Artículos con la etiqueta ‘computación’

Data Portraits: Connecting People of Opposing Views

Por • 4 dic, 2013 • Category: sociologia

Social networks allow people to connect with each other and have conversations on a wide variety of topics. However, users tend to connect with like-minded people and read agreeable information, a behavior that leads to group polarization. Motivated by this scenario, we study how to take advantage of partial homophily to suggest agreeable content to users authored by people with opposite views on sensitive issues. We introduce a paradigm to present a data portrait of users, in which their characterizing topics are visualized and their corresponding tweets are displayed using an organic design. Among their tweets we inject recommended tweets from other people considering their views on sensitive issues in addition to topical relevance, indirectly motivating connections between dissimilar people. To evaluate our approach, we present a case study on Twitter about a sensitive topic in Chile, where we estimate user stances for regular people and find intermediary topics.

When does a physical system compute?

Por • 3 oct, 2013 • Category: Filosofía

Computing is a high-level process of a physical system. Recent interest in non-standard computing systems, including quantum and biological computers, has brought this physical basis of computing to the forefront. There has been, however, no consensus on how to tell if a given physical system is acting as a computer or not; leading to confusion over novel computational devices, and even claims that every physical event is a computation. In this paper we introduce a formal framework that can be used to determine whether or not a physical system is performing a computation. We demonstrate how the abstract computational level interacts with the physical device level, drawing the comparison with the use of mathematical models to represent physical objects in experimental science. This powerful formulation allows a precise description of the similarities between experiments, computation, simulation, and technology. We give conditions that must be satisfied in order for computation to be occurring, and apply these to a range of non-standard computing scenarios. The framework also covers broader computing contexts, where there is no obvious human computer user. We define the critical notion of a ‘computational entity’, and show the role this plays in defining when computing is taking place in physical systems.

Towards a Church-Turing-Thesis for Infinitary Computations

Por • 3 ago, 2013 • Category: Ciencia y tecnología

We consider the question whether there is an infinitary analogue of the Church-Turing-thesis. To this end, we argue that there is an intuitive notion of transfinite computability and build a canonical model, called Idealized Agent Machines ($IAM$s) of this which will turn out to be equivalent in strength to the Ordinal Turing Machines defined by P. Koepke.

Nonlinear quantum search using the Gross–Pitaevskii equation

Por • 27 jun, 2013 • Category: Leyes

We solve the unstructured search problem in constant time by computing with a physically motivated nonlinearity of the Gross–Pitaevskii type. This speedup comes, however, at the novel expense of increasing the time-measurement precision. Jointly optimizing these resource requirements results in an overall scaling of N1/4. This is a significant, but not unreasonable, improvement over the N1/2 scaling of Grover’s algorithm. Since the Gross–Pitaevskii equation approximates the multi-particle (linear) Schrödinger equation, for which Grover’s algorithm is optimal, our result leads to a quantum information-theoretic lower bound on the number of particles needed for this approximation to hold, asymptotically

A global quantum network

Por • 17 jun, 2013 • Category: Ciencia y tecnología

By quantum-mechanically coupling laser-cooled atoms to glass fiber cables, Vienna University of Technology researchers have developed a way to store quantum information over a long enough period of time to allow for entangling atoms hundreds of kilometers apart via fiber cables. The problem with previous research is that after a short time, the quantum information stored in the atoms is lost as it leaks into the environment — an effect called “decoherence.” This finding is a fundamental building block for a global fiber-based quantum communication network, the researchers suggest.

Where the “it from bit” come from?

Por • 10 jun, 2013 • Category: Filosofía

In his 1989 essay, John Archibald Wheeler has tried to answer the eternal question of existence. He did it by searching for links between information, physics, and quanta. The main concept emerging from his essay is that “every physical quantity, every it, derives its ultimate significance from bits, binary yes-or-no indications”. This concept has been summarized in the catchphrase “it from bit”. In the Wheeler’s essay, it is possible to read several times the echoes of the philosophy of Niels Bohr. The Danish physicist has pointed out how the quantum and relativistic physics – forcing us to abandon the anchor of the visual reference of common sense – have imposed a greater attention to the language. Bohr did not deny the physical reality, but recognizes that there is always need of a language no matter what a person wants to do. To put it as Carlo Sini, language is the first toolbox that man has at hands to analyze the experience. It is not a thought translated into words, because to think is to operate with signs as reminded us by various philosophers from Leonardo da Vinci to Ludwig Wittgenstein. […]

On Dependence Logic

Por • 6 jun, 2013 • Category: Educacion

We give an overview of some developments in dependence and independence logic. This is a tiny selection, intended for a newcomer, from a rapidly growing literature on the topic. Furthermore, we discuss conditional independence atoms and we prove that conditional and non-conditional independence logic are equivalent. Finally, we briefly discuss an application of our logics to belief representation.

The Recomputation Manifesto

Por • 3 jun, 2013 • Category: Leyes

Replication of scientific experiments is critical to the advance of science. Unfortunately, the discipline of Computer Science has never treated replication seriously, even though computers are very good at doing the same thing over and over again. Not only are experiments rarely replicated, they are rarely even replicable in a meaningful way. Scientists are being encouraged to make their source code available, but this is only a small step. Even in the happy event that source code can be built and run successfully, running code is a long way away from being able to replicate the experiment that code was used for. I propose that the discipline of Computer Science must embrace replication of experiments as standard practice. I propose that the only credible technique to make experiments truly replicable is to provide copies of virtual machines in which the experiments are validated to run. I propose that tools and repositories should be made available to make this happen. I propose to be one of those who makes it happen.

The Unary Fragments of Metric Interval Temporal Logic: Bounded versus Lower bound Constraints (Full Version)

Por • 17 may, 2013 • Category: Filosofía

We study two unary fragments of the well-known metric interval temporal logic MITL[U_I,S_I] that was originally proposed by Alur and Henzinger, and we pin down their expressiveness as well as satisfaction complexities. We show that MITL[F_\inf,P_\inf] which has unary modalities with only lower-bound constraints is (surprisingly) expressively complete for Partially Ordered 2-Way Deterministic Timed Automata (po2DTA) and the reduction from logic to automaton gives us its NP-complete satisfiability. We also show that the fragment MITL[F_b,P_b] having unary modalities with only bounded intervals has \nexptime-complete satisfiability. But strangely, MITL[F_b,P_b] is strictly less expressive than MITL[F_\inf,P_\inf]. We provide a comprehensive picture of the decidability and expressiveness of various unary fragments of MITL.

Logical Fuzzy Preferences

Por • 20 abr, 2013 • Category: Crítica

We present a unified logical framework for representing and reasoning about both quantitative and qualitative preferences in fuzzy answer set programming, called fuzzy answer set optimization programs. The proposed framework is vital to allow defining quantitative preferences over the possible outcomes of qualitative preferences. We show the application of fuzzy answer set optimization programs to the course scheduling with fuzzy preferences problem. To the best of our knowledge, this development is the first to consider a logical framework for reasoning about quantitative preferences, in general, and reasoning about both quantitative and qualitative preferences in particular.