681 research outputs found
Clustering Memes in Social Media
The increasing pervasiveness of social media creates new opportunities to
study human social behavior, while challenging our capability to analyze their
massive data streams. One of the emerging tasks is to distinguish between
different kinds of activities, for example engineered misinformation campaigns
versus spontaneous communication. Such detection problems require a formal
definition of meme, or unit of information that can spread from person to
person through the social network. Once a meme is identified, supervised
learning methods can be applied to classify different types of communication.
The appropriate granularity of a meme, however, is hardly captured from
existing entities such as tags and keywords. Here we present a framework for
the novel task of detecting memes by clustering messages from large streams of
social data. We evaluate various similarity measures that leverage content,
metadata, network features, and their combinations. We also explore the idea of
pre-clustering on the basis of existing entities. A systematic evaluation is
carried out using a manually curated dataset as ground truth. Our analysis
shows that pre-clustering and a combination of heterogeneous features yield the
best trade-off between number of clusters and their quality, demonstrating that
a simple combination based on pairwise maximization of similarity is as
effective as a non-trivial optimization of parameters. Our approach is fully
automatic, unsupervised, and scalable for real-time detection of memes in
streaming data.Comment: Proceedings of the 2013 IEEE/ACM International Conference on Advances
in Social Networks Analysis and Mining (ASONAM'13), 201
Hard thermal loops with a background plasma velocity
I consider the calculation of the two and three-point functions for QED at
finite temperature in the presence of a background plasma velocity. The final
expressions are consistent with Lorentz invariance, gauge invariance and
current conservation, pointing to a straightforward generalization of the hard
thermal loop formalism to this physical situation. I also give the resulting
expression for the effective action and identify the various terms.Comment: 11 pages, no figure
Effective potential for Lifshitz type z=3 gauge theories
We consider the one-loop effective potential at zero temperature in field
theories with anisotropic space-time scaling, with critical exponent ,
including scalar, fermion and gauge fields. The fermion determinant generates a
symmetry breaking term at one loop in the effective potential and a local
minimum appears, for non zero scalar field, for every value of the Yukawa
coupling. Depending on the relative strength of the coupling constants for the
scalar and the gauge field, we find a second symmetry breaking local minimum in
the effective potential for a bigger value of the scalar field.Comment: 12 pages, 3 figures. Minor corrections in the text, results unchange
Effects of the cosmological expansion on the bubble nucleation rate for relativistic first-order phase transitions
I calculate the first corrections to the dynamical pre-exponential factor of
the bubble nucleation rate for a relativistic first-order phase transition in
an expanding cosmological background by estimating the effects of the Hubble
expansion rate on the critical bubbles of Langer's statistical theory of
metastability. I also comment on possible applications and problems that arise
when one considers the field theoretical extensions of these results (the
Coleman-De Luccia and Hawking-Moss instantons and decay rates).Comment: 14 pages, LaTeX, no figures, final version to appear in PR
Conference on a Disk: A Successful Experiment in Hypermedia Publishing (Extended Abstract)
Academic conferences are a long-standing and effective form of multimedia communication. Conference participants can transmit and recieve information through sight, speech, gesture, text, and touch. This same-time, same-place communication is sufficiently valuable to justify large investments in time and travel funds. Printed conference proceedings are attempts to recapture the value of a life conference, but they are limited by a fragmented and inefficient approach to the problem. We addressed this problem in the multimedia proceedings of the DAGS\u2792 conference. The recently published CD-ROM delibers text, graphic, audio, and video information as an integrated whole, with extensive provisions for random access and hypermedia linking. We belive that this project provides a model for future conference publications and highlights some of the research issues that must be resolved before similar publications can be quickly and inexpensively produced
Non-topological solitons as nucleation sites for cosmological phase transitions
I consider quantum field theories that admit charged non-topological solitons
of the Q-ball type, and use the fact that in a first-order cosmological phase
transition, below the critical temperature, there is a value of the soliton
charge above which the soliton becomes unstable and expands, converting space
to the true vacuum, much like a critical bubble in the case of ordinary
tunneling. Using a simple model for the production rate of Q-balls through
charge accretion during a random walk out of equilibrium, I calculate the
probability for the formation of critical charge solitons and estimate the
amount of supercooling needed for the phase transition to be completed.Comment: 20 pages, 2 figures, some comments and references adde
Predicting Ground Subsidence Induced by Pumping Combining Space Measurements and Geotechnical Modeling: Application in the Thessaly Region, Greece
Space technology is a new technology that provides cost-effective measurements of past displacement data. Based on these displacement measurements, within the framework of the European Space Agency’s GMES Terrafirma Project, an improved geotechnical design approach is proposed combining geotechnical modelling and space measurements to predict ground subsidence induced by the lowering of the water table. Then the proposed methodology is applied to predict future displacement at the Thessaly plain - Carla region, Greece due to excessive pumping
Operationalizing ecological connectivity in spatial conservation planning with Marxan Connect
1. Globally, protected areas are being established to protect biodiversity and to promote ecosystem resilience. The typical spatial conservation planning process leading to the creation of these protected areas focuses on representation and replication of ecological features, often using decision support tools such as Marxan. Yet, despite the important role ecological connectivity has in metapopulation persistence and resilience, Marxan currently requires manual input or specialized scripts to explicitly consider connectivity.
2. ‘Marxan Connect’ is a new open source, open access Graphical User Interface (GUI) tool designed to assist conservation planners with the appropriate use of data on ecological connectivity in protected area network planning.
3. Marxan Connect can facilitate the use of estimates of demographic connectivity (e.g. derived from animal tracking data, dispersal models, or genetic tools) or structural landscape connectivity (e.g. isolation by resistance). This is accomplished by calculating metapopulation‐relevant connectivity metrics (e.g. eigenvector centrality) and treating those as conservation features or by including the connectivity data as a spatial dependency amongst sites in the prioritization process.
4. Marxan Connect allows a wide group of users to incorporate directional ecological connectivity into conservation planning with Marxan. The solutions provided by Marxan Connect, combined with ecologically relevant post‐hoc testing, are more likely to support persistent and resilient metapopulations (e.g. fish stocks) and provide better protection for biodiversity
OmniLabel: A Challenging Benchmark for Language-Based Object Detection
Language-based object detection is a promising direction towards building a
natural interface to describe objects in images that goes far beyond plain
category names. While recent methods show great progress in that direction,
proper evaluation is lacking. With OmniLabel, we propose a novel task
definition, dataset, and evaluation metric. The task subsumes standard- and
open-vocabulary detection as well as referring expressions. With more than 28K
unique object descriptions on over 25K images, OmniLabel provides a challenging
benchmark with diverse and complex object descriptions in a naturally
open-vocabulary setting. Moreover, a key differentiation to existing benchmarks
is that our object descriptions can refer to one, multiple or even no object,
hence, providing negative examples in free-form text. The proposed evaluation
handles the large label space and judges performance via a modified average
precision metric, which we validate by evaluating strong language-based
baselines. OmniLabel indeed provides a challenging test bed for future research
on language-based detection.Comment: ICCV 2023 Oral - Visit our project website at
https://www.omnilabel.or
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