12,708 research outputs found
Finite-time Lyapunov exponents for products of random transformations
It is shown how continuous products of random transformations constrained by
a generic group structure can be studied by using Iwasawa's decomposition into
``angular'', ``diagonal'' and ``shear'' degrees of freedom. In the case of a
Gaussian process a set of variables, adapted to the Iwasawa decomposition and
still having a Gaussian distribution, is introduced and used to compute the
statistics of the finite-time Lyapunov spectrum of the process. The variables
also allow to show the exponential freezing of the ``shear'' degrees of
freedom, which contain information about the Lyapunov eigenvectors
On the Evolution of Preferences
A common feature of the literature on the evolution of preferences is that evolution favors nonmaterialistic preferences only if preference types are observable at least to some degree. We argue that this result is due to the assumption that in each state of the evolutionary dynamics some Bayesian Nash equilibrium is played. We show that under unobservability of preference types, conditional on selecting some self-confirming equilibrium as a rule for mapping preference into behavior, non-selfish preferences may be evolutionarily successful.evolution of preferences, altruism, learning, self-confirming equilibrium
Moduli Spaces of Curves with Homology Chains and c=1 Matrix Models
We show that introducing a periodic time coordinate in the models of
Penner-Kontsevich type generalizes the corresponding constructions to the case
of the moduli space of curves with homology chains
\gamma\in H_1(C,\zet_k). We make a minimal extension of the resulting models
by adding a kinetic term, and we get a new matrix model which realizes a simple
dynamics of \zet_k-chains on surfaces. This gives a representation of
matter coupled to two-dimensional quantum gravity with the target space being a
circle of finite radius, as studied by Gross and Klebanov.Comment: IFUM 459/FT (LaTeX, 9 pages; a few misprints have been corrected and
the introduction has been slightly modified
Impact of strong magnetic fields on collision mechanism for transport of charged particles
One of the main applications in plasma physics concerns the energy production
through thermo-nuclear fusion. The controlled fusion is achieved by magnetic
confinement i.e., the plasma is confined into a toroidal domain (tokamak) under
the action of huge magnetic fields. Several models exist for describing the
evolution of strongly magnetized plasmas, most of them by neglecting the
collisions between particles. The subject matter of this paper is to
investigate the effect of large magnetic fields with respect to a collision
mechanism. We consider here linear collision Boltzmann operators and derive, by
averaging with respect to the fast cyclotronic motion due to strong magnetic
forces, their effective collision kernels
Utility based pricing of contingent claims
In a discrete setting, we develop a model for pricing a contingent claim. Since the presence of hedging opportunities influences the price of a contingent claim, first we introduce the optimal hedging strategy assuming a contingent claim has been issued: a strategy implemented by investing the budget plus the selling price is optimal if it maximizes the expected utility of the agent's revenue, which is the difference between the outcome of the hedging portfolio and the payoff of the claim. Next, we introduce the `reservation price' as a subjective valuation of a contingent claim. This is defined as the minimum price to be added to the initial budget that makes the issue of the claim more preferable than optimally investing in the available securities. We define the reservation price both for a short position (reservation selling price) and for a long position (reservation buying price) in the contingent claim. When the contingent claim is redundant, both the selling and the buying price collapse in the usual Arrow-Debreu price. We develop a numerical procedure to evaluate the reservation price and two applications are provided. Different utility functions are used and some qualitative properties of the reservation price are shown.Incomplete markets, reservation price, expected utility, optimization
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