In this paper a real analysis approach to stock price modelling is considered. A stock price and its return are defined in a duality to each other provided there exist suitable limits along a sequence of nested partitions of a time interval, mimicking sum and product integrals. It extends the...

We consider an agent who invests in a stock and a money market and consumes in order to maximize the utility of consumption over an infinite planning horizon in the presence of a proportional transaction cost <InlineEquation ID="Equ1"> <EquationSource Format="TEX">$\lambda 0$</EquationSource> </InlineEquation>. The utility function is of the form U(c)=c <Superscript>1-p </Superscript>/(1-p) for p 0, <InlineEquation ID="Equ2"> <EquationSource Format="TEX">$p\neq...</equationsource></inlineequation></superscript></equationsource></inlineequation>

We study the problem of investing in securities in order to maximize the after-tax rate of return. We consider a single stock modeled as geometric Brownian motion along with the objective of maximizing the long-run growth rate of after-tax wealth. We show that it is optimal not only to cut short...

We consider a financial market with costs as in Kabanov and Last (1999). Given a utility function defined on ${\mathbb R}$, we analyze the problem of maximizing the expected utility of the liquidation value of terminal wealth diminished by some random claim. We prove that, under the Reasonable...

We consider a continuous-time stochastic optimization problem with infinite horizon, linear dynamics, and cone constraints which includes as a particular case portfolio selection problems under transaction costs for models of stock and currency markets. Using an appropriate geometric formalism...

<Para ID="Par1">For any positive diffusion with minimal regularity, there exists a semimartingale with uniformly close paths that is a martingale under an equivalent probability. As a result, in models of asset prices based on such diffusions, arbitrage and bubbles alike disappear under proportional transaction...</para>

In a market with one safe and one risky asset, an investor with a long horizon, constant investment opportunities and constant relative risk aversion trades with small proportional transaction costs. We derive explicit formulas for the optimal investment policy, its implied welfare, liquidity...

A duality for robust hedging with proportional transaction costs of path-dependent European options is obtained in a discrete-time financial market with one risky asset. The investor’s portfolio consists of a dynamically traded stock and a static position in vanilla options, which can be...