1,663 research outputs found
Ultrasmall volume Plasmons - yet with complete retardation effects
Nano particle-plasmons are attributed to quasi-static oscillation with no
wave propagation due to their subwavelength size. However, when located within
a band-gap medium (even in air if the particle is small enough), the particle
interfaces are acting as wave-mirrors, incurring small negative retardation.
The latter when compensated by a respective (short) propagation within the
particle substantiates a full-fledged resonator based on constructive
interference. This unusual wave interference in the deep subwavelength regime
(modal-volume<0.001lambda^3) significantly enhances the Q-factor, e.g. 50
compared to the quasi-static limit of 5.5.Comment: 16 pages, 6 figure
Representing Network Trust and Using It to Improve Anonymous Communication
Motivated by the effectiveness of correlation attacks against Tor, the
censorship arms race, and observations of malicious relays in Tor, we propose
that Tor users capture their trust in network elements using probability
distributions over the sets of elements observed by network adversaries. We
present a modular system that allows users to efficiently and conveniently
create such distributions and use them to improve their security. The major
components of this system are (i) an ontology of network-element types that
represents the main threats to and vulnerabilities of anonymous communication
over Tor, (ii) a formal language that allows users to naturally express trust
beliefs about network elements, and (iii) a conversion procedure that takes the
ontology, public information about the network, and user beliefs written in the
trust language and produce a Bayesian Belief Network that represents the
probability distribution in a way that is concise and easily sampleable. We
also present preliminary experimental results that show the distribution
produced by our system can improve security when employed by users; further
improvement is seen when the system is employed by both users and services.Comment: 24 pages; talk to be presented at HotPETs 201
Distributed Exact Shortest Paths in Sublinear Time
The distributed single-source shortest paths problem is one of the most
fundamental and central problems in the message-passing distributed computing.
Classical Bellman-Ford algorithm solves it in time, where is the
number of vertices in the input graph . Peleg and Rubinovich (FOCS'99)
showed a lower bound of for this problem, where
is the hop-diameter of .
Whether or not this problem can be solved in time when is
relatively small is a major notorious open question. Despite intensive research
\cite{LP13,N14,HKN15,EN16,BKKL16} that yielded near-optimal algorithms for the
approximate variant of this problem, no progress was reported for the original
problem.
In this paper we answer this question in the affirmative. We devise an
algorithm that requires time, for , and time, for larger . This
running time is sublinear in in almost the entire range of parameters,
specifically, for . For the all-pairs shortest paths
problem, our algorithm requires time, regardless of
the value of .
We also devise the first algorithm with non-trivial complexity guarantees for
computing exact shortest paths in the multipass semi-streaming model of
computation.
From the technical viewpoint, our algorithm computes a hopset of a
skeleton graph of without first computing itself. We then conduct
a Bellman-Ford exploration in , while computing the required edges
of on the fly. As a result, our algorithm computes exactly those edges of
that it really needs, rather than computing approximately the entire
KeyNote: Trust Management for Public-Key Infrastructures
This paper discusses the rationale for designing a simple trust-management system for public-key infrastructures, called KeyNote. The motivating principles are expressibility, simplicity, and extensibility. We believe that none of the existing public-key infrastructure proposals provide as good a combination of these three factors
Stochastics theory of log-periodic patterns
We introduce an analytical model based on birth-death clustering processes to
help understanding the empirical log-periodic corrections to power-law scaling
and the finite-time singularity as reported in several domains including
rupture, earthquakes, world population and financial systems. In our
stochastics theory log-periodicities are a consequence of transient clusters
induced by an entropy-like term that may reflect the amount of cooperative
information carried by the state of a large system of different species. The
clustering completion rates for the system are assumed to be given by a simple
linear death process. The singularity at t_{o} is derived in terms of
birth-death clustering coefficients.Comment: LaTeX, 1 ps figure - To appear J. Phys. A: Math & Ge
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