11,561 research outputs found
Smarter task assignment or greater effort: the impact of incentives on team performance
We use an experiment to study the impact of team-based incentives, exploiting rich data from personnel records and management information systems. Using a triple difference design, we show that the incentive scheme had an impact on team performance, even with quite large teams. We examine whether this effect was due to increased effort from workers or strategic task reallocation. We find that the provision of financial incentives did raise individual performance but that managers also disproportionately reallocated efficient workers to the incentivised tasks. We show that this reallocation was the more important contributor to the overall outcome
Brane Gases on K3 and Calabi-Yau Manifolds
We initiate the study of Brane Gas Cosmology (BGC) on manifolds with
non-trivial holonomy. Such compactifications are required within the context of
superstring theory in order to make connections with realistic particle
physics. We study the dynamics of brane gases constructed from various string
theories on background spaces having a K3 submanifold. The K3 compactifications
provide a stepping stone for generalising the model to the case of a full
Calabi-Yau three-fold. Duality symmetries are discussed within a cosmological
context. Using a duality, we arrive at an N=2 theory in four-dimensions
compactified on a Calabi-Yau manifold with SU(3) holonomy. We argue that the
Brane Gas model compactified on such spaces maintains the successes of the
trivial toroidal compactification while greatly enhancing its connection to
particle physics. The initial state of the universe is taken to be a small, hot
and dense gas of p-branes near thermal equilibrium. The universe has no initial
singularity and the dynamics of string winding modes allow three spatial
dimensions to grow large, providing a possible solution to the dimensionality
problem of string theory.Comment: 26 pages; Significant revisions: review material truncated;
presentation improve
On Bouncing Brane-Worlds, S-branes and Branonium Cosmology
We present several higher-dimensional spacetimes for which observers living
on 3-branes experience an induced metric which bounces. The classes of examples
include boundary branes on generalised S-brane backgrounds and probe branes in
D-brane/anti D-brane systems. The bounces we consider normally would be
expected to require an energy density which violates the weak energy condition,
and for our co-dimension one examples this is attributable to bulk curvature
terms in the effective Friedmann equation. We examine the features of the
acceleration which provides the bounce, including in some cases the existence
of positive acceleration without event horizons, and we give a geometrical
interpretation for it. We discuss the stability of the solutions from the point
of view of both the brane and the bulk. Some of our examples appear to be
stable from the bulk point of view, suggesting the possible existence of stable
bouncing cosmologies within the brane-world framework.Comment: 35 pages, 7 figures, JHEP style. Title changed and references adde
Scaling Solutions to 6D Gauged Chiral Supergravity
We construct explicitly time-dependent exact solutions to the field equations
of 6D gauged chiral supergravity, compactified to 4D in the presence of up to
two 3-branes situated within the extra dimensions. The solutions we find are
scaling solutions, and are plausibly attractors which represent the late-time
evolution of a broad class of initial conditions. By matching their near-brane
boundary conditions to physical brane properties we argue that these solutions
(together with the known maximally-symmetric solutions and a new class of
non-Lorentz-invariant static solutions, which we also present here) describe
the bulk geometry between a pair of 3-branes with non-trivial on-brane
equations of state.Comment: Contribution to the New Journal of Physics focus issue on Dark
Energy; 28 page
Conformal Field Theory Correlators from Classical Scalar Field Theory on
We use the correspondence between scalar field theory on and a
conformal field theory on to calculate the 3- and 4-point functions of
the latter. The classical scalar field theory action is evaluated at tree
level.Comment: 9 pages, LaTeX2e with amsmath, amsfonts packages, section 2
rewritten, references adde
Charged shells in Lovelock gravity: Hamiltonian treatment and physical implications
Using a Hamiltonian treatment, charged thin shells in spherically symmetric
spacetimes in d dimensional Lovelock-Maxwell theory are studied. The
coefficients of the theory are chosen to obtain a sensible theory, with a
negative cosmological constant appearing naturally. After writing the action
and the Lagrangian for a spacetime comprised of an interior and an exterior
regions, with a thin shell as a boundary in between, one finds the Hamiltonian
using an ADM description. For spherically symmetric spacetimes, one reduces the
relevant constraints. The dynamic and constraint equations are obtained. The
vacuum solutions yield a division of the theory into two branches, d-2k-1>0
(which includes general relativity, Born-Infeld type theories) and d-2k-1=0
(which includes Chern-Simons type theories), where k gives the highest power of
the curvature in the Lagrangian. An additional parameter, chi, gives the
character of the vacuum solutions. For chi=1 the solutions have a black hole
character. For chi=-1 the solutions have a totally naked singularity character.
The integration through the thin shell takes care of the smooth junction. The
subsequent analysis is divided into two cases: static charged thin shell
configurations, and gravitationally collapsing charged dust shells. Physical
implications are drawn: if such a large extra dimension scenario is correct,
one can extract enough information from the outcome of those collapses as to
know, not only the actual dimension of spacetime, but also which particular
Lovelock gravity, is the correct one.Comment: 25 pages, 9 figure
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