IA Scholar Query: Probabilistic Tree Automata
https://scholar.archive.org/
Internet Archive Scholar query results feedeninfo@archive.orgSat, 06 Aug 2022 00:00:00 GMTfatcat-scholarhttps://scholar.archive.org/help1440One-Clock Priced Timed Games with Negative Weights
https://scholar.archive.org/work/sd2mu6piy5gerjqnotqkoib62q
Priced timed games are two-player zero-sum games played on priced timed automata (whose locations and transitions are labeled by weights modelling the cost of spending time in a state and executing an action, respectively). The goals of the players are to minimise and maximise the cost to reach a target location, respectively. We consider priced timed games with one clock and arbitrary integer weights and show that, for an important subclass of them (the so-called simple priced timed games), one can compute, in pseudo-polynomial time, the optimal values that the players can achieve, with their associated optimal strategies. As side results, we also show that one-clock priced timed games are determined and that we can use our result on simple priced timed games to solve the more general class of so-called negative-reset-acyclic priced timed games (with arbitrary integer weights and one clock). The decidability status of the full class of priced timed games with one-clock and arbitrary integer weights still remains open.Thomas Brihaye, Gilles Geeraerts, Axel Haddad, Engel Lefaucheux, Benjamin Monmegework_sd2mu6piy5gerjqnotqkoib62qSat, 06 Aug 2022 00:00:00 GMTMinimality Notions via Factorization Systems and Examples
https://scholar.archive.org/work/dhxgf7e73vg5vfrmshopofkfzi
For the minimization of state-based systems (i.e. the reduction of the number of states while retaining the system's semantics), there are two obvious aspects: removing unnecessary states of the system and merging redundant states in the system. In the present article, we relate the two minimization aspects on coalgebras by defining an abstract notion of minimality. The abstract notions minimality and minimization live in a general category with a factorization system. We will find criteria on the category that ensure uniqueness, existence, and functoriality of the minimization aspects. The proofs of these results instantiate to those for reachability and observability minimization in the standard coalgebra literature. Finally, we will see how the two aspects of minimization interact and under which criteria they can be sequenced in any order, like in automata minimization.Thorsten Wißmannwork_dhxgf7e73vg5vfrmshopofkfziThu, 04 Aug 2022 00:00:00 GMTLIPIcs, Volume 238, DNA 28, Complete Volume
https://scholar.archive.org/work/627o3xn4vbbgpdox5dwolgcuny
LIPIcs, Volume 238, DNA 28, Complete VolumeThomas E. Ouldridge, Shelley F. J. Wickhamwork_627o3xn4vbbgpdox5dwolgcunyThu, 04 Aug 2022 00:00:00 GMTInfinite Separation between General and Chromatic Memory
https://scholar.archive.org/work/mnyhycxrkzbjjjj7gpvdyzfoze
In this note, we answer a question from [Alexander Kozachinskiy. State Complexity of Chromatic Memory in Infinite-Duration Games, arXiv:2201.09297]. Namely, we construct a winning condition W over a finite set of colors such that, first, every finite arena has a strategy with 2 states of general memory which is optimal with respect to W, and second, there exists no k such that every finite arena has a strategy with k states of chromatic memory which is optimal with respect to W.Alexander Kozachinskiywork_mnyhycxrkzbjjjj7gpvdyzfozeThu, 04 Aug 2022 00:00:00 GMTProbabilistic Verification Beyond Context-Freeness
https://scholar.archive.org/work/dkkxofw6wjdzvntebeldwiha3y
Probabilistic pushdown automata (recursive state machines) are a widely known model of probabilistic computation associated with many decidable problems concerning termination (time) and lineartime model checking. Higher-order recursion schemes (HORS) are a prominent formalism for the analysis of higher-order computation. Recent studies showed that, for the probabilistic variant of HORS, even the basic problem of determining whether a scheme terminates almost surely is undecidable. Moreover, the undecidability already holds for order-2 schemes (order-1 schemes are known to correspond to pushdown automata). Motivated by these results, we study restricted probabilistic treestack automata (rPTSA), which in the nondeterministic setting are known to characterise a proper extension of context-free languages, namely, the multiple context-free languages. We show that several verification problems, such as almost-sure termination, positive almost-sure termination and ω-regular model checking are