Cosmological Equations for a Thick Brane

Generalized Friedmann equations governing the cosmological evolution inside a thick brane embedded in a five-dimensional Anti-de Sitter spacetime are derived. These equations are written in terms of four-dimensional effective brane quantities obtained by integrating, along the fifth dimension, over the brane thickness. In the case of a Randall-Sundrum type cosmology, different limits of these effective quantities are considered yielding cosmological equations which interpolate between the thin brane limit (governed by unconventional brane cosmology), and the opposite limit of an ``infinite'' brane thickness corresponding to the familiar Kaluza-Klein approach. In the more restrictive case of a Minkowski bulk, it is shown that no effective four-dimensional reduction is possible in the regimes where the brane thickness is not small enough.Comment: 23 pages, Latex, 2 figure

Can Lightcone Fluctuations be Probed with Cosmological Backgrounds?

Finding signatures of quantum gravity in cosmological observations is now actively pursued both from the theoretical and the experimental side. Recent work has concentrated on finding signatures of light-cone fluctuations in the CMB. Because in inflationary scenarios a Gravitational Wave Background (GWB) is always emitted much before the CMB, we can ask, in the hypothesis where this GWB could be observed, what is the imprint of light cone fluctuations on this GWB. We show that due to the flat nature of the GWB spectrum, the effect of lightcone fluctuations are negligible.Comment: 10 pages, references adde

A theory of deception.

This paper proposes an equilibrium approach to belief manipulation and deception in which agents only have coarse knowledge of their opponent's strategy. Equilibrium requires the coarse knowledge available to agents to be correct, and the inferences and optimizations to be made on the basis of the simplest theories compatible with the available knowledge. The approach can be viewed as formalizing into a game theoretic setting a well documented bias in social psychology, the fundamental attribution error. It is applied to a bargaining problem, thereby revealing a deceptive tactic that is hard to explain in the full rationality paradigm.belief manipulation; deception; Bargaining Theory;

Precision Lattice Calculation of SU(2) 't Hooft loops

The [dual] string tension of a spatial 't Hooft loop in the deconfined phase of Yang-Mills theory can be formulated as the tension of an interface separating different Z_N deconfined vacua. We review the 1-loop perturbative calculation of this interface tension in the continuum and extend it to the lattice. The lattice corrections are large. Taking these corrections into account, we compare Monte Carlo measurements of the dual string tension with perturbation theory, for SU(2). Agreement is observed at the 2% level, down to temperatures O(10) T_c.Comment: 17 pages, 7 figures; reference added, typos correcte

Towards a theory of deception

This paper proposes an equilibrium approach to deception where deception is defined to be the process by which actions are chosen to induce erroneous inferences so as to take advantage of them. Specifically, we introduce a framework with boundedly rational players in which agents make inferences based on a coarse information about others' behaviors: Agents are assumed to know only the average reaction function of other agents over groups of situations. Equilibrium requires that the coarse information available to agents is correct, and that inferences and optimizations are made based on the simplest theories compatible with the available information. We illustrate the phenomenon of deception and how reputation concerns may arise even in zero-sum games in which there is no value to commitment. We further illustrate how the possibility of deception affects standard economic insights through a number of stylized applications including a monitoring game and two simple bargaining games. The approach can be viewed as formalizing into a game theoretic setting a well documented bias in social psychology, the Fundamental Attribution Error.deception ; game theory ; fundamental attribution error

No green growth without innovation. Bruegel Policy Brief 2009/07, November 2009

The 'green growth' debate is taking place in an oversimplified setting, largely disregarding the innovation factor. Technologies to mitigate climate change are being treated as given, or as emerging spontaneously, ignoring the fact that the portfolio of technologies available tomorrow depends on what is done today. This can easily lead to a misguided preference, either for subsidising the use of relatively inefficient technologies or for postponing action to later in the hope that new technologies will become available which will reduce the cost of fighting climate change. But the radical new emissions-free 'backstop technologies' we will need are not yet available, or else still far from the market. To foster their emergence the 'green innovation machine' must be turned on

Putting Money Back into Monetary Policy: A Monetary Anchor for Price and Financial Stability

The Bank of Canada should pay closer attention to the effects of money and credit growth on inflation and asset markets. The authors contend that maintaining price stability should remain the Bank’s only formal goal, but say greater attention should be paid to asset market stability. Once the role of asset markets in the mechanics of inflation or price-level targeting is made explicit, such a policy will promote orderly asset market behaviour. This hinges on the role broader money and credit aggregates play in the transmission mechanism that links monetary policy to the behaviour of the rest of the economy.Monetary Policy, Bank of Canada, inflation, price stability, asset market stability, price-level targeting, broad money aggregate (M2+)