5,107 research outputs found
Interconnection and Competition Among Asymmetric Networks in the Internet Backbone Market
We examine the interrelation between interconnection and competition in the internet backbone market.Networks asymmetric in size choose among different interconnection regimes and compete for end-users.We show that a direct interconnection regime, Peering, softens competition compared to indirect interconnection since asymmetries become less influential when networks peer.If interconnection fees are paid, the smaller network pays the larger one. Sufficiently symmetric networks enter a Peering agreement while others use an intermediary network for exchanging traffic.This is in line with considerations of a non-US policy maker.In contrast, US policy makers prefer Peerings among relatively asymmetric networks.Internet Backbone;Endogenous Network Interconnection;Asymmetric Networks;Two-Way Access Pricing
Initial ionization rates in shock-heated Argon, Krypton, and Xenon
The rate of ionization behind strong shock waves in argon, krypton, and xenon, is observed by
a transverse microwave probe, over a range of electron densities low enough that atom-atom inelastic
collisions are the rate-determining mechanism. Shocks of Mach number 7.0 to 10.0 propagate
down a 2-in. sq. aluminum shock tube into ambient gases at pressures of 3.0 to 17.0 mm. Hg., heating
them abruptly to atomic temperatures of 5500°K to 9600°K. The subsequent relaxation toward
ionization equilibrium is examined in its early stages by the reflection, transmission, and phase shifts
of a 24.0 Gc/sec (1.25 cm) transverse microwave beam propagating between two rectangular horns
abreast a glass test section. The data yield effective activation energies of 11.9 ± 0.5 eV for argon,
10.4 ± 0.5 eV for krypton, and 8.6 ± 0.5 eV for xenon. These coincide, within experimental error,
with the first excitation potentials, rather than the ionization potentials of the gases, indicating that
in this range ionization proceeds via a two-step process involving the first excited electronic states
of which the excitation step is rate controlling
Symmetry breaking in the self-consistent Kohn-Sham equations
The Kohn-Sham (KS) equations determine, in a self-consistent way, the
particle density of an interacting fermion system at thermal equilibrium. We
consider a situation when the KS equations are known to have a unique solution
at high temperatures and this solution is a uniform particle density. We show
that, at zero temperature, there are stable solutions that are not uniform. We
provide the general principles behind this phenomenon, namely the conditions
when it can be observed and how to construct these non-uniform solutions. Two
concrete examples are provided, including fermions on the sphere which are
shown to crystallize in a structure that resembles the C molecule.Comment: a few typos eliminate
Quasi-exact-solution of the Generalized Exe Jahn-Teller Hamiltonian
We consider the solution of a generalized Exe Jahn-Teller Hamiltonian in the
context of quasi-exactly solvable spectral problems. This Hamiltonian is
expressed in terms of the generators of the osp(2,2) Lie algebra. Analytical
expressions are obtained for eigenstates and eigenvalues. The solutions lead to
a number of earlier results discussed in the literature. However, our approach
renders a new understanding of ``exact isolated'' solutions
Phases of spin- and mass-imbalanced ultracold Fermi gases in harmonic traps
We analyze the phase structure of mass- and spin-imbalanced unitary Fermi
gases in harmonic traps. To this end, we employ Density Functional Theory in
the local density approximation. Depending on the values of the control
parameters measuring mass and spin imbalance, we observe that three regions
exist in the trap, namely: a superfluid region at the center, surrounded by a
mixed region of resonantly interacting spin-up and spin-down fermions, and
finally a fully polarized phase surrounding the previous two regions. We also
find regimes in the phase diagram where the existence of a superfluid region at
the center of the trap is not energetically favored. We point out the
limitations of our approach at the present stage, and call for more detailed
(ab initio) studies of the equation of state of uniform, mass-imbalanced
unitary Fermi gases.Comment: 10 pages, 7 figure
- …