Parity Symmetry in QED3

Schwinger-Dyson equations are used to study spontaneous chiral and parity symmetry breaking of three dimensional quantum electrodynamics with two-component fermions. This theory admits a topological photon mass that explicitly breaks parity symmetry and generates a fermion mass. We show that the pattern of symmetry breaking maintains parity but breaks chiral symmetry. We also find that chiral symmetry is restored at a critical number of fermion flavours in our truncation scheme. The Coleman-Hill theorem is used to demonstrate that the results are reasonably accurate.Comment: 11 pages, 5 figure

An application of the 3-dimensional q-deformed harmonic oscillator to the nuclear shell model

An analysis of the construction of a q-deformed version of the 3-dimensional harmonic oscillator, which is based on the application of q-deformed algebras, is presented. The results together with their applicability to the shell model are compared with the predictions of the modified harmonic oscillator.Comment: 12 pages, LaTe

Theory of the evolutionary minority game

We present a theory which describes a recently introduced model of an evolving, adaptive system in which agents compete to be in the minority. The agents themselves are able to evolve their strategies over time in an attempt to improve their performance. The present theory explicitly demonstrates the self-interaction, or so-called market impact, that agents in such systems experience

Language and coordination games

Conference Theme: Communication in Games and ExperimentsIntuitively, if players can communicate, they should be able to reach coordinated play in a coordination game. However, simply adding a communication stage before the play of the game does not render coordination as a unique prediction. To further refine the set of equilibria, Farrell suggested that a self-committing cheap talk statement about one’s planned behavior should be believed and thus would for sure lead to coordinated play. Aumann, however, argued that the statement has to be both self-committing and self-signaling for it to guarantee coordination. In this paper, the concept of common knowledge of language is formally incorporated into the cheap talk extension game. This paper shows that, if the stage game satisfies both the self-committing and the self-signaling condition, then every iteratively admissible outcome in the language game constitutes a coordinated play and gives the Sender her Stackelberg outcome. On the other hand, this paper identifies a class of generic games that violate self-signaling condition where every strategy profile of the stage game is an iteratively admissible outcome of the language game. This result supports Aumann’s argument that the self-signaling condition is necessary for coordinated play to be guaranteed by one-sided communication.postprintThe 26th Arne Ryde Symposium, Lund University, Sweden, 24-25 August 2007

Reputation and Competition among Information Intermediaries

Session 85: Topics in InformationThis paper investigates the e§ect of competition on the reputation mechanism in the market for information intermediaries, such as rating agencies. I use a dynamic model to endogenize the value of reputation so as to enable comparison of equilibria under di§erent market structures. In the model, behavior is determined by weighing the current rating fee against the future value the rating agency derives from having a higher reputation. I show that competition worsens the quality of ratings by reducing the value of high reputation but not the short-term gain of cheating.published_or_final_versio

Why Does New Hampshire Matter: Simultaneous vs. Sequential Election with Multiple Candidates

Session ID 38: Political EconomyIn a multi-candidate election, a voter may prefer to vote for his second choice in order to defeat his least favorite candidate. I study a model in which voters know their own preference but infer support of each candidate from a private signal. I show that if private signals are su¢ ciently precise, an equilibrium exists and is unique in the limit as the size of the electorate increases. In this unique equlibrium, supporters of a candidate vote more strategically when their hate for their worst choice becomes more domi- nant, but they vote less strategically when the same is true for the opposite camp. Using this property, I show that in sequential primaries, winning early primaries improves a candidate s chance of winning later primaries by making his supporters in later primaries vote more sincerely. I show that sequential primaries help with coordination, but puts more weight on the preference of the median voters in the early primaries. When voters worry enough about defeating their worst choice, sequential primaries are better at aggregating preferences than simultaneous primaries.published_or_final_versio

Language and coordination games

Intuitively, if players can communicate, they should be able to reach coordinated play in a coordination game. However, simply adding a communication stage before the play of the game does not render coordination as a unique prediction. To further refine the set of equilibria, Farrell suggested that a self-committing cheap talk statement about one’s planned behavior should be believed and thus would for sure lead to coordinated play. Aumann, however, argued that the statement has to be both self-committing and self-signaling for it to guarantee coordination. In this paper, the concept of common knowledge of language is formally incorporated into the cheap talk extension game. This paper shows that, if the stage game satisfies both the self-committing and the self-signaling condition, then every iteratively admissible outcome in the language game constitutes a coordinated play and gives the Sender her Stackelberg outcome. On the other hand, this paper identifies a class of generic games that violate self-signaling condition where every strategy profile of the stage game is an iteratively admissible outcome of the language game. This result supports Aumann’s argument that the self-signaling condition is necessary for coordinated play to be guaranteed by one-sided communication.postprintThe 18th International Conference on Game Theory, Stony Brook, N.Y., July 2007

Deep VLT infrared observations of X-ray Dim Isolated Neutron Stars

X-ray observations have unveiled the existence of a family of radio-quiet Isolated Neutron Stars whose X-ray emission is purely thermal, hence dubbed X-ray Dim Isolated Neutron Stars (XDINSs). While optical observations have allowed to relate the thermal emission to the neutron star cooling and to build the neutron star surface thermal map, IR observations are critical to pinpoint a spectral turnover produced by a so far unseen magnetospheric component, or by the presence of a fallback disk. The detection of such a turnover can provide further evidence of a link between this class of isolated neutron stars and the magnetars, which show a distinctive spectral flattening in the IR. Here we present the deepest IR observations ever of five XDINSs, which we use to constrain a spectral turnover in the IR and the presence of a fallback disk. The data are obtained using the ISAAC instrument at the VLT. For none of our targets it was possible to identify the IR counterpart down to limiting magnitudes H = 21.5 - 22.9. Although these limits are the deepest ever obtained for neutron stars of this class, they are not deep enough to rule out the existence and the nature of a possible spectral flattening in the IR. We also derive, by using disk models, the upper limits on the mass inflow rate in a fallback disk. We find the existence of a putative fallback disk consistent (although not confirmed) with our observations.Comment: 6 pages, 2 figures, accepted by A&A on 26-06-200

Extraction of Airways with Probabilistic State-space Models and Bayesian Smoothing

Segmenting tree structures is common in several image processing applications. In medical image analysis, reliable segmentations of airways, vessels, neurons and other tree structures can enable important clinical applications. We present a framework for tracking tree structures comprising of elongated branches using probabilistic state-space models and Bayesian smoothing. Unlike most existing methods that proceed with sequential tracking of branches, we present an exploratory method, that is less sensitive to local anomalies in the data due to acquisition noise and/or interfering structures. The evolution of individual branches is modelled using a process model and the observed data is incorporated into the update step of the Bayesian smoother using a measurement model that is based on a multi-scale blob detector. Bayesian smoothing is performed using the RTS (Rauch-Tung-Striebel) smoother, which provides Gaussian density estimates of branch states at each tracking step. We select likely branch seed points automatically based on the response of the blob detection and track from all such seed points using the RTS smoother. We use covariance of the marginal posterior density estimated for each branch to discriminate false positive and true positive branches. The method is evaluated on 3D chest CT scans to track airways. We show that the presented method results in additional branches compared to a baseline method based on region growing on probability images.Comment: 10 pages. Pre-print of the paper accepted at Workshop on Graphs in Biomedical Image Analysis. MICCAI 2017. Quebec Cit