66,550 research outputs found
Geographic concentration and firm survival
If localization economies are present, firms within denser industry concentrations should exhibit higher levels of performance than more isolated firms. Nevertheless, research in industrial organization that has focused on the influences on firm survival has largely ignored the potential effects from agglomeration. Recent studies in urban and regional economics suggests that agglomeration effects may be very localized. Analyses of industry concentration at the MSA or county-level may fail to detect important elements of intra-industry firm interaction that occur at the sub-MSA level. Using a highly detailed dataset on firm locations and characteristics for Texas, this paper analyses agglomeration effects on firm survival over geographic areas as small as a single mile radius. We find that greater firm density within very close proximity (within 1 mile) of firms in the same industry increases mortality rates while greater concentration over larger distances reduces mortality rates.Firm Survival, Agglomeration, Localization, and Knowledge Externalities
Anicut systems in Sri Lanka: The case of the Upper Walawe River Basin
Water resources / Tanks / Water use / River basins / Hydrology / Irrigation systems / Water shortage / Crops / Doemstic water / Fuelwood / Cultivation / Deforestation / Water supply / Economic development / Water management / Institutions / Land reform
Research universities and regional high-tech firm start-ups and exit
If localized knowledge spillovers are present in the university setting, higher rates of both start-ups and/or survival than in the broader economy would be observed in areas that are geographically proximate to the university. Using a fully-disclosed Quarterly Census of Employment and Wages for Texas for the years 1999:3-2006:2, this paper analyzes start-ups and exit rates for high-tech firms in Texas. We find that there is evidence that the presence of a research institution will affect the likelihood of technology start-ups. However, results suggest that geographic proximity to knowledge centers does not reduce hazard rates.Entry and Survival, R & D, Regional, Urban, and Rural Analyses
Asymmetrical bloch branes and the hierarchy problem
We investigate a two scalar fields split braneworld model which leads to a
possible approach to the hierarchy problem within the thick brane scenario. The
model exhibits a resulting asymmetric warp factor suitable for this purpose.
The solution is obtained by means of the orbit equation approach for a specific
value of one of the parameters. Besides, we analyze the model qualitative
behaviour for arbitrary parameters by inspecting the underlying dynamical
system defined by the equations which give rise to the braneworld model. We
finalize commenting on the metric fluctuation and stability issues.Comment: 8 pages, 7 figure
Joint Formation of QSOs and Spheroids: QSOs as clocks of star formation in Spheroids
Direct and indirect observational evidence leads to the conclusion that high
redshift QSOs did shine in the core of early type proto-galaxies during their
main episode of star formation. Exploting this fact, we derive the rate of
formation of this kind of stellar systems at high redshift by using the QSO
Luminosity Function. The elemental proportions in elliptical galaxies, the
descendents of the QSO hosts, suggest that the star formation was more rapid in
more massive objects. We show that this is expected to occur in Dark Matter
haloes, when the processes of cooling and heating is considered. This is also
confirmed by comparing the observed sub-mm counts to those derived by coupling
the formation rate and the star formation rate of the spheroidal galaxies with
a detailed model for their SED evolution. In this scenario SCUBA galaxies and
Lyman Break Galaxies are early type proto-galaxies forming the bulk of their
stars before the onset of QSO activity.Comment: 13 pages, 8 figures, accepted by MNRAS, major revision of the
formalis
- …