Trace Inclusion Research Articles

Early dark energy is not excluded by current large-scale structure data

We revisit the impact of early dark energy (EDE) on galaxy clustering using BOSS galaxy power spectra, analyzed using the effective field theory (EFT) of large-scale structure (LSS), and anisotropies of the cosmic microwave background (CMB) from Planck. Recent studies found that these data place stringent constraints on the maximum abundance of EDE allowed in the Universe. We argue here that their conclusions are a consequence of their choice of priors on the EDE parameter space, rather than any disagreement between the data and the model. For example, when considering EFT-LSS, CMB, and high-redshift supernovae data we find the EDE and $\Lambda$CDM models can provide statistically indistinguishable fits ($\Delta \chi^2 = 0.12$) with a relatively large value for the maximum fraction of energy density in the EDE ($f_{\rm ede} = 0.09$) and Hubble constant ($H_0 = 71$ km/s/Mpc) in the EDE model. Moreover, we demonstrate that the constraining power added from the inclusion of EFT-LSS traces to the potential tension between the power-spectrum amplitudes $A_s$ derived from BOSS and from Planck that arises even within the context of $\Lambda$CDM. Until this is better understood, caution should be used when interpreting EFT-BOSS+Planck constraints to models beyond $\Lambda$CDM. These findings suggest that EDE still provides a potential resolution to the Hubble tension and that it is worthwhile to test the predictions of EDE with future data-sets and further study its theoretical possibilities.

Abstraction refinement and antichains for trace inclusion of infinite state systems

A generic register automaton is a finite automaton equipped with variables (which may be viewed as counters or, more generally, registers) ranging over infinite data domains. A trace of a generic register automaton is an alternating sequence of alphabet symbols and values taken by the variables during an execution of the automaton. The problem addressed in this paper is the inclusion between the sets of traces (data languages) recognized by such automata. Since the problem is undecidable in general, we give a semi-algorithm based on a combination of abstraction refinement and antichains, which is proved to be sound and complete, but whose termination is not guaranteed. Moreover, we further enhance the proposed algorithm by exploiting a concept of data simulations, i.e., simulation relations aware of the data associated with the words. We have implemented our technique in a prototype tool and show promising results on multiple non-trivial examples.

Coexisting Rubies and Blue Sapphires from Major World Deposits: A Brief Review of Their Mineralogical Properties

Gem corundum deposits are typically divided into blue sapphire and ruby deposits. However, this classification often overlooks the fact that the precious stones produced are the same mineral with only an overall slight difference in their trace element profiles. It can take only a couple thousand ppm chromium to create the rich, red color expected of a ruby. This contribution deals specifically with economically important gem corundum mining regions that produce both blue sapphires and rubies either in comparable quantities (Mogok, Myanmar, and the basalt-related gem fields on the border between Thailand and Cambodia at Chanthaburi, Thailand, and Pailin, Cambodia) or predominantly blue sapphires with rare rubies (secondary Montana sapphire deposits and Yogo Gulch in Montana as well as the gem fields of Sri Lanka). Comparison of the trace element profiles and inclusions in the blue sapphire/ruby assemblages in these deposits shows that there are both monogenetic and polygenetic assemblages in which the blue sapphires and rubies have the same geological origin (monogenetic) or distinct geological origins (polygenetic). In the monogenetic assemblages, the rubies and blue sapphires have essentially indistinguishable inclusions and trace element chemistry profiles (with the exception of Cr contents). On the other hand, polygenetic assemblages are composed of rubies and blue sapphires with distinct inclusions and trace element chemistry profiles. Notably, in the monogenetic assemblages, chromium seems to vary independently from other trace elements. In these assemblages, Cr can vary by nearly four orders of magnitude with essentially no consistent relationship to other trace elements. The observations described herein are an attempt to address the question of what the geochemical and geological constraints are that turn gem corundum into a spectacular ruby.

