2,364 research outputs found
On Gorenstein Surfaces Dominated by P^2
In this paper we prove that a normal Gorenstein surface dominated by the
projective plane P^2 is isomorphic to a quotient P^2/G, where G is a finite
group of automorphisms of P^2 (except possibly for one surface V_8'). We can
completely classify all such quotients. Some natural conjectures when the
surface is not Gorenstein are also stated.Comment: Nagoya Mathematical Journal, to appea
On certain new integrable second order nonlinear differential equations and their connection with two dimensional Lotka-Volterra system
In this paper, we consider a second order nonlinear ordinary differential
equation of the form
,
where 's, are arbitrary parameters. By using the modified
Prelle-Singer procedure, we identify five new integrable cases in this equation
besides two known integrable cases, namely (i) and (ii) . Among these five, four equations admit time dependent first
integrals and the remaining one admits time independent first integral. From
the time independent first integral, nonstandard Hamiltonian structure is
deduced thereby proving the Liouville sense of integrability. In the case of
time dependent integrals, we either explicitly integrate the system or
transform to a time-independent case and deduce the underlying Hamiltonian
structure. We also demonstrate that the above second order ordinary
differential equation is intimately related to the two-dimensional
Lotka-Volterra (LV) system. From the integrable parameters of above nonlinear
equation and all the known integrable cases of the latter can be deduced
thereby.Comment: Accepted for publication in J. Math. Phy
PRODUCTIVITY SPILLOVERS IN INDIAN MANUFACTURING FIRMS
Indian economic reform since early 1990s aims at improving productivity and competitiveness of major industries. The paper examines spillovers from foreign direct investment (FDI), research and development (R&D) and exporting activities on productivity both for foreign and domestic manufacturing firms. The data is obtained from the PROWESS database provided by the Centre for Monitoring Indian Economy (CMIE). Balanced panel of over 1,000 manufacturing firms in India between 1994 and 2006 are considered for our empirical analysis. Findings indicate that foreign presence has a significant spillover effect on the productivity of the Indian manufacturing firms compared to the alternative spillovers such as from R&D and export initiatives.Productivity, Spillovers, Indian manufacturing, FDI.
Bidirectional motion of filaments: Role of motor proteins and passive cross linkers
In eukaryotic cells, motor proteins (MP) bind to cytoskeletal filaments and
move along them in a directed manner generating active stresses. During cell
division a spindle structure of overlapping antiparallel microtubules (MT) form
whose stability and dynamics under the influence of MPs has been studied
extensively. Although passive cross linkers (PCL) were known to provide
structural stability to filamentous network, consequences of the interplay
between ATP dependent active forces of MPs and passive entropic forces of PCLs
on MT overlap remains largely unexplored. Here, we formulate and characterize a
model to study this, using linear stability analysis and numerical integration.
In presence of PCLs, we find dynamic phase transitions with changing activity
exhibiting regimes of stable partial overlap with or without oscillations,
instability towards complete overlap, and stable limit cycle oscillations that
emerge via a supercritical Hopf bifurcation characterized by an oscillation
frequency determined by the MP and PCL parameters. We show that the overlap
dynamics and stability depend crucially on whether both the MTs of overlapping
pair are movable or one is immobilized, having potential implications for in
vivo and in vitro studies.Comment: 13 pages, 9 figure
- …