A simple fixed parameter tractable algorithm for computing the hybridization number of two (not necessarily binary) trees

Here we present a new fixed parameter tractable algorithm to compute the hybridization number r of two rooted, not necessarily binary phylogenetic trees on taxon set X in time (6^r.r!).poly(n)$, where n=|X|. The novelty of this approach is its use of terminals, which are maximal elements of a natural partial order on X, and several insights from the softwired clusters literature. This yields a surprisingly simple and practical bounded-search algorithm and offers an alternative perspective on the underlying combinatorial structure of the hybridization number problem

Conic approach to quantum graph parameters using linear optimization over the completely positive semidefinite cone

We investigate the completely positive semidefinite cone $\mathcal{CS}_+^n$, a new matrix cone consisting of all $n\times n$ matrices that admit a Gram representation by positive semidefinite matrices (of any size). In particular we study relationships between this cone and the completely positive and doubly nonnegative cones, and between its dual cone and trace positive non-commutative polynomials. We use this new cone to model quantum analogues of the classical independence and chromatic graph parameters $\alpha(G)$ and $\chi(G)$, which are roughly obtained by allowing variables to be positive semidefinite matrices instead of $0/1$ scalars in the programs defining the classical parameters. We can formulate these quantum parameters as conic linear programs over the cone $\mathcal{CS}_+^n$. Using this conic approach we can recover the bounds in terms of the theta number and define further approximations by exploiting the link to trace positive polynomials.Comment: Fixed some typo

Pay Dispersion and Work Performance

The effect of intra-firm pay dispersion on work performance is controversial and the empirical evidence is mixed. High pay dispersion may act as an extra incentive for employees' effort or it may reduce motivation and team cohesiveness. These effects can also coexist and the prevalence of one effect over the other may depend on the use of different definitions of what constitutes a "team." For this paper we collected a unique dataset from the men's major soccer league in Italy. For each match we computed the exact pay dispersion of each work team and estimated its effect on team performance. Our results show that when the work team is considered to consist of only the players who contribute to the result, high pay dispersion has a detrimental impact on team performance. Several robustness checks confirm this result. In addition, we show that enlarging the definition of work team causes this effect to disappear or even become positive. Finally, we find that the detrimental effect of pay dispersion is due to worst individual performance, rather than a reduction of team cooperation.Team productivity, Incentives, Pay dispersion.

Luck or Cheating? A Field Experiment on Honesty with Children

We ran an experiment with children to study the development of honesty with age. We asked each child to toss a fair coin in private and to record the outcome (white or black) in a paper sheet. We rewarded only those who reported white. We found a fraction of reported whites signifi…cantly larger than 50%, uniformly across age groups. This suggests that some children cheat when cheating is profi…table and they are not observed. In a second treatment we told children not to cheat. This reminder reduced the probability of reporting white by 18% on average, and signifi…cantly more in girls.honesty; children; fi…eld experiment

Fast or Fair? A Study of Response Times

This paper uses a modified dictator game to investigate the relationship between response times and social preferences. We find that egoistic subjects make faster decisions than subjects with social preferences. Moreover, our within-analysis reveals that, for a given individual, egoistic payoff maximizing decisions are reached quicker than choices expressing social preferences.response times; social preferences

Multi-party zero-error classical channel coding with entanglement

We study the effects of quantum entanglement on the performance of two classical zero-error communication tasks among multiple parties. Both tasks are generalizations of the two-party zero-error channel-coding problem, where a sender and a receiver want to perfectly communicate messages through a one-way classical noisy channel. If the two parties are allowed to share entanglement, there are several positive results that show the existence of channels for which they can communicate strictly more than what they could do with classical resources. In the first task, one sender wants to communicate a common message to multiple receivers. We show that if the number of receivers is greater than a certain threshold then entanglement does not allow for an improvement in the communication for any finite number of uses of the channel. On the other hand, when the number of receivers is fixed, we exhibit a class of channels for which entanglement gives an advantage. The second problem we consider features multiple collaborating senders and one receiver. Classically, cooperation among the senders might allow them to communicate on average more messages than the sum of their individual possibilities. We show that whenever a channel allows single-sender entanglement-assisted advantage, then the gain extends also to the multi-sender case. Furthermore, we show that entanglement allows for a peculiar amplification of information which cannot happen classically, for a fixed number of uses of a channel with multiple senders.Comment: Some proofs have been modifie

On the closure of the completely positive semidefinite cone and linear approximations to quantum colorings

We investigate structural properties of the completely positive semidefinite cone $\mathcal{CS}_+^n$, consisting of all the $n \times n$ symmetric matrices that admit a Gram representation by positive semidefinite matrices of any size. This cone has been introduced to model quantum graph parameters as conic optimization problems. Recently it has also been used to characterize the set $\mathcal Q$ of bipartite quantum correlations, as projection of an affine section of it. We have two main results concerning the structure of the completely positive semidefinite cone, namely about its interior and about its closure. On the one hand we construct a hierarchy of polyhedral cones which covers the interior of $\mathcal{CS}_+^n$, which we use for computing some variants of the quantum chromatic number by way of a linear program. On the other hand we give an explicit description of the closure of the completely positive semidefinite cone, by showing that it consists of all matrices admitting a Gram representation in the tracial ultraproduct of matrix algebras.Comment: 20 page

Social Preferences and Strategic Uncertainty: An Experiment on Markets and Contracts

This paper reports experimental evidence on a stylized labor market. The experiment is designed as a sequence of three phases. In the rst two phases, P1 and P2; agents face simple games, which we use to estimate subjects social and reciprocity concerns, together with their beliefs. In the last phase, P3; four principals, who face four teams of two agents, compete by o¤ering agents a contract from a xed menu. Then, each agent selects one of the available contracts (i.e. he "chooses to work" for a principal). Production is determined by the outcome of a simple effort game induced by the chosen contract. We nd that (heterogeneous) social preferences are signi cant determinants of choices in all phases of the experiment. Since the available contracts display a trade-of between fairness and strategic uncertainty, we observe that the latter is a much stronger determinant of choices, for both principals and agents. Finally, we also see that social preferences explain, to a large extent, matching between principals and agents, since agents display a marked propensity to work for principals with similar social preferences

Do not Trash the Incentive! Monetary incentives and waste sorting

This paper examines whether monetary incentives are an effective tool for increasing domestic waste sorting. We exploit the exogenous variation in the waste management policies experienced during the years 1999-2008 by the 95 municipalities in the district of Treviso (Italy). We estimate with a panel analysis that pay-as-you-throw (PAYT) incentive schemes increase by 12.3% the sorted-total waste ratio. This increase reflects a change in the behavior of households, who keep unaltered the production of total waste but sort it to a larger extent. Our data show that household behavior is also influenced by the policies of adjacent municipalities.Incentives, environment, waste management, PAYT

Temptation at work

To encourage worker productivity offices prohibit Internet use. Consequently, many employees delay Internet activity to the end of the workday. Recent work in social psychology, however, suggests that using willpower to delay gratification can negatively impact performance. We report data from an experiment where subjects in a Willpower Treatment are asked to resist the temptation to join others in watching a humorous video for 10 minutes. In relation to a baseline treatment that does not require willpower, we show that resisting this temptation detrimentally impacts economic productivity on a subsequent task.temptation, willpower, lab experiment.