Electronic and Structural Properties of Phase-Pure Magnetite Thin Films: Effect of Preferred Orientation

Materials in the form of thin films are getting worldwide attention because of their rapid development in the electronics industry. The demand is not only to prepare thin films using low-cost methods but also to induce tunable electronic properties (i.e., ferroelectricity, dielectric/impedance behavior, etc.) at room temperature. Keeping in view today’s demand for electronic materials, iron oxide thin films have been prepared using a low-cost sol–gel method with variation in the sol concentration in the range of 0.2–2.0 mM. Spin-coated films have been annealed at 300°C for 60 and 120 min in the presence of a magnetic field. The magnetite (Fe3O4) phase was observed at 1.4 mM, with preferred orientation along the (220) plane, under as-deposited and annealed conditions. The rest of the concentration range we studied results in the inclusion of small traces of maghemite (γ-Fe2O3) along with magnetite under all the preparation conditions. However, such inclusions result in the shift of preferred orientation from the (220) to the (400) plane of the magnetite (Fe3O4) phase. Formation of Fe3O4 phase has been confirmed using the Verwey transition at ∼ 124.8 K along with the appearance of a Raman A1g band at 667 cm−1. A high dielectric constant (∼ 80.23) and low tangent loss (∼ 0.00239) at log f = 5.0 were obtained at room temperature for 1.4 mM-based thin films. Such behavior may have been observed because of the high grain boundary resistance (5.5 × 104 Ω) and high grain boundary density (0.9939) at a sol concentration of 1.4 mM. An increase in dielectric constant and tangent loss was observed with the increase in temperature from 30 to 210°C. An activation energy of 2.007 eV was observed for the 1.4 mM-based thin films. The conductivity obeys Jonscher’s power law and has been associated with the overlapping large polaron tunneling model. Room-temperature ferroelectricity was observed for iron oxide thin films with maximum polarization (Pmax ∼ 14.74 μC/cm2) at 1.4 mM sol concentration.

TSO-to-TSO linearizability is undecidable

TSO-to-TSO linearizability is a variant of linearizability for concurrent libraries on the total store order (TSO) memory model. It is proved in this paper that TSO-to-TSO linearizability for a bounded number of processes is undecidable. We first show that the trace inclusion problem of a classic-lossy single-channel system, which is known undecidable, can be reduced to the history inclusion problem of specific libraries on the TSO memory model. Based on the equivalence between history inclusion and extended history inclusion for these libraries, we then prove that the extended history inclusion problem of libraries is undecidable on the TSO memory model. By means of extended history inclusion as an equivalent characterization of TSO-to-TSO linearizability, we finally prove that TSO-to-TSO linearizability is undecidable for a bounded number of processes. Additionally, we prove that all variants of history inclusion problems are undecidable on TSO for a bounded number of processes.

Trace inclusion for one-counter nets revisited

One-counter nets ( OCN) consist of a nondeterministic finite control and a single integer counter that cannot be fully tested for zero. They form a natural subclass of both One-Counter Automata, which allow zero-tests and Petri Nets/VASS, which allow multiple such weak counters. The trace inclusion problem has recently been shown to be undecidable for OCN. In this paper, we contrast the complexity of two natural restrictions which imply decidability.We show that trace inclusion between a OCN and a deterministic OCN is NL-complete, even with arbitrary binary-encoded initial counter-values as part of the input. Secondly, we show that the trace universality problem of nondeterministic OCN, which is equivalent to checking trace inclusion between a finite system and a OCN-process, is Ackermann-complete.

Effects of QCD equation of state on the stochastic gravitational wave background

Cosmological phase transitions can be a source of Stochastic Gravitational Wave (SGW) background. Apart from the dynamics of the phase transition, the characteristic frequency and the fractional energy density Ωgw of the SGW depends upon the temperature of the transition. In this article, we compute the SGW spectrum in the light of QCD equation of state provided by the lattice results. We find that the inclusion of trace anomaly from lattice QCD, enhances the SGW signal generated during QCD phase transition by ∼ 50% and the peak frequency of the QCD era SGW are shifted higher by ∼ 25% as compared to the earlier estimates without trace anomaly. This result is extremely significant for testing the phase transition dynamics near QCD epoch.