decidable for this class. At the level of higher-order recursion schemes, this corresponds to being able to verify a probabilistic version of MAHORS (which are a multiplicative-additive version of higher-order recursion schemes). MAHORS extend order-1 recursion schemes and are incomparable with order-2 schemes. CCS CONCEPTS • Theory of computation → Grammars and context-free languages; Probabilistic computation; Program verification. KEYWORDS probabilistic (affine additive) higher-order recursion schemes; restricted (probabilistic) tree stack automata; computing termination probability; deciding almost sure termination; first-order theory of the realsGuanyan Li, Andrzej Murawski, Luke Ongwork_dkkxofw6wjdzvntebeldwiha3yTue, 02 Aug 2022 00:00:00 GMTGraded Monads and Behavioural Equivalence Games
https://scholar.archive.org/work/5vvsxffo3nelfjcksilzdw2xha
The framework of graded semantics uses graded monads to capture behavioural equivalences of varying granularity, for example as found in the linear-time / branching-time spectrum, over general system types. We describe a generic Spoiler-Duplicator game for graded semantics that is extracted from the given graded monad, and may be seen as playing out an equational proof; instances include standard pebble games for simulation and bisimulation as well as games for trace-like equivalences and coalgebraic behavioural equivalence. Considerations on an infinite variant of such games lead to a novel notion of infinite-depth graded semantics. Under reasonable restrictions, the infinite-depth graded semantics associated to a given graded equivalence can be characterized in terms of a determinization construction for coalgebras under the equivalence at hand.Chase Ford, Stefan Milius, Lutz Schröder, Harsh Beohar, Barbara Königwork_5vvsxffo3nelfjcksilzdw2xhaTue, 02 Aug 2022 00:00:00 GMTIdentity Testing for Radical Expressions
https://scholar.archive.org/work/n3pc3gbumfcvjflpgwlwc6axsu
We study the Radical Identity Testing problem (RIT): Given an algebraic circuit representing a polynomial f ∈ Z[x 1 , . . . , x k ] and nonnegative integers a 1 , . . . , a k and d 1 , . . . , d k , written in binary, test whether the polynomial vanishes at the real radicals We place the problem in coNP assuming the Generalised Riemann Hypothesis (GRH), improving on the straightforward PSPACE upper bound obtained by reduction to the existential theory of reals. Next we consider a restricted version, called 2-RIT, where the radicals are square roots of prime numbers, written in binary. It was known since the work of Chen and Kao [16] that 2-RIT is at least as hard as the polynomial identity testing problem, however no better upper bound than PSPACE was known prior to our work. We show that 2-RIT is in coRP assuming GRH and in coNP unconditionally. Our proof relies on theorems from algebraic and analytic number theory, such as the Chebotarev density theorem and quadratic reciprocity. CCS CONCEPTS • Mathematics of computing → Probabilistic algorithms; • Computing methodologies → Algebraic algorithms; Number theory algorithms.Nikhil Balaji, Klara Nosan, Mahsa Shirmohammadi, James Worrellwork_n3pc3gbumfcvjflpgwlwc6axsuTue, 02 Aug 2022 00:00:00 GMTTemporal Team Semantics Revisited
https://scholar.archive.org/work/xtaqjvpgrfbmjjjqjn3q7gcvfy
In this paper, we study a novel approach to asynchronous hyperproperties by reconsidering the foundations of temporal team semantics. We consider three logics: TeamLTL, TeamCTL and TeamCTL * , which are obtained by adding quantification over so-called time evaluation functions controlling the asynchronous progress of traces. We then relate synchronous TeamLTL to our new logics and show how it can be embedded into them. We show that the model checking problem for ∃TeamCTL with Boolean disjunctions is highly undecidable by encoding recurrent computations of non-deterministic 2-counter machines. Finally, we present a translation from TeamCTL * to Alternating Asynchronous Büchi Automata and obtain decidability results for the path checking problem as well as restricted variants of the model checking and satisfiability problems. CCS CONCEPTS • Theory of computation → Modal and temporal logics; Problems, reductions and completeness; Logic and verification.Jens Oliver Gutsfeld, Arne Meier, Christoph Ohrem, Jonni Virtemawork_xtaqjvpgrfbmjjjqjn3q7gcvfyTue, 02 Aug 2022 00:00:00 GMTTensor types and their use in physics
https://scholar.archive.org/work/26gqbpepizdk7oon7jz5tbeyym
