23,949 research outputs found
Energy Harvesting for Secure OFDMA Systems
Energy harvesting and physical-layer security in wireless networks are of
great significance. In this paper, we study the simultaneous wireless
information and power transfer (SWIPT) in downlink orthogonal
frequency-division multiple access (OFDMA) systems, where each user applies
power splitting to coordinate the energy harvesting and information decoding
processes while secrecy information requirement is guaranteed. The problem is
formulated to maximize the aggregate harvested power at the users while
satisfying secrecy rate requirements of all users by subcarrier allocation and
the optimal power splitting ratio selection. Due to the NP-hardness of the
problem, we propose an efficient iterative algorithm. The numerical results
show that the proposed method outperforms conventional methods.Comment: Accepted by WCSP 201
Quantum Spin Liquid with Even Ising Gauge Field Structure on Kagome Lattice
Employing large-scale quantum Monte Carlo simulations, we study the extended
model on the kagome lattice. A quantum spin liquid phase
with effective even Ising gauge field structure emerges from the delicate
balance among three symmetry-breaking phases including stripe solid, staggered
solid and ferromagnet. This spin liquid is stabilized by an
extended interaction related to the Rokhsar-Kivelson potential in the quantum
dimer model limit. The phase transitions from the staggered solid to a spin
liquid or ferromagnet are found to be first order and so is the transition
between the stripe solid and ferromagnet. However, the transition between a
spin liquid and ferromagnet is found to be continuous and belongs to the 3D
universality class associated with the condensation of spinons. The
transition between a spin liquid and stripe solid appears to be continuous and
associated with the condensation of visons.Comment: 7 pages, 8 figure
Massive Overlap Fermions on Anisotropic Lattices
We formulate the massive overlap fermions on anisotropic lattices.
We find that the dispersion relation for the overlap fermion resembles the
continuum form in the low-momentum region once the bare parameters are properly
tuned. The quark self-energy and the quark field renormalization constants are
calculated to one-loop in bare lattice perturbation theory.
We argue that massive domain wall quarks might be helpful in lattice QCD
studies on heavy-light hadron spectroscopy.Comment: 21 pages, 5 figures, one reference added compared with v.
Query-Efficient Locally Decodable Codes of Subexponential Length
We develop the algebraic theory behind the constructions of Yekhanin (2008)
and Efremenko (2009), in an attempt to understand the ``algebraic niceness''
phenomenon in . We show that every integer ,
where , and are prime, possesses the same good algebraic property as
that allows savings in query complexity. We identify 50 numbers of this
form by computer search, which together with 511, are then applied to gain
improvements on query complexity via Itoh and Suzuki's composition method. More
precisely, we construct a -query LDC for every positive
integer and a -query
LDC for every integer , both of length , improving the
queries used by Efremenko (2009) and queries used by Itoh and
Suzuki (2010).
We also obtain new efficient private information retrieval (PIR) schemes from
the new query-efficient LDCs.Comment: to appear in Computational Complexit
The effects of massive graviton on the equilibrium between the black hole and radiation gas in an isolated box
It is well known that the black hole can has temperature and radiate the
particles with black body spectrum, i.e. Hawking radiation. Therefore, if the
black hole is surrounded by an isolated box, there is a thermal equilibrium
between the black hole and radiation gas. A simple case considering the thermal
equilibrium between the Schwarzschild black hole and radiation gas in an
isolated box has been well investigated previously in detail, i.e. taking the
conservation of energy and principle of maximal entropy for the isolated system
into account. In this paper, following the above spirit, the effects of massive
graviton on the thermal equilibrium will be investigated. For the gravity with
massive graviton, we will use the de Rham-Gabadadze-Tolley (dRGT) massive
gravity which has been proven to be ghost free. Because the graviton mass
depends on two parameters in the dRGT massive gravity, here we just investigate
two simple cases related to the two parameters, respectively. Our results show
that in the first case the massive graviton can suppress or increase the
condensation of black hole in the radiation gas although the diagram is
similar like the Schwarzschild black hole case. For the second case, a new
diagram has been obtained. Moreover, an interesting and important
prediction is that the condensation of black hole just increases from the zero
radius of horizon in this case, which is very different from the Schwarzschild
black hole case.Comment: 9 pages, 4 figure
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