7,440 research outputs found
Duality and separation theorems in idempotent semimodules
We consider subsemimodules and convex subsets of semimodules over semirings
with an idempotent addition. We introduce a nonlinear projection on
subsemimodules: the projection of a point is the maximal approximation from
below of the point in the subsemimodule. We use this projection to separate a
point from a convex set. We also show that the projection minimizes the
analogue of Hilbert's projective metric. We develop more generally a theory of
dual pairs for idempotent semimodules. We obtain as a corollary duality results
between the row and column spaces of matrices with entries in idempotent
semirings. We illustrate the results by showing polyhedra and half-spaces over
the max-plus semiring.Comment: 24 pages, 5 Postscript figures, revised (v2
Variable elimination for building interpreters
In this paper, we build an interpreter by reusing host language functions
instead of recoding mechanisms of function application that are already
available in the host language (the language which is used to build the
interpreter). In order to transform user-defined functions into host language
functions we use combinatory logic : lambda-abstractions are transformed into a
composition of combinators. We provide a mechanically checked proof that this
step is correct for the call-by-value strategy with imperative features.Comment: 33 page
Multiple Production, Transport in Atmosphere and Detection of High Energy Cosmic Rays
We describe the general aspects of Monte Carlo Collision Generators suitable
for cosmic ray nucleon-Air and nuclei-Air interactions, including accelerator
and collider data. The problem of the extrapolation at 3 energy decades above
the LHC of the main features of high energy collisions is discussed and under
theoretical and phenomenological assumptions, the properties of the
longitudinal and lateral development of giant extensive air showers simulated
with the CORSIKA program are presented. The determination of the primary energy
near eV is examined for different observables, total size, densities
of charged particles interpolated at 600~m from shower core. The extensive air
shower data collected around LHC energy is in better agreement with models of
large multiplicities. Beyond this energy, the extrapolation carried assuming
the diquark breaking mechanism can change the classic conversion to primary
energy and such circumstance can have consequences on the validity of the GZK
cut off. In those conditions, we have simulated large and giant air showers
taking into account, in addition, new processes, such as diquark breaking, and
topological problems involving adequate structure functions for lateral
distributions, up to energies exceeding eV for P.AUGER and EUSO
experiments.Comment: 10 pages, 8 figures (6 in eps, 2 in ps) talk given at XXXI
International Symposium on Multiparticle Dynamics, Sep. 1-7, 2001, Datong
China URL http://ismd31.ccnu.edu.cn
Decision under Uncertainty : the Classical Models
This chapiter of a collective book is dedicated to classical decision models under uncertainty, i.e. under situations where events do not have "objective" probabilities with which the Decision Marker agrees. We present successively the two main theories, their axiomatic, the interpretation and the justification of their axioms and their main properties : first, the general model of Subjective Expected Utility due to Savage (Savage, 1954), second, the Anscombe-Aumann (1963) theory, in a different framework. Both theories enforce the universal use of a probabilistic representation. We then discuss this issue in connection with the experimental result known as the Ellsberg paradox.Uncertainty, subjective probability, Subjective Expected Utility, Savage, Anscombe and Aumann, Ellsberg paradox.
Decision under risk : The classical Expected Utility model
This chapter of a collective book aims at presenting the basics of decision making under risk. We first define notions of risk and increasing risk and recall definitions and classifications (that are valid independently of any representation) of behavior under risk. We then review the classical model of expected utility due to von Neumann and Morgenstern andd its main properties. Issues raised by this model are then discussed and two models generalizing the expected utility model are briefly discussed.Risk, risk aversion, expected utility, von Neumann and Morgenstern, Allais paradox.
Asia-Europe: the third link
The report provides a comprehensive analysis of Europe-East Asia interdependences (in terms of relative economic weights, trade and financial integration, trade and financial flows, exchange rate and wealth transfers). The prime motivation of the paper is that linkages between Europe and East Asia remain frequently underestimated. While the ĂąâŹĆthird linkù⏠between them is in many respects as important as the linkages between the two regions and North America, it is too often regarded only as of secondary importance.Regional integration, Financial integration, Trade integration, East Asia, European Monetary Union, Pisani-Ferry , Cohen-Setton
The use of colloquial words in advanced French interlanguage
This article addresses the issue of underrepresentation or avoidance of colloquial words in a cross-sectional corpus of advanced French interlanguage (IL) of 29 Dutch L1 speakers and in a longitudinal corpus of 6 Hiberno-Irish English L1 speakers compared with a control of 6 native speakers of French. The main independent variable analysed in the latter corpus is the effect of spending a year in a francophone environment. This analysis is supplemented by a separate study of sociobiographical and psychological factors that affect the use of colloquial vocabulary in the cross-sectional corpus. Colloquial words are not exceptionally complex morphologically and present no specific grammatical difficulties, yet they are very rare in our data. Multivariate regression analyses suggest that only active authentic communication in the target language (TL) predicts the use of colloquial lexemes in the cross-sectional corpus. This result was confirmed in the longitudinal corpus where a t-test showed that the proportion of colloquial lexemes increased significantly after a year abroad
Dynamic consistency for Stochastic Optimal Control problems
For a sequence of dynamic optimization problems, we aim at discussing a
notion of consistency over time. This notion can be informally introduced as
follows. At the very first time step , the decision maker formulates an
optimization problem that yields optimal decision rules for all the forthcoming
time step ; at the next time step , he is able to
formulate a new optimization problem starting at time that yields a new
sequence of optimal decision rules. This process can be continued until final
time is reached. A family of optimization problems formulated in this way
is said to be time consistent if the optimal strategies obtained when solving
the original problem remain optimal for all subsequent problems. The notion of
time consistency, well-known in the field of Economics, has been recently
introduced in the context of risk measures, notably by Artzner et al. (2007)
and studied in the Stochastic Programming framework by Shapiro (2009) and for
Markov Decision Processes (MDP) by Ruszczynski (2009). We here link this notion
with the concept of "state variable" in MDP, and show that a significant class
of dynamic optimization problems are dynamically consistent, provided that an
adequate state variable is chosen
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