The content of this paper can be roughly organized into a three-level hierarchy of generality. At the first, most general level, we introduce a new language which allows us to express various categorical structures in a systematic and explicit manner in terms of so-called 2-schemes. Although 2-schemes can formalize categorical structures such as symmetric monoidal categories, they are not limited to this, and can be used to define structures with no categorical analogue. Most categorical structures come with an effective graphical calculus such as string diagrams for symmetric monoidal categories, and the same is true more generally for interesting 2-schemes. In this work, we focus on one particular non-categorical 2-scheme, whose instances we refer to as tensor types. At the second level of the hierarchy, we work out different flavors of this 2-scheme in detail. The effective graphical calculus of tensor types is that of tensor networks or Penrose diagrams, that is, string diagrams without a flow of time. As such, tensor types are similar to compact closed categories, though there are various small but potentially important differences. Also, the two definitions use completely different mechanisms despite both being examples of 2-schemes. At the third level of the hierarchy, we provide a long list of different families of concrete tensor types, in a way which makes them accessible to concrete computations, motivated by their potential use in physics. Different tensor types describe different types of physical models, such as classical or quantum physics, deterministic or statistical physics, many-body or single-body physics, or matter with or without symmetries or fermions.Andreas Bauer, Alexander Nietnerwork_26gqbpepizdk7oon7jz5tbeyymMon, 01 Aug 2022 00:00:00 GMTPSAA: Provable Secure and Anti-Quantum Authentication Based on Randomized RLWE for Space Information Network
https://scholar.archive.org/work/z72u23jyb5anjcjkspn6y5vqxi
Currently, due to the high scalability and global coverage of space information network (SIN), more service providers and users are willing to provide or subscribe to personal services through the satellite network. However, the messages are transmitted in public satellite-ground links, which makes access users vulnerable to various forms of attacks. Existing authentication protocols do not meet the expected security and short delay requirements to ensure the security of real-time user access and the confidentiality of communication content. Moreover, with the development of quantum computers, the difficult problems such as ECDLP and DLP have also been proven to be solvable in polynomial time, leading to new threats. Therefore, in this paper, we propose a provably secure and anti-quantum authentication protocol based on randomized RLWE. The protocol not only meets the pre-defined security requirements, but also reduces the total delay of the authentication phase based on the pre-negotiation and fewer authentication transmission. In addition, a concise handover scheme is designed for signal handover scenarios caused by satellite dynamic topology. Further rigorous formal and informal security proofs and performance analysis show that our proposed protocol is more applicable to SIN, while ensuring higher security and resisting various attacks with lower authentication delay.Junyan Guo and Ye Du and Xuesong Wu and Meihong Li and Runfang Wu and Zhichao Sunwork_z72u23jyb5anjcjkspn6y5vqxiMon, 01 Aug 2022 00:00:00 GMTCardiac Comorbidity Risk Score: Zero-Burden Machine Learning to Improve Prediction of Postoperative Major Adverse Cardiac Events in Hip and Knee Arthroplasty
https://scholar.archive.org/work/b5kzej4nlfalte4vixaquejwvq
In this retrospective, observational study we introduce the Cardiac Comorbidity Risk Score, predicting perioperative major adverse cardiac events (MACE) after elective hip and knee arthroplasty. MACE is a rare but important driver of mortality, and existing tools, eg, the Revised Cardiac Risk Index demonstrate only modest accuracy. We demonstrate an artificial intelligence-based approach to identify patients at high risk of MACE within 4 weeks (primary outcome) of arthroplasty, that imposes zero additional burden of cost/resources. Methods and Results Cardiac Comorbidity Risk Score calculation uses novel machine learning to estimate MACE risk from patient electronic health records, without requiring blood work or access to any demographic data beyond that of sex and age, and accounts for variable/missing/incomplete information across patient records. Validated on a deidentified cohort (age >45 years, n=445 391), performance was evaluated using the area under the receiver operator characteristics curve (AUROC), sensitivity/specificity, positive