10,820 research outputs found
Locate QCD Critical End Point in a Continuum Model Study
With a modified chemical potential dependent effective model for the gluon
propagator, we try to locate the critical end point (CEP) of strongly
interacting matter in the framework of Dyson-Schwinger equations (DSE). Beyond
the chiral limit, we find that Nambu solution and Wigner solution could coexist
in some area. Using the CornwallJackiw-Tomboulis (CJT) effective action, we
show that these two phases are connected by a first order phase transition. We
then locate CEP as the end point of the first order phase transition line.
Meanwhile, based on CJT effective action, we give a direct calculation for the
chiral susceptibility and thereby study the crossover.Comment: 9 pages, 7 figures; Version published in JHE
Aggregate Analytic Window Query over Spatial Data
Analytic window query is a commonly used query in the relational databases.
It answers the aggregations of data over a sliding window. For example, to get
the average prices of a stock for each day. However, it is not supported in the
spatial databases. Because the spatial data are not in a one-dimension space,
there is no straightforward way to extend the original analytic window query to
spatial databases. But these queries are useful and meaningful. For example, to
find the average number of visits for all the POIs in the circle with a fixed
radius for each POI as the centre. In this paper, we define the aggregate
analytic window query over spatial data and propose algorithms for grid index
and tree-index. We also analyze the complexity of the algorithms to prove they
are efficient and practical
The Wigner Solution and QCD Phase Transitions in a Modified PNJL Model
By employing some modification to the widely used two-flavor Polyakov-loop
extended Nambu-Jona-Lasinio (PNJL) model, we discuss the Wigner solution of the
quark gap equation at finite temperature and zero quark chemical potential
beyond the chiral limit, and then try to explore its influences on the chiral
and deconfinement phase transitions of QCD at finite temperature and zero
chemical potential. The discovery of the coexistence of the Nambu and the
Wigner solutions of the quark gap equation with nonzero current quark mass at
zero temperature and zero chemical potential, as well as their evolutions with
temperature is very interesting for the studies of the phase transitions of
QCD. According to our results, the chiral phase transition might be of first
order (while the deconfinement phase transition is still a crossover, as in the
normal PNJL model), and the corresponding phase transition temperature is lower
than that of the deconfinement phase transition, instead of coinciding with
each other, which are not the same as the conclusions obtained from the normal
PNJL model. In addition, we also discuss the sensibility of our final results
on the choice of model parameters
Semileptonic Decays of Meson to a P-Wave Charmonium State or
The semileptonic decays of meson to a P-wave charmonium state
or are computed. The results show that the decays
are sizable so they are accessible in Tevatron and in LHC, especially, with the
detectors LHCB and BTeV in the foreseeable future, and of them, the one to the
charmonium state potentially offers us a novel window to see the
unconfirmed particle. In addition, it is pointed out that since the two
charmonium radiative decays have sizable
branching ratios, the cascade decays of the concerned decays and the charmonium
radiative decays may affect the result of the observing the meson through
the semileptonic decays substantially.Comment: 8 pages, 2 figure
Bayes-Optimal Joint Channel-and-Data Estimation for Massive MIMO with Low-Precision ADCs
This paper considers a multiple-input multiple-output (MIMO) receiver with
very low-precision analog-to-digital convertors (ADCs) with the goal of
developing massive MIMO antenna systems that require minimal cost and power.
Previous studies demonstrated that the training duration should be {\em
relatively long} to obtain acceptable channel state information. To address
this requirement, we adopt a joint channel-and-data (JCD) estimation method
based on Bayes-optimal inference. This method yields minimal mean square errors
with respect to the channels and payload data. We develop a Bayes-optimal JCD
estimator using a recent technique based on approximate message passing. We
then present an analytical framework to study the theoretical performance of
the estimator in the large-system limit. Simulation results confirm our
analytical results, which allow the efficient evaluation of the performance of
quantized massive MIMO systems and provide insights into effective system
design.Comment: accepted in IEEE Transactions on Signal Processin
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