Quantitative fair simulation games

Simulation is an attractive alternative to language inclusion for automata as it is an under-approximation of language inclusion, but usually has much lower complexity. Simulation has also been extended in two orthogonal directions, namely, (1) fair simulation, for simulation over specified set of infinite runs; and (2) quantitative simulation, for simulation between weighted automata. While fair trace inclusion is PSPACE-complete, fair simulation can be computed in polynomial time. For weighted automata, the (quantitative) language inclusion problem is undecidable in general, whereas the (quantitative) simulation reduces to quantitative games, which admit pseudo-polynomial time algorithms.In this work, we study (quantitative) simulation for weighted automata with Büchi acceptance conditions, i.e., we generalize fair simulation from non-weighted automata to weighted automata. We show that imposing Büchi acceptance conditions on weighted automata changes many fundamental properties of the simulation games, yet they still admit pseudo-polynomial time algorithms.

Dynamic input/output automata: A formal and compositional model for dynamic systems

We present dynamic I/O automata (DIOA), a compositional model of dynamic systems. In DIOA, automata can be created and destroyed dynamically, as computation proceeds, and an automaton can dynamically change its signature, i.e., the set of actions in which it can participate.DIOA features operators for parallel composition, action hiding, action renaming, a notion of automaton creation, and a notion of behavioral subtyping by means of trace inclusion. DIOA can model mobility, using signature modification, and is hierarchical: a dynamically changing system of interacting automata is itself modeled as a single automaton.We also show that parallel composition, action hiding, action renaming, and (subject to some technical conditions) automaton creation are all monotonic with respect to trace inclusion: if one component is replaced by another whose traces are a subset of the former, then the set of traces of the system as a whole can only be reduced.

Specifying and Verifying External Behaviour of Fair Input/Output Automata by Using the Temporal Logic of Actions

Fair input/output (or I/O) automata are a state-machine model for specifying and verifying reactive and concurrent systems. For the verification purposes, one is usually interested only in the sequences of interactions fair I/O automata offer to their environment. These sequences are called fair traces. The usual approach to the verification consists in proving fair trace inclusion between fair I/O automata. This paper presents a simple approach to the specification of fair traces and shows how to establish a fair trace inclusion relation for a pair of fair I/O automata by using the temporal logic of actions.

Choreographies and Behavioural Contracts on the Way to Dynamic Updates

We survey our work on choreographies and behavioural contracts in multiparty interactions. In particular theories of behavioural contracts are presented which enable reasoning about correct service composition (contract compliance) and service substitutability (contract refinement preorder) under different assumptions concerning service communication: synchronous address or name based communication with patient non-preemptable or impatient invocations, or asynchronous communication. Correspondingly relations between behavioural contracts and choreographic descriptions are considered, where a contract for each communicating party is, e.g., derived by projection. The considered relations are induced as the maximal preoders which preserve contract compliance and global traces: we show maximality to hold (permitting services to be discovered/substituted independently for each party) when contract refinement preorders with all the above asymmetric communication means are considered and, instead, not to hold if the standard symmetric CCS/pi-calculus communication is considered (or when directly relating choreographies to behavioral contracts via a preorder, no matter the communication mean). The obtained maximal preorders are then characterized in terms of a new form of testing, called compliance testing, where not only tests must succeed but also the system under test (thus relating to controllability theory), and compared with classical preorders such as may/must testing, trace inclusion, etc. Finally, recent work about adaptable choreographies and behavioural contracts is presented, where the theory above is extended to update mechanisms allowing choreographies/contracts to be modified at run-time by internal (self-adaptation) or external intervention.

Generalizing the DS-Methods for Testing Non-Deterministic FSMs

There exists a significant body of work devoted to so-called complete tests which guarantee the detection of all the faults in a given fault domain. Several methods for generating complete tests for finite state machines (FSMs) which are based on a distinguishing sequence (DS) have been proposed. These methods even if extended to use adaptive DSs apply only to deterministic FSMs and the question arises whether they can be extended to non-deterministic FSMs to test for trace inclusion. In this paper, we generalize the notion of DS to a so-called total state separator, which is an adaptive experiment distinguishing states in any FSM that is trace included into the specification FSM. We then propose a method to test non-deterministic FSMs for trace inclusion. State separator is a key means of the proposed method, which has two phases: in the first phase, a preset test is constructed, which should be repeatedly applied to a non-deterministic implementation, thus requiring its resetting; in the second phase, the implementation is tested online and no reset is required. To the best of our knowledge, this is the first method which tests non-deterministic FSMs for the trace inclusion conformance relation, while avoiding resetting implementations to re-execute tests for transition verification.

