20,701 research outputs found
Higher-Derivative Gravity with Non-minimally Coupled Maxwell Field
We construct higher-derivative gravities with a non-minimally coupled Maxwell
field. The Lagrangian consists of polynomial invariants built from the Riemann
tensor and the Maxwell field strength in such a way that the equations of
motion are second order for both the metric and the Maxwell potential. We also
generalize the construction to involve a generic non-minimally coupled -form
field strength. We then focus on one low-lying example in four dimensions and
construct the exact magnetically-charged black holes. We also construct exact
electrically-charged Lifshitz black holes. We obtain approximate dyonic
black holes for the small coupling constant or small charges. We find that the
thermodynamics based on the Wald formalism disagrees with that derived from the
Euclidean action procedure, suggesting this may be a general situation in
higher-derivative gravities with non-minimally coupled form fields. As an
application in the AdS/CFT correspondence, we study the entropy/viscosity ratio
for the AdS or Lifshitz planar black holes, and find that the exact ratio can
be obtained without having to know the details of the solutions, even for this
higher-derivative theory.Comment: Latex, 23 page
On the Role of Absorptive Capacity: FDI Matters to Growth
The paper studies the effects of foreign direct investment (FDI) on economic growth when sufficient provisions of infrastructure is a pre-requisite. In the overlapping generations setting, we show that technology spillovers via FDI take place only when the host country has the sufficient level of infrastructure. Infrastructure has a subsequent positive feedback on further investment which leads the country to grow faster. If infrastructure falls short of the critical level, however, then FDI has little effect on growth as the country is trapped in a low growth equilibrium. We also present the simulations and empirical results based on panel data for 42 developing countries between 1970 and 2000. They support the model that FDI and infrastructure are complementary in affecting per capita GDP growth.http://deepblue.lib.umich.edu/bitstream/2027.42/57225/1/wp845 .pd
Improving Routing Efficiency through Intermediate Target Based Geographic Routing
The greedy strategy of geographical routing may cause the local minimum
problem when there is a hole in the routing area. It depends on other
strategies such as perimeter routing to find a detour path, which can be long
and result in inefficiency of the routing protocol. In this paper, we propose a
new approach called Intermediate Target based Geographic Routing (ITGR) to
solve the long detour path problem. The basic idea is to use previous
experience to determine the destination areas that are shaded by the holes. The
novelty of the approach is that a single forwarding path can be used to
determine a shaded area that may cover many destination nodes. We design an
efficient method for the source to find out whether a destination node belongs
to a shaded area. The source then selects an intermediate node as the tentative
target and greedily forwards packets to it, which in turn forwards the packet
to the final destination by greedy routing. ITGR can combine multiple shaded
areas to improve the efficiency of representation and routing. We perform
simulations and demonstrate that ITGR significantly reduces the routing path
length, compared with existing geographic routing protocols
On the Role of Absorptive Capacity: FDI Matters to Growth
The paper studies the effects of foreign direct investment (FDI) on economic growth when sufficient provisions of infrastructure is a pre-requisite. In the overlapping generations setting, we show that technology spillovers via FDI take place only when the host country has the sufficient level of infrastructure. Infrastructure has a subsequent positive feedback on further investment which leads the country to grow faster. If infrastructure falls short of the critical level, however, then FDI has little effect on growth as the country is trapped in a lowgrowth equilibrium. We also present the simulations and empirical results based on panel data for 42 developing countries between 1970 and 2000. They support the model that FDI and infrastructure are complementary in affecting per capita GDP growth.foreign direct investment; economic growth, technology diffusion, infrastructure
On the Role of Absorptive Capacity: FDI Matters to Growth
The paper studies the e®ects of foreign direct investment (FDI) on economic growth when su±cient provisions of infrastructure is a pre-requisite. In the overlap-ping generations structure setting, we show that technology spillovers via FDI take place only when the host country has the su±cient level of infrastructure. Infras-tructure has a subsequent positive feedback on further investment which leads the country grow faster. If infrastructure falls short of the critical level, however, then FDI has little e®ect on growth as the country is trapped in a low-growth equilibrium. We also present the simulations and empirical results based on panel data for 42 developing countries between 1970 and 2000. They provide support to the model that FDI and infrastructure are complements in a®ecting per capita GDP growth.
Horndeski Gravity and the Violation of Reverse Isoperimetric Inequality
We consider Einstein-Horndeski-Maxwell gravity, together with a cosmological
constant and multiple Horndeski axions. We construct charged AdS planar black
holes in general dimensions where the Horndeski anxions span over the planar
directions. We analyse the thermodynamics and obtain the black hole volumes. We
show that the reverse isoperimetric inequality can be violated, implying that
these black holes can store information more efficiently than the Schwarzschild
black hole.Comment: Latex, 25 pages, 1 figure, references adde
Second-harmonic generation in graded metallic films
We study the effective second-harmonic generation (SHG) susceptibility in
graded metallic films by invoking the local field effects exactly, and further
numerically demonstrate that the graded metallic films can serve as a novel
optical material for producing a broad structure in both the linear and SHG
response and an enhancement in the SHG signal.Comment: 10 pages, 2 EPS figures. Minor revision
- …