405,680 research outputs found

### Viability Theory and Economic Modeling

A brief introduction into the theory of differential inclusions, viability theory and selections of set valued mappings is presented. As an application the implicit scheme of the Leontief dynamic input-output model is considered

### VIABILITY THEORY AND SOIL DEVELOPMENT

We utilize Viability theory to evaluate the effects of CAP. A differential equation describes the dynamic development of soil productivity. If farmers do without entitlement, they are free in soil handling. And as we assume they are short-term profit maximizers, they miss to pay attention to soil conservation. Soil productivity is at risk; correspondingly, economic sustainability is at risk. But if farmers activate their entitlements, they become obliged to soil conserving measures. The model demonstrates that the decision to participate or not at the "entitlement & cross compliance"-program, depends on payment-level and the effects of the decision depend on the dynamics of the environmental system.Sustainability, Agriculture, Viability Theory, Environmental Economics and Policy, Farm Management,

### On the Viability of Lattice Perturbation Theory

In this paper we show that the apparent failure of QCD lattice perturbation
theory to account for Monte Carlo measurements of perturbative quantities
results from choosing the bare lattice coupling constant as the expansion
parameter. Using instead ``renormalized'' coupling constants defined in terms
of physical quantities, like the heavy-quark potential, greatly enhances the
predictive power of lattice perturbation theory. The quality of these
predictions is further enhanced by a method for automatically determining the
coupling-constant scale most appropriate to a particular quantity. We present a
mean-field analysis that explains the large renormalizations relating lattice
quantities, like the coupling constant, to their continuum analogues. This
suggests a new prescription for designing lattice operators that are more
continuum-like than conventional operators. Finally, we provide evidence that
the scaling of physical quantities is asymptotic or perturbative already at
$\beta$'s as low as 5.7, provided the evolution from scale to scale is analyzed
using renormalized perturbation theory. This result indicates that reliable
simulations of (quenched) QCD are possible at these same low $\beta$'s.Comment: 3

### Phenomenological viability of string and M-theory scenarios

We analyze the constraints that a correct phenomenology and the absence of
dangerous charge and color breaking (CCB) minima or unbounded from below (UFB)
directions impose on the parameter space of different superstring and M-theory
scenarios. Namely, we analyze in detail the case where supersymmetry (SUSY)
breaking is driven by non-vanishing dilaton and/or moduli F-terms in weakly and
strongly coupled strings, and the specific case where the mechanism of SUSY
breaking is gaugino condensation with or without the participation of
non-perturbative contributions to the K{\"a}hler potential. The results
indicate that, only in some small windows of the parameter space all the
previous tests are succesfully passed. We also discuss the impact of
non-universality of the soft breaking terms on CCB/UFB bounds.Comment: 18 pages + 10 figures, PostScript fil

### Differential games through viability theory : old and recent results.

This article is devoted to a survey of results for differential games obtained through Viability Theory. We recall the basic theory for differential games (obtained in the 1990s), but we also give an overview of recent advances in the following areas : games with hard constraints, stochastic differential games, and hybrid differential games. We also discuss several applications.Game theory; Differential game; viability algorithm;

### On the Viability of a Non-Analytical f(R)-Theory

In this paper, we show how a power-law correction to the Einstein-Hilbert
action provides a viable modified theory of gravity, passing the Solar-System
tests, when the exponent is between the values 2 and 3. Then, we implement this
paradigm on a cosmological setting outlining how the main phases of the
Universe thermal history are properly reproduced. As a result, we find two
distinct constraints on the characteristic length scale of the model, i.e., a
lower bound from the Solar-System test and an upper one by guaranteeing the
matter dominated Universe evolution.Comment: 9 pages, 2 figure

### A note on viability of nonminimally coupled $f(R)$ theory

Consistency conditions for nonminimally coupled $f(R)$ theories have been
derived by requiring the absence of tachyons and instabilities in the scalar
fluctuations. This note confirms these results and clarifies a subtlety
regarding different definitions of sound speeds.Comment: 4 pages. -added acknowledgemen

### Viability of Noether symmetry of F(R) theory of gravity

Canonization of F(R) theory of gravity to explore Noether symmetry is
performed treating R - 6(\frac{\ddot a}{a} + \frac{\dot a^2}{a^2} +
\frac{k}{a^2}) = 0 as a constraint of the theory in Robertson-Walker
space-time, which implies that R is taken as an auxiliary variable. Although it
yields correct field equations, Noether symmetry does not allow linear term in
the action, and as such does not produce a viable cosmological model. Here, we
show that this technique of exploring Noether symmetry does not allow even a
non-linear form of F(R), if the configuration space is enlarged by including a
scalar field in addition, or taking anisotropic models into account.
Surprisingly enough, it does not reproduce the symmetry that already exists in
the literature (A. K. Sanyal, B. Modak, C. Rubano and E. Piedipalumbo,
Gen.Relativ.Grav.37, 407 (2005), arXiv:astro-ph/0310610) for scalar tensor
theory of gravity in the presence of R^2 term. Thus, R can not be treated as an
auxiliary variable and hence Noether symmetry of arbitrary form of F(R) theory
of gravity remains obscure. However, there exists in general, a conserved
current for F(R) theory of gravity in the presence of a non-minimally coupled
scalar-tensor theory (A. K. Sanyal, Phys.Lett.B624, 81 (2005),
arXiv:hep-th/0504021 and Mod.Phys.Lett.A25, 2667 (2010), arXiv:0910.2385
[astro-ph.CO]). Here, we briefly expatiate the non-Noether conserved current
and cite an example to reveal its importance in finding cosmological solution
for such an action, taking F(R) \propto R^{3/2}.Comment: 16 pages, 1 figure. appears in Int J Theoretical Phys (2012

### Differential Inclusions and Viability Theory

We present a summary of the basic results on differential inclusions and viability theory. A comprehensive exposition of these two theories is the purpose of the book on the same subject by the authors

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