5,647 research outputs found
Symmetry energy systematics and its high density behavior
We explore the systematics of the density dependence of nuclear matter
symmetry energy in the ambit of microscopic calculations with various energy
density functionals, and find that the symmetry energy from subsaturation
density to supra-saturation density can be well determined by three
characteristic parameters of the symmetry energy at saturation density , i.e., the magnitude , the density slope and
the density curvature . This finding opens a new window to
constrain the supra-saturation density behavior of the symmetry energy from its
(sub-)saturation density behavior. In particular, we obtain
MeV and MeV as well as MeV and
MeV based on the present knowledge of MeV, MeV and MeV at fm extracted from nuclear
mass and the neutron skin thickness of Sn isotopes. Our results indicate that
the symmetry energy cannot be stiffer than a linear density dependence.In
addition, we also discuss the quark matter symmetry energy since the deconfined
quarks could be the right degree of freedom in dense matter at high baryon
densities.Comment: 10 pages, 5 figures. Contribution to International Workshop on Multi
facets of Eos and Clustering (IWM-EC 2014), May 6-9, 2014, Catania, Ital
Recent progress on the determination of the symmetry Energy
We summarize the current status on constraining the density dependence of the
symmetry energy from terrestrial laboratory measurements and astrophysical
observations. While the value and density slope of
the symmetry energy at saturation density can vary largely depending
on the data or methods, all the existing constraints are essentially consistent
with MeV and MeV. The
determination of the supra-saturation density behavior of the symmetry energy
remains a big challenge.Comment: 12 pages, 2 figures. Plenary talk at 14th National Conference on
Nuclear Structure in China, Huzhou, Zhejiang, 12-16 April, 201
Empirical information on nuclear matter fourth-order symmetry energy from an extended nuclear mass formula
We establish a relation between the equation of state (EOS) of nuclear matter
and the fourth-order symmetry energy of finite nuclei in a
semi-empirical nuclear mass formula by self-consistently considering the bulk,
surface and Coulomb contributions to the nuclear mass. Such a relation allows
us to extract information on nuclear matter fourth-order symmetry energy
at normal nuclear density from analyzing
nuclear mass data. Based on the recent precise extraction of
via the double difference of the "experimental" symmetry
energy extracted from nuclear masses, for the first time, we estimate a value
of MeV. Such a value of
is significantly larger than the predictions from
mean-field models and thus suggests the importance of considering the effects
of beyond the mean-field approximation in nuclear matter calculations.Comment: 7 pages, 1 figure. Presentation improved and discussions added.
Accepted version to appear in PL
Downlink MBER beamforming transmitter based on uplink MBER beamforming receiver for TDD-SDMA systems
The downlink minimum bit error rate (MBER) transmit beamforming is directly derived based on the uplink MBER receive beamforming for time division duplex (TDD) space-division multiple-access (SDMA) multiple-input multiple-output systems, where the base station (BS) is equipped with multiple antennas to support multiple single-antenna mobile terminals (MTs). It is shown that the relationship between multiuser detection and multiuser transmission can still be applied for the rank-deficient system where the number of users supported is more than the number of transmit antennas available at the BS, if the MBER design is adopted. The proposed MBER transmit beamforming scheme is capable of achieving good performance for rank-deficient TDD-SDMA systems with the support of low-complexity and high power-efficient MTs, and its robustness to the downlink and uplink noise or channel mismatch is verified using simulation
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