106 research outputs found
Power-Law Distributions in a Two-sided Market and Net Neutrality
"Net neutrality" often refers to the policy dictating that an Internet
service provider (ISP) cannot charge content providers (CPs) for delivering
their content to consumers. Many past quantitative models designed to determine
whether net neutrality is a good idea have been rather equivocal in their
conclusions. Here we propose a very simple two-sided market model, in which the
types of the consumers and the CPs are {\em power-law distributed} --- a kind
of distribution known to often arise precisely in connection with
Internet-related phenomena. We derive mostly analytical, closed-form results
for several regimes: (a) Net neutrality, (b) social optimum, (c) maximum
revenue by the ISP, or (d) maximum ISP revenue under quality differentiation.
One unexpected conclusion is that (a) and (b) will differ significantly, unless
average CP productivity is very high
Prochlo: Strong Privacy for Analytics in the Crowd
The large-scale monitoring of computer users' software activities has become
commonplace, e.g., for application telemetry, error reporting, or demographic
profiling. This paper describes a principled systems architecture---Encode,
Shuffle, Analyze (ESA)---for performing such monitoring with high utility while
also protecting user privacy. The ESA design, and its Prochlo implementation,
are informed by our practical experiences with an existing, large deployment of
privacy-preserving software monitoring.
(cont.; see the paper
Comparing P and S wave heterogeneity in the mantle
From the reprocessed data set of Engdahl and
co-workers we have carefully selected matching P and S data
for tomographic imaging. We assess data and model error
and conclude that our S model uncertainty is twice that of
the P model. We account for this in our comparison of the
perturbations in P and S-wavespeed. In accord with previous
studies we find that P and S perturbations are positively
correlated at all depths. However, in the deep mantle systematic
di fferences occur between regions that have undergone
subduction in the last 120 million years and those that
have not. In particular, below 1500 km depth ∂ ln Vs/∂ ln Vp
is signifi cantly larger in mantle regions away from subduction
than in mantle beneath convergent margins. This inference
is substantiated by wavespeed analyses with random realizations
of the slab/non-slab distribution. Through much
of the mantle there is no signi ficant correlation between bulk
sound and S-wave perturbations, but they appear to be negatively
correlated between 1700 and 2100 km depth, which
is also where the largest di erences in ∂ ln Vs/∂ ln Vp occur.
This finding supports convection models with compositional
heterogeneity in the lowermost mantle
High-rate quantum cryptography in untrusted networks
We extend the field of continuous-variable quantum cryptography to a network
formulation where two honest parties connect to an untrusted relay by insecure
quantum links. To generate secret correlations, they transmit coherent states
to the relay where a continuous-variable Bell detection is performed and the
outcome broadcast. Even though the detection could be fully corrupted and the
links subject to optimal coherent attacks, the honest parties can still extract
a secret key, achieving high rates when the relay is proximal to one party, as
typical in public networks with access points or proxy servers. Our theory is
confirmed by an experiment generating key-rates which are orders of magnitude
higher than those achievable with discrete-variable protocols. Thus, using the
cheapest possible quantum resources, we experimentally show the possibility of
high-rate quantum key distribution in network topologies where direct links are
missing between end-users and intermediate relays cannot be trusted.Comment: Theory and Experiment. Main article (6 pages) plus Supplementary
Information (additional 13 pages
Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New Directions
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