Localization
We use an external spin as a dynamical probe of many body localization. The
probe spin is coupled to an interacting and disordered environment described by
a Heisenberg spin chain in a random field. The spin-chain environment can be
tuned between a thermalizing delocalized phase and non-thermalizing localized
phase, both in its ground- and high-energy states. We study the decoherence of
the probe spin when it couples to the environment prepared in three states: the
ground state, the infinite temperature state and a high energy N\'eel state. In
the non-thermalizing many body localized regime, the coherence shows scaling
behaviour in the disorder strength. The long-time dynamics of the probe spin
shows a logarithmic dephasing in analogy with the logarithmic growth of
entanglement entropy for a bi-partition of a many-body localized system. In
summary, we show that decoherence of the probe spin provides clear signatures
of many-body localization.Comment: 5 pages, 4 figure
Effect of unsupervised home based proprioceptive training on recurrences of ankle sprain: randomised controlled trial
Objective To evaluate the effectiveness of an unsupervised proprioceptive training programme on recurrences of ankle sprain after usual care in athletes who had sustained an acute sports related injury to the lateral ankle ligament
Integrating Neural Networks with a Quantum Simulator for State Reconstruction
We demonstrate quantum many-body state reconstruction from experimental data
generated by a programmable quantum simulator, by means of a neural network
model incorporating known experimental errors. Specifically, we extract
restricted Boltzmann machine (RBM) wavefunctions from data produced by a
Rydberg quantum simulator with eight and nine atoms in a single measurement
basis, and apply a novel regularization technique to mitigate the effects of
measurement errors in the training data. Reconstructions of modest complexity
are able to capture one- and two-body observables not accessible to
experimentalists, as well as more sophisticated observables such as the R\'enyi
mutual information. Our results open the door to integration of machine
learning architectures with intermediate-scale quantum hardware.Comment: 15 pages, 13 figure
How Special Are Dark Gamma-Ray Bursts: A Diagnostic Tool
We present here a comprehensive study of the optical/near-infrared (IR) upper
limits for gamma-ray bursts that have an X-ray afterglow. We have extrapolated
the X-ray afterglows to optical wavelengths based on the physics of the
fireball blast wave model (e.g. Rees & Meszaors 1992; Meszaros & Rees 1997),
and compared these results with optical upper limits for a large sample of
bursts. We find a small set of only three bursts out of a sample of 20 for
which the upper limits are not compatible with their X-ray afterglow properties
within the context of any blast wave model. This sparse sample does not allow
us to conclusively determine the cause of this optical/near-IR deficit.
Extinction in the host galaxy is a likely cause, but high redshifts and
different afterglow mechanisms might also explain the deficit in some cases. We
note that the three bursts appear to have higher than average gamma-ray peak
fluxes. In a magnitude versus time diagram the bursts are separated from the
majority of bursts with a detected optical/near-IR afterglow. However, two GRBs
with an optical afterglow (one of which is highly reddened) also fall in this
region with dark bursts, making it likely that dark bursts are at the faint end
of the set of optically detected bursts, and therefore the dark bursts likely
form a continuum with the bursts with a detected optical afterglow. Our work
provides a useful diagnostic tool for follow-up observations for potentially
dark bursts; applied to the events detected with the Swift satellite, it will
significantly increase our sample of truly dark bursts and shed light upon
their nature.Comment: 19 pages; accepted to Ap
The effect of good agricultural management practices on soil biological quality indicators in a European context
Polygenic liability for schizophrenia and childhood adversity influences daily‐life emotion dysregulation and psychosis proneness
Objective To test whether polygenic risk score for schizophrenia (PRS-S) interacts with childhood adversity and daily-life stressors to influence momentary mental state domains (negative affect, positive affect, and subtle psychosis expression) and stress-sensitivity measures.
Methods The data were retrieved from a general population twin cohort including 593 adolescents and young adults. Childhood adversity was assessed using the Childhood Trauma Questionnaire. Daily-life stressors and momentary mental state domains were measured using ecological momentary assessment. PRS-S was trained on the latest Psychiatric Genetics Consortium schizophrenia meta-analysis. The analyses were conducted using multilevel mixed-effects tobit regression models.
Results Both childhood adversity and daily-life stressors were associated with increased negative affect, decreased positive affect, and increased subtle psychosis expression, while PRS-S was only associated with increased positive affect. No gene-environment correlation was detected. There is novel evidence for interaction effects between PRS-S and childhood adversity to influence momentary mental states [negative affect (b = 0.07, P = 0.013), positive affect (b = -0.05, P = 0.043), and subtle psychosis expression (b = 0.11, P = 0.007)] and stress-sensitivity measures.
Conclusion Exposure to childhood adversities, particularly in individuals with high PRS-S, is pleiotropically associated with emotion dysregulation and psychosis proneness
Cold Nuclear Matter Effects on J/psi Yields as a Function of Rapidity and Nuclear Geometry in Deuteron-Gold Collisions at sqrt(s_NN) = 200 GeV
We present measurements of J/psi yields in d+Au collisions at sqrt(s_NN) =
200 GeV recorded by the PHENIX experiment and compare with yields in p+p
collisions at the same energy per nucleon-nucleon collision. The measurements
cover a large kinematic range in J/psi rapidity (-2.2 < y < 2.4) with high
statistical precision and are compared with two theoretical models: one with
nuclear shadowing combined with final state breakup and one with coherent gluon
saturation effects. To remove model dependent systematic uncertainties we also
compare the data to a simple geometric model. We find that calculations where
the nuclear modification is linear or exponential in the density weighted
longitudinal thickness are difficult to reconcile with the forward rapidity
data.Comment: 449 authors from 66 institutions, 6 pages, 3 figures. Submitted to
Physical Review Letters. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be) publicly
available at http://www.phenix.bnl.gov/papers.htm
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