Causality - Complexity - Consistency: Can Space-Time Be Based on Logic and Computation?

The difficulty of explaining non-local correlations in a fixed causal structure sheds new light on the old debate on whether space and time are to be seen as fundamental. Refraining from assuming space-time as given a priori has a number of consequences. First, the usual definitions of randomness depend on a causal structure and turn meaningless. So motivated, we propose an intrinsic, physically motivated measure for the randomness of a string of bits: its length minus its normalized work value, a quantity we closely relate to its Kolmogorov complexity (the length of the shortest program making a universal Turing machine output this string). We test this alternative concept of randomness for the example of non-local correlations, and we end up with a reasoning that leads to similar conclusions as in, but is conceptually more direct than, the probabilistic view since only the outcomes of measurements that can actually all be carried out together are put into relation to each other. In the same context-free spirit, we connect the logical reversibility of an evolution to the second law of thermodynamics and the arrow of time. Refining this, we end up with a speculation on the emergence of a space-time structure on bit strings in terms of data-compressibility relations. Finally, we show that logical consistency, by which we replace the abandoned causality, it strictly weaker a constraint than the latter in the multi-party case.Comment: 17 pages, 16 figures, small correction

A Conflict-Resilient Lock-Free Calendar Queue for Scalable Share-Everything PDES Platforms

Emerging share-everything Parallel Discrete Event Simulation (PDES) platforms rely on worker threads fully sharing the workload of events to be processed. These platforms require efficient event pool data structures enabling high concurrency of extraction/insertion operations. Non-blocking event pool algorithms are raising as promising solutions for this problem. However, the classical non-blocking paradigm leads concurrent conflicting operations, acting on a same portion of the event pool data structure, to abort and then retry. In this article we present a conflict-resilient non-blocking calendar queue that enables conflicting dequeue operations, concurrently attempting to extract the minimum element, to survive, thus improving the level of scalability of accesses to the hot portion of the data structure---namely the bucket to which the current locality of the events to be processed is bound. We have integrated our solution within an open source share-everything PDES platform and report the results of an experimental analysis of the proposed concurrent data structure compared to some literature solutions

Traveling Trends: Social Butterflies or Frequent Fliers?

Trending topics are the online conversations that grab collective attention on social media. They are continually changing and often reflect exogenous events that happen in the real world. Trends are localized in space and time as they are driven by activity in specific geographic areas that act as sources of traffic and information flow. Taken independently, trends and geography have been discussed in recent literature on online social media; although, so far, little has been done to characterize the relation between trends and geography. Here we investigate more than eleven thousand topics that trended on Twitter in 63 main US locations during a period of 50 days in 2013. This data allows us to study the origins and pathways of trends, how they compete for popularity at the local level to emerge as winners at the country level, and what dynamics underlie their production and consumption in different geographic areas. We identify two main classes of trending topics: those that surface locally, coinciding with three different geographic clusters (East coast, Midwest and Southwest); and those that emerge globally from several metropolitan areas, coinciding with the major air traffic hubs of the country. These hubs act as trendsetters, generating topics that eventually trend at the country level, and driving the conversation across the country. This poses an intriguing conjecture, drawing a parallel between the spread of information and diseases: Do trends travel faster by airplane than over the Internet?Comment: Proceedings of the first ACM conference on Online social networks, pp. 213-222, 201

A quantum-information-theoretic complement to a general-relativistic implementation of a beyond-Turing computer

There exists a growing literature on the so-called physical Church-Turing thesis in a relativistic spacetime setting. The physical Church-Turing thesis is the conjecture that no computing device that is physically realizable (even in principle) can exceed the computational barriers of a Turing machine. By suggesting a concrete implementation of a beyond-Turing computer in a spacetime setting, Istv\'an N\'emeti and Gyula D\'avid (2006) have shown how an appreciation of the physical Church-Turing thesis necessitates the confluence of mathematical, computational, physical, and indeed cosmological ideas. In this essay, I will honour Istv\'an's seventieth birthday, as well as his longstanding interest in, and his seminal contributions to, this field going back to as early as 1987 by modestly proposing how the concrete implementation in N\'emeti and D\'avid (2006) might be complemented by a quantum-information-theoretic communication protocol between the computing device and the logician who sets the beyond-Turing computer a task such as determining the consistency of Zermelo-Fraenkel set theory. This suggests that even the foundations of quantum theory and, ultimately, quantum gravity may play an important role in determining the validity of the physical Church-Turing thesis.Comment: 27 pages, 5 figures. Forthcoming in Synthese. Matches published versio

Energy constrained sandpile models

We study two driven dynamical systems with conserved energy. The two automata contain the basic dynamical rules of the Bak, Tang and Wiesenfeld sandpile model. In addition a global constraint on the energy contained in the lattice is imposed. In the limit of an infinitely slow driving of the system, the conserved energy $E$ becomes the only parameter governing the dynamical behavior of the system. Both models show scale free behavior at a critical value $E_c$ of the fixed energy. The scaling with respect to the relevant scaling field points out that the developing of critical correlations is in a different universality class than self-organized critical sandpiles. Despite this difference, the activity (avalanche) probability distributions appear to coincide with the one of the standard self-organized critical sandpile.Comment: 4 pages including 3 figure

