30,955 research outputs found
Cache-Aided Non-Orthogonal Multiple Access
In this paper, we propose a novel joint caching and non-orthogonal multiple
access (NOMA) scheme to facilitate advanced downlink transmission for next
generation cellular networks. In addition to reaping the conventional
advantages of caching and NOMA transmission, the proposed cache-aided NOMA
scheme also exploits cached data for interference cancellation which is not
possible with separate caching and NOMA transmission designs. Furthermore, as
caching can help to reduce the residual interference power, several decoding
orders are feasible at the receivers, and these decoding orders can be flexibly
selected for performance optimization. We characterize the achievable rate
region of cache-aided NOMA and investigate its benefits for minimizing the time
required to complete video file delivery. Our simulation results reveal that,
compared to several baseline schemes, the proposed cache-aided NOMA scheme
significantly expands the achievable rate region for downlink transmission,
which translates into substantially reduced file delivery times.Comment: Accepted for presentation at IEEE ICC 201
Shear viscosity, instability and the upper bound of the Gauss-Bonnet coupling constant
We compute the dimensionality dependence of for charged black branes
with Gauss-Bonnet correction. We find that both causality and stability
constrain the value of Gauss-Bonnet coupling constant to be bounded by 1/4 in
the infinite dimensionality limit. We further show that higher dimensionality
stabilize the gravitational perturbation. The stabilization of the perturbation
in higher dimensional space-time is a straightforward consequence of the
Gauss-Bonnet coupling constant bound.Comment: 16 pages,3 figures+3 tables,typos corrected, published versio
Predicting leptonic CP violation in the light of Daya Bay result
In the light of the recent Daya Bay result the reactor angle is about 9
degrees, we reconsider the model presented in arXiv:1005.3482 showing that,
when all neutrino oscillation parameters are taken at their best fit values of
Schwetz et al and the reactor angle to be the central value of Daya Bay, the
predicted value of the CP phase is approximately 45 degrees.Comment: 4 pages, 2 figures, update of arXiv:1005.348
Entropy in the NUT-Kerr-Newman Black Holes Due to an Arbitrary Spin Field
Membrane method is used to compute the entropy of the NUT-Kerr-Newman black
holes. It is found that even though the Euler characteristic is greater than
two, the Bekenstein-Hawking area law is still satisfied. The formula relating the entropy and the Euler characteristic becomes inapplicable for
non-extreme four dimensional NUT-Kerr-Newman black holes
Su(3) Algebraic Structure of the Cuprate Superconductors Model based on the Analogy with Atomic Nuclei
A cuprate superconductor model based on the analogy with atomic nuclei was
shown by Iachello to have an structure. The mean-field approximation
Hamiltonian can be written as a linear function of the generators of
algebra. Using algebraic method, we derive the eigenvalues of the reduced
Hamiltonian beyond the subalgebras and of
algebra. In particular, by considering the coherence between s- and d-wave
pairs as perturbation, the effects of coherent term upon the energy spectrum
are investigated
Induction-heated nanoimprint on soda-lime glass using sapphire molds
published_or_final_versio
Directed Molecular Stacking for Engineered Fluorescent Three-Dimensional Reduced Graphene Oxide and Coronene Frameworks
[EN] Threeâdimensional fluorescent graphene frameworks with controlled porous morphologies are of significant importance for practical applications reliant on controlled structural and electronic properties, such as organic electronics and photochemistry. Here we report a synthetically accessible approach concerning directed aromatic stacking interactions to give rise to new fluorogenic 3D frameworks with tuneable porosities achieved through molecular variations. The binding interactions between the grapheneâlike domains present in the inâ
situâformed reduced graphene oxide (rGO) with functional porphyrin molecules lead to new hybrids via an unprecedented solvothermal reaction. Functional freeâbase porphyrins featuring perfluorinated aryl groups or hexyl chains at their mesoâ and ÎČâpositions were employed in turn to act as directing entities for the assembly of new grapheneâbased and foamâlike frameworks and of their corresponding coroneneâbased hybrids. Investigations in the dispersed phase and in thinâfilm by XPS, SEM and FLIM shed light onto the nature of the aromatic stacking within functional rGO frameworks (denoted rGOFs) which was then modelled semiâempirically and by DFT calculations. The pore sizes of the new emerging reduced graphene oxide hybrids are tuneable at the molecular level and mediated by the bonding forces with the functional porphyrins acting as the âmolecular glueâ. Single crystal Xâray crystallography described the stacking of a perfluorinated porphyrin with coronene, which can be employed as a molecular model for understanding the local aromatic stacking order and charge transfer interactions within these rGOFs for the first time. This opens up a new route to controllable 3D framework morphologies and pore size from the Ă
