1,888 research outputs found
On Match Lengths, Zero Entropy and Large Deviations - with Application to Sliding Window Lempel-Ziv Algorithm
The Sliding Window Lempel-Ziv (SWLZ) algorithm that makes use of recurrence
times and match lengths has been studied from various perspectives in
information theory literature. In this paper, we undertake a finer study of
these quantities under two different scenarios, i) \emph{zero entropy} sources
that are characterized by strong long-term memory, and ii) the processes with
weak memory as described through various mixing conditions.
For zero entropy sources, a general statement on match length is obtained. It
is used in the proof of almost sure optimality of Fixed Shift Variant of
Lempel-Ziv (FSLZ) and SWLZ algorithms given in literature. Through an example
of stationary and ergodic processes generated by an irrational rotation we
establish that for a window of size , a compression ratio given by
where depends on and approaches 1 as
, is obtained under the application of FSLZ and SWLZ
algorithms. Also, we give a general expression for the compression ratio for a
class of stationary and ergodic processes with zero entropy.
Next, we extend the study of Ornstein and Weiss on the asymptotic behavior of
the \emph{normalized} version of recurrence times and establish the \emph{large
deviation property} (LDP) for a class of mixing processes. Also, an estimator
of entropy based on recurrence times is proposed for which large deviation
principle is proved for sources satisfying similar mixing conditions.Comment: accepted to appear in IEEE Transactions on Information Theor
Fragility of the Commons under Prospect-Theoretic Risk Attitudes
We study a common-pool resource game where the resource experiences failure
with a probability that grows with the aggregate investment in the resource. To
capture decision making under such uncertainty, we model each player's risk
preference according to the value function from prospect theory. We show the
existence and uniqueness of a pure Nash equilibrium when the players have
heterogeneous risk preferences and under certain assumptions on the rate of
return and failure probability of the resource. Greater competition, vis-a-vis
the number of players, increases the failure probability at the Nash
equilibrium; we quantify this effect by obtaining bounds on the ratio of the
failure probability at the Nash equilibrium to the failure probability under
investment by a single user. We further show that heterogeneity in attitudes
towards loss aversion leads to higher failure probability of the resource at
the equilibrium.Comment: Accepted for publication in Games and Economic Behavior, 201
On the origin of reverse transcriptase-using CRISPR-Cas systems and their hyperdiverse, enigmatic spacer repertoires
Learning in the Repeated Secretary Problem
In the classical secretary problem, one attempts to find the maximum of an
unknown and unlearnable distribution through sequential search. In many
real-world searches, however, distributions are not entirely unknown and can be
learned through experience. To investigate learning in such a repeated
secretary problem we conduct a large-scale behavioral experiment in which
people search repeatedly from fixed distributions. In contrast to prior
investigations that find no evidence for learning in the classical scenario, in
the repeated setting we observe substantial learning resulting in near-optimal
stopping behavior. We conduct a Bayesian comparison of multiple behavioral
models which shows that participants' behavior is best described by a class of
threshold-based models that contains the theoretically optimal strategy.
Fitting such a threshold-based model to data reveals players' estimated
thresholds to be surprisingly close to the optimal thresholds after only a
small number of games
Stationary mass distribution and nonlocality in models of coalescence and shattering
We study the asymptotic properties of the steady state mass distribution for
a class of collision kernels in an aggregation-shattering model in the limit of
small shattering probabilities. It is shown that the exponents characterizing
the large and small mass asymptotic behavior of the mass distribution depend on
whether the collision kernel is local (the aggregation mass flux is essentially
generated by collisions between particles of similar masses), or non-local
(collision between particles of widely different masses give the main
contribution to the mass flux). We show that the non-local regime is further
divided into two sub-regimes corresponding to weak and strong non-locality. We
also observe that at the boundaries between the local and non-local regimes,
the mass distribution acquires logarithmic corrections to scaling and calculate
these corrections. Exact solutions for special kernels and numerical
simulations are used to validate some non-rigorous steps used in the analysis.
Our results show that for local kernels, the scaling solutions carry a constant
flux of mass due to aggregation, whereas for the non-local case there is a
correction to the constant flux exponent. Our results suggest that for general
scale-invariant kernels, the universality classes of mass distributions are
labeled by two parameters: the homogeneity degree of the kernel and one further
number measuring the degree of the non-locality of the kernel.Comment: Published versio
Trunk Robot for Extended Environments
We describe the design and physical realization of a novel type of large-scale continuum robot. The design, based on a hybrid concentric-tube/tendon actuated structure, is realized at a significantly larger scale than previous concentric tube continuum robots, with an extended length well over one meter. While operation at this scale opens up new types of potential applications, realization at this scale presents interesting challenges. We detail and discuss the associated issues via the prototyping and testing of the physical system with the help of experiments
A Search for Dark Matter Annihilation in Galaxy Groups
We use 413 weeks of publicly-available Pass 8 gamma-ray
data, combined with recently-developed galaxy group catalogs, to search for
evidence of dark matter annihilation in extragalactic halos. In our study, we
use luminosity-based mass estimates and mass-to-concentration relations to
infer the -factors and associated uncertainties for hundreds of galaxy
groups within a redshift range . We employ a conservative
substructure boost-factor model, which only enhances the sensitivity by an
factor. No significant evidence for dark matter annihilation
is found and we exclude thermal relic cross sections for dark matter masses
below 30 GeV to 95% confidence in the annihilation channel.
These bounds are comparable to those from Milky Way dwarf spheroidal satellite
galaxies. The results of our analysis increase the tension, but do not rule
out, the dark matter interpretation of the Galactic Center excess. We provide a
catalog of the galaxy groups used in this study and their inferred properties,
which can be broadly applied to searches for extragalactic dark matter.Comment: 5+18 pages, 1+14 figures, catalog available at:
https://github.com/bsafdi/DMCat; v2 updated to journal version with several
updates, results and conclusions unchange
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