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Jaume Gin 《Chaos, solitons, and fractals》2007,31(5):1118-1134
This review paper contains a brief summary of topics and concepts related with some open problems of planar differential systems. Most of them are related with 16th Hilbert problem which refers to the existence of a uniform upper bound on the number of limit cycles of a polynomial system in function of its degree. These open problems are proposed as open questions throughout the text. Finally, an extensive bibliography, which does not intend to be exhaustive, is also given. 相似文献
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Jaume Haro 《International Journal of Theoretical Physics》2003,42(12):2839-2846
We apply the formal W.K.B. method in the complex plane to the quantum field theory to obtain the Schwinger formula for spin and spinless particles; i.e., we obtain the probability that the vacuum state remains unchanged in presence of a constant electric field. Finally, from Schwinger formula we calculate the probability that n pairs are produced. 相似文献
46.
Option pricing and perfect hedging on correlated stocks 总被引:2,自引:0,他引:2
We develop a theory for option pricing with perfect hedging in an inefficient market model where the underlying price variations are autocorrelated over a time τ0. This is accomplished by assuming that the underlying noise in the system is derived by an Ornstein-Uhlenbeck, rather than from a Wiener process. With a modified portfolio consisting in calls, secondary calls and bonds we achieve a riskless strategy which results in a closed and exact expression for the European call price which is always lower than Black-Scholes price. We obtain the same price and a modified delta hedging if we start from an effective one-dimensional market model. We compare these strategies and study the sensitivity of the call price to several parameters where the correlation effects are also observed. 相似文献
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Cairó Laurent Giacomini Hector Llibre Jaume 《Rendiconti del Circolo Matematico di Palermo》2003,52(3):389-418
We complete the classication of all Lotka-Volterra systemsx=x(ax+by+c),y=y(Ax+By+C), having a Liouvillian first integral. In our classification we take into account the first integrals coming from the existence
of exponential factors. 相似文献
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Jaume Garriga 《International Journal of Theoretical Physics》2003,42(6):1343-1367
We discuss the effective action of moduli fields in warped brane-world compactifications. For definiteness, a two-brane model with a bulk dilaton field and a power-law warp factor is considered. After deriving the classical four-dimensional effective action for the moduli, we present the calculation of the one-loop effective potential induced by bulk fields. A detailed discussion of renormalization is given, with emphasis on the local worldsheet operators which are generated. Finally, we outline the possible role of these operators in the stabilization of the moduli. 相似文献
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In this work we study the centers of planar analytic vector fields which are limit of linear type centers. It is proved that all the nilpotent centers are limit of linear type centers and consequently the Poincaré-Liapunov method to find linear type centers can be also used to find the nilpotent centers. Moreover, we show that the degenerate centers which are limit of linear type centers are also detectable with the Poincaré-Liapunov method. 相似文献