The epsilon regime with twisted mass Wilson fermions

We investigate the leading lattice spacing effects in mesonic two-point correlators computed with twisted mass Wilson fermions in the epsilon-regime. By generalizing the procedure already introduced for the untwisted Wilson chiral effective theory, we extend the continuum chiral epsilon expansion to twisted mass WChPT. We define different regimes, depending on the relative power counting for the quark masses and the lattice spacing. We explicitly compute, for arbitrary twist angle, the leading O(a^2) corrections appearing at NLO in the so-called GSM^* regime. As in untwisted WChPT, we find that in this situation the impact of explicit chiral symmetry breaking due to lattice artefacts is strongly suppressed. Of particular interest is the case of maximal twist, which corresponds to the setup usually adopted in lattice simulations with twisted mass Wilson fermions. The formulae we obtain can be matched to lattice data to extract physical low energy couplings, and to estimate systematic uncertainties coming from discretization errors.Comment: 26 pages, 3 figure

The Limit of Public Policy: Endogenous Preferences

In designing public policy it is not enough to consider the possible reaction of individuals to the chosen policy.Public policy may also affect the formation of preferences and norms in a society.The endogenous evolution of preferences, in addition to introducing a conceptual difficulty in evaluating policies, may also eventually affect actual behavior.In order to demonstrate the implications of endogenous preferences on the design of optimal public policy, we present a model in which a subsidy policy is set to encourage contributions towards a public good.However this policy triggers an endogenous preference change that results in a lower level of contribution towards the public good despite the explicit monetary incentives to raise that level.public policy

Interpolation between the epsilon and p regimes

We reconsider chiral perturbation theory in a finite volume and develop a new computational scheme which smoothly interpolates the conventional epsilon and p regimes. The counting rule is kept essentially the same as in the p expansion. The zero-momentum modes of Nambu-Goldstone bosons are, however, treated separately and partly integrated out to all orders as in the epsilon expansion. In this new scheme, the theory remains infra-red finite even in the chiral limit, while the chiral-logarithmic effects are kept present. We calculate the two-point function in the pseudoscalar channel and show that the correlator has a constant contribution in addition to the conventional hyperbolic cosine function of time t. This constant term rapidly disappears in the p regime but it is indispensable for a smooth convergence of the formula to the epsilon regime result. Our calculation is useful to precisely estimate the finite volume effects in lattice QCD simulations on the pion mass Mpi and kaon mass MK, as well as their decay constants Fpi and FK.Comment: 49 pages, 6 figures, minor corrections, references added, version to appear in PR

Informing Consumers About Themselves

Consumers make mistakes. Imperfect information and imperfect rationality lead to misperception of benefits and costs associated with a product. As a result, consumers might fail to maximise their preferences in product choice or product use. A proposed taxonomy of consumer mistakes draws attention to a less-studied category of mistakes: use-pattern mistakes – mistakes about how the consumer will use the product. Use-pattern mistakes are prevalent. Sellers respond strategically to use-pattern mistakes by redesigning their products, contracts and pricing schemes. These strategic design responses often exacerbate the welfare costs associated with consumer mistakes. From a policy perspective, focusing on disclosure regulation, the importance of use-pattern mistakes requires more, and better, use-pattern disclosure. In particular, sellers should be required to provide individualised use-pattern information

A spectroscopic search for White Dwarf companions to 101 nearby M dwarfs

Recent studies of the stellar population in the solar neighborhood (<20 pc) suggest that there are undetected white dwarfs (WDs) in multiple systems with main sequence companions. Detecting these hidden stars and obtaining a more complete census of nearby WDs is important for our understanding of binary and galactic evolution, as well as the study of explosive phenomena. In an attempt to uncover these hidden WDs, we present intermediate resolution spectroscopy over the wavelength range 3000-25000 \AA\ of 101 nearby M dwarfs (dMs), observed with the Very Large Telescope X-Shooter spectrograph. For each star we search for a hot component superimposed on the dM spectrum. X-Shooter has excellent blue sensitivity and thus can reveal a faint hot WD despite the brightness of its red companion. Visual examination shows no clear evidence of a WD in any of the spectra. We place upper limits on the effective temperatures of WDs that may still be hiding by fitting dM templates to the spectra, and modeling WD spectra. On average our survey is sensitive to WDs hotter than about 5300 K. This suggests that the frequency of WD companions of T<5300 K with separation of order <50 AU among the local dM population is <3% at the 95% confidence level. The reduced spectra are made available on via WISeREP repository.Comment: 41 pages, 105 figures, 2 tables. Submitted to AAS journal

Signatures of Strong Momentum Localization via Translational-Internal Entanglement

We show that atoms or molecules subject to fields that couple their internal and translational (momentum) states may undergo a crossover from randomization (diffusion) to strong localization (sharpening) of their momentum distribution. The predicted crossover should be manifest by a drastic change of the interference pattern as a function of the coupling fields.Comment: 4 pages, 3 figure

The Limit of Public Policy:Endogenous Preferences

In designing public policy it is not enough to consider the possible reaction of individuals to the chosen policy.Public policy may also affect the formation of preferences and norms in a society.The endogenous evolution of preferences, in addition to introducing a conceptual difficulty in evaluating policies, may also eventually affect actual behavior.In order to demonstrate the implications of endogenous preferences on the design of optimal public policy, we present a model in which a subsidy policy is set to encourage contributions towards a public good.However this policy triggers an endogenous preference change that results in a lower level of contribution towards the public good despite the explicit monetary incentives to raise that level.

Bargaining in the Absence of Property Rights. An Experiment

The Coase theorem posits that if (1) property rights are perfect, (2) contracts are perfectly enforceable, (3) transaction costs are zero, (4) preferences are common knowledge, and (5) parties are rational, then the initial allocation of entitlements matters only for distribution, not for efficiency. We study, in an experimental setting, whether condition 1 is necessary. Our results suggest that property rights have a limited effect on efficiency