predictive value, and positive/negative likelihood ratios. In our cohort (age 63.5±10.5 years, 58.2% women, 34.2%/65.8% hip/knee procedures), 0.19% (882) experienced the primary outcome. Cardiac Comorbidity Risk Score achieved area under the receiver operator characteristics curve=80.0±0.4% (95% CI) for women and 80.1±0.5% (95% CI) for males, with 36.4% and 35.1% sensitivities, respectively, at 95% specificity, significantly outperforming Revised Cardiac Risk Index across all studied age-, sex-, risk-, and comorbidity-based subgroups. Conclusions Cardiac Comorbidity Risk Score, a novel artificial intelligence-based screening tool using known and unknown comorbidity patterns, outperforms state-of-the-art in predicting MACE within 4 weeks postarthroplasty, and can identify patients at high risk that do not demonstrate traditional risk factors.Dmytro Onishchenko, Daniel S Rubin, James R van Horne, R Parker Ward, Ishanu Chattopadhyaywork_b5kzej4nlfalte4vixaquejwvqFri, 29 Jul 2022 00:00:00 GMTAI Makes Crypto Evolve
https://scholar.archive.org/work/q6saodcy2zgd3afclzbrlsbvum
The recent literature reveals a dichotomy formed by a coevolution between cryptography and Artificial Intelligence (AI). This dichotomy consists of two sides, namely Crypto-Influenced AI (CIAI) and AI-Influenced Cryptography (AIIC). While it is pertinent to investigate this dichotomy from both sides, the first side has already been studied. In this review, we focused on AIIC. We identified and analyzed the stages on the evolutionary path of AIIC. Moreover, we attempted to anticipate what the future may hold for AIIC given the impact of quantum computing on the present and the future of AI.Behrouz Zolfaghari, Takeshi Koshibawork_q6saodcy2zgd3afclzbrlsbvumFri, 29 Jul 2022 00:00:00 GMTSupporting and Verifying Transient Behavior Specifications in Chaos Engineering - Supplementary Materials
https://scholar.archive.org/work/rtvoup2pk5gkpap4yqvd3hjodi
Context: Chaos Engineering is an approach for investigating the resilience of software systems, i.e. their ability to withstand unexpected events, adapt accordingly, and continue providing functionality. An integral part of the approach is continuous experimentation, expressed in continuously executing so-called Chaos Experiments. A Chaos Experiment consists of two crucial elements, namely a steady-state hypothesis and an anomaly injection. Traditionally, during the experimentation process, the steady-state hypothesis is verified at the start of an experiment, after which the anomaly is injected, followed by a second evaluation of the steady-state hypothesis. This chaos experimentation process is well suited for identifying whether a system is in a steady-state after a failure is introduced. Problem: When applied, the traditional chaos experimentation approach can only verify whether the system is in a steady-state without providing any information about the time between the state changes, e.g. the recovery of the system. The experimentation process does not explicitly allow the specification of hypotheses regarding the transient behavior, i.e. the behaviors experienced during the transition between steady-states after a failure has been introduced. As a result, the experimentation process also does not support explicit verification of requirements on the transient behavior during the experiment, e.g, whether the response time stays below a given threshold all the time or whether a circuit breaker opens within a given time. Knowledge about such transient behaviors is beneficial for the stakeholders of the system. For example, assuming that high availability is of utmost importance for the business model of an application, a long period of recovery during which the application is unavailable after an unexpected failure could lead to considerable losses for various stakeholders. Objective: The first objective of the thesis is to examine how a transient behavior req [...]Denis Zahariev, Sebastian Frank, André van Hoorn, Mir Alireza Hakamianwork_rtvoup2pk5gkpap4yqvd3hjodiThu, 28 Jul 2022 00:00:00 GMTEmergence of nonlinear dynamics from spatial structure in tropical forest-grassland landscapes
https://scholar.archive.org/work/xwjxu54gobeyphkeq6ugjnnh5a
