Non-robustness of the Cash-in-Advance Equilibrium in the Trading-Post Model

The main justification for cash-in-advance (CIA) equilibria when there are multiple assets is a Shapley-Shubik trading-post model where the agents coordinate on a particular medium of exchange. Of course, there are other equilibria. We introduce a refinement and show that the CIA equilibrium does not satisfy our refinement while there exist equilibria that do.

Extended Conversations in Sender-Receiver Games

Aumann and Hart (Econometrica, Nov. 2003) have shown that in games of one-sided incomplete information, the set of equilibrium outcomes achievable can be expanded considerably if the players are allowed to communicate without exogenous time limits and completely characterise the equilibria from such communication. Their research provokes (at least) four questions. (i) Is it true that the set of equilibriumpayoffs stabilises (i.e. remains unchanged) if there are sufficiently many rounds of communication? (ii) Is the set of equilibria from communication which is unbounded but finite with probability one is the same as equilibria from communication which is just unbounded? (iii) Are any of these sets of equilibria “simple” and if so, is there an algorithm to compute them? (iv) Does unbounded communication (of order type w) exhaust all possibilities so that further communication is irrelevant? We show that in the context of finite Sender-Receiver games, the answer to all four is yes if the game satisfies a certain geometric condition. We then relate this condition to some geometric facts about the notion of bi-convexity and argue that if any of the questions has a negative answer then all three of the questions are likely to have a negative answer.

Epidermoid Cyst of Spleen

Splenic cysts are very rare lesions, most of them being parasitic systs. Nonparasitic cysts are uncommon. We report a case of young female who presented with mass and pain abdomen. Ultrasound examination revealed splenic syst. The diagnosis of epidermoid cyst was made based on characteristic lining on histopathological examinatio

New Methods for Characterizing Phases of 2D Supersymmetric Gauge Theories

We study the physics of two-dimensional N=(2,2) gauged linear sigma models (GLSMs) via the two-sphere partition function. We show that the classical phase boundaries separating distinct GLSM phases, which are described by the secondary fan construction for abelian GLSMs, are completely encoded in the analytic structure of the partition function. The partition function of a non-abelian GLSM can be obtained as a limit from an abelian theory; we utilize this fact to show that the phases of non-abelian GLSMs can be obtained from the secondary fan of the associated abelian GLSM. We prove that the partition function of any abelian GLSM satisfies a set of linear differential equations; these reduce to the familiar A-hypergeometric system of Gel'fand, Kapranov, and Zelevinski for GLSMs describing complete intersections in toric varieties. We develop a set of conditions that are necessary for a GLSM phase to admit an interpretation as the low-energy limit of a non-linear sigma model with a Calabi-Yau threefold target space. Through the application of these criteria we discover a class of GLSMs with novel geometric phases corresponding to Calabi-Yau manifolds that are branched double-covers of Fano threefolds. These criteria provide a promising approach for constructing new Calabi-Yau geometries.Comment: 25 pages + references, appendices. v2: references added, typos corrected. v3: two small typos correcte

Observation of quantum jumps in a superconducting artificial atom

A continuously monitored quantum system prepared in an excited state will decay to its ground state with an abrupt jump. The jump occurs stochastically on a characteristic time scale T1, the lifetime of the excited state. These quantum jumps, originally envisioned by Bohr, have been observed in trapped atoms and ions, single molecules, photons, and single electrons in cyclotrons. Here we report the first observation of quantum jumps in a macroscopic quantum system, in our case a superconducting "artificial atom" or quantum bit (qubit) coupled to a superconducting microwave cavity. We use a fast, ultralow-noise parametric amplifier to amplify the microwave photons used to probe the qubit state, enabling continuous high-fidelity monitoring of the qubit. This technique represents a major step forward for solid state quantum information processing, potentially enabling quantum error correction and feedback, which are essential for building a quantum computer. Our technology can also be readily integrated into hybrid circuits involving molecular magnets, nitrogen vacancies in diamond, or semiconductor quantum dots.Comment: Updated draft including supplementary information. 8 pages, 6 figures. Supplementary videos are available on our website at http://physics.berkeley.edu/research/siddiqi/docs/supps

Spin asymmetries for confined Dirac particles

We study the Bjorken `x' (or equivalently Nachtmann `xi') dependence of the virtual photon spin asymmetry in polarized deep inelastic scattering of electrons from hadrons. We use an exactly solved relativistic potential model of the hadron, treating the constituents as independent massless Dirac particles confined to an infinitely massive force center. The importance of including the p-wave components of the Dirac wave function is demonstrated. Comparisons are made to the observed data on the proton by taking into account the observed flavor dependence of the valence quark distribution functions.Comment: 4 pages, 4 figues; submitted to Phys. Lett.