Antithetic multilevel Monte Carlo estimation for multi-dimensional SDEs without L\'{e}vy area simulation

In this paper we introduce a new multilevel Monte Carlo (MLMC) estimator for multi-dimensional SDEs driven by Brownian motions. Giles has previously shown that if we combine a numerical approximation with strong order of convergence $O(\Delta t)$ with MLMC we can reduce the computational complexity to estimate expected values of functionals of SDE solutions with a root-mean-square error of $\epsilon$ from $O(\epsilon^{-3})$ to $O(\epsilon^{-2})$. However, in general, to obtain a rate of strong convergence higher than $O(\Delta t^{1/2})$ requires simulation, or approximation, of L\'{e}vy areas. In this paper, through the construction of a suitable antithetic multilevel correction estimator, we are able to avoid the simulation of L\'{e}vy areas and still achieve an $O(\Delta t^2)$ multilevel correction variance for smooth payoffs, and almost an $O(\Delta t^{3/2})$ variance for piecewise smooth payoffs, even though there is only $O(\Delta t^{1/2})$ strong convergence. This results in an $O(\epsilon^{-2})$ complexity for estimating the value of European and Asian put and call options.Comment: Published in at http://dx.doi.org/10.1214/13-AAP957 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Understanding international prices: customers as capital

This paper develops a theory of pricing-to-market driven by marketing and bargaining frictions. Our key innovation is a capital theoretic model of marketing in which relations with customers are valuable. In our model, producers search and form long-lasting relations with their customers, and marketing helps overcome the search frictions involved in forming such matches. In the context of international business cycle patterns, the model accounts for observations that are puzzles for a large class of theories: (i) pricing-to-market, (ii) positive correlation of aggregate real export and import prices, (iii) excess volatility of the real exchange rate over the terms of trade, and (iv) low short-run and high long-run price elasticity of international trade flows. The behavior of quantities is shown to be on par with standard international business cycle theories that, in contrast to our model, assume low intrinsic elasticity of substitution between domestic and foreign goods.Business cycles ; Prices ; International business enterprises

Pricing to Market in Business Cycle Models

This paper evaluates the performance of leading micro-founded pricing-to-market frictions vis-a-vis a set of robust stylized facts about international prices. In order to make that evaluation meaningful, we embed each friction into a unified IRBC framework and parameterize the models in a uniform way. Our goal is to evaluate the broad-based applicability of these frictions for policy-oriented DSGE modeling by documenting their strengths and weaknesses. We make three points: (i) the mechanisms generating pricing to market are not always neutral to business cycle dynamics of quantities, (ii) some mechanisms require producer markups at least 50% to account for the full range of estimates of the empirical exchange rate pass-through to export prices of 35%-50%, (iii) some frictions crucially depend on a particular driver of uncertainty in the underlying model.pricing to market, law of one price, incomplete pass-through, international correlations, international business cycle, sticky prices, pass-through coefficient

Topological phases of fermions in one dimension

In this paper we show how the classification of topological phases in insulators and superconductors is changed by interactions, in the case of 1D systems. We focus on the TR-invariant Majorana chain (BDI symmetry class). While the band classification yields an integer topological index $k$, it is known that phases characterized by values of $k$ in the same equivalence class modulo 8 can be adiabatically transformed one to another by adding suitable interaction terms. Here we show that the eight equivalence classes are distinct and exhaustive, and provide a physical interpretation for the interacting invariant modulo 8. The different phases realize different Altland-Zirnbauer classes of the reduced density matrix for an entanglement bipartition into two half-chains. We generalize these results to the classification of all one dimensional gapped phases of fermionic systems with possible anti-unitary symmetries, utilizing the algebraic framework of central extensions. We use matrix product state methods to prove our results.Comment: 14 pages, 3 figures, v2: references adde

"Bayesian anchoring" and the fourfold pattern of risk attitudes

Experiments on decision making under uncertainty are known to display a classical pattern of risk aversion and risk seeking referred to as "fourfold pattern" (or "reflection effect") , but recent experiments varying the speed and order of mental processing have brought to light a more nuanced phenomenology. We model experiments though a Bayesian formalization of the anchor-and-adjust heuristic observed in empirical studies on cognitive bias. Using only elementary assumptions on constrained information processing, we are able to infer three separate effects found in recent observations: (1) the reported enhancement of the fourfold pattern for quicker decision processes; (2) the observed decrease of fluctuations for slower decision-making trials; (3) the reported dependence of the outcome on the order in which options are processed. The application of Bayesian modeling offers a solution to recent empirical riddles by bridging two heretofore separate domains of experimental inquiry on bounded rationality.Comment: 26 pages, 7 figure