It is thought that tropical forests can exist as an alternative stable state to savanna [1, 2]. Therefore, the cumulative effects of perturbation by climate change or human impact may lead to crossing of a tipping point beyond which there is rapid large-scale forest dieback that is not easily reversed [3, 4]. Empirical evidence for bistability due to fire-vegetation feedbacks relies on tree cover bimodality in satellite-observed data [1, 2], but this may also be explained by spatial heterogeneity [5], or by biases in the data [6, 7]. Most modelling studies of alternative stable tree cover states have so far either relied on mean-field assumptions [5, 8-12] or not included the spatiotemporal dynamics of fire [13], making it hard to compare model results to spatial data. In this work, we analyse a microscopic model of tropical forest dynamics and fire spread, proposed by [14], to show how dynamics of forest area emerge from spatial structure. We find that the relation between forest perimeter and area determines the nonlinearity in forest growth while forest perimeter weighted by adjacent grassland area determines the nonlinearity in forest loss. Together with the linear changes, which are independent of spatial structure, these two effects lead to an emergent relation between forest area change and forest area, defining a single-variable ordinary differential equation. Such a relation between pattern and dynamics offers falsifiable theoretical predictions of the bistability hypothesis that are more closely linked to the underlying mechanism than bimodality and provides a criterion for forest vulnerability.Bert Wuyts, Jan Sieberwork_xwjxu54gobeyphkeq6ugjnnh5aThu, 28 Jul 2022 00:00:00 GMTRandom Quantum Circuits
https://scholar.archive.org/work/57bh7e2hhbawvbw6cngsbn555e
Quantum circuits -- built from local unitary gates and local measurements -- are a new playground for quantum many-body physics and a tractable setting to explore universal collective phenomena far-from-equilibrium. These models have shed light on longstanding questions about thermalization and chaos, and on the underlying universal dynamics of quantum information and entanglement. In addition, such models generate new sets of questions and give rise to phenomena with no traditional analog, such as new dynamical phases in quantum systems that are monitored by an external observer. Quantum circuit dynamics is also topical in view of experimental progress in building digital quantum simulators that allow control of precisely these ingredients. Randomness in the circuit elements allows a high level of theoretical control, with a key theme being mappings between real-time quantum dynamics and effective classical lattice models or dynamical processes. Many of the universal phenomena that can be identified in this tractable setting apply to much wider classes of more structured many-body dynamics.Matthew P. A. Fisher, Vedika Khemani, Adam Nahum, Sagar Vijaywork_57bh7e2hhbawvbw6cngsbn555eThu, 28 Jul 2022 00:00:00 GMTShort Synchronizing Words for Random Automata
https://scholar.archive.org/work/p7b2qjlwwvf5rkj4k2li723bce
We prove that a uniformly random automaton with n states on a 2-letter alphabet has a synchronizing word of length O(n^1/2log n) with high probability (w.h.p.). That is to say, w.h.p. there exists a word ω of such length, and a state v_0, such that ω sends all states to v_0. Prior to this work, the best upper bound was the quasilinear bound O(nlog^3n) due to Nicaud (2016). The correct scaling exponent had been subject to various estimates by other authors between 0.5 and 0.56 based on numerical simulations, and our result confirms that the smallest one indeed gives a valid upper bound (with a log factor). Our proof introduces the concept of w-trees, for a word w, that is, automata in which the w-transitions induce a (loop-rooted) tree. We prove a strong structure result that says that, w.h.p., a random automaton on n states is a w-tree for some word w of length at most (1+ϵ)log_2(n), for any ϵ>0. The existence of the (random) word w is proved by the probabilistic method. This structure result is key to proving that a short synchronizing word exists.Guillaume Chapuy, Guillem Perarnauwork_p7b2qjlwwvf5rkj4k2li723bceThu, 28 Jul 2022 00:00:00 GMTA generalized regionalization framework for geographical modelling and its application in spatial regression
https://scholar.archive.org/work/tqzj7lq7hbb4hdeqifpwn3zfei
