858 research outputs found
Revisiting the Pion Leading-Twist Distribution Amplitude within the QCD Background Field Theory
We study the pion leading-twist distribution amplitude (DA) within the
framework of SVZ sum rules under the background field theory. To improve the
accuracy of the sum rules, we expand both the quark propagator and the vertex
(z\cdot \tensor{D})^n of the correlator up to dimension-six operators in the
background field theory. The sum rules for the pion DA moments are obtained, in
which all condensates up to dimension-six have been taken into consideration.
Using the sum rules, we obtain \left|_{\rm 1\;GeV} = 0.338 \pm
0.032, \left|_{\rm 1\;GeV} = 0.211 \pm 0.030 and
\left|_{\rm 1\;GeV} = 0.163 \pm 0.030. It is shown that the
dimension-six condensates shall provide sizable contributions to the pion DA
moments. We show that the first Gegenbauer moment of the pion leading-twist DA
is , which is consistent with those
obtained in the literature within errors but prefers a larger central value as
indicated by lattice QCD predictions.Comment: 13 pages, 7 figure
Empirical metallicity-dependent calibrations of effective temperature against colours for dwarfs and giants based on interferometric data
We present empirical metallicity-dependent calibrations of effective
temperature against colours for dwarfs of luminosity classes IV and V and for
giants of luminosity classes II and III, based on a collection from the
literature of about two hundred nearby stars with direct effective temperature
measurements of better than 2.5 per cent. The calibrations are valid for an
effective temperature range 3,100 - 10,000 K for dwarfs of spectral types M5 to
A0 and 3,100 - 5,700 K for giants of spectral types K5 to G5. A total of
twenty-one colours for dwarfs and eighteen colours for giants of bands of four
photometric systems, i.e. the Johnson (), the Cousins
(), the Sloan Digital Sky Survey (SDSS, ) and the Two
Micron All Sky Survey (2MASS, ), have been calibrated. Restricted
by the metallicity range of the current sample, the calibrations are mainly
applicable for disk stars ([Fe/H]). The normalized percentage
residuals of the calibrations are typically 2.0 and 1.5 per cent for dwarfs and
giants, respectively. Some systematic discrepancies at various levels are found
between the current scales and those available in the literature (e.g. those
based on the infrared flux method IRFM or spectroscopy). Based on the current
calibrations, we have re-determined the colours of the Sun. We have also
investigated the systematic errors in effective temperatures yielded by the
current on-going large scale low- to intermediate-resolution stellar
spectroscopic surveys. We show that the calibration of colour ()
presented in the current work provides an invaluable tool for the estimation of
stellar effective temperature for those on-going or upcoming surveys.Comment: 28 pages, 19 figures, 8 tables, accepted for publication in MNRA
Quantum-accelerated algorithms for generating random primitive polynomials over finite fields
Primitive polynomials over finite fields are crucial for various domains of
computer science, including classical pseudo-random number generation, coding
theory and post-quantum cryptography. Nevertheless, the pursuit of an efficient
classical algorithm for generating random primitive polynomials over finite
fields remains an ongoing challenge. In this paper, we show how to solve this
problem efficiently through hybrid quantum-classical algorithms, and designs of
the specific quantum circuits to implement them are also presented. Our
research paves the way for the rapid and real-time generation of random
primitive polynomials in diverse quantum communication and computation
applications
Quasi-Periodic Variations in X-ray Emission and Long-Term Radio Observations: Evidence for a Two-Component Jet in Sw J1644+57
The continued observations of Sw J1644+57 in X-ray and radio bands
accumulated a rich data set to study the relativistic jet launched in this
tidal disruption event. The X-ray light curve of Sw J1644+57 from 5-30 days
presents two kinds of quasi-periodic variations: a 200 second quasi-periodic
oscillation (QPO) and a 2.7-day quasi-periodic variation. The latter has been
interpreted by a precessing jet launched near the Bardeen-Petterson radius of a
warped disk. Here we suggest that the 200s QPO could be associated with
a second, narrower jet sweeping the observer line-of-sight periodically, which
is launched from a spinning black hole in the misaligned direction with respect
to the black hole's angular momentum. In addition, we show that this
two-component jet model can interpret the radio light curve of the event,
especially the re-brightening feature starting days after the
trigger. From the data we infer that inner jet may have a Lorentz factor of
and a kinetic energy of , while the outer jet may have a Lorentz factor of
and a kinetic energy of .Comment: 11 pages, 7 figures, accepted for publication in Ap
General framework of quantum complementarity from a measurement-based perspective
One of the most remarkable features of quantum physics is that attributes of
quantum objects, such as the wave-like and particle-like behaviors of single
photons, can be complementary in the sense that they are equally real but
cannot be observed simultaneously. Quantum measurements, serving as windows
providing views into the abstract edifice of quantum theory, are basic tools
for manifesting the intrinsic behaviors of quantum objects. However,
quantitative formulation of complementarity that highlights its manifestations
in sophisticated measurements remains elusive. Here we develop a general
framework for demonstrating quantum complementarity in the form of information
exclusion relations (IERs), which incorporates the wave-particle duality
relations as particular examples. Moreover, we explore the applications of our
theory in entanglement witnessing and elucidate that our IERs lead to an
extended form of entropic uncertainty relations, providing intriguing insights
into the connection between quantum complementarity and the preparation
uncertainty.Comment: 13 pages (including 7 pages in the main text), 6 figure
Experimental quantum secure network with digital signatures and encryption
Cryptography promises four information security objectives, namely,
confidentiality, integrity, authenticity, and non-repudiation, to support
trillions of transactions annually in the digital economy. Efficient digital
signatures, ensuring the integrity, authenticity, and non-repudiation of data
with information-theoretical security are highly urgent and intractable open
problems in cryptography. Here, we propose a protocol of high-efficiency
quantum digital signatures using secret sharing, one-time universal
hashing, and the one-time pad. We just need to use a 384-bit key to sign
documents of up to lengths with a security bound of . If
one-megabit document is signed, the signature efficiency is improved by more
than times compared with previous quantum digital signature protocols.
Furthermore, we build the first all-in-one quantum secure network integrating
information-theoretically secure communication, digital signatures, secret
sharing, and conference key agreement and experimentally demonstrate this
signature efficiency advantage. Our work completes the cryptography toolbox of
the four information security objectives.Comment: 19 pages, 7 figures, 4 tables. Quantum digital signatures and quantum
private communication maintain a consistent level of practicalit
- …