28,493 research outputs found
Timed Automata Approach for Motion Planning Using Metric Interval Temporal Logic
In this paper, we consider the robot motion (or task) planning problem under
some given time bounded high level specifications. We use metric interval
temporal logic (MITL), a member of the temporal logic family, to represent the
task specification and then we provide a constructive way to generate a timed
automaton and methods to look for accepting runs on the automaton to find a
feasible motion (or path) sequence for the robot to complete the task.Comment: Full Version for ECC 201
Universal quantum modifications to general relativistic time dilation in delocalised clocks
The theory of relativity associates a proper time with each moving object via
its world line. In quantum theory however, such well-defined trajectories are
forbidden. After introducing a general characterisation of quantum clocks, we
demonstrate that, in the weak-field, low-velocity limit, all "good" quantum
clocks experience time dilation as dictated by general relativity when their
state of motion is classical (i.e. Gaussian). For nonclassical states of
motion, on the other hand, we find that quantum interference effects may give
rise to a significant discrepancy between the proper time and the time measured
by the clock. The universality of this discrepancy implies that it is not
simply a systematic error, but rather a quantum modification to the proper time
itself. We also show how the clock's delocalisation leads to a larger
uncertainty in the time it measures -- a consequence of the unavoidable
entanglement between the clock time and its center-of-mass degrees of freedom.
We demonstrate how this lost precision can be recovered by performing a
measurement of the clock's state of motion alongside its time reading.Comment: 7 + 10 pages. V3: accepted versio
On the decidability and complexity of Metric Temporal Logic over finite words
Metric Temporal Logic (MTL) is a prominent specification formalism for
real-time systems. In this paper, we show that the satisfiability problem for
MTL over finite timed words is decidable, with non-primitive recursive
complexity. We also consider the model-checking problem for MTL: whether all
words accepted by a given Alur-Dill timed automaton satisfy a given MTL
formula. We show that this problem is decidable over finite words. Over
infinite words, we show that model checking the safety fragment of MTL--which
includes invariance and time-bounded response properties--is also decidable.
These results are quite surprising in that they contradict various claims to
the contrary that have appeared in the literature
Histories quantisation of parameterised systems: I. Development of a general algorithm
We develop a new algorithm for the quantisation of systems with first-class
constraints. Our approach lies within the (History Projection Operator)
continuous-time histories quantisation programme. In particular, the
Hamiltonian treatment (either classical or quantum) of parameterised systems is
characterised by the loss of the notion of time in the space of true degrees of
freedom (i.e. the `problem of time'). The novel temporal structure of the HPO
theory (two laws of time transformation that distinguish between the temporal
logical structure and the dynamics) persists after the imposition of the
constraints, hence the problem of time does not arise. We expound the algorithm
for both the classical and quantum cases and apply it to simple models.Comment: 34 pages, Late
On Zone-Based Analysis of Duration Probabilistic Automata
We propose an extension of the zone-based algorithmics for analyzing timed
automata to handle systems where timing uncertainty is considered as
probabilistic rather than set-theoretic. We study duration probabilistic
automata (DPA), expressing multiple parallel processes admitting memoryfull
continuously-distributed durations. For this model we develop an extension of
the zone-based forward reachability algorithm whose successor operator is a
density transformer, thus providing a solution to verification and performance
evaluation problems concerning acyclic DPA (or the bounded-horizon behavior of
cyclic DPA).Comment: In Proceedings INFINITY 2010, arXiv:1010.611
Deciding the Satisfiability of MITL Specifications
In this paper we present a satisfiability-preserving reduction from MITL
interpreted over finitely-variable continuous behaviors to Constraint LTL over
clocks, a variant of CLTL that is decidable, and for which an SMT-based bounded
satisfiability checker is available. The result is a new complete and effective
decision procedure for MITL. Although decision procedures for MITL already
exist, the automata-based techniques they employ appear to be very difficult to
realize in practice, and, to the best of our knowledge, no implementation
currently exists for them. A prototype tool for MITL based on the encoding
presented here has, instead, been implemented and is publicly available.Comment: In Proceedings GandALF 2013, arXiv:1307.416
OUTLINE OF A GENERALLY COVARIANT QUANTUM FIELD THEORY AND A QUANTUM THEORY OF GRAVITY
We study a tentative generally covariant quantum field theory, denoted the
T-Theory, as a tool to investigate the consistency of quantum general
relativity. The theory describes the gravitational field and a minimally
coupled scalar field; it is based on the loop representation, and on a certain
number of quantization choices. Four-dimensional diffeomorphism-invariant
quantum transition probabilities can be computed from the theory. We present
the explicit calculation of the transition probability between two volume
eigenstates as an example. We discuss the choices on which the T-theory relies,
and the possibilities of modifying them.Comment: Latex file, 33 page
Autonomous Ticking Clocks from Axiomatic Principles
There are many different types of time keeping devices. We use the phrase
ticking clock to describe those which -- simply put -- "tick" at approximately
regular intervals. Various important results have been derived for ticking
clocks, and more are in the pipeline. It is thus important to understand the
underlying models on which these results are founded. The aim of this paper is
to introduce a new ticking clock model from axiomatic principles that overcomes
concerns in the community about the physicality of the assumptions made in
previous models. The ticking clock model in [arXiv:1806.00491] achieves high
accuracy, yet lacks the autonomy of the less accurate model in
[10.1103/PhysRevX.7.031022]. Importantly, the model we introduce here achieves
the best of both models: it retains the autonomy of [10.1103/PhysRevX.7.031022]
while allowing for the high accuracies of [arXiv:1806.00491]. What is more,
[10.1103/PhysRevX.7.031022] is revealed to be a special case of the new ticking
clock model.Comment: 14 + 14 page
Analog Property Checkers: A Ddr2 Case Study
The formal specification component of verification can be exported to simulation through the idea of property checkers. The essence of this approach is the automatic construction of an observer from the specification in the form of a program that can be interfaced with a simulator and alert the user if the property is violated by a simulation trace. Although not complete, this lighter approach to formal verification has been effectively used in software and digital hardware to detect errors. Recently, the idea of property checkers has been extended to analog and mixed-signal systems.
In this paper, we apply the property-based checking methodology to an industrial and realistic example of a DDR2 memory interface. The properties describing the DDR2 analog behavior are expressed in the formal specification language stl/psl in form of assertions. The simulation traces generated from an actual DDR2 interface design are checked with respect to the stl/psl assertions using the amt tool. The focus of this paper is on the translation of the official (informal and descriptive) specification of two non-trivial DDR2 properties into stl/psl assertions. We study both the benefits and the current limits of such approach
Logics of Temporal-Epistemic Actions
We present Dynamic Epistemic Temporal Logic, a framework for reasoning about
operations on multi-agent Kripke models that contain a designated temporal
relation. These operations are natural extensions of the well-known "action
models" from Dynamic Epistemic Logic. Our "temporal action models" may be used
to define a number of informational actions that can modify the "objective"
temporal structure of a model along with the agents' basic and higher-order
knowledge and beliefs about this structure, including their beliefs about the
time. In essence, this approach provides one way to extend the domain of action
model-style operations from atemporal Kripke models to temporal Kripke models
in a manner that allows actions to control the flow of time. We present a
number of examples to illustrate the subtleties involved in interpreting the
effects of our extended action models on temporal Kripke models. We also study
preservation of important epistemic-temporal properties of temporal Kripke
models under temporal action model-induced operations, provide complete
axiomatizations for two theories of temporal action models, and connect our
approach with previous work on time in Dynamic Epistemic Logic
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