Models applied to geographic data face a trade-off between producing general results and capturing local variations due to spatial heterogeneity. Spatial modelling within carefully defined regions offers an intermediate position between global and local models. However, current spatial optimization approaches to delineate homogeneous regions consider the similarity of attribute values, thus unable to identify regions with similar data generation processes described by geographical models. We propose a generalized regionalization framework, which optimizes region delineation corresponding to a model with region-specific parameters. Within this framework, we introduce three regionalization algorithms, namely automatic zoning procedure (AZP), K-Models, and Regional-K-Models. We adopt an objective function that jointly minimizes modelling errors and the complexity of the region scheme. Results from regression experiments indicate that the K-Models algorithm reconstructs the regions better than the baseline, according to Rand index and mutual information measures. Our suggested framework contributes to better capturing processes exhibiting spatial heterogeneity and may be applied to a wide range of modelling scenarios.Hao Guo, Andre Python, Yu Liuwork_tqzj7lq7hbb4hdeqifpwn3zfeiWed, 27 Jul 2022 00:00:00 GMTDynamic Shielding for Reinforcement Learning in Black-Box Environments
https://scholar.archive.org/work/mjoxnji3cbhldoasy7o3pdbuqi
It is challenging to use reinforcement learning (RL) in cyber-physical systems due to the lack of safety guarantees during learning. Although there have been various proposals to reduce undesired behaviors during learning, most of these techniques require prior system knowledge, and their applicability is limited. This paper aims to reduce undesired behaviors during learning without requiring any prior system knowledge. We propose dynamic shielding: an extension of a model-based safe RL technique called shielding using automata learning. The dynamic shielding technique constructs an approximate system model in parallel with RL using a variant of the RPNI algorithm and suppresses undesired explorations due to the shield constructed from the learned model. Through this combination, potentially unsafe actions can be foreseen before the agent experiences them. Experiments show that our dynamic shield significantly decreases the number of undesired events during training.Masaki Waga, Ezequiel Castellano, Sasinee Pruekprasert, Stefan Klikovits, Toru Takisaka, Ichiro Hasuowork_mjoxnji3cbhldoasy7o3pdbuqiWed, 27 Jul 2022 00:00:00 GMTPlanning and Learning: A Review of Methods involving Path-Planning for Autonomous Vehicles
https://scholar.archive.org/work/ifrzkwcunffpdgap6utq4ydiwi
This short review aims to make the reader familiar with state-of-the-art works relating to planning, scheduling and learning. First, we study state-of-the-art planning algorithms. We give a brief introduction of neural networks. Then we explore in more detail graph neural networks, a recent variant of neural networks suited for processing graph-structured inputs. We describe briefly the concept of reinforcement learning algorithms and some approaches designed to date. Next, we study some successful approaches combining neural networks for path-planning. Lastly, we focus on temporal planning problems with uncertainty.Kevin Osanlou, Christophe Guettier, Tristan Cazenave, Eric Jacopinwork_ifrzkwcunffpdgap6utq4ydiwiTue, 26 Jul 2022 00:00:00 GMTA Risk-Averse Preview-based Q-Learning Algorithm: Application to Highway Driving of Autonomous Vehicles
https://scholar.archive.org/work/r32unea4uzdhfeg3n4fj5osxri
A risk-averse preview-based Q-learning planner is presented for navigation of autonomous vehicles. To this end, the multi-lane road ahead of a vehicle is represented by a finite-state non-stationary Markov decision process (MDP). A risk assessment unit module is then presented that leverages the preview information provided by sensors along with a stochastic reachability module to assign reward values to the MDP states and update them as scenarios develop. A sampling-based risk-averse preview-based Q-learning algorithm is finally developed that generates samples using the preview information and reward function to learn risk-averse optimal planning strategies without actual interaction with the environment. The risk factor is imposed on the objective function to avoid fluctuation of the Q values, which can jeopardize the vehicle's safety and/or performance. The overall hybrid automaton model of the system is leveraged to develop a feasibility check unit module that detects unfeasible plans and enables the planner system to proactively react to the changes of the environment. Theoretical results are provided to bound the number of samples required to guarantee ϵ-optimal planning with a high probability. Finally, to verify the efficiency of the presented algorithm, its implementation on highway driving of an autonomous vehicle in a varying traffic density is considered.Majid Mazouchi, Subramanya Nageshrao, Hamidreza Modareswork_r32unea4uzdhfeg3n4fj5osxriMon, 25 Jul 2022 00:00:00 GMT