Analyzing an embedded sensor with timed automata in uppaal

An infrared sensor is modeled and analyzed in Uppaal. The sensor typifies the sort of component that engineers regularly integrate into larger systems by writing interface hardware and software. In all, three main models are developed. In the first model, the timing diagram of the sensor is interpreted and modeled as a timed safety automaton. This model serves as a specification for the complete system. A second model that emphasizes the separate roles of driver and sensor is then developed. It is validated against the timing diagram model using an existing construction that permits the verification of timed trace inclusion, for certain models, by reachability analysis (i.e., model checking). A transmission correctness property is also stated by means of an auxiliary automaton and shown to be satisfied by the model. A third model is created from an assembly language driver program, using a direct translation from the instruction set of a processor with simple timing behavior. This model is validated against the driver component of the second timing diagram model using the timed trace inclusion validation technique. The approach and its limitations offer insight into the nature and challenges of programming in real time.

Conformance Testing of Preemptive Real-Time Systems

The paper presents an approach for model-based black-box conformance testing of preemptive real-time systems using Labeled Prioritized Time Petri Nets with Stopwatches (LPrSwTPN). These models not only specify system/environment interactions and time constraints. They further enable modelling of suspend/resume operations in real-time systems. The test specification used to generate test primitives, to check the correctness of system responses and to draw test verdicts is an LPrSwTPN made up of two concurrent sub-nets that respectively specify the system under test and its environment. The algorithms used in the TINA model analyzer have been extended to support concurrent composed subnets. Relativized stopwatch timed input/output conformance serves as the notion of implementation correctness, essentially timed trace inclusion taking environment assumptions into account. Assuming the modelled systems are non deterministic and partially observable, the paper proposes a test generation and execution algorithm which is based on symbolic techniques and implements an online testing policy and outputs test results for the (part of the) selected environment.

Advanced automata minimization

We present an efficient algorithm to reduce the size of nondeterministic Buchi word automata, while retaining their language. Additionally, we describe methods to solve PSPACE-complete automata problems like universality, equivalence and inclusion for much larger instances (1-3 orders of magnitude) than before. This can be used to scale up applications of automata in formal verification tools and decision procedures for logical theories. The algorithm is based on new transition pruning techniques. These use criteria based on combinations of backward and forward trace inclusions. Since these relations are themselves PSPACE-complete, we describe methods to compute good approximations of them in polynomial time. Extensive experiments show that the average-case complexity of our algorithm scales quadratically. The size reduction of the automata depends very much on the class of instances, but our algorithm consistently outperforms all previous techniques by a wide margin. We tested our algorithm on Buchi automata derived from LTL-formulae, many classes of random automata and automata derived from mutual exclusion protocols, and compared its performance to the well-known automata tool GOAL.

The reservoir-wave paradigm

Hughes, Aluna; Wang, Jiun-Jrb; Bouwmeester, Chrisc; Davies, Justina; Shrive, Nigeld; Tyberg, Johnc; Parker, Kime Author Information

Prevention and Intensification of Melt-Water Explosive Interactions

The combination of a hot fluid (e.g., molten metals) and a cold vaporizing fluid (e.g., water) can undergo spontaneous or externally assisted explosive interactions. Such explosions are a well-established contributor to the risk for nuclear reactors exemplified by the infamous Chernobyl accident. Once fundamentals are understood, it may be possible to not only prevent but also, more importantly, control the intensity for useful applications in the areas covering variable thrust propulsion with tailored pressure profiles, for enhancing rapid heat transfer, and also for powder metallurgy (i.e., supercooled powder production, wherein materials turn superplastic with enhanced ductility). This paper discusses results of experiments conducted with various molten metals, specifically, tin, gallium, galinstan, and aluminum interacting with water (with and without salt), and with and without noncondensable gases such as hydrogen or air. It is found that under the appropriate conditions, spontaneous and energetic phase changes can be initiated within milliseconds if the hot metal is tin or galinstan, including the timed feedback of shocks leading to chain-type reactions. Using 3–10 g of tin or galinstan, shock pressures up to 25 bars (350 psig) and mechanical power over ∼2-4 kW were monitored about 4 cm from the explosion zone. The interaction could be intensified more than ten folds by dropping the melt through an argon atmosphere. A slow metal quenching interaction occurring over tens of seconds could be turned explosive to transpire within milliseconds if the thermal states are within the so-called thermal interaction zone. Such explosive interactions did not transpire with gallium or aluminum due to tough oxide coatings. However, by adding ∼10 w/o of salt in water, molten Gallium readily exploded. It was also conclusively revealed that, for an otherwise spontaneously explosive interaction of tin-water or galinstan-water, the inclusion of trace (0.3 w/o) quantities of aluminum has a radical influence on stabilizing the system and ensuring conclusive prevention of explosion triggering. This paper compares and presents the results obtained in this study and draws analogies with industrial scale aluminum casthouse safety involving thousands of kilograms of melt. Insights are provided for enabling physics-based prevention, or, alternately, the intentional initiation of explosions.

