Bose-glass to Superfluid transition in the three-dimensional Bose-Hubbard Model

We present a Monte Carlo study of the Bose-glass to superfluid transition in the three-dimensional Bose-Hubbard model. Simulations are performed on the classical (3 + 1) dimensional link-current representation using the geometrical worm algorithm. Finite-size scaling analysis (on lattices as large as 16x16x16x512 sites) of the superfluid stiffness and the compressibility is consistent with a value of the dynamical critical exponent z = 3, in agreement with existing scaling and renormalization group arguments that z = d. We find also a value of $\nu = 0.70(12)$ for the correlation length exponent, satisfying the relation $\nu >= 2/d$. However, a detailed study of the correlation functions, C(r, tau), at the quantum critical point are not consistent with this value of z. We speculate that this discrepancy could be due to the fact that the correlation functions have not reached their true asymptotic behavior because of the relatively small spatial extent of the lattices used in the present study.Comment: 9 pages, 8 figures, submitted to PR

Professional Advice: The Theory of Reputational Cheap Talk.

Professional experts offer advice with the objective of appearing well informed. Their ability is evaluated on the basis of the advice given and of the realized state of the world. This situation is modeled as a reputational cheap-talk game in which the expert receives a signal of continuously varying intensity with ability-dependent precision about a continuum of states. Despite allowing an arbitrarily rich message space, at most two messages are sent in equilibrium. The expert can only credibly transmit the direction but not the intensity of the information possessed. Equilibrium advice is then systematically less informative than under truthtelling.reputation; cheap talk; advice; herding

Informational Herding and Optimal Experimentation

We show that far from capturing a formally new phenomenon, informational herding is really a special case of single-person experimentation -- and 'bad herds' the typical failure of complete learning. We then analyze the analogous team equilibrium, where individuals maximize the present discounted welfare of posterity. To do so, we generalize Gittins indices to our non-bandit learning problem, and thereby characterize when contrarian behaviour arises: (i) While herds are still constrained efficient, they arise for a strictly smaller belief set. (ii) A log-concave log-likelihood ratio density robustly ensures that individuals should lean more against their myopic preference for an action the more popular it becomes.Bayesian learning, value function, herding, experimentation, log concavity, Gittins index, team equilibrium

The Strategy of Professional Forecasting

This paper develops and compares two theories of strategic behavior of professional forecasters. The first theory posits that forecasters compete in a forecasting contest with pre-specified rules. In equilibrium of a winner-take-all contest, forecasts are excessively differentiated. According to the alternative reputational cheap talk theory, forecasters aim at convincing the market that they are well informed. The market evaluates their forecasting talent on the basis of the forecasts and the realized state. If the market has naive views on forecasters' behavior, forecasts are biased toward the prior mean. Otherwise, equilibrium forecasts are unbiased but imprecise.Forecasting; Contest; Reputation; Cheap Talk

Nuclear recoil energy scale in liquid xenon with application to the direct detection of dark matter

We show for the first time that the quenching of electronic excitation from nuclear recoils in liquid xenon is well-described by Lindhard theory, if the nuclear recoil energy is reconstructed using the combined (scintillation and ionization) energy scale proposed by Shutt {\it et al.}. We argue for the adoption of this perspective in favor of the existing preference for reconstructing nuclear recoil energy solely from primary scintillation. We show that signal partitioning into scintillation and ionization is well-described by the Thomas-Imel box model. We discuss the implications for liquid xenon detectors aimed at the direct detection of dark matter