Preference Falsification and Patronage

In this paper we develop a model of patronage where the king's subjects exert a decentralized social sanction on the dissidents. We are able to show that depending on the succession rule in case of a revolution, the optimal co-optation strategy of the king differs. When the succeeding king is the strongest revolutionary the actual king adopts the weakest among the potential opponents. When any member of the clientele has a claim on the throne, however, the actual king has two distinct co-optation strategies. He either approaches his most powerful subjects, in which the size of the clientele is relatively modest, but the clients' individual price is relatively high or else he randomly co-opts subjects to contain the bargaining power of his clients. The ambiguity as to the optimal strategy rests in that in this latter scenario the size of the clientele is larger.

Endogenous Elites: Power Structure and Patron-Client Relationships

In weak institutional settings, autocrats barter political and economic concessions for support to remain in power and extract rents. Instead of viewing the favors’ beneficiaries, i.e. the elites, as an exogenous entity, we allow the king to decide whom to coopt provided the subjects are heterogeneous in the potential support - their strength - they could bring to the regime. While the ruler can select the elites on the basis of their personal characteristics, an alternative strategy consists in introducing some uncertainty in the cooptation process. The latter strategy allows the king to reduce the clients’ cooptation price since in the event of a revolution the likelihood of being included in the future body of elites is lower. We show that weak rulers are more likely to coopt the society’s strongest individuals, while powerful rulers diversify the composition of their clientele. Moreover, when agents value more future discounted outcomes, the king is more likely to randomly coopt subjects. Weak institutions Autocracy Rent seeking ElitesWeak Institutions, Autocracy, Rent Seeking, Elites.

Economic Determinants of Third Party Intervention in Civil Conflict

Our paper explores the economic conditions that lead third parties to intervene in ongoing internal wars. We develop a formal model that ties together some of the main forces driving the decision to interfere in a civil war, including the economic benefits accruing from the intervention and the potential costs associated with such choice. We predict that third party interventions are most likely in civil conflicts where the country at war harbors a profitable industry as a consequence of its high levels of peace-time production and state strength, while the opposition forces’ strength reduces the likelihood of intervention. We also present novel empirical results on the role of valuable goods, i.e. oil, in prompting third party military intervention in contexts of high state stability, by using a dataset on intrastate conflicts on the period 1960-1999.Intrastate Conflict; Third party intervention

The Calcium Phosphate−Calcium Carbonate System: Growth of Octacalcium Phosphate on Calcium Carbonates

The kinetics of nucleation and crystal growth of octacalcium phosphate [Ca8(PO4)6H2·5H2O, OCP] from calcium phosphate supersaturated solutions inoculated with seed crystals was investigated at 37 °C, pH 7.40, at conditions of constant solution supersaturation. Stable calcium phosphate solutions, supersaturated with respect to OCP and hydroxyapatite [Ca5(PO4)3OH, HAP] were inoculated with calcium carbonate-based bone cement powder consisting of mixed aragonite and calcite crystals and with well-characterized calcite seed crystals. On all substrates tested, OCP nucleated followed by crystal growth of the nuclei formed past the lapse of induction times, inversely proportional to the solution supersaturation. From the dependence of the induction time on the solution supersaturation with respect to OCP, a value of 10 mJ m−2 was calculated for the nucleating phase. The rates of OCP crystal growth on the carbonate substrates showed linear dependence on the solution supersaturation that in combination with the independence from the fluid dynamics in the reactor suggested a surface diffusion-controlled mechanism. Moreover, the independence of the crystallization rates on the amount of the inoculating seed crystals suggested that nucleation and growth took place exclusively on the crystalline substrates. The transient calcium phosphate phase, OCP, was stabilized in our experiments, and it was the only phase growing at constant driving force, despite the fact the solutions were supersaturated with respect to HAP as well

Dual Rate Control for Security in Cyber-physical Systems

We consider malicious attacks on actuators and sensors of a feedback system which can be modeled as additive, possibly unbounded, disturbances at the digital (cyber) part of the feedback loop. We precisely characterize the role of the unstable poles and zeros of the system in the ability to detect stealthy attacks in the context of the sampled data implementation of the controller in feedback with the continuous (physical) plant. We show that, if there is a single sensor that is guaranteed to be secure and the plant is observable from that sensor, then there exist a class of multirate sampled data controllers that ensure that all attacks remain detectable. These dual rate controllers are sampling the output faster than the zero order hold rate that operates on the control input and as such, they can even provide better nominal performance than single rate, at the price of higher sampling of the continuous output

Target Assignment in Robotic Networks: Distance Optimality Guarantees and Hierarchical Strategies

We study the problem of multi-robot target assignment to minimize the total distance traveled by the robots until they all reach an equal number of static targets. In the first half of the paper, we present a necessary and sufficient condition under which true distance optimality can be achieved for robots with limited communication and target-sensing ranges. Moreover, we provide an explicit, non-asymptotic formula for computing the number of robots needed to achieve distance optimality in terms of the robots' communication and target-sensing ranges with arbitrary guaranteed probabilities. The same bounds are also shown to be asymptotically tight. In the second half of the paper, we present suboptimal strategies for use when the number of robots cannot be chosen freely. Assuming first that all targets are known to all robots, we employ a hierarchical communication model in which robots communicate only with other robots in the same partitioned region. This hierarchical communication model leads to constant approximations of true distance-optimal solutions under mild assumptions. We then revisit the limited communication and sensing models. By combining simple rendezvous-based strategies with a hierarchical communication model, we obtain decentralized hierarchical strategies that achieve constant approximation ratios with respect to true distance optimality. Results of simulation show that the approximation ratio is as low as 1.4

Canonical Quantization of the BTZ Black Hole using Noether Symmetries

The well-known BTZ black hole solution of (2+1) Einstein's gravity, in the presence of a cosmological constant, is treated both at the classical and quantum level. Classically, the imposition of the two manifest local Killing fields of the BTZ geometry at the level of the full action results in a mini-superspace constraint action with the radial coordinate playing the role of the independent dynamical variable. The Noether symmetries of this reduced action are then shown to completely determine the classical solution space, without any further need to solve the dynamical equations of motion. At a quantum mechanical level, all the admissible sets of the quantum counterparts of the generators of the above mentioned symmetries are utilized as supplementary conditions acting on the wave-function. These additional restrictions, in conjunction with the Wheeler-DeWitt equation, help to determine (up to constants) the wave-function which is then treated semiclassically, in the sense of Bohm. The ensuing space-times are, either identical to the classical geometry, thus exhibiting a good correlation of the corresponding quantization to the classical theory, or are less symmetric but exhibit no Killing or event horizon and no curvature singularity, thus indicating a softening of the classical conical singularity of the BTZ geometry.Comment: 24 pages, no figures, LaTeX 2e source fil

Multi-jet Production in Hadron Collisions

The advent of high-energy hadron colliders necessitates efficient and accurate computation of multi-jet production processes, both as QCD processes in their own right and as backgrounds for other physics. The algorithm that performs these tasks and a brief numerical study of multi-jet processes are presented.Comment: 21 pages, 9 figure