Robust implementation under alternative information structures

In this paper we consider a model in which agents have complete information about their neighbours and, possibly, incomplete information about the rest of the economy. We consider two different informational frameworks. In the first, agents do not have priors about what is going on in the rest of the economy. In the second, agents are supposed to have priors about the unknown characteristics. We present a mechanism which any social choice correspondence satisfying monotonicity and no veto powet in both informational settings for every possible prior thus requiring little knowledge from the point of view of the designer of the information possesed by agents about the economy

The Problem of Holdout Creditors in Eurozone Sovereign Debt Restructuring

The Eurozone official sector has declared that the belated restructuring of Greek bonds held by private sector creditors in 2012 was a “unique and exceptional” event, never, ever to be repeated in any other Eurozone country. Maybe so. But if this assurance proves in time to be as fragile as the official sector’s prior pronouncements on the subject of “private sector involvement” in Eurozone sovereign debt problems, any future Eurozone debt restructuring will be surely plagued by the problem of non-participating creditors --- holdouts. Indeed, it is the undisguised fear of holdouts and the prospect of a messy, Argentine-style debt restructuring in the belly of Europe that has been one of the principal motivations for the official sector’s willingness to use its taxpayer money to repay, in full and on time, all of the private sector creditors of Eurozone countries receiving bailouts (the belated Greek restructuring being the sole exception). This article argues that a simple amendment of the Treaty Establishing the European Stability Mechanism (the Eurozone’s new bailout facility) could immunize within the confines of the Eurozone the assets of a Eurozone country receiving ESM bailout assistance from attachment by litigious holdout creditors. By thus increasing the difficulties that holdouts would face in enforcing court judgments against a debtor country, the objective of the amendment is to deflate creditor expectations that staying out of an ESM-supported sovereign debt restructuring will lead to a preferential recovery for the holdouts. This measure would also, when taken together with the other steps that the Eurozone has already implemented, substantially replicate the important features of the Sovereign Debt Restructuring Mechanism proposed by the IMF in 2002

Charm rescattering contribution in rare Bc+→K+K−π+B^+_c \to K^+ K^- \pi^+ decay

Following the experimental results from LHCb on the rare decay $B^+_c \to K^-K^+\pi^+$, we investigate the possibility where this process is dominated by a double charm rescattering. The $B_c$ decay to double charm channels have a weak topology that is favoured in comparison with the direct production of $K^-K^+\pi^+$ in the final state, suppressed by quark annihilation. The decay amplitude for $B^+_c \to K^-K^+\pi^+$ with $B_c$ decaying first to double charm channels is described by a charm penguin diagram, represented by charm hadronic triangle loops, which reach the final state of interest after $D\bar{D}\to K\bar{K}$ or $D^+ D^-_s \to \pi^+ K^-$ transitions. We show that these processes give rise to non-resonant amplitudes with a clear signature in the Dalitz plot. In a near future, the new data from LHCb run II will be able to confirme if the main hypotheses of this work is correct and the dominant mechanism to produce $K^+K^+\pi^-$ from the decay of $B^+_c$ is through charm rescattering

Reprofiling Sovereign Debt

• The IMF staff’s 2013 proposal to reprofile (i.e., stretch out for a short period without haircutting principal or interest) the maturing debt of a country that has lost market access is a sensible policy in cases where the IMF is uncertain whether the country’s debt stock is sustainable. • The motivation for the policy is to avoid situations, such as occurred during the Eurozone debt crisis, in which Fund resources are used to bail-out commercial creditors in full. • But a debt reprofiling is a species of debt restructuring and as such is susceptible to holdout creditor behaviour. • By allowing a small portion of its loans to the debtor country to be used to neutralise some or all of the additional credit risk caused by the reprofiling, the IMF could minimise holdout creditors in these operations. • The authors propose a technique for minimizing the risk that certain creditors may elect to decline a reprofiling proposal, no matter how lenient its terms

Robust implementation under alternative information structures.

In this paper we consider a model in which agents have complete information about their neighbors and, possibly, incomplete information about the rest of the environment. We consider two different informational frameworks. In the firts, agents do not have priors about the relevant characteristics in the rest of the environment. In the second, agents are supposed to have priors about the unknown characteristics. We present a mechinism which implements any social choice correspondence satisfying monotonicity and no veto powe in both informational settings for every possible prior thus requiring little knowledge from the point of view ofthe desinner of the information possessed by agents about the environment.Nash implementation; Incomplete information; Local information;

Optomechanics assisted with a qubit: From dissipative state preparation to many-body physics

We propose and analyze nonlinear optomechanical protocols that can be implemented by adding a single atom to an optomechanical cavity. In particular, we show how to engineer the environment in order to dissipatively prepare the mechanical oscillator in a superposition of Fock states with fidelity close to one. Furthermore, we discuss how a single atom in a cavity with several mechanical oscillators can be exploited to realize nonlinear many-body physics by stroboscopically driving the mechanical oscillators. We show how to prepare non-classical many-body states by either applying coherent protocols or engineering dissipation. The analysis of the protocols is carried out using a perturbation theory for degenerate Liouvillians and numerical tools. Our results apply to other systems where a qubit is coupled to a mechanical oscillator via a bosonic mode, e.g., in cavity quantum electromechanics

Master equation approach to optomechanics with arbitrary dielectrics

We present a master equation describing the interaction of light with dielectric objects of arbitrary sizes and shapes. The quantum motion of the object, the quantum nature of light, as well as scattering processes to all orders in perturbation theory are taken into account. This formalism extends the standard master equation approach to the case where interactions among different modes of the environment are considered. It yields a genuine quantum description, including a renormalization of the couplings and decoherence terms. We apply this approach to analyze cavity cooling of the center-of-mass mode of large spheres. Furthermore, we derive an expression for the steady-state phonon numbers without relying on resolved-sideband or bad-cavity approximations.Comment: 17 pages, 5 figure