On application of weaker simulations to parameterized model checking by network invariants technique

In this paper we consider parameterized model checking problem of asynchronous communicating processes in the framework of network invariants. The framework of network invariants relies on relations over labelled transition systems such as simulation, bisimulation, trace equivalence and trace inclusion. In the case of asynchronous parallel composition simulation and bisimulation appear to be rather strong and thus require additional abstractions. In our work three weaker simulation relations are proposed namely quasi-block simulation, block simulation and semi-block simulation. Quasi-block simulation has all the properties to be applied to the technique of network invariants. Block simulation is a stronger relation than a quasi-block simulation. It is used to find an invariant. An initial semi-block simulation over two models exists if and only if an initial block simulation over that models exists. Thus, it is sufficient to compute a semi-block simulation on the models. The sketch of an algorithm to perform such a computation is presented. Previously, we used the framework to check a parameterized model of RSVP protocol. In this paper a series of optimizations that decrease the time of computation are shown.

On trace inclusion optimization problems

The following four optimization problems over a finite set of traces are considered: (i) find the longest trace that is included in each trace from a given finite set T of traces, (ii) find the shortest trace that is not included in every trace from a given finite set T of traces, (iii) find the shortest trace that includes every trace from a given finite set T of traces, (iv) find the longest trace that does not include each trace from a given finite set T of traces.

Structure, morphology and chemical composition of sputter deposited nanostructured Cr–WS 2 solid lubricant coatings

WS 2 and Cr–WS 2 nanocomposite coatings were deposited at different Cr contents (approximately 15–50 at.%) on silicon and mild steel substrates using an unbalanced magnetron sputtering system. X-ray diffraction (XRD) was used to study the structure of Cr–WS 2 coatings and the bonding structure of the coatings was studied using X-ray photoelectron spectroscopy (XPS). The characterization of different phases present in Cr–WS 2 coatings was carried out using micro-Raman spectroscopy. The XPS and Raman data indicated the formation of a thin layer of WO 3 on the surface of Cr–WS 2 coatings and the intensity of the oxide phase decreased with an increase in the Cr content, which was also confirmed using energy-dispersive X-ray analysis results. The surface morphologies of WS 2 and Cr–WS 2 coatings were examined using field emission scanning electron microscopy (FESEM) and atomic force microscopy. It has been demonstrated that incorporation of Cr in WS 2 strongly influences the structure and morphology of Cr–WS 2 coatings. The XRD and FESEM results suggested that increase in the Cr content of Cr–WS 2 coatings resulted in a structural transition from a mixture of nanocrystalline and amorphous phases to a complete amorphous phase. The cross-sectional FESEM data of WS 2 coating showed a porous and columnar microstructure. For the Cr–WS 2 coatings, a mixture of columnar and featureless microstructure was observed at low Cr contents (≤ 23 at.%), whereas, a dense and featureless microstructure was observed at high Cr contents. Detailed cross-sectional transmission electron microscopy (TEM) studies of Cr–WS 2 coatings prepared at Cr content ≤ 23 at.% indicated the presence of both nanocrystalline (near the interface) and amorphous phases (near the surface). Furthermore, high-resolution TEM data obtained from the nanocrystalline region showed inclusion of traces of amorphous phase in the nanocrystalline WS 2 phase. Potentiodynamic polarization measurements indicated that the corrosion resistance of Cr–WS 2 coatings was superior to that of the uncoated mild steel substrate and the corrosion rate decreased with an increase in the Cr content.