6,265 research outputs found
Lorentz invariance of entanglement classes in multipartite systems
We analyze multipartite entanglement in systems of spin-1/2 particles from a
relativistic perspective. General conditions which have to be met for any
classification of multipartite entanglement to be Lorentz invariant are
derived, which contributes to a physical understanding of entanglement
classification. We show that quantum information in a relativistic setting
requires the partition of the Hilbert space into particles to be taken
seriously. Furthermore, we study exemplary cases and show how the spin and
momentum entanglement transforms relativistically in a multipartite setting.Comment: v2: 5 pages, 4 figures, minor changes to main body, journal
references update
Interannual variability of the outflow of Weddell Sea bottom water
The Weddell Sea Bottom Water (WSBW) export from 1999 to 2019 displays distinct seasonal and interannual variability. From 2014 into 2017 a marked salinity decrease was recorded, with the lowest salinity, 34.615, attained in early 2016. The reduced salinity is derived from the Vâshaped trough formed by a double front along the shelf break of the Weddell Gyre's western boundary, which is filled with a blend of surface water and modified Weddell Deep Water. We estimate that when the Vâshaped apex attains a depth of greater than ~700m, the thermobaric effect promotes its descent into the WSBW. We propose that this occurred during anomalously strong cyclonic wind stress curl over the Weddell Gyre from 2014 into 2017, which increased the intensity of the gyre and its western boundary current, deepening the Vâshape trough. The WSBW salinity increased to its prior to 2014 values as the wind stress relaxed in 2018
MOST Detects g-Modes in the Late-Type be Star beta CMi (B8Ve)
The Microvariability and Oscillations of stars (MOST) satellite has detected
low-amplitude light variations (1 mmag) in the Be star
CMi (B8Ve). The observations lasted 41 days and the variations have typical
periods days. We demonstrate that the dominant frequencies are
consistent with prograde high-order g-modes of excited by the Fe-bump of
opacity in an intermediate-mass () star with a nearly
critical rotation period of 0.38 days. This is the first detection of nonradial
g-mode pulsations in a Be star later than B6 leading to the possibility that
pulsations are excited in all classical Be stars.Comment: 17 pages, 6 figures; Astrophysical Journal part 1 in pres
Quantum gate in the decoherence-free subspace of trapped ion qubits
We propose a geometric phase gate in a decoherence-free subspace with trapped
ions. The quantum information is encoded in the Zeeman sublevels of the
ground-state and two physical qubits to make up one logical qubit with ultra
long coherence time. Single- and two-qubit operations together with the
transport and splitting of linear ion crystals allow for a robust and
decoherence-free scalable quantum processor. For the ease of the phase gate
realization we employ one Raman laser field on four ions simultaneously, i.e.
no tight focus for addressing. The decoherence-free subspace is left neither
during gate operations nor during the transport of quantum information.Comment: 6 pages, 6 figure
Formation and abundance of 5-hydroxymethylcytosine in RNA.
RNA methylation is emerging as a regulatory RNA modification that could have important roles in the control and coordination of gene transcription and protein translation. Herein, we describe an in vivo isotope-tracing methodology to demonstrate that the ribonucleoside 5-methylcytidine (m(5)C) is subject to oxidative processing in mammals, forming 5-hydroxymethylcytidine (hm(5)C) and 5-formylcytidine (f(5)C). Furthermore, we have identified hm(5)C in total RNA from all three domains of life and in polyA-enriched RNA fractions from mammalian cells. This suggests m(5)C oxidation is a conserved process that could have critical regulatory functions inside cells.This work was supported by the Cambridge PhD Training Programme
in Chemical Biology and Molecular Medicine and the
Wellcome Trust (grant number 099232/Z/12/Z). Dr. Donna Bond
is thanked for the provision of A. thaliana total RNA and Drs.
