2,903 research outputs found
Toward Equilibration in the Early Stages After a High Energy Heavy Ion Collision
The early stages in the evolution of the gluons produced in the central
region of a head-on high-energy heavy ion collision is studied. An equation is
given for the rate of change of transverse momentum into longitudinal momentum
where the longitudinal direction is along the collision axis. We are able to
follow the system up to the time where equilibration seems to be setting in,
but we are unable to actually follow the system as it reaches equilibrium.Comment: 18 pages, Late
Exact solutions of noncommutative vacuum Einstein field equations and plane-fronted gravitational waves
We construct a class of exact solutions of the noncommutative vacuum Einstein
field equations, which are noncommutative analogues of the plane-fronted
gravitational waves in classical gravity.Comment: 10 pages, comments adde
Performance Analysis of Dense Small Cell Networks with Practical Antenna Heights under Rician Fading
In this paper, we examine the combined impacts of distance-dependent Rician fading channel model and the absolute difference between the heights of base station (BS) and user equipment (UE) antennas on the coverage probability and the area spectral efficiency in an interference-limited ultra-dense (UD) small cell network (SCN). Exploiting distance dependent models for both path loss and multi-path fading, we show that in interference-limited UD-SCNs, Rician fading with variant Rician K factor aggravates the performance loss caused by the difference between the heights of the BS and UE antennas in comparison to Rayleigh fading. In particular, we demonstrate that due to presence of the specular LOS component in the Rician fading, both the coverage probability and the area spectral efficiency experience a more steep decline towards zero as the BS density increases. Our performance analysis has a prominent impact on the deployment of UD-SCNs in the 5th-generation of mobile networks, as it indicates that the right modelling of multi-path fading makes a significant difference when assessing the performance of UD-SCNs with non-identical UE-BS antenna heights
Electronic Properties of Two-Dimensional Carbon
We present a theoretical description of the electronic properties of graphene
in the presence of disorder, electron-electron interactions, and particle-hole
symmetry breaking. We show that while particle-hole asymmetry, long-range
Coulomb interactions, and extended defects lead to the phenomenon of
self-doping, local defects determine the transport and spectroscopic
properties. Our results explain recent experiments in graphitic devices and
predict new electronic behavior.Comment: 4 pages, 5 figures. The paper was originally submitted on May, 12th,
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A Multi-Phase Transport model for nuclear collisions at RHIC
To study heavy ion collisions at energies available from the Relativistic
Heavy Ion Collider, we have developed a multi-phase transport model that
includes both initial partonic and final hadronic interactions. Specifically,
the parton cascade model ZPC, which uses as input the parton distribution from
the HIJING model, is extended to include the quark-gluon to hadronic matter
transition and also final-state hadronic interactions based on the ART model.
Predictions of the model for central Au on Au collisions at RHIC are reported.Comment: 7 pages, 4 figure
Network Slicing Based 5G and Future Mobile Networks: Mobility, Resource Management, and Challenges
5G networks are expected to be able to satisfy users' different QoS requirements. Network slicing is a promising technology for 5G networks to provide services tailored for users' specific QoS demands. Driven by the increased massive wireless data traffic from different application scenarios, efficient resource allocation schemes should be exploited to improve the flexibility of network resource allocation and capacity of 5G networks based on network slicing. Due to the diversity of 5G application scenarios, new mobility management schemes are greatly needed to guarantee seamless handover in network-slicing-based 5G systems. In this article, we introduce a logical architecture for network-slicing-based 5G systems, and present a scheme for managing mobility between different access networks, as well as a joint power and subchannel allocation scheme in spectrum-sharing two-tier systems based on network slicing, where both the co-tier interference and cross-tier interference are taken into account. Simulation results demonstrate that the proposed resource allocation scheme can flexibly allocate network resources between different slices in 5G systems. Finally, several open issues and challenges in network-slicing-based 5G networks are discussed, including network reconstruction, network slicing management, and cooperation with other 5G technologies
Edge and Bulk of the Fractional Quantum Hall Liquids
An effective Chern-Simons theory for the Abelian quantum Hall states with
edges is proposed to study the edge and bulk properties in a unified fashion.
We impose a condition that the currents do not flow outside the sample. With
this boundary condition, the action remains gauge invariant and the edge modes
are naturally derived. We find that the integer coupling matrix should
satisfy the condition (: filling of Landau
levels, : the number of gauge fields ) for the quantum Hall liquids. Then
the Hall conductance is always quantized irrespective of the detailed dynamics
or the randomness at the edge.Comment: 13 pages, REVTEX, one figure appended as a postscript fil
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