41 research outputs found
Spam - solutions and their problems
We analyze the success of filtering as a solution to the spam problem when used alone or concurrently with sender and/or receiver pricing. We find that filters alone may exacerbate the spam problem if the spammer attempts to evade them by sending multiple variants of the message to each consumer. Sender and receiver prices can effectively reduce or eliminating spam, either on their own or when used together with filtering. Finally, we discuss the impli- cations for social welfare of using the different spam controls.Spam; filtering; email; receiver pricing; sender pricing
Spam: solutions and their problems
We analyze the success of filtering as a solution to the spam problem
when used alone or concurrently with sender and/or receiver pricing. We find
that filters alone may exacerbate the spam problem if the spammer attempts
to evade them by sending multiple variants of the message to each consumer.
Sender and receiver prices can effectively reduce or eliminating spam, either on
their own or when used together with filtering. Finally, we discuss the implications for social welfare of using the different spam controls
Polarization of tightly focused laser beams
The polarization properties of monochromatic light beams are studied. In
contrast to the idealization of an electromagnetic plane wave, finite beams
which are everywhere linearly polarized in the same direction do not exist.
Neither do beams which are everywhere circularly polarized in a fixed plane. It
is also shown that transversely finite beams cannot be purely transverse in
both their electric and magnetic vectors, and that their electromagnetic energy
travels at less than c. The electric and magnetic fields in an electromagnetic
beam have different polarization properties in general, but there exists a
class of steady beams in which the electric and magnetic polarizations are the
same (and in which energy density and energy flux are independent of time).
Examples are given of exactly and approximately linearly polarized beams, and
of approximately circularly polarized beams.Comment: 9 pages, 6 figure
Quenched Computation of the Complexity of the Sherrington-Kirkpatrick Model
The quenched computation of the complexity in the
Sherrington-Kirkpatrick model is presented. A modified Full Replica
Symmetry Breaking Ansatz is introduced in order to study the complexity
dependence on the free energy. Such an Ansatz corresponds to require
Becchi-Rouet-Stora-Tyutin supersymmetry. The complexity computed this way is
the Legendre transform of the free energy averaged over the quenched disorder.
The stability analysis shows that this complexity is inconsistent at any free
energy level but the equilibirum one. The further problem of building a
physically well defined solution not invariant under supersymmetry and
predicting an extensive number of metastable states is also discussed.Comment: 19 pages, 13 figures. Some formulas added corrected, changes in
discussion and conclusion, one figure adde
Faster Random Walks By Rewiring Online Social Networks On-The-Fly
Many online social networks feature restrictive web interfaces which only
allow the query of a user's local neighborhood through the interface. To enable
analytics over such an online social network through its restrictive web
interface, many recent efforts reuse the existing Markov Chain Monte Carlo
methods such as random walks to sample the social network and support analytics
based on the samples. The problem with such an approach, however, is the large
amount of queries often required (i.e., a long "mixing time") for a random walk
to reach a desired (stationary) sampling distribution.
In this paper, we consider a novel problem of enabling a faster random walk
over online social networks by "rewiring" the social network on-the-fly.
Specifically, we develop Modified TOpology (MTO)-Sampler which, by using only
information exposed by the restrictive web interface, constructs a "virtual"
overlay topology of the social network while performing a random walk, and
ensures that the random walk follows the modified overlay topology rather than
the original one. We show that MTO-Sampler not only provably enhances the
efficiency of sampling, but also achieves significant savings on query cost
over real-world online social networks such as Google Plus, Epinion etc.Comment: 15 pages, 14 figure, technical report for ICDE2013 paper. Appendix
has all the theorems' proofs; ICDE'201
Dungeon Masterâs Sheet Aid
The Dungeon Masterâs Sheet Aid is a program made to assist players of tabletop rpg games in keeping track of and using their âcharacter sheetsâ, a vital part of the game. In particular. It is made to be helpful to the players taking the role of âDungeonâ or âGameâ Master, as these players need to manage many more character sheets than anyone else