Santiago Uribe-Lewis and Adele Murrell are acknowledged for
the labelled mouse tissue supply.This is the final published version. It first appeared at http://onlinelibrary.wiley.com/doi/10.1002/cbic.201500013/abstract;jsessionid=61B9B3D8937FE50CFA4954A4C4B445B6.f02t04
Less than 50% sublattice polarization in an insulating S=3/2 kagome' antiferromagnet at low T
We have found weak long range antiferromagnetic order in the
quasi-two-dimensional insulating oxide which contains
Cr S=3/2 ions on a kagom\'{e} lattice. In a sample with 76%
occupancy of the chromium sites the ordered moment is 1.1(3) per
chromium ion which is only one third of the N\'{e}el value .
The magnetic unit cell equals the chemical unit cell, a situation which is
favored by inter-plane interactions. Gapless quantum spin-fluctuations
(T_NS(Q,\omega)$ in the ordered
phase.Comment: 18 pages, RevTex/Latex, with 6 figure
Non-global Structure of the O({\alpha}_s^2) Dijet Soft Function
High energy scattering processes involving jets generically involve matrix
elements of light- like Wilson lines, known as soft functions. These describe
the structure of soft contributions to observables and encode color and
kinematic correlations between jets. We compute the dijet soft function to
O({\alpha}_s^2) as a function of the two jet invariant masses, focusing on
terms not determined by its renormalization group evolution that have a
non-separable dependence on these masses. Our results include non-global single
and double logarithms, and analytic results for the full set of non-logarithmic
contributions as well. Using a recent result for the thrust constant, we
present the complete O({\alpha}_s^2) soft function for dijet production in both
position and momentum space.Comment: 55 pages, 8 figures. v2: extended discussion of double logs in the
hard regime. v3: minor typos corrected, version published in JHEP. v4: typos
in Eq. (3.33), (3.39), (3.43) corrected; this does not affect the main
result, numerical results, or conclusion
On the Nature of Small Planets around the Coolest Kepler Stars
We constrain the densities of Earth- to Neptune-size planets around very cool
(Te =3660-4660K) Kepler stars by comparing 1202 Keck/HIRES radial velocity
measurements of 150 nearby stars to a model based on Kepler candidate planet
radii and a power-law mass-radius relation. Our analysis is based on the
presumption that the planet populations around the two sets of stars are the
same. The model can reproduce the observed distribution of radial velocity
variation over a range of parameter values, but, for the expected level of
Doppler systematic error, the highest Kolmogorov-Smirnov probabilities occur
for a power-law index alpha ~ 4, indicating that rocky-metal planets dominate
the planet population in this size range. A single population of gas-rich,
low-density planets with alpha = 2 is ruled out unless our Doppler errors are
>= 5m/s, i.e., much larger than expected based on observations and stellar
chromospheric emission. If small planets are a mix of gamma rocky planets
(alpha = 3.85) and 1-gamma gas-rich planets (alpha = 2), then gamma > 0.5
unless Doppler errors are >=4 m/s. Our comparison also suggests that Kepler's
detection efficiency relative to ideal calculations is less than unity. One
possible source of incompleteness is target stars that are misclassified
subgiants or giants, for which the transits of small planets would be
impossible to detect. Our results are robust to systematic effects, and
plausible errors in the estimated radii of Kepler stars have only moderate
impact.Comment: Accepted to the Astrophysical Journa
The vertex at four loops and hard matching coefficients in SCET for various currents
We compute the four-loop corrections to the Higgs-bottom vertex within
massless QCD and present analytic results for all color structures. The
infrared poles of the renormalized form factor agree with the predicted
four-loop pattern. Furthermore, we use the results for the Higgs-bottom,
photon-quark, and Higgs-gluon form factors to provide hard matching
coefficients in soft-collinear effective theory up to four-loop accuracy.Comment: 19 pages, 1 figure, ancillary files with analytic result
Hbb vertex at four loops and hard matching coefficients in SCET for various currents
We compute the four-loop corrections to the Higgs-bottom vertex within massless QCD and present analytic results for all color structures. The infrared poles of the renormalized form factor agree with the predicted four-loop pattern. Furthermore, we use the results for the Higgs-bottom, photon-quark, and Higgs-gluon form factors to provide hard matching coefficients in soft-collinear effective theory up to four-loop accuracy
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