Positivity in the presence of initial system-environment correlation

The constraints imposed by the initial system-environment correlation can lead to nonpositive Dynamical maps. We find the conditions for positivity and complete positivity of such dynamical maps by using the concept of an assignment map. Any initial system-environment correlations make the assignment map nonpositive, while the positivity of the dynamical map depends on the interplay between the assignment map and the system-environment coupling. We show how this interplay can reveal or hide the nonpositivity of the assignment map. We discuss the role of this interplay in Markovian models.Comment: close to the published version. 5 pages, 1 figur

On the variable capacity property of CC/DS-CDMA systems

A complete complementary code based direct sequence code division multiple access (CC/DS-CDMA) system has been proposed recently as a potential candidate for beyond third generation (B3G) wireless communications. This paper addresses the issues that design of efficient code assignment schemes should be based on a flexible physical layer support, which is extremely important for emerging cross-layer designs in future wireless applications. The study in this paper considers a CC/DS-CDMA system with multiple time slots, three traffic classes and two dynamic code-flock assignment schemes, namely random assignment (RA) and compact assignment (CA). Simulation results show that the CC/DS-CDMA system has variable capacity property (VCP), which is sensitively affected by different code-flock assignment schemes. In general, CA can offer lower blocking probability, whereas RA can offer a larger mean system capacity and higher throughput when offered traffic is heavy

Frictional Assignment

This paper examines the time-consuming process of matching the two sides of a market each having diverse characteristics. This is cast in a labor market setting where workers of different skills need be matched with different machine qualities to produce output. I characterize the efficient allocation and then show that it can be decentralized by a competitive framework. A prominent feature of the frictional assignment is that each skill level is associated with a market tightness in addition to a machine quality. The differential market tightness as an additional allocative device implies that the assignment is not always positively assortative, i.e., high quality machines are not necessarily assigned to high skills even though machine qualities and skills are complementary in production. The market mechanism that decentralizes the efficient assignment has the feature that firms post wages to attract workers in addition to choosing machine qualities. A steady state is established and numerical exercices are used to show that the differential market tightness for different skills is also quantitatively important for the wage function and wage distribution. Ce papier étudie le processus coûteux en temps d'appariement des deux côtés du marché, chacun ayant des caractéristiques diverses. Ceci est placé dans un marché du travail où les travailleurs ont des qualifications qui doivent être appariées avec différents qualités de machine pour la production. Je caractérise l'allocation efficace puis montre qu'elle peut être décentralisée dans un cadre concurrentiel. Un trait saillant de l'assignation frictionnelle est que chaque niveau de qualification est associé à un degré d'étroitesse du marché en plus d'une qualité de machine. L'étroitesse du marché différenciée en tant qu'instrument supplémentaire d'allocation implique que l'assignation n'est pas toujours positivement assortative, par exemple que des machines de haute qualité ne sont pas nécessairement assignées à des travailleurs hautement qualifiés malgré que qualité et qualification soient complémentaires dans la production. Le mécanisme de marché qui décentralise l'assignation efficace a la particularité que la firme affiche des salaires qui attirent des travailleurs en plus de choisir les qualités de machine. Un état stationnaire est établi et des exercices numériques sont utilisés pour montrer que le différentiel d'étroitesse du marché pour les différentes qualifications est également quantitativement important pour la fonction de salaire et la distribution des salaires.Frictional matching; Market tightness; Skills; Machines; Wage distribution

Probabilistic Argumentation with Epistemic Extensions and Incomplete Information

Abstract argumentation offers an appealing way of representing and evaluating arguments and counterarguments. This approach can be enhanced by a probability assignment to each argument. There are various interpretations that can be ascribed to this assignment. In this paper, we regard the assignment as denoting the belief that an agent has that an argument is justifiable, i.e., that both the premises of the argument and the derivation of the claim of the argument from its premises are valid. This leads to the notion of an epistemic extension which is the subset of the arguments in the graph that are believed to some degree (which we defined as the arguments that have a probability assignment greater than 0.5). We consider various constraints on the probability assignment. Some constraints correspond to standard notions of extensions, such as grounded or stable extensions, and some constraints give us new kinds of extensions

Constrained speaker linking

In this paper we study speaker linking (a.k.a.\ partitioning) given constraints of the distribution of speaker identities over speech recordings. Specifically, we show that the intractable partitioning problem becomes tractable when the constraints pre-partition the data in smaller cliques with non-overlapping speakers. The surprisingly common case where speakers in telephone conversations are known, but the assignment of channels to identities is unspecified, is treated in a Bayesian way. We show that for the Dutch CGN database, where this channel assignment task is at hand, a lightweight speaker recognition system can quite effectively solve the channel assignment problem, with 93% of the cliques solved. We further show that the posterior distribution over channel assignment configurations is well calibrated.Comment: Submitted to Interspeech 2014, some typos fixe

Consistency and Monotonicity in One-Sided Assignment Problems

One-sided assignment problems combine important features of two well-known matching models. First, as in roommate problems, any two agents can be matched and second, as in two-sided assignment problems, the payoffs of a matching can be divided between the agents. We take a similar approach to one-sided assignment problems as Sasaki (1995) for two-sided assignment problems and we analyze various desirable properties of solutions including consistency and weak pairwise-monotonicity. We show that for the class of solvable one-sided assignment problems (i.e., the subset of one-sided assignment problems with a non-empty core), if a subsolution of the core satisfies [indifference with respect to dummy agents, continuity, and consistency] or [Pareto indifference and consistency], then it coincides with the core (Theorems 1 and 2). However, we also prove that on the class of all one-sided assignment problems (solvable or not), no solution satisfies consistency and coincides with the core whenever the core is non-empty (Theorem 3). Finally, we comment on the difficulty in obtaining further positive results for the class of solvable one-sided assignment problems in line with Sasaki's (1995) characterizations of the core for two-sided assignment problems.(One-sided) assignment problems, consistency, core, matching.