8,383 research outputs found
Subjective and objective performance evaluation
We study executive compensation in an environment in which firms compete offering
contingent contracts to managers with private information about their ability. We ask whether equilibrium executive compensation depends on subjective evaluations, i.e., on assessments made by the firm which are based on noncontractible information. We also allow for objective (i.e., contractible) performance measures and we depart from the rest of the literature
on the topic by assuming that subjective evaluations are made before the uncertainty on the objective performance measures is resolved. We find that even in this case, equilibrium contracts ignore subjective evaluations regardless of their informativeness
HyperANF: Approximating the Neighbourhood Function of Very Large Graphs on a Budget
The neighbourhood function N(t) of a graph G gives, for each t, the number of
pairs of nodes such that y is reachable from x in less that t hops. The
neighbourhood function provides a wealth of information about the graph (e.g.,
it easily allows one to compute its diameter), but it is very expensive to
compute it exactly. Recently, the ANF algorithm (approximate neighbourhood
function) has been proposed with the purpose of approximating NG(t) on large
graphs. We describe a breakthrough improvement over ANF in terms of speed and
scalability. Our algorithm, called HyperANF, uses the new HyperLogLog counters
and combines them efficiently through broadword programming; our implementation
uses overdecomposition to exploit multi-core parallelism. With HyperANF, for
the first time we can compute in a few hours the neighbourhood function of
graphs with billions of nodes with a small error and good confidence using a
standard workstation. Then, we turn to the study of the distribution of the
shortest paths between reachable nodes (that can be efficiently approximated by
means of HyperANF), and discover the surprising fact that its index of
dispersion provides a clear-cut characterisation of proper social networks vs.
web graphs. We thus propose the spid (Shortest-Paths Index of Dispersion) of a
graph as a new, informative statistics that is able to discriminate between the
above two types of graphs. We believe this is the first proposal of a
significant new non-local structural index for complex networks whose
computation is highly scalable
What form of relative performance evaluation?
We study relative performance evaluation in executive compensation when executives have private information about their ability. We assume that the joint distribution of an individual firm’s profit and market movements depends on the ability of the executive that runs the firm. In the equilibrium of the executive labor market, compensation schemes exploit this fact to sort executives of di ?erent abilities. This implies that executive compensation is increasing in own performance, but may also be increasing in industry performance-a sharp departure from standard relative performance evaluation. This result provides an explanation for the scarcity of relative performance considerations in executive compensation documented by the empirical literature.Executive compensation, relative performance evaluation
All AdS_7 solutions of type II supergravity
In M-theory, the only AdS_7 supersymmetric solutions are AdS_7 x S^4 and its
orbifolds. In this paper, we find and classify new supersymmetric solutions of
the type AdS_7 x M_3 in type II supergravity. While in IIB none exist, in IIA
with Romans mass (which does not lift to M-theory) there are many new ones. We
use a pure spinor approach reminiscent of generalized complex geometry. Without
the need for any Ansatz, the system determines uniquely the form of the metric
and fluxes, up to solving a system of ODEs. Namely, the metric on M_3 is that
of an S^2 fibered over an interval; this is consistent with the Sp(1)
R-symmetry of the holographically dual (1,0) theory. By including D8 brane
sources, one can numerically obtain regular solutions, where topologically M_3
= S^3.Comment: 45 pages, 4 figures. v2: solution with single D8 added; references
added; minor correction
Layered Label Propagation: A MultiResolution Coordinate-Free Ordering for Compressing Social Networks
We continue the line of research on graph compression started with WebGraph,
but we move our focus to the compression of social networks in a proper sense
(e.g., LiveJournal): the approaches that have been used for a long time to
compress web graphs rely on a specific ordering of the nodes (lexicographical
URL ordering) whose extension to general social networks is not trivial. In
this paper, we propose a solution that mixes clusterings and orders, and devise
a new algorithm, called Layered Label Propagation, that builds on previous work
on scalable clustering and can be used to reorder very large graphs (billions
of nodes). Our implementation uses overdecomposition to perform aggressively on
multi-core architecture, making it possible to reorder graphs of more than 600
millions nodes in a few hours. Experiments performed on a wide array of web
graphs and social networks show that combining the order produced by the
proposed algorithm with the WebGraph compression framework provides a major
increase in compression with respect to all currently known techniques, both on
web graphs and on social networks. These improvements make it possible to
analyse in main memory significantly larger graphs
Noiseless Linear Amplification and Quantum Channels
The employ of a noiseless linear amplifier (NLA) has been proven as a useful
tool for mitigating imperfections in quantum channels. Its analysis is usually
conducted within specific frameworks, for which the set of input states for a
given protocol is fixed. Here we obtain a more general description by showing
that a noisy and lossy Gaussian channel followed by a NLA has a general
description in terms of effective channels. This has the advantage of offering
a simpler mathematical description, best suitable for mixed states, both
Gaussian and non-Gaussian. We investigate the main properties of this effective
system, and illustrate its potential by applying it to loss compensation and
reduction of phase uncertainty.Comment: 8 pages, 3 figure
Submerged PV Solar Panel for Swimming Pools: SP3
Abstract The possibility to use photovoltaic (PV) modules submerged in water or simply covered by a water veil suggest the possibility to use this renewable energy source (RES) integrated with swimming pools or with decorative pools and fountains. SP3 solution (Submerged PV Solar Panel for Swimming Pools) is discussed for underflow pools as well as for pools with skimmer. The extension of this concept to the possibility to store solar radiation for heating the water of the pool is explored using the results of experimentation already done for hybrid photovoltaic/thermal (PV/T) modules. Simulation results for Mediterranean latitudes are discussed
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