Extracting News Events from Microblogs

Twitter stream has become a large source of information for many people, but the magnitude of tweets and the noisy nature of its content have made harvesting the knowledge from Twitter a challenging task for researchers for a long time. Aiming at overcoming some of the main challenges of extracting the hidden information from tweet streams, this work proposes a new approach for real-time detection of news events from the Twitter stream. We divide our approach into three steps. The first step is to use a neural network or deep learning to detect news-relevant tweets from the stream. The second step is to apply a novel streaming data clustering algorithm to the detected news tweets to form news events. The third and final step is to rank the detected events based on the size of the event clusters and growth speed of the tweet frequencies. We evaluate the proposed system on a large, publicly available corpus of annotated news events from Twitter. As part of the evaluation, we compare our approach with a related state-of-the-art solution. Overall, our experiments and user-based evaluation show that our approach on detecting current (real) news events delivers a state-of-the-art performance

Geodetic and seismological observations applied for investigation of subsidence formation in the CSM Mine (Czech Republic)

Purpose. Undermined areas are affected by the creation of subsidence depressions due to long-term underground mining. In general, different geodetic methods are applied to obtain further information needed to determine the spatial development of the formation of a subsidence depression. Methods. Application of these surveying methods enables us to investigate spatio-temporal changes of landscape relief in detail. Although the development of surveying technologies is in progress at present, conventional geodetic methods are still in use. Nowadays Global Navigation Satellite System (GNSS) surveying is mostly used for obtaining the actual degree of relief affection in undermined areas. Considering that during coal extraction induced seismic events are observed underground and on the surface, some seismological methods for their parameters determination were applied, e.g. foci location of induced seismic events, their classification by units of magnitude and by released seismic energy, frequency energy distribution, construction of Benioff graph and its derivation for assessment of adjacent working endangerment. Findings. The results of the assessment and analyses of spatial data demonstrate the real development of the sub-sidence depression under study and the relief changes of the landscape during the investigated period, respectively. Originality. It was recognized that all methods applied in this study represent very helpful tools for surveying subsidence depression and simultaneous monitoring of seismic activity development on an undermined area. Practical implications. Based on obtained results it is possible to perform a comparison of current subsidence dimensions with the original rate of affection.Мета. Дослідження причин утворення просідань земної поверхні в околиці шахти CSM (Чеська Республіка) за допомогою геодезичних і сейсмологічних методів спостереження. Методика. В роботі використано сейсмічні методи для визначення локалізації місць явищ техногенної сейсмічності, їх класифікації за магнітудами і кількістю виділеної сейсмічної енергії та її частотного розподілу; побудову графіка Беньофа та його модифікацію для оцінки безпеки суміжних до шахти територій; моделювання просторово-часового розвитку опускання поверхні за допомогою GPS-вимірювань. Результати. У результаті оцінки та аналізу просторових даних була визначена реальна область просідань і зміни навколишнього рельєфу протягом всього часу проведення досліджень. Ґрунтуючись на аналізі наявних сейсмічних даних та наземних GPS-вимірювань, встановлено, що протягом досліджуваного періоду ніякого виразного впливу розвитку зсувів і деформацій поверхні через сейсмічну активність не спостерігалося. Виконано моделювання просторово-часового розвитку опускання поверхні у досліджуваній області, що дозволило визначити швидкість осідання поверхні з часом. Визначено горизонтальні переміщення окремих точок і встановлено, що великі тектонічні розломи створюють природний бар’єр зсувам у масиві. Наукова новизна. Використання унікального комплексу методів дослідження та моніторингу, застосовані у даній роботі, дозволили точно виявити область просідання поверхні й причини її утворення, а також здійснити моніторинг сейсмічної активності в районі, порушеному гірничими роботами. Практична значимість. Отримані результати дозволяють порівняти сучасний стан утворених просідань з їх початковими параметрами, а також прогнозувати інтенсивність їх розвитку у часі.Цель. Исследование причин образования проседания земной поверхности в окрестности шахты CSM (Чешская Республика) при помощи геодезических и сейсмологических методов наблюдения. Методика. В работе использовано сейсмические методы для определения локализации очагов явлений техногенной сейсмичности, их классификации по магнитудам и количеству выделенной сейсмической энергии и ее частотного распределения; построение графика Беньофа и его модификацию для оценки безопасности прилегающих к шахте территорий; моделирование пространственно-временного развития опускания поверхности при помощи GPS-измерений. Результаты. В результате оценки и анализа пространственных данных была определена реальная область проседаний и изменения окружающего рельефа в течение всего времени проведения исследований. Основываясь на анализе имеющихся сейсмических данных и наземных GPS-измерений, установлено, что в течение исследуемого периода никакого выразительного влияния развития смещений и деформаций поверхности из-за сейсмической активности не наблюдалось. Выполнено моделирование пространственно-временного развития опускания поверхности в исследуемой области, позволившее определить скорость оседания поверхности с течением времени. Определены горизонтальные перемещения отдельных точек и установлено, что крупные тектонические разломы создают естественный барьер смещениям в массиве. Научная новизна. Использование уникального комплекса методов исследования и мониторинга, примененные в данной работе, позволили точно выявить область проседания поверхности и причины ее образования, а также осуществить мониторинг сейсмической активности в районе, затронутом горными работами. Практическая значимость. Полученные результаты позволяют сравнить современное состояние образовавшейся впадины с ее первоначальными параметрами, а также прогнозировать интенсивность ее развития со временем.This article was written in connection with the Project Institute of Clean Technologies for Mining and Utilization of Raw Materials for Energy Use – Sustainability Program (reg. No.CZ.1.05/2.1.00/03.0082 and MSMT LO1406), which is supported by the Research and Development for Innovations Operational Programme financed by the Structural Funds of the European Union and the Czech Republic project for the longterm conceptual development of research organisations (RVO: 68145535). Many thanks to Dr. Karel Holub, emeritus researcher from the Institute of Geonics of the Czech Academy of Sciences, for his helpful comments and advices during preparation of manuscript. R.I.P