ngstrom to the micrometre scale. Theoretical modelling showed that the porosity of these materials is mainly due to the controlled interâplanar distance between the rGO, coronene or graphene sheets. The hostâguest chemistry involves the porphyrins acting as guests held through ÏâÏ stacking, as demonstrated by XPS. The objective of this study is also to shed light into the fundamental localised electronic and energy transfer properties in these new molecularly engineered porous and fluorogenic architectures, aiming in turn to understand how functional porphyrins may exert stacking control over the notoriously disordered local structure present in porous reduced graphene oxide fragments. By tuning the porosity and the distance between the graphene sheets using aromatic stacking with porphyrins, it is also possible to tune the electronic structure of the final nanohybrid material, as indicated by FLIM experiments on thin films. Such nanohybrids with highly controlled pores dimensions and morphologies open the way to new design and assembly of storage devices and applications incorporating Ïâconjugated molecules and materials and their Ïâstacks may be relevant towards selective separation membranes, water purification and biosensing applications.S.I.P. and S.W.B. thank The Royal Society and STFC for funding. B.Y.M. thanks the University of Bath for a studentship (ORS). D.G.C. thanks the FundaciĂłn General CSIC for funding (ComFuturo Program). Dr. Jose A. Ribeiro Martins, Professors Jeremy K. M. Sanders and Paul Raithby are acknowledged for training, helpful discussions and porphyrin supramolecular chemistry. The S.I.P. group thanks the EPSRC for funding to the Centre of Graphene Science (EP/K017160/1) and to the Centre for Doctoral Training in Sustainable Chemical Technologies (EP/L016354/1). The authors thank EPSRC National Service for Mass Spectrometry at Swansea and EPSRC National Service for Crystallography at Southampton for data collection. The authors also acknowledge the ERC for the Consolidator Grant O2SENSE (617107, 2014â2019)
Antikaon production in nucleon-nucleon reactions near threshold
The antikaon production cross section from nucleon-nucleon reactions near
threshold is studied in a meson exchange model. We include both pion and kaon
exchange, but neglect the interference between the amplitudes. In case of pion
exchange the antikaon production cross section can be expressed in terms of the
antikaon production cross section from a pion-nucleon interaction, which we
take from the experimental data if available. Otherwise, a -resonance
exchange model is introduced to relate the different reaction cross sections.
In case of kaon exchange the antikaon production cross section is related to
the elastic and cross sections, which are again taken from
experimental measurements. We find that the one-meson exchange model gives a
satisfactory fit to the available data for the cross section
at high energies. We compare our predictions for the cross section near
threshold with an earlier empirical parameterization and that from phase space
models.Comment: 16 pages, LaTeX, 5 postscript figures included, submitted to Z. Phys.
A Model of Strongly Correlated Electrons with Condensed Resonating-Valence-Bond Ground States
We propose a new exactly solvable model of strongly correlated electrons. The
model is based on a - model of the CuO plane with infinitely large
repulsive interactions on Cu-sites, and it contains additional
correlated-hopping, pair-hopping and charge-charge interactions of electrons.
For even numbers of electrons less than or equal to 2/3-filling, we construct
the exact ground states of the model, all of which have the same energy and
each of which is the unique ground state for a fixed electron number. It is
shown that these ground states are the resonating-valence-bond states which are
also regarded as condensed states in which all electrons are in a single
two-electron state. We also show that the ground states exhibit off-diagonal
long-range order.Comment: 17 pages, 1 figure, v2: minor changes, v3: minor changes and typos
correction
R^2 Corrections to Asymptotically Lifshitz Spacetimes
We study corrections to five-dimensional asymptotically Lifshitz
spacetimes by adding Gauss-Bonnet terms in the effective action. For the
zero-temperature backgrounds we obtain exact solutions in both pure
Gauss-Bonnet gravity and Gauss-Bonnet gravity with non-trivial matter. The
dynamical exponent undergoes finite renormalization in the latter case. For the
finite-temperature backgrounds we obtain black brane solutions perturbatively
and calculate the ratio of shear viscosity to entropy density . The KSS
bound is still violated but unlike the relativistic counterparts, the causality
of the boundary field theory cannot be taken as a constraint.Comment: 24 pages, Latex, typos fixed, accepted by JHE
- âŠ